CN1307510A - Method of laser welding tailored blanks - Google Patents

Abstract

A method of laser welding apparatus for use in industrial processing, which is operable to emit laser energy to weld blanks and the like together along a seamline. The emitted laser energy comprises either a single or a multiple beam of two or more coherent light sources. The apparatus is adapted to selectively reposition the orientation on the multiple beam relative to the seamline to achieve maximum weld efficiency having regard to any gaps between the abutting portions of the workpieces to be joined or the relative thicknesses of the sheet blanks to be joined.

Description

The method of laser welding tailored blanks

The field of the invention

The present invention relates to a kind of with Laser Welding with two or more multi-sheets along improving one's methods that a suture is stitched together, more particularly, relate to and a kind ofly utilize a branch of or multi beam will splice sheet material butt welding improving one's methods together from the light beam of yttrium aluminium garnet (YAG) laser instrument.

Background technology of the present invention

In existing manufacturing process, have a kind of method to be, by two or more the sheet metal of polylith different-thickness and shape weld and make a splicing sheet material, make the finished product workpiece thus.By the different plates of different size, overlay coating and/or performance is welded, make finished product workpiece thus with maximum intensity and minimum consumptive material and light weight, just produce splicing sheet material.Auto industry is one and splices the field that sheet material is more important and be used to produce various auto parts and components and vehicle panel.For example, known manufacturing adds the car door of some small-sized reinforcements by spot welding.

But the method for making jigsaw has following drawback, utilize laser, just sheet edge to be welded must be prefabricated into high accuracy, and looking-glass finish fineness is wanted at its edge.

Summary of the present invention

In the international application No.PCT/CA98/00153 that submitted on February 24th, 1998, the applicant discloses a kind of modifying device that sheet metal is welded of being used for, and is a kind of multiple laser welder.International application No.PCT/CA98/00153 relates to a kind of industrial welder that is used for, and for example, it can comprise splicing sheet materials such as making auto parts and components.This device has used the multiple laser source that the neighboring edge of sheet material is welded.In addition, have a mechanism be used for alternative displacement coherent source with respect to suture the position to, thereby can weld along the slit between the sheet material.

An object of the present invention is to provide a kind of position with respect to suture optimization ground displacement multi-beam to method, no matter the relative thickness of the gap size between the sheet material, sheet material docking site or material to be welded how, can both be guaranteed sheet material is fully welded.

The present invention design utilize the YAG laser instrument or more particularly the Nd:YAG laser instrument weld splicing sheet material as optimum coherent source.Should be understood that, the laser instrument such as the CO of other kinds ₂Laser instrument also can be used for this method.List Nd:YAG laser instrument and CO as table 1 ₂The comparison of laser instrument relevant parameter.

Table 1 Nd:YAG laser instrument and CO ₂The performance of laser instrument

	????CO 2-laser instrument	The ND:YAG-laser instrument
			Wavelength (μ m)	????10.6	????1.06
Beam quality (mm mrad)	????4-15	????20-60
			Light beam sends	The metal reflective mirror	Glass fibre
Light beam focuses on	The metal reflective mirror	Glass lens
			Intensity distributions	Gaussian distribution	Flat-top distributes
Efficient	About 10%	????2-5％
			Polarity	Plane or circle	Do not have
Work	Continuously or pulse	Continuously or pulse
			Working loss	Gas He, CO 2、N 2	The Kr lamp
Power (W)	????5000-6000*	????3000-4000

* splice the laser instrument of installing in the sheet material in manufacturing

The Nd:YAG laser instrument can be used for docking the steel plate of desirable strength, and speed of welding satisfies the needs of auto industry.With CO ₂As if laser is compared, and Nd:YAG laser is more superior because it can compatible better gap at joint fluctuation, the nonstraightness of weld edge and the weldering departure of shear.

Though this method can be used for single beam laser technology, the advantage of carrying out material laser processing with multiple laser is, utilizes higher laser power to reach speed of welding faster, better quality, higher efficient and bigger system flexibility.Two main purposes of welding different assembly unit sheet material with two bundles or multi beam technology are: have bigger edge and slit tolerance because can weld, thereby can improve speed of welding and quality.

Therefore, one aspect of the invention, a kind of method of utilizing the recombination laser bundle that the adjacent edge portion of two blocks of workpiece sheet materials is welded along a suture is provided, described recombination laser bundle comprises one first laser beam and one second laser instrument, each light beam all focuses on the corresponding focal zone with an optical centre to the part to be welded of described sheet material, the optical centre of each laser beam is spaced from each other certain distance and limits an end of the focal line of described composite light beam, along being limited perpendicular to the largest extension district on the direction of welding direction and weld line, described sheet material is welded by following step the effective diameter doff of composite light beam by first and second laser beams:

(a) determine that sheet material is to be welded to the gap width between the edge fit;

(b) regulate the recombination laser bundle effective diameter and substantially according to the described slit of following formula filling: $r_f+d_{\mathrm{off}}=\frac{2g}{({\mathrm{<figure-callout\; id="2"\; label="h"\; filenames="A9980802500552.png,A9980802500581.png"\; state="\{\{state\}\}">h</figure-callout>}}_2/h_1-1)}$ D wherein _Off=2r _f

G is a gap width;

d _OffIt is the lateral separation that staggers between laser beam center and the weld line;

h ₁Be first than gauge of sheet; With

h ₂Be second thickness than slab.

(c) change the anglec of rotation φ of the focal line of composite light beam according to following formula substantially with respect to weld seam $r_f=\frac{\mathrm{df}+b\&CenterDot;\sin \mathrm{\&phi;}}{2}$

D wherein _fIt is the focal diameter of first laser beam; With

B is a distance between the optical centre.

(d) move laser beam and workpiece sheet material is welded along the adjacent part of described sheet material.

On the other hand, the invention provides a kind of device that is got up along a weld line butt welding in the marginal portion of the first and second workpiece sheet materials, the thickness of first workpiece is h ₁, the thickness of second workpiece is h ₂, h wherein ₁＜h ₂, described device comprises: a laser instrument, come described sheet material is welded and the slit between the portion of the described limit of filling basically along described weld line but can launch a coherent source; With a controller that is used to control described coherent source, wherein, in welding process, described controller is keeping its effective power according to following formula with described coherent source substantially. $P_F=S\&CenterDot;\mathrm{\&nu;}\&CenterDot;\mathrm{\&rho;}(C_{\mathrm{sol}}\&CenterDot;T_m+h_m+C_{\mathrm{liq}}\&CenterDot;\mathrm{\&Delta;T})$

Wherein, P _FIt is effective laser power;

ν is a speed of welding;

ρ is a panel density;

C _SolAnd C _LiqBe respectively the solid phase and the liquid phase specific heat of sheet material;

Δ T is the average overtemperature that the molten bath surpasses fusing point; With

S is the cross-sectional area of weld seam.

S determines according to following formula substantially.

S=h ₂(r _f+d _off)+h ₁(r _f-d _off-g)

Wherein, r _fBe at the radius of weld line place coherent light source point perpendicular to weld line;

d _OffIt is the lateral separation that coherent source center and weld line stagger; With

G is the gap width between the neighboring edge part.

In yet another aspect, the invention provides a kind of method of utilizing a device that the marginal portion of first and second sheet materials is welded along a weld line, the thickness of first sheet material is h ₁, the thickness of second sheet material is h ₂, h wherein ₁≤ h ₂, this device comprises:

A laser instrument can be launched a coherent laser source and along described weld line described sheet material be welded,

Described sheet material is welded into by following step:

(a) with the marginal portion of first and second sheet materials to getting up; With

(b) start described laser instrument and weld described marginal portion, keep gap width (g) between the adjacent marginal portion according to following formula $g=\frac{1}{2}(\frac{h_2}{h1}-1)(r_f+d_{\mathrm{off}})$

Wherein, r _fBe the radius of coherent source perpendicular to the weld line direction; With

d _OffBe that the coherent source central cross departs from the distance between the weld line.

Brief description

By reading explanation hereinafter with reference to the accompanying drawings, can understand other purposes of the present invention and advantage, in the accompanying drawing:

Fig. 1 is the diagrammatic top view that is used for the assembly line of combination workpiece constructed in accordance;

Fig. 2 is the schematic side view of laser weld head used in the assembly line shown in Figure 1;

Laser soldering device in the assembly line of Fig. 3 presentation graphs 1 represents to use laser welded along 3-3 ' line;

Fig. 4 schematically shows with the Nd:YAG laser instrument and carries out the used trial production equipment of double beams laser welding;

Fig. 5 a represents the curvilinear motion figure of focused radius with respect to lens distance;

Fig. 6 represents processing and the welding parameter that testing equipment shown in Figure 4 is used;

Fig. 7 is the energy density distribution figure line chart that the used double beams laser test of the inventive method records;

Fig. 8 a and 8b illustrate the influence to Laser Welding of weldering deviator and slit;

Fig. 9 is illustrated in used welding die cavity in the solderability evaluation;

Figure 10 illustrates the slit filling theory principle of Laser Welding;

Figure 11 illustrates with respect to the maximum acceptable gap at joint width of sheet metal thickness with curve map;

Figure 12 illustrates the influence of gap width butt welded seam depression with the section of weld joint samples;

Figure 13 illustrates the influence curve of gap width and laser beam size butt welding depression;

The Energy distribution of the schematically illustrated Laser Welding of Figure 14;

Figure 15 illustrate laser energy absorption with to the relation of workpiece incidence angle;

Figure 16 illustrates the coupling percentage that is calculated gained by thickness of workpiece and spot diameter;

Figure 17 illustrates the relation curve between speed of welding and the thickness of workpiece;

The used model of surperficial absorptivity of the schematically illustrated calculating laser power of Figure 18;

Figure 19 illustrates the slit and welds the influence curve of deviator to surperficial absorptivity;

Figure 20 illustrates speed of welding to the relation curve between slit and the weldering deviator;

Figure 21 illustrates the difference of speed of welding between Dan Shu and the two-beam welding procedure;

Figure 22 illustrates the influence of horn angle to the laser welded seam depression with the section of joint;

Figure 23 illustrates the relation between weldering deviator and the welding depression;

Figure 24 illustrates the relation between slit and the welding depression;

Figure 25 illustrates with respect to the maximum acceptable gap width of horn angle;

Figure 26 illustrates the relation between speed of welding and the horn angle, wherein welds fast 2-1.5mm, laser power 300W, weldering deviator 0.3mm;

The relational model of schematically illustrated surperficial absorptivity of Figure 27 and horn angle;

Figure 28 illustrates the surperficial absorptivity of calculating and the relation between the horn angle with curve;

Figure 29 illustrates the influence of gap width to speed of welding with curve;

Figure 30 a-c illustrates the influence of weldering deviator butt welded seam depression with the section photo of welding point;

Figure 31 illustrates the influence of weldering deviator butt welded seam depression with curve;

Figure 32 illustrates the influence that the slit butt welded seam caves in curve, adopts two-beam technology, and the weldering deviator is 0.3mm, and horn angle is 6 °, the galvanized sheet of 2-1.5mm;

Figure 33 a-33d illustrates the invalid position that is caused by the Olsen test method on the welded specimen with photo respectively;

Figure 34 illustrates the influence of weldering deviator and the behavior of slit butt welded seam cracking;

The schematically illustrated employing double laser beam of Figure 35 increases the efficient beam size;

Figure 36 illustrates the burnt partially influence to speed of welding of laser with curve;

Figure 37 illustrates the influence of rotation two-beam coherent source to speed of welding with curve;

Figure 38 a and 38b illustrate the relation of melting efficiency and speed of welding and beam diameter;

Figure 39 illustrates the relation between the anglec of rotation of the profile of sample weld seam and laser beam focal line with sectional view;

Figure 40 (with Figure 38) illustrates the influence of light beam rotation to the welding depression of welding 2.0-1.5mm sheet material;

