CN102689090B - Friction stir welding method for magnesium and aluminum alloy medium plate - Google Patents

Friction stir welding method for magnesium and aluminum alloy medium plate Download PDF

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CN102689090B
CN102689090B CN201210212639.7A CN201210212639A CN102689090B CN 102689090 B CN102689090 B CN 102689090B CN 201210212639 A CN201210212639 A CN 201210212639A CN 102689090 B CN102689090 B CN 102689090B
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welding
friction stir
resistance material
stir welding
stirring
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CN102689090A (en
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游国强
张均成
谭霞
王向杰
杜鹃
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Chongqing University
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Chongqing University
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Abstract

The invention discloses a friction stir welding method for a magnesium and aluminum alloy medium plate. The method is characterized by comprising the following steps of: rigidly fixing base materials of two medium plates to be welded in a butt joint form by adopting a clamp; performing friction stir welding on the base materials; applying a controllable heat source to the welding line back before welding, wherein the controllable heat source only is acted on a stirring head advancing side of the welding line back and is used for heating the side; and traveling the stirring head along a welding line for the welding while friction stir welding. The friction stir welding method has the advantages of low cost, relatively low energy consumption, high operability and the like, the connection strength at the welding line can be improved, and simultaneously the welding speed is improved.

Description

A kind of magnesium, Aluminum Alloy Plate friction stir welding method
Technical field
The invention belongs to Metal Material Welding technical field, be specifically related to a kind of method of magnesium, Aluminum Alloy Plate friction stir welding.
Background technology
The density of aluminium, magnesium metal is little, is respectively 2.7g/cm 3 with 1.7g/cm 3 , aluminium alloy has: proportion is little, thermal conductivity good, be easy to advantages such as being shaped, cheap, and being widely used in the fields such as Aero-Space, communications and transportation, light industry building materials, is most widely used in light-alloy, that consumption is maximum alloys.It is little that magnesium alloy has proportion, specific strength, specific stiffness are high, and damping and amortization, machinability, thermal conductivity are good, and electromagnetic shielding capability is strong, dimensionally stable, the advantages such as aboundresources, easily reclaims, pollution-free, therefore, just obtaining increasingly extensive application in fields such as auto industry, communications electronics industry and aerospace industries, the annual growth of whole world magnesium alloy output is up to 20% in recent years, shows application prospect very widely.
In engineering reality, the welding of Al alloys andMg alloys is essential, adopts common melting connecting aluminum alloy, is easy to occur following problem: 1, welded joints in aluminium alloy is softening serious, and strength factor is low, and this is also the biggest obstacle hindering aluminium alloy application; 2, aluminum alloy surface easily produces the oxide-film (Al of infusibility 2o 3its fusing point is 2060 DEG C), this just needs the welding procedure adopting high power density; 3, Welded easily produces pore; 4, Welded easily produces fire check; 5, linear expansion coefficient is large, easily produces welding deformation; 6 aluminum alloy heat conductances large (being about 4 times of steel), under same weld speed, heat input is than welding large 2 ~ 4 times of steel.Magnesium alloy adopts common melting to be easy to occur following problem: 1, magnesium is at high temperature very easily combined with oxygen and generates unsound Welding seam inclusion, seriously reduces weldquality; 2, magnesium and alloying elements form low melting eutectics body, under brittleness temperature, very easily form fire check; 3, hydrogen has decline in the solubility of magnesium alloy along with the reduction of temperature, therefore in weld seam, forms hydrogen blistering, and during especially welding pressure as-cast magnesium alloy, cavitations is particularly serious, sharply reduces the mechanical property of welding line joint.
Friction stir welding is a kind of solid phase joining technique that Britain's institute of welding invents (US5460317) for 1991.It is a kind of pure mechanization continuous print solid phase joining technique, during welding, the stirring-head of a special shape is rotating insertion welded piece, stirring-head and the shaft shoulder are respectively and rub between materials to be welded and produce frictional heat, material is made to reach mecystasis, maximum temperature in welding process is no more than 80% of material melting point, when stirring-head moves forward along joint to be welded, the material reaching plastification is posteriorly shifted by the front portion of stirring-head, and under the action of mechanical pressure of the shaft shoulder, realize the solid diffusivity between workpiece.Do not need to add packing material in friction stir welding process, there is no complicated preparation before weldering, do not form the defect of molten solder.The mode of this friction stir welding is particularly suitable for Al alloys andMg alloys, the welding particularly between Al alloys andMg alloys cut deal.
Although adopt the mode of friction stir welding to Al alloys andMg alloys cut deal (referring to Aluminum Alloy Plate or magnesium alloy cut deal), the problem such as bubble, crackle can be solved.But carry out stretching at the Al alloys andMg alloys cut deal that butt welding connects, fatigue test time, if strengthen proof strength, then still easily rupture at welding line joint place, its welding line joint place remains and belongs to weakness zone.Therefore the bonding strength how improved after the welding of Al alloys andMg alloys cut deal, be still worth research.
At present, in prior art, also the method that existence part is improved friction stir welding, such as: a kind of heating friction stir welding method disclosed in patent CN201010188310.2, while friction stir welding, adopt resistance furnace to heat in this technology, its energy charge is comparatively large, and still cannot solve the problem better.In addition, in the patented technologies such as CN200710092974.7, CN200810236447.3, C N200910103686.6 and CN200910103687.0, also friction stir welding is improved, utilize galvanic circle to add composite heat power supply, but its galvanic circle comprises stirring-head, the stirring-head lost of life can be caused, conductive region is large simultaneously, cause operation dangerous, the defects such as energy charge is larger, make operability reduce; These technology still can not solve the rear easy problem in the fracture of weld seam advance side of Al alloys andMg alloys cut deal welding better simultaneously.