Figure 41 (with Figure 38) illustrates relation between the welding depression and the light beam anglec of rotation with curve map, and wherein welding deviator is 0.3mm;

Figure 42 illustrates the comparative result that positive and negative light beam anglec of rotation butt welded seam depression influences with curve, utilizes the zinc-plated sheet material of double beams laser welding 2.0-1.5mm, and the weldering deviator is 0.3mm, and horn angle is negative 6 °;

Figure 43 illustrates the light beam anglec of rotation allows the slit to maximum influence;

Figure 44 illustrates the light beam anglec of rotation, speed of welding and the gap size correlation in the two-beam automatic welding process with curve;

Figure 45 illustrates weldering deviator tolerance limit in the double beams laser welding procedure and the relation between the gap size;

Figure 46 illustrates the welding that will reach qualified with curve and relation between horn angle and the weldering deviator tolerance limit;

Figure 47 illustrates the relation between weldering deviator tolerance limit and the sheet metal thickness ratio to be welded;

Figure 48 illustrates the relation between different gap size and the weldering deviator tolerance limit;

Figure 49 illustrates the influence of the anglec of rotation butt welding deviator tolerance limit of two-beam coherent source;

The influence of the anglec of rotation butt welding deviator tolerance limit of two-beam coherent source when Figure 50 is illustrated in welding 2.0-0.75mm sheet material;

The schematically illustrated prototype splicing sheet material of making by method of the present invention of Figure 51;

Figure 52 a-52b illustrates single bundle weld seam and the two-beam weld seam in the prototype of Figure 51 with section;

Figure 53 is the photo of the Olsen test carried out on the prototype that the inventive method is made;

Figure 54 illustrates and is used for making the prototype splicing sheet material at Cadillac car (Cadillac) back door and the section of weld joint that is formed by the inventive method;

Figure 55 illustrates the prototype splicing sheet material that is used for Jeep Cherokee car (Jeep Cherokee);

Figure 56-58 illustrates the welding point profile of the prototype Jeep Cherokee car of the present invention's production respectively;

Figure 59 is illustrated in the Olsen result of the test of carrying out on the welding point in the Jeep Cherokee car; With

Figure 60 (I) and (II) are the various curved welding seams of producing according to the inventive method.

The present invention describes in detail

See also Fig. 1, it shows the production and assembly line 10 that is used for producing simultaneously two compound splicing sheet material workpiece 12a and 12b, in production line 10, robotic vacuum inhales fortune device 18a and 18b takes out paired sheet metal 14a, 16a and 14b, 16b from corresponding raw material heap.18a of each robot and 18b are used for that paired sheet material 14,16a and 14b, 16b are transplanted on a conveyer respectively and arrange 20, the latter is used for along production line 10 transportation sheet material 14a, 16a and 14b, 16b, conveyor sets 20 comprises the step-like conveyer 22,24 and 26 of three cover strip magnet, and the latter can move sheet material 14a, 16a and 14b, 16b and workpiece 12a and 12b along the longitudinally shown in the arrow 28.The step-like conveyer of magnetic that constitutes by conveyor sets 22,24 and 26 placement that is parallel to each other as shown in Figure 1.Should be understood that also to have other to place the mode of conveyer.

The first cover conveyer 22 is used for initial placement sheet material 14a, 16a and 14b, 16b on production line 10, and sheet material 14a, 16a and 14b, the 16b that places is transported on the second cover conveyer 24.

Conveyer 24 is parts of a laser weld platform 32, at this, with YAG laser instrument 36 along a weld line being connected together with sheet material 14a, 16a and 14b, 16b near edge joint weld.Conveyer 24 be used for do not weld sheet material 14a, 16a and 14b, 16b is transplanted on the welding position, then, after the welding workpiece 12a and the 12b that welds is being transported on the 3rd group of conveyer 26.Conveyer 26 is used for the composite plate members 12a that will be welded into and 12b and is transported to robotic vacuum and inhales fortune device 38a and 38b, and the latter can mention workpiece 12a and 12b and be placed on the finished product stockpile.

Production line 10 shown in Figure 1 can be welded into two workpiece 12a and 12b simultaneously by a laser instrument 36.Represent the most clearly as Fig. 1-3, YAG laser instrument 36 comprises the laser welding head assembly 42 (Fig. 2) and the fiber coupling device 44 that laser welding head assembly 42 optics of generator 40 are joined that are used to produce 40, one activities of coherent source generator of two bundle coherent sources or laser.Fiber coupling device 44 comprises two bursts of intrafascicular optical cable (not shown)s.Two energy of restrainting coherent sources that produced by generator 40 are transferred to weldering flush weld head assembly 42 through corresponding optical cable thus.

Fig. 2 illustrates a laser welding head assembly 42, comprising a light emitting laser soldering tip 46 that sends the laser energy.As previously mentioned, laser can comprise the composite light beam that is made of two coherent sources.Assembly 42 comprises that also a support 48 that is being rotatably mounted laser welding head 46 and one are used for the drive motors 52 of on support 48 rotary laser soldering tip 46.Laser welding head assembly 46 is provided with the suture tracking transducer 49 (Fig. 2) of microprocessor control, but latter's perception each to the slit between sheet material 14a to be welded, 16a and 14b, the 16b neighboring edge part.Sensor 49 for example can be the Canadian patent application No.2 that submitted on March 6th, 1997,199,355 disclosed types.Sensor 49 comprises an independently coherent source, a branch of coherent light is projected downwards on the adjacent part of sheet material; With one be used for perception from the catoptrical optical sensor on it.Sensor 49 to drive motors 52 and 46 and portal frame mechanism 54 control signal is provided, change position laser welding head 42 automatically and make composite light beam 30 point to weld seams.

Fig. 1 is clearly shown that laser instrument 36 whole being enclosed among the case 50.Case 50 is provided with the import and export 51 and 53 that resemble on the mailbox.Being provided with clamping device 60 in case 50 is used for keeping sheet material in place in welding.Although can select the anchor clamps of many types for use, clamping device 60 preferably respectively comprise one on July 12nd, 1997 disclosed Canadian patent application No.2,167,111 disclosed magnetic clamps.

Whole laser welding head assembly 42 can move horizontally by two reference axises.Suspension holdfast that assembly 42 is paired in conveyer 24 and sheet material 14a, 16a and 14b, 16b upper edge and auxiliary stand 56a and 56b move in first horizontal direction through a portal frame mechanism 42.Laser welding head assembly 42 moves along a track 58 (Fig. 3) that is located on the suspension holdfast 56a through portal frame mechanism 42.Each can be along sliding on be parallel to each other the end frame 62a that separates and 62b perpendicular to first direction to suspension holdfast 56a and 56b.

End frame 62a and 62b are supporting the end of parallel bracket 56a and 56b again movably.A servo-drive motor 64 (Fig. 1) the track 66 that extends along support 62a one end in the engaged at end of support 56a.Laser welding head assembly 42 can make laser welding head 46 move along any horizontal direction above sheet material 14a, 16a and 14b, 16b along moving with support 56a and 56b of support 56a and 56b moving on end frame 62a and the 62b.Laser welding head 42 can also can tilt with respect to vertical direction by means of pneumatic slide arrangement 68 vertical motions, for example is indexed to the position shown in Fig. 2 dotted line.

In welding process, coherent source generator 40 produces two bundle coherent sources.The corresponding optical cable of coherent source in coupling device 44 is transferred to laser welding head 42, and is transmitted into the weld line part that will weld thus.Send the neighboring edge of two bundle LASER BEAM WELDING sheet material 14a, 16a and 14b, 16b from laser welding head 42, recombination laser bundle 30 has the optical centre that a lengthwise focal line is connecting each light beam.

For reaching optimum welding, experimentize with two Nd:YAG laser instruments, weld the characteristic of method and set up a series of experimental datas with two-beam optical cable research two-beam, develop suitable welding procedure and the advanced laser welding system of structure with this.A) experimental facilities

Research equipment shown in Figure 4 comprises two Haas HL 3006D type Nd:YAG laser instruments, a 1.2m * 1.2m portal frame mechanism and a welding bench of being furnished with a tracking system as Figure 1-3.Laser beam is introduced workbench and is undertaken by two rank refractive index glass fiber, and the individual glass fibers that the latter is linked together by two ends constitutes.Light beam is to focus on by 1: 1 shaven head of standard Haas that has two 200mm lens.Provide transverse compression air stream as the protection air-flow, prevent the injury that shaven head is subjected to weld fumes and splashes.

For fully understanding the Nd:YAG laser beam, the characteristic of used optical parametric (focal length) and glass fibre light-conducting system is measured the laser beam that focuses on.Following data record by a) simple optical fiber and b) a whole set of experimental result of the laser beam of bifilar optic fibre guide, be to utilize PROMETEC ^TMLaser imager carries out.Accurately determined to have 100,150 and focal spot size, intensity distributions and the relative position of the optical system of 200mm focal length lenses.The scattering laser bundle

Measured the focussed laser beam of three kinds of optical systems, f=100,150 and the 200mm optical system in minimum focal radius be respectively 0.3mm, 0.43mm and 0.56mm, shown in Fig. 5 a.Optical parametric is littler, and curve rises suddenly more when leaving real focus.Reaching a minimum of a value, increase progressively by index conditions along with the distance of leaving focus near focus place radius.Different performance number place measuring beam radiuses the results are shown in Fig. 5 b, it is almost constant that the radius of focused beam keeps, power then changes to 3000W from 300W.This is an advantage of the Nd:YAG laser of fiber optic conduction.The demonstration of comparing of the beam characteristics of different optical parameter, focal length is long more, and as 200mm, its focusing distance is long more.Understand the fundamental characteristics of monochromatic laser beam, with the accurate welding parameter of setting of accurate data.The interval that beam radius keeps constant is bigger, and welding technique is stable more.Therefore, in research and production, select the lens of 200mm focal length for use.

The focal position of each concrete optical system is extremely important, and when welding, focus is set in plate surface usually.The focal position of 200mm optical system is 179mm, and this is the distance that measures the cover glass lid from plate surface.If lens are identical with the lens chuck, then this size will remain unchanged.

The main technologic parameters of laser welding tailored blanks sheet material schematically is shown in Fig. 6.These parameters can be divided into two groups: a) welding parameter; And b) is used to produce the sheet material parameter of jigsaw.First group of power P that is included in the laser beam 1 at plate surface place ₁, laser beam 2 power P ₂, speed of welding v, focal position z, horn angle θ, laser beam butt joint light beam anglec of rotation φ and leave the weldering deviator d of seam _Off

Fig. 7 represents that two-beam intensity and two focuses close the stereogram when tying up to 2 * 3000W.Distribution map illustrates, and the whole diameter that power is distributed in focus upper edge light beam almost is invariable.Each light beam is launched from the 3000W laser instrument.The about 0.6mm of the diameter of each focus and identical substantially.Distance between the bifocal is 1.2mm, and the interval of a 0.6mm is arranged between bifocal.The Breadth Maximum that double beams laser half-twist (focal line that promptly connects beam center is perpendicular to weld seam) is covered is 1.8mm, and in addition, the power of each luminous point can change respectively on request.This is of great use for some concrete joint of processing.

Slit between second group of material, coating and thickness, shearing seamed edge situation and sheet material that comprises the two boards material.As described below, the slit is one of most important parameters that influences welding parameter selection and welding depression Olsen result of the test.Usually set welding parameter according to following method:

1) laser power is chosen the peak power output of two laser instruments usually, to reach maximum speed of welding;

2) focal position is an important technical parameter of Laser Welding, and correct and accurate setting focal position is in order to obtain the welding procedure of stability and high efficiency.The focal position of the laser beam of welding jigsaw preferably is positioned at the surface of thin plate;

3) when the jigsaw of welding 0.8-2mm, select ± 6 ° horn angle usually.Select horn angle to depend on the thickness of slab ratio of a joint basically.For the joint of welding large thickness ratio rate, a positive horn angle is selected in suggestion; For the joint of little thickness ratio, Fu angle preferably;

4) the weldering deviator also is an important welding condition.But measuring weldering deviator reduces welding depression to greatest extent and reaches optimum seam sectional form;

Whether 5) need the light beam rotation then will come according to the maximum slit of joint fixed.Being only when only surpassing the slit filling capacity of single bundle technology in maximum slit needs.

6) determine speed of welding up to can not through welding the time by progressively increasing speed of welding.Can find a maximum welding speed like this.It is 90% to form and optimize reliable welding procedure that speed of welding is chosen maximum.

Concentrated research weldering deviator of two test methods that propose and slit are to the influence of welding procedure.One of them is to change the weldering deviator to weld that (Fig. 8 a), wherein welding deviator is to continuously change along whole joint.In weld start position, the weldering deviator is 0; In the sample end, the weldering deviator reaches determined value, and for example 0.3,0.6 or 0.9mm.In some cases, in soldering test, add a certain amount of slit.At postwelding, check sample and find lack of penetration or unwelded minimum of sheet material and maximum weldering deviator.At specific weldering deviator place, for example 0,0.1mm ... at the place, cut sample and check section of weld joint and measure welding depression.Can determine that welding depression is lower than the weldering deviator tolerance limit under certain value (the being generally 10%) condition according to Fig. 8.In many cases, can obtain a preferred weldering deviator from these results.

Another method is to weld by changing the slit, shown in Fig. 8 b.The clamping of two boards material is become: putting at a welding position does not have the slit between the sheet material; And be provided with certain slit at solder terminal.Measure the width in slit and do mark with finger gauge in this position.Under certain weldering deviator (being typically about optimum weldering deviator) condition, weld.After welding, open sample in the accurate shearing of mark position and check weld shape.The typical consequence that is obtained by soldering test is shown in Fig. 8 b.Usually, welding depression increases with the slit.The welding depression that allows according to maximum (for example 10% or 15%) is determined the maximum slit that allows from this curve map.

For the error that the nonstraightness that reduces to cut the limit causes, the welded specimen in this research workpiece adopts short slab (600mm).Whether the assessment welding point can be accepted is to adopt two characteristics: welding depression and Olsen test.

As shown in Figure 9, (600 purpose granularity) and corrosion (12% nitric acid) are ground in the cross section of welding point, detect the fusion area of weld seam, and measure the minimum perforation gauge of weld seam at microscopically.The section that reduces that records is exactly the depression rate with ratio than the original thickness of thin plate, just than a percentage of lamella thickness.The depression rate is an important Weld Performance.Be quality and the matching of guaranteeing welding point, be limited to 15% on the depression rate that welding code is determined.

The Olsen test is the quantification test of weld seam matching.The welded specimen reinforcing is made it fracture.Note fracture position.If crackle starts from and along the base metals cracking, weld joint samples is exactly acceptable, that is to say does not have the matching problem.Olsen test than the molded test strictness many, thereby the welding point by the test of Olsen weld seam matching does not just have problem in penetrator test.B) fill in the slit of Laser Welding

For the welding procedure that does not add packing material, can utilize a simple model to describe the relation of welding between deviator, slit, laser spot and the two boards material thickness.Suppose that than the metal molten blind on the slab edge, the shape at this edge is roughly triangular in shape.The scope of deposite metal is determined that by laser beam size promptly only the material under light beam irradiates just melts.In order to fill up slit (S _g), the area S than heavy-gauge sheeting of fusing _mMust equal slit S _gArea, so just have following relation

S _g=g·h ₁????(3.1)

Therefore, maximum acceptable gap width is: $g=\frac{1}{2}(\frac{h_2}{h_1}-1)(r_f+d_{\mathrm{off}})=\frac{1}{2}(\mathrm{TR}-1)(r_f+d_{\mathrm{off}})$ Wherein: d _OffBe the weldering deviator, g is a gap width, r _fBe focal radius, h ₂And h ₁Be respectively thicker shown in Fig. 3 .1 and than the thickness of light sheet, TR is the thickness ratio (h of welding point ₂/ h ₁).By this model, the slit will be filled up.Check technological parameter as a result the time must consider following factors: d (a) walks to setover _OffIncrease; (b) will melt more or less effectively by changing shape that horn angle changes the fusion area than heavy-gauge sheeting; (c) then can increase focal radius r by utilizing double beams laser or light beam not to focus _f

But the weldering deviator is wanted the restriction of Stimulated Light spot size and gap size, and promptly maximum weldering deviator is r _f-g.If the weldering deviator is worth greater than this, laser beam just can not contact and be heated to the edge than light sheet.This causes the welding procedure instability.Therefore, maximum slit is: $g_{\max }=\frac{r_f(\mathrm{TR}-1)}{1+0.5(\mathrm{TR}-1)}----\left(3.3\right)$

Figure 11 is illustrated under the situation of two laser beam spot spot sizes, the maximum function that allows the slit to change with thickness ratio.r _f=0.3mm is meant single bundle welding, and r _f=0.6mm then refers to the two-beam welding, and the anglec of rotation is 30 °.On the one hand, this shows that the maximum slit that allows is relevant with the joint configuration.Thickness is bigger than Yu, the easy more weld seam that obtains not having depression.On the other hand, when a certain joint of welding, utilize the laser point of large focal spot can reach the filling of better slit.The maximum of listing the several typical jigsaw of laser weld in table 2 allows the slit.

The maximum slit of calculating during table 2 Laser Welding jigsaw

Slab	Thin plate	????TR	Maximum slit	Maximum slit
					(mm)	(mm)		(single bundle d f0.6mm)	(two-beam d f1.2mm)
????1.8	????0.8	????2.25	????0.23mm	????0.46mm
					????2.0	????1.0	????2.0	????0.20mm	????0.40mm
????1.3	????0.8	????1.6	????0.14mm	????0.28mm
					????1.3	????1.0	????1.3	????0.08mm	????0.16mm
????1.0	????0.8	????1.25	????0.07mm	????0.13mm

The influence in butt welded seam cross section, slit when Figure 12 is illustrated in the zinc-plated jigsaw of welding 2.0-0.75mm.Therefrom can know and find out how the slit is filled in welding process.Laser beam melts the edge of heavy-gauge sheeting and makes it to flowing in the seam.Zero or the situation of small gap under, in the material volume of slab side fusing requirement greater than the slit.Thus, molten material overflows on the thin plate and forms the section of weld joint at a band angle.If it is big that the slit becomes, then this part molten material enters the slit, and weld seam then flattens smooth.Another noticeable useful consequence is to be issued to the cross-sectional area maximum that melts in zero slit condition.This means that the slit is more little, the quantity of material that melt is big more, just needs bigger effective fusing power.

Figure 13 illustrates the influence of laser beam size and thickness ratio butt welded seam depression, and has verified aforementioned model.Generally speaking, weld the jigsaw of large thickness ratio rate (TR), be easier to fill up the slit.Even utilize single bundle welding procedure still can weld the slit to such an extent that its welding depression is no more than the user acceptance standard for the weld seam of 0.3mm, as 10%.According to formula (3.3), it is 0.085mm that the maximum of the sheet material of 2.0-1.5mm allows the slit, if the slit is too big, is not enough to then guarantee that as single bundle or two-beam welding procedure depression does not appear in weld seam.For this reason, more advanced two-beam welding procedure such as light beam rotate the weld seam that is applied to weld big slit and low thickness ratio.The energy balance of laser welding tailored blanks

Stable and continuous welding procedure is the result of energy between laser power, coupling efficiency, energy loss and the effective power (or power) balance, as shown in figure 14.Welding institute energy requirement is from laser beam.Material absorbs a part of laser energy and converts thereof into heat energy, and this process can characterize with an important coefficient, i.e. coupling efficiency.It represents laser energy P _LThere is great percentage to absorb on earth by material.Remaining (P _R) reflect by material surface.The laser energy that absorbs can be further divided into two parts again, and wherein a part is used for molten material and forms weld seam, is referred to as effective power P _FAnd another part is to conduct the power loss P that spills in the base metals by heat _pFor laser welding process, the laser power of absorption comprises effective summed horsepower and power loss, is following formula:

A·P _L=P _F+P _p????(3.4)

Go out from welding procedure principle angle, this formula shows that the laser power of absorption should equal effective power and power loss sum.If AP _LLess than P _F+ P _p, then mean the underpower in welding point, and may cause lack of penetration; If AP _LGreater than P _F+ P _p, show that then power is too big, often cause overheated, bore a hole, send forth or or even the cutting.

The purpose of introducing energy balance is exactly to set up a mathematical formulae to study relation between welding material and the welding parameter.Thereby can quantize maximal rate and slit and weldering deviator to the influence of welding procedure and to the requirement of tracking system.

The absorptivity of material for laser light energy depends on the wavelength of optical characteristics (relevant with temperature), laser beam of material and polarised direction and the laser incident angle with respect to material surface.Correlation between these parameters is provided by the Fresnel equation.Iron (common iron also is suitable for) is shown in Fig. 3 .6 at its fusing point to the absorptivity of Nd:YAG laser (1.06 microns of wavelength).

Yet by " open-work " (Keyhole) mechanism through welding, coupling efficiency is not only relevant with surperficial absorptivity, and is also relevant with the shape of open-work, and this is because there is laser multipath reflection sink effect.Figure 16 illustrates coupling efficiency.

For laser welding tailored blanks, the thickness of sheet material is in the 0.75-3.00mm scope, and lasing beam diameter is 0.6mm for 0.6mm optical fiber and is 1: 1 focusing parameter, thereby the ratio of the thickness/diameter of welding procedure is about 1.25-5.The coupling efficiency of Nd:YAG laser welding process is about 60-80%; And CO ₂Laser Welding then is 35-60%.Therefore, even in utilizing the saturating welder's skill of open-work mechanism, the coupling efficiency of Nd:YAG can be greater than CO ₂Laser Welding.For the sheet material of welding different-thickness, the ratio of thickness/diameter can be calculated to be: The effective power of heating and fusing weld metal can be calculated by following formula:

P _F=S ν ρ (C _SolT _m+ h _m+ c _LiqΔ T) (3.6) wherein: v is a speed of welding, and ρ is a density of material, C _SolAnd c _LiqBe respectively the specific heat of the solid phase and the liquid phase of sheet material, T _mBe fusion temperature, h _mBe the latent heat of fusion, Δ T is surpass fusing point overheated.For Laser Welding, under normal conditions, average overtemperature Δ T=0.2-0.4T _mS is the cross-sectional area of weld seam, is determined by sheet metal thickness, weldering deviator and slit, can be calculated as follows:

S=h ₂(r _f+d _off)+h ₁(r _f-d _off-g)????(3.7)

Applicable elements is-r _f≤ d _Off≤ r _f-g.Wherein, h ₂And h ₁Be respectively slab and gauge of sheet, r _fBe the radius of LASER SPECKLE, d _OffBe the weldering deviator, g is a gap width.