Summary of the invention
For the problems referred to above and deficiency, technical problem to be solved by this invention is: how to provide a kind of with low cost, consume energy less, the magnesium that operability is high, Aluminum Alloy Plate friction stir welding method, improve commissure bonding strength.
In order to solve the problem, present invention employs following technical scheme.
A kind of magnesium, Aluminum Alloy Plate friction stir welding method, it is characterized in that, fixture is adopted to rigidly fix with docking form to be welded two pieces of cut deal mother metals, then friction stir welding is implemented to mother metal, before welding, apply controlled thermal source at weld seam back, described controlled thermal source only acts on weld seam back stirring-head advance side and heats this side, during friction stir welding, stirring-head welds along weld seam walking.
In the technical program, described cut deal refers to the material of thickness in 4mm to 50mm scope, and in this programme, limiting material thickness is because Al alloys andMg alloys thin plate just can connect without the need to compound thermal efficiently in friction stir welding process; If material thickness is excessive, just need just welding by both sides (such as taking double-shaft shoulder stirring-head), this programme is just not suitable for.Meanwhile, in this programme, described stirring-head advance side refers to that this side consistent with welding direction of travel with stirring-head contact position stirring-head direction of rotation is advance side, and opposite side is for retreating side.
In order to solve prior art Problems existing, applicant carefully observes and studies, and finds to carry out stretching at Al alloys andMg alloys cut deal, in fatigue test, after producing fracture, breaking part is distributed in the advance side of weld seam more; Applicant analyzes further, find in stir friction welding process, the advance side of weld seam is reverse by power forward for the rotation of stirring-head, this side region can be greater than opposite side by the pressure extruding force of stirring-head, after causing welding, transition of organizing between advance side nugget district and the heat engine zone of influence can present sudden change trend, but return to nugget district, side and the heat engine zone of influence organize transitional face to gently, therefore cause weld seam both sides uneven, and then just make advance side become the weakness zone of whole welding line joint in stretching, fatigue test; If improve this situation, can it be made by the mode slowing down speed of welding necessarily to be improved, but cause again speed of welding lower like this, welding cost increases.So in order to solve this problem, applicant creatively adopts the advance side of the independent butt welded seam of controlled thermal source to heat when welding.Such advance side is softened after the heating to a certain extent, improve this side metal fluidity, when friction stir welding this side is reduced the pressure extruding force of stirring-head and and the stressed of opposite side be balanced, during welding, stirring-head both sides metal flow performance tends to be balanced.After such welding, the transient condition of organizing between the nugget district of weld seam both sides and the heat engine zone of influence trends towards symmetry, balance.This improves welding quality, improve commissure bonding strength, improve the rear advance side performance of welding, higher pressure and impulsive force can be born.Meanwhile, in this programme, thermal source applies from weld seam back, so can not affect normally carrying out of friction stir welding, two come back of weld be stirring-head energy be difficult to arrive weak location, carry out from here heat energy supplement, also be more beneficial to sheet material energy and reach balance, improve welding effect.
As the optimization of technical scheme, described controlled thermal source adopts following firing equipment to provide, and described firing equipment comprises:
Controllable electric power, for changing heating current and voltage;
Back backing plate, back backing plate Surface Machining one installs groove, installs bucket groove and is used for laying resistance material;
Resistance material, resistance material is arranged in the installation groove of back backing plate, and resistance material outer surface and backing plate surface, back are in same plane, and resistance material is electrically connected with controllable electric power; Separate with insulating materials and heat-insulating material successively between resistance material and back backing plate; Resistance material upper surface is coated with one deck insulating materials; In friction stir welding process, the insulating materials of resistance material upper surface and the mother metal of weld seam back stirring-head advance side are affixed and provide heat for it.
After such optimization, this firing equipment structure is simple, is beneficial to enforcement, adds the convenient size regulating heating load in man-hour, makes the welding situation of weld seam both sides trend towards balance, can at utmost save the energy expended, cut down finished cost.During concrete enforcement, the corresponding relation between the size of heat supply and wlding actual conditions, can calculate according to above-mentioned principle analysis or obtain according to specific experiment, makes welding effect reach best.Meanwhile, as further optimization, adopt the heat supply of this device, after welding terminates, heat supply can be continued to carry out slow cooling, regulate temperature plateau ground to reduce gradually during slow cooling, welding effect can be improved further.
In sum, the present invention compared with prior art has following remarkable result:
1), method of the present invention when can make friction stir welding the metal flow situation of weld seam both sides to trend towards balance consistent, and then improve welding quality, improve weld strength, improve speed of welding.