Power attenuation can roughly be calculated as follows: ${\mathrm{<figure-callout\; id="1"\; label="P"\; filenames="A9980802500571.png,A9980802500581.png"\; state="\{\{state\}\}">P</figure-callout>}}_{1^{\&prime;}}=4.4\&times;K\&times;T_m\&times;\frac{{\mathrm{<figure-callout\; id="2"\; label="h"\; filenames="A9980802500552.png,A9980802500581.png"\; state="\{\{state\}\}">h</figure-callout>}}_2+{\mathrm{<figure-callout\; id="1"\; label="h"\; filenames="A9980802500571.png,A9980802500581.png"\; state="\{\{state\}\}">h</figure-callout>}}_1}{2}\&times;\frac{\mathrm{\&nu;}\&CenterDot;h}{4D}----\left(3.8\right)$

Wherein K is a thermal conductivity, and D is the temperature diffusivity of material, and W is a weld width.D) theoretical speed of welding

According to formula (3.4), (3.5), (3.6), (3.7) and (3.8) and energy balance, can derive theoretical speed of welding and be $\mathrm{\&nu;}=\frac{A\&CenterDot;P_L}{S_{\mathrm{eff}}\&CenterDot;\mathrm{\&rho;}\&CenterDot;(c_{\mathrm{sol}}{T}_m+H_m+\mathrm{\&Delta;T}\&CenterDot;c_{\mathrm{liq}})+0.55({\mathrm{<figure-callout\; id="2"\; label="h"\; filenames="A9980802500552.png,A9980802500581.png"\; state="\{\{state\}\}">h</figure-callout>}}_2+h_1)\mathrm{Kw}{T}_m/D}----\left(3.9\right)$

For the single beam laser weldering, weld width is usually greater than the LASER SPECKLE diameter.According to experimental observation, W is 1.3d approximately at last _fThe effective area S of seam cross-section _EffRoughly 1.1 and 1.55S between, 1.3S preferably.Average overtemperature Δ T=0.2T _m, for the double beams laser weldering,, estimate that the overtemperature in molten bath can be higher because the energy of input is higher and have two spots arranged side by side, weld width can be slightly larger than the single beam laser weldering, so getting, w makes 1.4d _f, and Δ T is 0.4T _mUtilize formula (3.9) to calculate the theoretical speed of welding of welding several typical steel jigsaw, and compare, be shown in Figure 17 with result of the test.Can find out, very meet between calculated value and the experiment value.

Slit and weldering deviator affect speed of welding both ways.On the one hand, they influences molten metal amount in weld seam, this discussed at formula (3.9); On the other hand, they can change absorptivity A.In order to be described in the absorbent properties between laser beam and sheet material joint under different slits and the weldering deviator condition, be incorporated herein a naive model, as shown in figure 18.Absorption laser can occur in three positions on the joint; Part laser power is absorbed by the end face of two boards material, and this is that the incidence angle of laser beam equals horn angle; Second portion is absorbed by the edge that exceeds thin plate on the slab, and its incidence angle is 90 °-θ; The third part laser power is absorbed by the slit by multipath reflection one absorption process that takes place between slab and the thin plate edge, and its incidence angle also equals 90 ° of one θ.The absorptivity of laser power is the function of horn angle, focus diameter, gap width, weldering deviator and two boards material thickness.During absorptivity in calculating joint, also to consider the thickness of incidence angle, gap width, weldering deviator and two boards material.2.0-1.0mm result of calculation be shown in Figure 19.Can know thus and find out that surperficial absorptivity and gap size relation are very big.For a certain splice combinations, it begins to increase with the slit, is issued to peak value in certain slit.If the slit is excessive, absorptivity can descend again.In contrast, the weldering deviator influences surperficial absorptivity hardly.

Utilize formula (3.9), model promptly shown in Figure 16 can estimate that the slit is to slit and the influence of weldering deviator to speed of welding.Sheet material combination for certain utilizes result shown in Figure 15 to calculate coupling efficiency A, must be revised with result shown in Figure 19 then.Figure 20 illustrates the speed of welding to different slits and the calculating of weldering deviator.

Utilize the laser irradiation of tilting, gap width changes to certain value from zero, and then absorptivity increases with the slit, and reaches maximum in certain gap width.This is because slit Yu is wide, then has more laser power to enter slit and interreflection and absorption therein, thereby forms higher absorptivity.The molten metal amount then descends with gap size.Two kinds of factors all make speed of welding higher.If the slit is too big, because the number of times that laser beam absorbs in the slit and reflects descends with gap size, a part of laser passes the slit even does not touch panel edges, thereby absorptivity then diminishes.Though the amount of deposite metal has reduced, the energy loss that laser power is passed the slit then becomes a deciding factor.Thereby speed of welding has descended.Select speed of welding to determine, to guarantee along the abundant through welding in the whole welding joints according to the maximum slit between zero slit and the shear.The weldering deviator influences coupling efficiency hardly, and only changes the amount of deposite metal, and speed of welding then descends with the increase of weldering deviator.E) utilize two-beam along the seam welding jigsaw

Below introduce in detail to guide through bifilar glass dimension and weld jigsaw with two Nd:YAG laser instruments.To become to make bifilar optical registration the bifocus of laser beam and the connection focal line between the focus to be parallel to seam (along seam).Test is concentrated with Olsen matching test method and is determined that soldering tip Aligning degree, laser beam weld profile (depression) and other Effect on Performance of deviator to slit filling, speed of welding and welding parameter butt welded seam.

1. the comparison of two-beam speed of welding

One of purpose of utilizing two-beam technology in laser welding tailored blanks is to improve welding productivity, promptly improves speed of welding.For relatively two-beam and single bundle speed of welding, under the same experimental condition similar thick-carried out a series of tests in the thin plate combination, it the results are shown in Figure 21.Single beam laser power is 3000W, and double beams laser power is 2 * 3000W, and horn angle is about 6 °.The slit is selected in 0-0.2mm, and the weldering deviator is according to then changing between 0.15-0.3mm than lamella thickness.Studies show that speed of welding is normally subject to the thickness of two boards material.Yet the thickness of thin side plays a part bigger on the decision speed of welding.Figure 21 illustrates, and the speed of welding that makes up with two-beam welding different plates almost is the twice of Dan Shu.Speed of welding has been turned over one times with laser power substantially.The two-beam solder technology can make the client reach more high production rate (speed of welding) and manifest effect immediately, and needn't wait for the appearance of more powerful novel Nd:YAG laser instrument.The advantage of two-beam welding procedure is to use two-beam can reduce the technical risk of welding system.If a laser instrument breaks down and needs repair, still available another laser instrument is kept continuous production, is that speed of welding has reduced.

2. horn angle is to the influence of welding procedure

Horn angle is an important technical parameters.Horn angle has been determined open-work direction, through welding and melting pool shape.On the other hand, workpiece is very big to the absorptivity and the beam incident angle degree relation of laser power.In order to study the influence of horn angle, selected four horn angle to come welded blank to welding procedure.They are shown in Figure 22 to the influence of molten bath and weld shape.

As can be seen from Figure 22, can select three kinds of horn angle scopes to weld the jigsaw of different-thickness.First kind is, laser beam is mapped to from the thin side of joint and reaches thick side, and this expression horn angle is for just.Second kind be laser beam perpendicular to plate surface, promptly horn angle is zero.Horn angle is that positive advantage is that joint is easier to through welding because laser beam only need the through welding thin plate and melt away on the slab side some come blind.Can improve speed of welding like this.Double beams laser technology can provide bigger laser power, thereby makes laser beam be selected in the third scope, and promptly laser beam that is to say that from the thin side of thick side directive of joint horn angle is negative.The influence of horn angle butt welded seam depression is shown in Figure 23 (changing the weldering deviator) and Figure 24 (change slit).Welding under the constant situation of deviator, the maximum slit that allows is shown in Figure 25 to the influence of horn angle.

Generally speaking, from Figure 23,24 and 25 as can be seen, welding depression descends with the increase of weldering deviator, and has an optimum weldering deviator that makes the welding depression minimum; Welding depression reduces with the increase of gap size, or the like.This shows, can reduce welding depression by suitable setting horn angle.Weld 2.0-1.5mm sheet material, horn angle is that 0.18mm can reach optimum slit filling for-6 ° with the slit.Negative horn angle Yu is big, and laser beam enters slab Yu Shen, more slab material fusing can be fused in the molten bath.Compare with positive horn angle, another advantage of negative horn angle is the penetration direction of open-work.For positive horn angle, open-work points to the slab root edges, and distance increases with the increase of weldering deviator or horn angle between open-work and the joint bottom.But this distance does not surpass a fixed number, otherwise the thin plate bottom margin just can fully not melt and may cause lack of fusion.For negative horn angle, open-work passes joint and points to thin plate from slab, and points to the root edges of thin plate.Suitably increase weldering deviator and horn angle simultaneously and can not cause the variation of open-work position in the joint bottom.Therefore, on the one hand, can set big weldering deviator and horn angle and melt more slabs; And on the other hand, still will melt the root of joint and reach firm welding.For the little joint of welding thickness of slab difference, for reaching good filling, negative horn angle is particularly useful.Its shortcoming then is to melt more material and then mean laser power that need be bigger and reduce speed of welding.

Can be clear that from figure, be that zero slit filling is the poorest if having slit, horn angle.Its reason is the reciprocation between open-work and the slit.Because the part of open-work is made of slit surfaces, open-work then can become big in the sheet material bottom.Utilize open-work mechanism to reach degree of depth through welding, this means by open-work to lose more material.Another reason may be, by changing irradiating angle, and causes the variation of absorptivity and interaction aspect between laser beam and the joint.

Relation between speed of welding and the horn angle is shown in Figure 26.According to these experiments, just can reach higher speed of welding with zero horn angle.Generally speaking, speed of welding reduces to negative direction decline with horn angle.

Speed of welding is to be determined by the energy balance of heating process.For Laser Welding, speed of welding is determined by following factors: 1) laser power of workpiece absorption, i.e. absorptivity; 2) quantity of material that under the situation that the heat-energy losses that enters mother metal by the heat conduction remains unchanged to a certain extent, melts.As mentioned above, horn angle influences the fusing amount of material.Negative horn angle can melt more slab material and obtain the filling of better slit, and then needs more energy or laser power.Speed of welding has just reduced naturally.Zero or positive horn angle situation under, the material of fusing lacks during than positive horn angle, thereby can reach higher speed of welding.

Under different horn angle conditions, the absorption behavior between laser beam and the sheet material joint is shown in Figure 27.For simplifying computational process, suppose that the percentage of second portion equals the ratio of Sa focusing area.When calculating the slit absorptivity, also to consider the thickness of incidence angle, gap width, weldering deviator and two boards material.Result of calculation is shown in Figure 28.Can note several interesting results.In three kinds of horn angle scopes, the absorptivity maximum of positive horn angle.Zero horn angle has minimum absorptivity.And for zero horn angle, the absorptivity of laser power reduces with the increase in slit.The slit is big more, enters the slit and laser beam Yu with material effects is not many, and this is because incidence angle is 90 ° with respect to sheet edge.For laser welding tailored blanks, constant if the quantity of material of fusing keeps, mean that then speed of welding descends with the increase in slit.

This conclusion is by Figure 29 experimental verification, and Figure 29 promptly represents the functional relation between speed of welding and the gap size.Speed of welding increases with gap width, is that the 0.1mm place reaches maximum in the slit, then descends then.Its tendency is closely consistent with laser power absorption behavior shown in Figure 28.

Therefore, horn angle is an important parameter, can influence welding procedure consumingly.Be blind better, laser welding head should be set in negative angular range.Yet this horn angle is set and is only applicable to the two boards material that throat thickness differs less (promptly less than 25%).For the big sheet material of throat thickness difference, do not advocate and adopt negative horn angle, because laser beam must penetrate slab, this means that the speed of welding loss is big, welding productivity is low.More effectively to absorb laser power and improve speed of welding in order to reach, selecting positive horn angle is highly significant.In this case, speed of welding is determined in the slit of usable zero slit and maximum possible.Zero horn angle is the ability minimum of blind not only, and minimum to the absorptivity of laser energy, tries not to adopt when the welding jigsaw.F) the weldering deviator is to the influence of depression

When welding common jigsaw, the fusion area comprises the slab of a part of thin plate and bigger portion.If between the two boards material slit is arranged, just it must be filled up to form firm weld seam.As previously mentioned, in order to overcome welding depression, when laser beam is aimed at the more slab of irradiation, then can reach good result.The weldering deviator of laser beam is another important technical parameters.The influence substantially of weldering deviator butt welded seam cross section is shown as Figure 30.For the optimum weldering deviator that quantizes to determine the influence of weldering deviator butt welded seam depression and seek the sheet material combination, a series of soldering tests have been carried out with the joint of three kinds of speeds of welding and three kinds of gap sizes.The results are shown among Figure 31 of the influence of weldering deviator butt welded seam depression.