2), external heat source loop involved in the present invention do not comprise stirring-head, and direct butt welded seam heats.The first, stirring-head can be made directly not occur by external heat source effect softening, improve the service life of stirring-head.The second, because external heat source is placed in back backing plate, and between backing plate, adopt insulating materials to separate, directly act on weld seam back, improve operability, external heat source utilization rate is high, reduce heat waste and improve security.
3), external heat source of the present invention, do not change along with the movement of stirring-head at whole loop resistance, additional heat can be quantized, improve the controllability of additional heat.
4) device, designed by the present invention is simple, and it is convenient to implement, and implementation cost is cheap and workable.
Figure of description
The structural representation of the firing equipment that Fig. 1 adopts when being this method enforcement.
Detailed description of the invention
During concrete enforcement, a kind of magnesium, Aluminum Alloy Plate friction stir welding method, first fixture is adopted to rigidly fix with docking form to be welded two pieces of cut deal mother metals, then friction stir welding is implemented to mother metal, before welding, apply controlled thermal source at weld seam back, described controlled thermal source only acts on weld seam back stirring-head advance side and heats this side, during friction stir welding, stirring-head welds along weld seam walking.
During concrete enforcement, described controlled thermal source adopts following firing equipment to provide, and described firing equipment structure as shown in Figure 1, comprising:
Controllable electric power 1, for changing heating current and voltage;
Back backing plate 2, back backing plate 2 Surface Machining one installs groove, installs bucket groove and is used for laying resistance material 3;
Resistance material 3, resistance material 3 is arranged in the installation groove of back backing plate 2, and resistance material 3 outer surface and backing plate surface, back are in same plane, and resistance material 3 is electrically connected with controllable electric power 1; Separate with insulating materials 4 and heat-insulating material 5 successively between resistance material 3 and back backing plate 2; Resistance material 3 upper surface spray applied insulation; In friction stir welding process, the mother metal of resistance material 3 outer surface and weld seam back stirring-head advance side is affixed and provides heat for it.During concrete enforcement, as the further optimization of firing equipment, in the back backing plate adopted, also be provided with joint chute, joint chute and installation groove are arranged side by side, be mounted slidably a pair in joint chute and keep with resistance material the electrical connector connected, resistance material is electrically connected with controllable electric power by electrical connector.After such optimization, this firing equipment can adopt the concrete welding situation of the different fusion length of same set of device processes, by regulating the position of electrical connector, heating section switched in resistance material is mated with fusion length.
In order to verify principle of the present invention and effect further.Applicant, on above-mentioned detailed description of the invention basis, has carried out contrast test further and has verified, to prove the difference between the present invention and normal agitation friction welding (FW).
Example 1:
The present invention is adopted to weld the thick die casting state magnesium alloy AZ31 of 4mm, joint form is docking, the shaft shoulder diameter 10mm of stirring-head, top diameter 2.8mm, root diameter (RD) 4.2mm, length 4.0mm, before weldering, physics and chemistry removing surface is carried out to mother metal, remove the greasy dirt, moisture, oxide-film etc. on surface.Rigidly fixed with docking form by mother metal with fixture, butt-joint clearance is within 0.3mm.Implement friction stir welding to mother metal to connect, experiment parameter: shaft shoulder volume under pressure 3.8mm, 2.5 °, stirring-head inclination angle; Speed of welding 80mm/min, rotary speed 1500r/min; Employing firing equipment butt welded seam back advance side heat supply during welding, setting auxiliary electrical flow valuve is 400A, loop voltage value is 30V.
Welded the weld appearance beautiful appearance obtained by this example, without any gross imperfection, nugget district microstructure is equiax crystal, advance side nugget district and the heat engine zone of influence transition significantly changed, organize transition to present gradual.Carry out stretching mechanical property testing, hot strength arrives 86% of mother metal.
Comparison example 1
The friction stir welding of employing and example 1 identical parameters welds, but does not adopt firing equipment heat supply.
Analysis welding line joint finds.There is incomplete penetration defect in back, advance side nugget district and the transition of the heat engine zone of influence present sudden change trend.After process, carry out stretching mechanical property testing, the tensile strength of joint is only 68% of mother metal.
Comparison example 2
The friction stir welding of employing and example 1 identical parameters welds, but does not adopt firing equipment heat supply, and during welding, speed of welding slows down to 45mm/min simultaneously.
The weld appearance beautiful appearance that this example obtains, without any gross imperfection, nugget district microstructure is equiax crystal, advance side nugget district and the heat engine zone of influence transition present sudden change trend.Carry out stretching mechanical property testing, hot strength arrives 80% of mother metal.
By concrete comparison example 1 and comparison example 1,2 known, adopt equipment of the present invention to weld magnesium alloy, at identical conditions, the weldquality obtained is far away higher than not adopting equipment of the present invention.The speed of welding of friction stir welding obtains certain raising simultaneously, and the transition of weld seam advance side nugget district and the heat engine zone of influence improves, and presents gradual change trend.
In sum, the feature of patent of the present invention is effectively simple, overcome thermal source utilization rate in existing patent low, heat effect interval is pointed greatly and not, do not directly act on weld seam, and stirring-head softens, and shortens the stirring-head life-span, heating process loop resistance changes, vertical many problems such as add thermally labile, thermal source controllability is low, and operability, security are low.Effectively can be practically applicable to the composite heating of Al alloys andMg alloys friction stir welding process, improve friction stir welding speed, increase stirring-head service life, improve welding quality.