The weldering deviator plays an important role when the welding jigsaw, and it is applicable to gap size when speed of welding is constant.If there is not the slit, can form quality weld under the weldering deviator on a large scale.The weldering deviator is from 0 to 0.3mm, and the welding depression rate is lower than 10%, and weld seam is filled good.Along with the increase of weldering deviator, because melt away more heavy-gauge sheeting, welding depression descends thereupon.If there is the slit, should keep certain weldering deviator to keep welding depression to be lower than 10%.When adopting automatic tracking system, preferably maintain this weldering deviator.If the slit is too big, then can not form quality weld.Usually at weld seam both sides (Figure 30) depression and undercut appear.

There is an optimum weldering deviator that makes the welding depression minimum.In the test of 2.0mm-1.5mm sheet material combination, optimum weldering deviator is about 0.25-0.3mm.Increase the weldering deviator again above this value and then cause bigger depression.Yet, should note another phenomenon, different speeds of welding and slit respectively there are a weldering deviator upper limit.In case the weldering deviator surpasses this limit, then can not be welded into the high-quality joint.If laser beam only heats slab and then can burn down.Eight jiao in the bottom of thin plate is incomplete fusion (Figure 30 c) then.In the case, a unfilled corner is then arranged, also just can not get good weld seam at the root of weld.

In the scope of optimum weldering deviator, the speed of welding influence is minimum.Preferably carry out high-speed welding, because highly weld not only productivity ratio height, and welding depression also can remain on below 10% in much bigger weldering deviator tolerance limit, that is to say the anti-interference and the security that have increased welding procedure.G) the maximum slit that allows

Between the two boards material, exist the slit to it is said inevitably, be meant certainly to surpass one meter fusion length.Studies show that the sheet material of conventional cutting does not have straight flange, under certain welding condition,, have a maximum that can obtain satisfied joint to allow the slit with regard to any concrete welding procedure.

The influence of gap at joint butt welded seam depression is shown as Figure 32.As expected, welding depression increases with the increase of gap size.From Figure 32, just can read the maximum slit that allows by setting different maximum welding depressions.For example, maximum to allow the slit be 0.1-0.15mm, adopts the two-beam welding procedure in 0.3mm weldering deviator, 6 ° of horn angle and 2-1.5mm galvanized sheet, and the depression rate that reaches is 10%.Should also be noted that the speed of welding slit that can have the greatest impact.For constant weldering deviator, reduce the method that speed of welding can not prove a kind of to the greatest extent wideer slit of filling that the people is satisfied.This be because, speed of welding is slow more, loss amount Yu that the evaporation and splash of deposite metal by open-work produces is big.In order to reach better weld seam filling, speed of welding must be welded deviator and slow down along with corresponding inclined to one side Jiao of light beam or increase simultaneously.

It is intensity and matching and the Olsen result of the test of carrying out that Figure 33 is depicted as the quantitative study properties of its welded joints.The photo of Figure 33 illustrates welded specimen and produces the position of losing efficacy through the Olsen test.Crackle starts from mother metal (normally in thin plate) and is parallel to seam and extends in mother metal or stride across weld seam (Figure 33 a and 33b).Under these circumstances, the mechanical performance of welding point is qualified.Figure 33 c illustrates, and crackle, and is parallel to weld seam and extends in thin plate near the commissure in mother metal.In this case, joint has satisfactory performance, and thinks not dangerous; If crackle starts from weld seam and stretches (Figure 33 d) therein, then joint is defective.

The weldering deviator is shown Figure 34 and the slit is how to influence the cracking behavior of welding point in the Olsen test.If the weldering deviator is too big, then thin plate just can not fully melt, and the formability of joint is the poorest.Must carefully avoid this situation.The joint of wide slit and/or inappropriate weldering deviator may ftracture in welded joints, and this is because the cross section that excessive depression and undercut meeting significantly reduce weld seam.Suitable technological parameter can guarantee that joint is no problem in the Olsen test.Crackle starts from mother metal and expansion has therein guaranteed that weld seam has proper mechanical capacity.H) adopt two-beam technology

The purpose that adopts two-beam technology welding jigsaw is to increase speed of welding and enlarge processing quality, promptly welds with bigger weldering deviator/slit.As shown in Figure 11, one of possibility that reaches the filling of better slit is to increase focal spot size.For example, if, must adopt the focus that is about the 1.8mm diameter to reach good weld seam and fill with the slit of 0.2mm and the weldering deviator welding 2-1.5mm sheet material of 0.3mm.In order to make laser beam reach such technical indicator, single bundle weldering method increases inclined to one side Jiao exactly or adopts long-focus lens.Under which kind of situation, all greatly weakened the basic performance of laser beam, i.e. power level.This can change to the laser fusion weldering by open-work weldering (deep welding) with welding mechanism, will lose the advantage that Laser Welding produces because of high power intensity.

With two-beam technology laser welding tailored blanks is an inventive process that addresses this problem.Crucial technology is rotation double beams laser and increase the efficient beam size to satisfy the specific (special) requirements to welding heat source.As can be seen from Figure 35, can change the effective diameter of laser beam continuously by then not reducing the power level of laser beam around its center two spots of rotation.But deal with the joint that Dan Shu is difficult to weld light beam rotation maximum flexibility.

No matter be to make the burnt partially or rotation of laser beam, increase the efficient beam size and then mean the more workpiece material of fusing and be welded into wideer weld seam.Can reckon with that speed of welding can reduce.In order to determine the influence of beam sizes to speed of welding with two technological concepts, on the zinc-plated sheet material of 2.0-1.5mm, carried out the contrast experiment, it the results are shown in Figure 36 and 37.In Figure 36, beam diameter is by Prometec ^TMLaser imager is determined.Beam effective diameter is calculated by following formula in Figure 37:

d _Eff=d _f+ bsin φ wherein, d _fBe the diameter of single focus, b is a distance between two focus center, and φ is the light beam anglec of rotation.Clearly express the relation between speed of welding and the laser spot size.With inclined to one side Jiao or slewed laser beam welding, an important relationship is arranged, shown in Figure 36,37,38a and 38b between speed of welding and spot diameter.

For the single beam laser weldering, melting efficiency is proportional to speed of welding and beam diameter is long-pending, and for next at the certain joint of constant laser power two-beam welding, it is constant in a certain speed of welding that melting efficiency can keep.This result is applicable to that also (referring to Figure 38 a), the long-pending of speed of welding and beam diameter keeps almost constant or slightly decline bifocus along with the increase of beam diameter along the seam Laser Welding.This shows that speed of welding is inversely proportional to beam diameter.In last example, if gap at joint is elected 0.2mm as, then need the LASER SPECKLE of 1.8mm, speed of welding then drops to 2.7m/ minute.Yet this conclusion is not suitable for the double beams laser weldering of rotatable light beam.Melting efficiency improves with the increase of beam effective diameter.This may be interpreted as, and the heat energy by heat conduction loss reduces, with regard to the ratio of the degree of depth/focus diameter and the coupling efficiency height.Though speed of welding still reduces (seeing Figure 38 b) with the increase of effective focal spot radius (anglec of rotation), the speed of welding of the rotation light velocity is all much higher when burnt partially.For the zinc-plated jigsaw that welds 2-1.5mm with 90 ° the anglec of rotation, speed of welding is 5.4m/ minute, than the burnt partially Laser Welding to the same equivalent spot diameter of laser is fast again.

Figure 39 is illustrated in the photo of the seam cross-section under the different light beam anglecs of rotation, therefrom can clearly be seen that the influence of the light beam anglec of rotation.The width of weld seam end face is determined that by beam effective diameter promptly by the decision of the light beam anglec of rotation, and the width of weld seam bottom and the light beam anglec of rotation are almost irrelevant.Beam sizes is big more, and then the weld seam top is wide more.

In addition, two bundle laser play a part different in welding process, and one is mainly used in the through welding seam, and another is mainly used in fusing slab material and reach good slit filling.Under the positive light beam anglec of rotation, front or leading light beam incide on the slab and heating and fusing slab, and the back or the laser beam of following produce and penetrate.Can not penetrate the slab side.The laser beam of front only stays next bead and partly penetrates slab on slab.Can find out expressly that weld seam comprises two vallates.Leading light beam has very big contribution to welding procedure, carries out the slit filling better because it has not only melted the slab side, but also has connect joint material in advance, thereby make the easier through welding joint of light beam of back.The speed of welding heat of this combination also thereby higher.

The two-beam welding of the negative anglec of rotation antithesis.Preceding light beam penetration joints, the slab of light beam fusing then comes blind.In this case, preceding light beam is wanted the through welding cold drawing, and speed of welding is low during than the positive light beam anglec of rotation.Because the pre-heat effect of preceding light beam is in the material showed increased of thick side fusing.Under the situation for the penlight anglec of rotation, for example be 30 °, then form deep molten bath in thick side by the back light beam.Two molten baths are formed together.For this light beam anglec of rotation,, should suitably reduce the laser power of back light beam in order to reach optimum appearance of weld.This provides another sample laser welding process: weld with the synthetic laser power of two bundles.For certain light beam anglec of rotation, weld shape is similar.Figure 39 illustrates the comparison of the weld shape under 60 ° and-60 ° of light beam anglecs of rotation.

Figure 40 and 41 is illustrated in the influence of light beam anglec of rotation butt welded seam depression under different weldering deviators and the slit condition.Figure 42 is illustrated in the comparison of welding depression of the light beam anglec of rotation of negative, positive under the different slits.The maximum that Figure 43 illustrates under the different light beam anglecs of rotation allows the slit.

Therefore, fill, can obtain following results: can increase beam effective diameter by slewed laser beam, fill thereby can reach better slit with regard to the light beam anglec of rotation, welding procedure and slit.And the positive light beam anglec of rotation can improve speed of welding slightly.Yet the negative light beam anglec of rotation can obtain better slit and fill.In a word, by increasing the light beam anglec of rotation, can weld sheet material well with bigger slit.Under the positive light beam anglec of rotation, the maximum slit that allows increases also not obviously with the light beam rotation.Under the negative light beam anglec of rotation, can reach good much better slit and fill.From 0-30 °, rate of change is comparatively obvious.Surpass 30 ° and be further rotated laser beam again, then allow the slit influence little maximum.

Fig. 3 comprehensively illustrates the basic parameter of double beams laser welding 2-1.5mm sheet material.Three important parameters are speed of welding, maximum slit and the maximum weldering deviator of allowing.

The basic technology parameter of table 3 two-beam welding procedure (2-1.5mm)

Slit Mm	Power W	Horn angle (degree)	The light beam anglec of rotation (degree)	Speed m/ minute	Weldering deviator Mm
						0-0.10*??	300*	????6	?????-	?4.5-5	?0.15-0.25*
0-0.15	?2×3000	????6	????0	?9.0	?0.15-0.30
						?0-0.17	?2×3000	????-6	????0	?8.0	?0.05-0.10
?0-0.17	?2×3000	????-6	????0	?7.0	?0.05-0.35
						?0-0.18	?2×3000	????-6	????30	?7.0	?0.25-0.3?5
?0-0.22	?2×3000	????-6	????-30	?6.6	?0.05-0.50
						?0-0.23	?2×3000	????-6	????-60	?6.0	?0.05-0.75
?0-0.24	?2×3000	????-6	????90	?5.4	?0.05-0.90

The reference value of * single bundle welding

The rim condition relation of economic and effective welding procedure and sheet material is very big.Along the whole linearity of cutting edge lengths is an important parameters, because the maximum slit under worst condition is the twice of normal sheet material nonstraightness.In other words, if nonstraightness is 0.05mm, it is 0.1mm that then maximum slit can reach.Following Example is used for illustrating the welding of 2.0-1.5mm sheet material.The maximum slit of sheet material is lower than 0.1mm

Can select single bundle or two-beam welding procedure according to the requirement of productivity ratio.In the slit during less than 0.1mm, needn't slewed laser beam.Horn angle should be positive and the light beam anglec of rotation is made as 0 degree, to reach the highest speed of welding.If there is not the slit, maximum welding speed depends on light-beam position, needn't change speed of welding and come adaptive slit.The two-beam welding procedure is more economical, and speed improves 100%, and cost only increases 10-15%.For keeping optimum weldering deviator, then the precision of tracking system will reach ± 0.05mm.The maximum slit of sheet material is about 0.15mm

If the slit is about 0.15mm, should select the two-beam welding procedure.If maximum slit is less than 0.15mm, two-beam should be optimum along seam (the light beam anglec of rotation is 0 degree) welding, and speed of welding is the twice of single bundle weldering.The precision of tracking system is ± 0.075mm.If maximum slit is 0.17-0.18mm, optimum selection is zero degree or less (as 30 °) for the light beam anglec of rotation still.Laser welding head should be set in negative angle.The tracking accuracy that high speed of welding needs are high (8m/ minute, ± 0.025mm); Under the low speed of welding, deviation can be more greatly (7m/ minute, ± 0.15mm).The two-beam weldering is than the high approximately 40-60% of speed of single bundle weldering.Under negative horn angle, speed of welding changes with the slit hardly, can simply adopt by constant weld speed minimum or that maximum slit is determined and weld.Maximum slit surpasses 0.2mm

If along whole welding joints, the slit changes in the 0-0.25mm scope, does not utilize the two-beam welding of rotation light beam, with regard to unavailable good weld seam.In the case, in whole laser welding system, can consider two different processes.A simple method is to weld with the fixing light beam anglec of rotation, and the light beam anglec of rotation and speed of welding are then determined by maximum slit and zero slit.The weak point of this welding procedure is slightly to lose a little speed of welding.Welding has the sheet material in 0.25mm slit, and speed of welding is 5.4m/ minute, and this is higher by 12% than the speed of single speed welding procedure approximately.

The best way is to weld by the automatic adjusting light beam anglec of rotation and speed of welding, and its mechanism is based on the fundamental relation between slit, the light beam anglec of rotation and the speed of welding.In tracking system, there is a sensor to detect gap size.Gap width is sent in the control module of welding system, utilize the functional relation between gap size, the anglec of rotation and the speed of welding to calculate the optimum light beam anglec of rotation and corresponding speed of welding at this.Data are distributed to the control driver element of corresponding servomotor and continuously change the light beam anglec of rotation and speed of welding at the same time.But the advantage of regulating the light beam anglec of rotation and speed of welding automatically is optimal two-beam welding procedure.For example, if the slit fades to 0.25mm from 0, be under 6.7m/ minute the condition, the light beam anglec of rotation can be changed to 90 ° from 0 in speed of welding.This speed of welding is high by 24% when welding than by the constant light beam anglec of rotation, and is high more about 40% than single bundle weldering, and the reliability of two-beam welding procedure is higher and more insensitive to deviation.One is utilized the simplification process program of above-mentioned principle is to weld with two fixed speeds and the light beam anglec of rotation.Can clearly be seen that from Figure 44 less than 0.1mm, the speed of welding and the light beam anglec of rotation change minimum as if the slit.Therefore, the light beam anglec of rotation can be made as 0 degree, and weld with higher speed of welding.In case the bigger light beam anglec of rotation and lower speed of welding at 0.1-0.2mm, shown in the dotted line among Figure 44, can be set in the slit, as 30 ° and 7m/ minute.Only need two the fixing speeds of welding and the light beam anglec of rotation.The advantage of this scheme is that the structure of light beam rotating mechanism and control are simple, lower to the requirement of gap width sensor.

As mentioned above, the weldering deviator of the relative seam of laser beam also is a crucial technological parameter.The edge that factor that can cause welding the deviator numerical fluctuations is a sheet material is not absolute straight line, and its shape is different because of different shearings or cutting method.And focusing distance also makes because of plate surface fluctuates and changing.Horn angle also can cause the variation of weldering deviator.Another factor may be that sheet material location on magnetic suction platform is improper, perhaps the center line of suture position deviation mechanical movement.And, through working long hours, wearing and tearing are arranged on the alignment pin or fly low-pricedly, also can cause the minor fluctuations of alignment pin position.The mechanical precision of reference axis and portal frame motion also is limited.

Weldering deviator tolerance limit is exactly to realize welding when stablizing welding procedure and forming the high-quality joint scope at deviator place.Generally speaking, there are two critical values to determine a weldering deviator tolerance limit.The lower limit of weldering deviator is by weld shape decision, and this is anticipating and will melt a certain amount of metal material and fill seam to reduce welding depression.The upper limit of weldering deviator is determined by weld seam through welding situation, that is to say and will avoid lack of penetration.Weldering deviator tolerance limit is big more, and welding procedure can be born the deviation of material and welding system more.

Figure 45 illustrates the influence of speed of welding butt welding deviator tolerance limit.For 0 slit, it increases with the decline of speed of welding.For welding operation, this means and to obtain the upper limit that bigger fusion penetration is expanded the weldering deviator by the speed of welding that slows down.Yet,, can reduce this higher limit by slowing down speed of welding if having the slit between the sheet material.Also can be observed, weldering deviator tolerance limit can be with the increase in slit broadening.

As shown in figure 46, horn angle can cause the change of weldering deviator tolerance limit.Normally, positive horn angle can make weldering deviator tolerance limit wideer.In contrast, it is narrower that Fu horn angle can make weldering deviator tolerance limit.For reaching more stable and welding process widely, recommend positive horn angle generally.It is the occasion of deciding factor that negative horn angle is only applicable to the slit filling.

Figure 47 illustrates the influence of the thickness ratio butt welding deviator tolerance limit of joint.As previously mentioned, big thickness ratio is easier to obtain good slit filling.Yet, much smaller when welding the deviator tolerance limit than little thickness ratio.The thickness ratio of joint is big more, and weldering deviator tolerance limit is narrower, and for welding the joint of large thickness ratio rate, needs locating laser spot more accurately.

When welding, the slit can change along whole jointing edge usually.Minimum slit is 0, and maximum slit is determined by the mated condition of two abutting edges.As shown in figure 48, weldering deviator tolerance limit also can diminish because of the fluctuation of gap size.For example, when using the jigsaw of the suitable seam welding 2.0-0.15mm of two-beam, then welding the deviator tolerance limit for 0 slit is 0.1-0.23mm, and then welding the deviator tolerance limit for the maximum slit of 0.2mm is 0.13-0.26mm.In the case, minimum weldering deviator is then limited by maximum slit, is 0.13mm, and maximum weldering deviator is then limited by zero slit, is 0.23mm.This means that weldering deviator tolerance limit is 0.13-0.23mm, is significantly less than the weldering deviator tolerance limit in constant slit.By weldering deviator tolerance limit is divided into the weldering deviator that two districts determine welding procedure.Optimum weldering deviator is just in time at a center of welding the deviator tolerance limit.For above-mentioned example, the weldering deviator should be decided to be 0.18mm.The maximum weldering deviator fluctuation that allows is for ± 0.05mm and be applicable to the slit of 0-0.2mm.

Nd:YAG laser two-beam welding procedure welding jigsaw demonstrates and can weld big slit welding point.It also has the ability of expansion weldering deviator tolerance limit, as shown in figure 49.Welded the jigsaw of 2.0-1.5mm at different laser angular rotation degree.The zero degree light beam anglec of rotation (light beam or focal line are parallel with edge to be welded), weldering deviator tolerance limit is 0.21mm; If 30 ° of two-beam rotations then are 0.5mm, this is that the suitable twice of stitching when welding of two-beam is many.

Weldering deviator tolerance limit increases along with the light beam anglec of rotation.For the jigsaw of welding large thickness ratio rate, weldering deviator tolerance limit is minimum usually, and that is to say need very accurate beam position.By light beam rotation also can expansion weldering deviator tolerance limit.Figure 50 illustrates the example of a welding 2.0-0.75mm jigsaw.Adopt two-beam along seam welding, weldering deviator tolerance limit is 0.13-0.26mm; Adopt 30 ° light beam rotation it can be expanded as 0-0.39mm.In actual welding, this means that the deviations of LASER SPECKLE is ± 0.2mm, single bundle or two-beam along seam then are ± 0.065mm.H) actual welding

Shown in Figure 51, a GMT800 ^TMCar body side ring original paper comprises 4 (two 2mm and two 1.0mm galvanized sheets), and they are that three weld seams of 5.5m (about 18 inches) are pieced together along length overall.This is a kind of typical straight bead, and welding sequence is: at first weld A and B; Next welds AB and C; With last welding ABC and D.The GMT800 car body side plate is welded into Dan Shu and two-beam technology.Its welding parameter is listed in table 4.

The welding parameter of table 4 GMT800 parts

Welding procedure	The focal length of lens	Horn angle	The light beam rotation	Laser power	Speed of welding	Maximum slit
							Dan Shu	200mm	????6°	????-	3000W	5.0m/ minute	0.20mm
Two-beam	200mm	????6°	????0°	2×3000W	9.0m/ minute	0.20mm
							Two-beam	200mm	????6°	????15°	2×3000W	8.0m/ minute	0.35mm
Two-beam	150mm	????6°	????30°	2×2800W??	9.0m/ minute	0.30mm

The speed of welding of two-beam technology was than the speed height of single bundle technology, was reduced to two-beam 42 seconds along 30 ° of 37 seconds of seam and two-beam rotations weld interval from 66 seconds of Dan Shu.The slit tolerance is brought up to 0.35mm from 0.2mm, the then more stable and safety of welding process by the light beam rotation.Table 4 also illustrates the test of making of the lens of focal length 150mm.The advantage of short focal length is that speed of welding is higher under same welding condition.

Figure 52 illustrates the cross section of various weld seams.Can find out that therefrom weld seam is level and smooth.The weld seam of two-beam welding procedure is compared with Dan Shu, and its weld shape is more beautiful.Figure 52 illustrates a typical Olsen tension force matching sample.Crackle starts from thin side mother metal.The parts performance is gratifying, and reaches the mold pressing matching.Except the difficulty of incipient stage, crackle appears in the parts of also not reporting delivery in forming process.

Figure 54 illustrates Cadillac ^TMThe back door inner panel also will be addressed Jeep Cherokee below ^TMSide panel.Cadillac has two orthogonal straight beads.Shear each parts with same cutting die, connect thereby have accurately.According to each time shearing, be 0.1-0.35mm along the slit that whole joint records.

As Figure 54 the cross section of weld seam is shown, on photo, does not see welding depression.In order to overcome the aperture in the infall appearance of two weld seams, laser power slowly reduces to fill up the weldering hole at the last 10mm of weld seam I.Then, in the incipient stage of weld seam II, laser power is cumulative.Weld and turn round along a weld seam in the corner.Turn off light beam in long-armed terminal, and after turning over soldering tip, restart from corner.

Adopt following method to weld: a) the vision tracking system can keep accurately location with laser beam and seam; B) detect the precision and the stability of portal frame in some cases; And c) portal frame of a 1m * 1m and a special procedure relate to a compound angle.If do not adopt tracking system, can be much strict to the quality requirement of sheet material.If the cross cutting edge conforms with rules, need not follow the tracks of and also can obtain satisfied weld seam.The weld seam that adopts tracking system is in outward appearance and there is no significant difference in shape.The welding parameter that adopts when these parts of welding is shown in table 5.In addition, the two-beam welding procedure allows much bigger slit.