Claims (1)

1. a magnesium, Aluminum Alloy Plate friction stir welding method, it is characterized in that, fixture is adopted to rigidly fix with docking form to be welded two pieces of cut deal mother metals, then friction stir welding is implemented to mother metal, before welding, apply controlled thermal source at weld seam back, described controlled thermal source only acts on weld seam back stirring-head advance side and heats this side, during friction stir welding, stirring-head welds along weld seam walking; Described controlled thermal source adopts following firing equipment to provide, and described firing equipment comprises: controllable electric power, for changing heating current and voltage; Back backing plate, back backing plate Surface Machining one installs groove, installs groove and is used for laying resistance material; Resistance material, resistance material is arranged in the installation groove of back backing plate, and resistance material outer surface and backing plate surface, back are in same plane, and resistance material is electrically connected with controllable electric power; Separate with insulating materials and heat-insulating material successively between resistance material and back backing plate; Resistance material upper surface is coated with one deck insulating materials; In friction stir welding process, the insulating materials of resistance material upper surface and the mother metal of weld seam back advance side are affixed and provide heat for it; In the back backing plate adopted, be also provided with joint chute, joint chute and install groove and be arranged side by side, be mounted slidably a pair in joint chute and keep with resistance material the electrical connector connected, resistance material is electrically connected with controllable electric power by electrical connector; Described stirring-head advance side refers to that this side consistent with welding direction of travel with stirring-head contact position stirring-head direction of rotation is advance side.
CN201210212639.7A 2012-06-26 2012-06-26 Friction stir welding method for magnesium and aluminum alloy medium plate Expired - Fee Related CN102689090B (en)

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Cited By (1)

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Publication number Priority date Publication date Assignee Title
CN107962291A (en) * 2017-11-29 2018-04-27 北京石油化工学院 A kind of method for improving aluminum alloy stirring friction welding welding point corrosion resistance

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CN104070287B (en) * 2014-04-30 2016-05-18 燕山大学 A kind of softening method of high strength alumin ium alloy friction stir welding and device of suppressing
CN107486621A (en) * 2017-08-17 2017-12-19 中国兵器科学研究院宁波分院 A kind of method for improving big thickness aluminium alloy stir friction welding seam thickness direction thermograde
CN107876963A (en) * 2017-11-28 2018-04-06 重庆派馨特机电有限公司 Agitating friction mounted welder with heating function
CN108890118B (en) * 2018-08-28 2020-08-28 中国船舶重工集团公司第七二五研究所 Back auxiliary heating device for titanium and titanium alloy friction stir welding
CN108907538B (en) * 2018-09-19 2024-01-26 西南交通大学 Multifunctional backing plate for welding and auxiliary welding system
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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN107962291A (en) * 2017-11-29 2018-04-27 北京石油化工学院 A kind of method for improving aluminum alloy stirring friction welding welding point corrosion resistance

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