The welding parameter of table 5 Cadillac back door inner panel

Welding procedure	The focal length of lens	Horn angle	The light beam rotation	Laser power	Speed of welding	Maximum slit
							Dan Shu	200mm		6°+6°	????-	????3000W	5.0m/ minute	0.10mm
Two-beam	200mm	????6°	????0°	2500+3000W	9.0m/ minute	0.15mm
							Two-beam	200mm	????6°	????30°	2500+3000W	7.2m/ minute	0.35mm

* compound angle

The prototype and the welding sequence thereof of Jeep car side plate are shown in Figure 55.The jigsaw of Figure 55 comprises the sheet material of three kinds of specifications, and article one weld seam reaches 2.4m.The long 3.6m of whole parts, sheet material is extremely thin, and minimum thickness ratio is 1.25, and very difficulty is filled in this slit.In addition, in a weld seam, there are two kinds of thickness combinations, can not weld with single speed.Sheet material A (0.8mm is thick) and sheet material B (1.0mm is thick) are trimmed to the width shown in Figure 55 and send in the portal frame.At first be welded into an intermediate products AB.The sheet material that welds is cut into length and angle accurately, then it is re-positioned under the welding portal frame.Parts C cuts into shape and size accurately in advance.Again components A B and C are welded at last.

In order to make the prototype jigsaw, listed as table 6, adopt Dan Shu and two-beam welding procedure.In order to weld 1.0-0.8mm sheet material, because thickness is than very little, so select a negative horn angle.The two-beam welding procedure is utilized the light beam rotation that higher speed of welding then is provided and is filled the ability in big slit.This is a particular importance for the long light sheet that is formed by common shearing.And, adopted the lens of 150mm focal length in the test.Its advantage is, the laser power that needs when welding with same speed still less, this has prolonged the working life of laser lamp and has reduced manufacturing cost.In order to weld the second weld seam, speed of welding has been heightened in combination according to sheet material.For the 1.3-0.8mm combination, used speed of welding has slightly been heightened a bit.

The welding parameter of table 6 welding Jeep Cherokee car body side plate

Welding procedure	The focal length of lens	Horn angle	The light beam rotation	Laser power	Speed of welding	Maximum slit
							Single bundle 1.0-08mm	?200mm	????-6°	????-	????3000W	7.5m/ minute	0.15mm
Single bundle 1.3-08mm	?200mm	????+6°	????-	????3000W	7.0m/ minute	?0.20mm
							Single bundle 1.3-1.0mm	?200mm	????+6°	????-	????3000W	6.5m/ minute	0.15mm
Two-beam 1.0-08mm	?200mm	????-6°	????30°	2800+3000W	12m/ minute	0.20mm
							Two-beam 1.3-0.8mm	?200mm	????+6°	????30°	2600+2800W	10m/ minute	0.25mm
Two-beam 1.3-1.0mm	?200mm	????+6°	????30°	2600+2800W	9.5m/ minute	0.22mm
							Two-beam 1.0-0.8mm	?150mm	????-6°	????30°	?2500+2500W	12m/ minute	0.20mm
Two-beam 1.3-0.8mm	?150mm	????+6°	????30°	?2500+2500W	10m/ minute	0.20mm
							Two-beam 1.3-1.0mm	?150mm	????+6°	????30°	?2500+2500W	9.5m/ minute	0.20mm

Its allusion quotation seam cross-section is shown in Figure 56-58, and wherein Figure 56 illustrates the 0.8-1.0mm joint, and Figure 57 and 58 illustrates the 1.3-1.0mm joint.The welding depression rate of sheet material 1.0-0.8mm is 0%-8%, satisfy the weld seam rules of Auto Steel Parthership Standard (97 years suggestion original texts) to jigsaw welding defined, utilize the seam cross-section two of 150mm and 200mm focal length to contrast, weld seam does not have notable difference.

Olsen stretches the matching molded test and shows, fracture occurs in the thin side mother metal outside the weld seam.Welding point satisfies the regulation of current standard, and has not reported the welding point inefficacy.

Use the jigsaw of curved welding seam in the future.Vehicle designers is more considered to adopt the non-rectilinear jigsaw to optimize structure and is improved the matching of parts.Two kinds of curved welding seams shown in Figure 60.First parts comprise that two sections straight lines and three sections radiuses are respectively 100 and the arc-shaped welding seam of 475mm.Second parts are full circle weld seams that a diameter is 200mm, and this is generally used for making the impact absorption tower.Utilize the applicant's as Figure 1-3 AWS3 ^TMReference axis welding machine and in conjunction with two-beam technology successfully has been welded into this two non-rectilinear weld seams.The two-beam rotation has been reduced along the accuracy of alignment in slit and the requirement of slit tolerance for 30 °.

In the prototype weldment, also accumulated the experience of relevant weld defect and inferior product.Its objective is the defect ware during examining prototype again closely produces, and seek the reason that produces, to reduce the defect ware rate most possibly.The GMT800 type parts that firm incipient stage of actual production produces have been selected as an example.In having welded more than 600 car body side ring, 23 left side defective goods and 12 right side defective goods have been noted.Table 7 and 8 has been listed detailed data.

The inferior parts in Fig. 7 left side

Part number	Weld seam number	Defective	The position	Remarks
					AWS014	?BC	Overlapping	Terminal point	Sheet material is defective
AWS025	?AB	Not seam	Starting point	Follow the tracks of careless mistake
					ASW026	?BC	Lack of penetration	Starting point	Follow the tracks of careless mistake
ASW036	?AB	Not seam	Terminal point	The slit is excessive
					ASW038	?AB	Stop weldering	Terminal point	Sheet material is defective
ASW039	?CD	Stop weldering	Terminal point	Sheet material is defective
					ASW048	?BC	Overlapping	Terminal point	Sheet material is defective
ASW049	?CD	Stop weldering	Terminal point	Sheet material is defective
					AWS052	?BC	Overlapping	Terminal point	Sheet material is defective
AWS058	?AB	Lack of penetration	Starting point	Miss tracking
					AWS069	?AB	Lack of penetration	Starting point	Miss tracking
AWS082	?BC	Lack of penetration	Middle	Miss tracking
					AWS101	?BC	Stop weldering		Laser failure
AWS142	?AB	Not seam	Terminal point	The slit is excessive
					AWS143	?CD			Use wrong plate
AWS144	?BC	Cutting		Sheet material is defective
					AWS147	?BC	Stop weldering		Sheet material is defective
AWS183	?CD	Blow and spatter	Terminal point	The slit is excessive
					AWS184	?AB	Stop weldering	Terminal point	Sheet material is defective
AWS196	?AB	Cutting	Terminal point	The slit is excessive
					AWS259	?CD	Lack of penetration	Terminal point	Miss tracking
AWS269	?AB	Stop weldering	Terminal point	Sheet material is defective
					AWS278	?AB	Lack of penetration	Terminal point	Miss tracking

Table 8 right side defect ware

Part number	Weld seam number	Defective	The position	Remarks
					AWS414	?BC	Not seam		A laser instrument is not worked
AWS428	?CD	Cutting	Terminal point	The slit is excessive
					AWS430	?BC	Cutting	Terminal point	The slit is excessive
AWS450	?BC	Cutting		The slit is excessive
					AWS451	?BC	Cutting		The slit is excessive
AWS454	?BC	Stop weldering	Terminal point	Sheet material is defective
					AWS536	?CD	Stop weldering	Terminal point	Sheet material is defective
AWS558	?BC	Overlapping	Starting point	Sheet material is defective
					AWS650	?BC			The welding sequence mistake
AWS653	?CD	Stop weldering	Terminal point	Sheet material is defective
					AWS688	?BC	Stop weldering		Sheet material is defective
AWS707	?BC	Cutting	Terminal point	The slit is excessive

As can be seen, 35 defect ware half (17) wherein are by defective the causing in the location of sheet material on the magnetic platform from table 7 and 8.A reason is that sheet material pushes up tightly inadequately to alignment pin, causes a part of slit to go to outside the tracking tolerance limit.Another reason is that slab is laminated on the thin plate, and this squeezes mutually because of both and causes (weld seam BC).The defect ware of 25% (9) is caused by excessive slit, causes cutting, blows and spatter and open-work.20% defect ware (7) is because miss tracking.Weld defect in this case is that some local weld seam (usually in starting point) is lack of penetration.In most of the cases, can be observed laser beam and obviously jump to the slab side.Also have, two defect wares are because laser failure.

The defect ware rate is subjected to the influence of sheet material fixed mass on portal frame to a great extent.In order to reduce the defect ware rate, importantly guarantee fixed mass, even adopted tracking system.More solid alignment pin helps to improve fixed mass, is laminated on the thin plate in order to prevent slab, should at first place and fixing slab.First alignment pin is answered as close as possible welding starting point, thereby reduces " introducing " miss tracking.The quality of sheared edge also is very important.In order to reduce the defect ware rate, strict edges of boards nonstraightness tolerance also is effective.Should optimize tracking parameter as much as possible, to reduce the frequent degree of following the tracks of careless mistake.After these improve, in the actual production of second stage, reached extremely low defect ware rate (less than 1%).

Fig. 1 illustrates and produces two workpiece 12a and 12b simultaneously, and straight line weld seam 34 is respectively arranged.Yet the present invention equally can be as required along straight line, curve or weld seams shaped zigzag line welding one, two or more workpiece.

Though the production and assembly line 10 shown in Fig. 1-3 only welds each to sheet material 14a, 16a and 14b, 16b with a laser instrument 36, the present invention is not limited to this.If need then can adopt two or more laser instruments, each respectively has a movable laser welding head to come to weld a pair of corresponding sheet material 14 and 16 along a weld seam simultaneously.

Though preferred embodiment of the present invention comprises a sensor 49 and comes the slit between the continuous detecting sheet material 14 that the present invention is not limit by this.In an embodiment who saves more money, can save sensor 46.Wherein, when welding, can be by the position of the real-time manual adjustments laser welding head of operating personnel, or carry out programming Control.For example, when the sheet material 14 of welding different-thickness, laser welding head 42 can be moved on to a fixing original position and in welding, remain unchanged.

Although coherent beam generator 40 produces the light beam of two separation in the present invention, if need, energy can be produced a single bundle coherent source, then it is split into two or more laser beams through laser welding head 42.Although the present invention welds with two coherent sources, also can adopt and singly restraint or have three, four or the multi beam of more heterogeneous dried light source.

Though specification is described and illustrated the preferred embodiments of the present invention, the present invention is not limit by this.Those of ordinary skills can carry out many modifications and changes, and the present invention is limited by appended claims.

The symbol inventory

A absorptivity or coupling efficiency b weld width c_solThe specific heat c of solid phase material_lioThe temperature diffusivity d of the specific heat D material of liquid phase material_fThe diameter d of laser beam_effBeam effective diameter d_offLaser beam is with respect to the focal length g gap width H of the amount of the being partially welded f lens in slit_mThe latent heat of fusion h sheet metal thickness h of material₁Lamella thickness h₂The thermal conductivity factor P of slab thickness K material_LLaser power (to the output of workpiece) P_FEffective power (absorbed power) P_FBy heat conducting wasted power r_fLaser beam radius T temperature T_mThe average overtemperature of thickness ratio U speed of welding α beam incident angle degree φ Beam rotation angle θ laser welding head angle ρ density of material Δ T of the fusing point TR joint of material

Claims (20)

1. method of utilizing a recombination laser bundle along the adjacent edge portion of suture welding two boards material, described composite light beam comprises one first laser beam and one second laser beam, each part to sheet material to be welded of first and second laser beams focuses on two focal areas respectively, the latter respectively has an optical centre, the optical centre of described first and second laser beams is spaced from each other certain distance and respectively limits an end of the focal line of described recombination laser bundle, wherein the effective diameter d of composite light beam _OffBe defined as first and second laser beams perpendicular to welding direction just the maximum on the direction of suture account for widely, the step that sheet material is welded comprises:

A) determine sheet material to be welded to the gap width between the edge fit;

B) basic effective diameter according to following formula adjusting recombination laser bundle fills up the slit: $(r_f+d_{\mathrm{off}})=\frac{2g}{(h_2/h_1-1)}$ Wherein: d _Off=2r _f, g is a gap width, h ₁Be first thickness than light sheet, h ₂Be second thickness than heavy-gauge sheeting, d _OffBe the lateral separation of laser beam misalignment than the heavy-gauge sheeting neighboring edge;

C) substantially according to the anglec of rotation of following formula with respect to weld line change composite light beam focal line, $r_f=\frac{d_f+b\&CenterDot;\sin \mathrm{\&phi;}}{2}$ Wherein: d _fBe the focus diameter of first laser beam, b be between the beam center distance and

D) moving laser beam along the adjacent part of described sheet material welds workpiece sheet material.

2. the method for claim 1 is characterized in that, moves laser beam according to the determined speed of following formula along described adjacent part, $\mathrm{\&nu;}=\frac{A\&CenterDot;P_L}{S_{\mathrm{eff}}\&CenterDot;\mathrm{\&rho;}\&CenterDot;(C_{\mathrm{sol}}{T}_m+H_m+\mathrm{\&Delta;T}\&CenterDot;C_{\mathrm{lig}})+0.55(h_2+H_1)\mathrm{Kw}{T}_m/D}$ Wherein, A is the absorption coupling efficiency of laser energy, P _LBe laser power, S _EffThe effective cross section that is weld seam is long-pending, and ρ is the density of material to be welded, C _SolAnd C _CiqBe the specific heat of the solid phase and the liquid phase of sheet material, T _mBe the fusing point of sheet material, H _mBe the latent heat of fusion of sheet material, Δ T is average overtemperature, and K is the thermal conductivity factor of sheet material, and w is a weld width, and D is the temperature diffusivity of sheet material.

3. the method for claim 1 is characterized in that, in the tight front of the step of described mobile laser beam, determine the gap width of described adjacent part with a gap sensor, and, in mobile laser beam, continuously change the anglec of rotation of focal line.

4. the method for claim 1 is characterized in that, the focus area of first and second laser beams is equal substantially.

5. the method for claim 1 is characterized in that, the material of each workpiece sheet material is identical, is selected from the group that is made of steel, aluminium, aluminium alloy and titanium.

6. the method for claim 1 is characterized in that, determines laser bias (d by the cardinal principle straight edge that follows these steps to two test panels of test weld _Off), the thickness of two boards material is respectively h ₁And h ₂,

The straight edge of described test panels is close side by side mutually;

Weld described neighboring edge by the change laser path with respect to described submarginal bias and form an experiment weld seam;

The contour shape of analytical test weld seam determine to reach required Weld Performance from described submarginal optimum deviation distance; With

The Laser Welding deviator set for equal determined optimum deviation distance substantially.

7. method as claimed in claim 6 is characterized in that, when the welding neighboring edge, continuously changes the weldering deviator of laser beam with constant speed.

8. the method for claim 1 is characterized in that, determines laser bias (d by the cardinal principle straight edge that follows these steps to two test panels of test weld _Off), the thickness of two boards material is respectively h ₁And h ₂,

The straight edge of described test panels is close side by side mutually;

Weld described neighboring edge by the change laser path with respect to described submarginal bias and form an experiment weld seam;

The contour shape of analytical test weld seam determine to reach required Weld Performance from described submarginal optimum deviation distance; With

In the process of mobile laser beam, keep the slit spacing between the test panels abutting edge part to be less than or equal to maximum slit spacing.

Under the utilization array apparatus along the edge part of one first workpiece sheet material of a suture butt welding and the marginal portion of one second workpiece sheet material, the thickness h of the first workpiece sheet material ₁Less than the second workpiece sheet material thickness h ₂, described device comprises:

A laser instrument is launched a coherent source and is welded described sheet material and to fill up slit between the described marginal portion basically along described suture; With a controller, be used to control described coherent source, described sheet material is welded into by following step:

Select a described coherent source effective power, and reach good through welding and significantly overheated or perforation do not occur;

Described coherent source is shone on the described sheet material, wherein, in welding process, described controller substantially according to following formula maintain speed of welding and seam cross-section long-pending at least one of them: $P_F=S\&CenterDot;\mathrm{\&nu;}\&CenterDot;\mathrm{\&rho;}\&CenterDot;(C_{\mathrm{sol}}\&CenterDot;T_m+h_m+C_{\mathrm{liq}}\&CenterDot;\mathrm{\&Delta;T})$ Wherein, P _FBe laser effective power, ν is a speed of welding, and ρ is a panel density, C _SolAnd C _LiqBe the solid phase and the liquid phase specific heat of sheet material, T _mBe material melting point, h _mBe the latent heat of fusion of sheet material, Δ T is the average overtemperature that the molten bath surpasses fusing point, and S is that seam cross-section is amassed and cardinal principle is determined by following formula: $S=h_2\&CenterDot;(r_f+d_{\mathrm{off}})+h_1\&CenterDot;(r_f-d_{\mathrm{off}}-g)$ Wherein, r _fBe the diameter of the coherent source spot at suture place perpendicular to the suture direction, d _OffBe the horizontal weldering deviator of second block of workpiece sheet material of coherent source spot misalignment, g is the gap width between the marginal portion.

10. method as claimed in claim 9 is characterized in that, average overtemperature Δ T is selected in 0.2-0.4T _mBetween.

11. method as claimed in claim 9 is characterized in that, determines laser bias (d by the cardinal principle straight edge that follows these steps to two test panels of test weld _Off), the thickness of two boards material is respectively h ₁And h ₂,

The straight edge of described test panels is close side by side mutually;

Weld described neighboring edge by the change laser path with respect to described submarginal bias and form an experiment weld seam;

The contour shape of analytical test weld seam determine to reach required Weld Performance from described submarginal optimum deviation distance; With

With Laser Welding deviator (d _Off) set for and equal determined optimum deviation distance substantially.

12. method as claimed in claim 9 is characterized in that, determines laser bias (d by the cardinal principle straight edge that follows these steps to two test panels of test weld _Off), the thickness of two boards material is respectively h ₁And h ₂,

The straight edge of described test panels is close side by side mutually;

Weld described neighboring edge by the change laser path with respect to described submarginal bias and form an experiment weld seam;

The contour shape of analytical test weld seam determine to reach required Weld Performance from described submarginal optimum deviation distance; With

In the process of mobile laser beam, keep the slit spacing between the test panels abutting edge part to be less than or equal to maximum slit spacing.

13. array apparatus is along the edge part of one first workpiece sheet material of a suture butt welding and the marginal portion of one second workpiece sheet material, the thickness h of the first workpiece sheet material under the utilization ₁Less than the second workpiece sheet material thickness h ₂, described device comprises:

A laser instrument is launched a coherent source and is come along the described sheet material of described suture butt welding as laser;

Described sheet material is welded into by following step:

A) make the marginal portion of described first and second sheet materials close;

B) start laser instrument and weld described marginal portion, keep gap width (g) between described the keeping to the side according to following formula: $g=\frac{1}{2}(\frac{h_2}{h_1}-1)(r_f+d_{\mathrm{off}})$ Wherein, r _fBe that coherent source is at the radius perpendicular to the suture direction, d _OffIt is the lateral separation that the coherent source center and the second workpiece sheet material stagger.

14. method as claimed in claim 13 is characterized in that, moves laser beam according to the determined speed of following formula along described adjacent part, $\mathrm{\&nu;}=\frac{A\&CenterDot;P_L}{S_{\mathrm{eff}}\&CenterDot;\mathrm{\&rho;}\&CenterDot;(C_{\mathrm{sol}}{T}_m+H_m+\mathrm{\&Delta;T}\&CenterDot;C_{\mathrm{liq}})+0.55(h_2+H_1)\mathrm{Kw}{T}_m/D}$ Wherein, A is the absorption coupling efficiency of laser energy, P _LBe laser power, S _EffThe effective cross section that is weld seam is long-pending, and ρ is the density of material to be welded, C _SolAnd C _LiqBe the specific heat of the solid phase and the liquid phase of sheet material, T _mBe the fusing point of sheet material, H _mBe the latent heat of fusion of sheet material, Δ T is average overtemperature, and K is the thermal conductivity factor of sheet material, and w is a weld width, and D is the temperature diffusivity of sheet material.

15. method as claimed in claim 14 is characterized in that, w=1.4d _f, d wherein _f=2r _f

16. method as claimed in claim 13 is characterized in that, described coherent source is a composite light beam that comprises at least one first laser beam and one second laser beam.

17. method as claimed in claim 13 is characterized in that, determines laser bias (d by the cardinal principle straight edge that follows these steps to two test panels of test weld _Off), the thickness of two boards material is respectively h ₁And h ₂,

The straight edge of described test panels is close side by side mutually;

Weld described neighboring edge by the change laser path with respect to described submarginal bias and form an experiment weld seam;

The contour shape of analytical test weld seam determine to reach required Weld Performance from described submarginal optimum deviation distance; With

With Laser Welding deviator (d _Off) set for and equal determined optimum deviation distance substantially.

18. method as claimed in claim 13 is characterized in that, determines laser bias (d by the cardinal principle straight edge that follows these steps to two test panels of test weld _Off), the thickness of two boards material is respectively h ₁And h ₂,

The straight edge of described test panels is close side by side mutually;

Weld described neighboring edge by the change laser path with respect to described submarginal bias and form an experiment weld seam;

The contour shape of analytical test weld seam determine to reach required Weld Performance from described submarginal optimum deviation distance; With

In the process of mobile laser beam, keep the slit spacing between the test panels abutting edge part to be less than or equal to maximum slit spacing.

19. method as claimed in claim 13 is characterized in that, also comprises a controller, wherein, in welding process, described controller keeps the effective power of coherent source substantially according to following formula: $P_F=S\&CenterDot;\mathrm{\&nu;}\&CenterDot;\mathrm{\&rho;}\&CenterDot;(C_{\mathrm{sol}}\&CenterDot;T_m+h_m+C_{\mathrm{liq}}\&CenterDot;\mathrm{\&Delta;T})$ Wherein, P _FBe laser effective power, v is a speed of welding, and ρ is a panel density, C _SolAnd C _LiqBe the solid phase and the liquid phase specific heat of sheet material, T _mBe material melting point, h _mBe the latent heat of fusion of sheet material, Δ T is the average overtemperature that the molten bath surpasses fusing point, and S is that seam cross-section is amassed and cardinal principle is determined by following formula: $S=h_2\&CenterDot;(r_f+d_{\mathrm{off}})+h_1\&CenterDot;(r_f-d_{\mathrm{off}}-g)$

20. method as claimed in claim 16, it is characterized in that, each part to sheet material to be welded of first and second laser beams focuses on two focal areas respectively, the latter respectively has an optical centre, the optical centre of described first and second laser beams is spaced from each other certain distance and respectively limits an end of the focal line of described recombination laser bundle, wherein the effective diameter d of composite light beam _OffBe defined as first and second laser beams perpendicular to welding direction just the maximum on the direction of suture account for widely, the step that sheet material is welded comprises:

A) determine sheet material to be welded to the gap width between the edge fit;

B) basic effective diameter according to following formula adjusting recombination laser bundle fills up the slit: $(r_f+d_{\mathrm{off}})=\frac{2g}{(h_2/h_1-1)}$ Wherein: d _Off=2r _f, g is a gap width, h ₁Be first thickness than light sheet, h ₂Be second thickness than heavy-gauge sheeting, d _OffBe the lateral separation of laser beam misalignment than the heavy-gauge sheeting neighboring edge;

C) substantially according to the anglec of rotation of following formula with respect to weld line change composite light beam focal line, $r_f=\frac{d_f+b\&CenterDot;\sin \mathrm{\&phi;}}{2}$ Wherein: d _fBe the focus diameter of first laser beam, b be between the beam center distance and

D) when moving laser beam, the adjacent part of described sheet material continuously changes the anglec of rotation of focal line.

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