JP4710190B2 - Surface treatment method and surface treatment apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to, for example, a surface treatment method and a surface treatment apparatus for an aluminum alloy casting. Place About.
[0002]
[Prior art]
In JP-A-10-183316, in a surface treatment of a casting such as a mating surface of a cylinder head with respect to a cylinder block, a rotary tool provided with a protruding portion on a shoulder portion at the tip is pushed in while rotating, and is not melted by heat. A surface treatment method of stirring in a state is disclosed.
[0003]
[Problems to be solved by the invention]
When performing surface treatment by continuous friction stirring using a single rotating tool, the higher the actual operation rate of the surface treatment equipment, the more easily heat generated by friction between the workpiece and the rotating tool is accumulated in the rotating tool. The amount of thermal expansion of the tool itself and the spindle to which the tool is attached increases, and the position of the protrusion with respect to the workpiece surface changes.
[0004]
Due to the influence of this change, although the NC control data is the same, the pushing amount of the rotary tool with respect to the workpiece surface becomes larger in the warmer time than in the colder time. As a result, the depth of the surface modification region varies, and the generation of unfilled defects is affected.
[0005]
The present invention has been made in view of the above problems, and its purpose is to perform friction stir processing and burr removal processing using the same machine tool, suppress variation in processing depth due to thermal expansion of the rotary tool, and unfilled defects. Treatment method and surface treatment equipment Place Is to provide.
[0006]
[Means for Solving the Problems]
In order to solve the above-mentioned problems and achieve the object, the surface treatment method of the present invention inserts a rotary tool removably supported by a tool support means of a machine tool into the workpiece surface, and rotates the rotary tool. A surface treatment method in which the work surface is agitated and modified without melting the generated frictional heat, A plurality of rotary tools are supported on the tool support means, The surface treatment area of the workpiece is the One of the rotating tools Stirring with a rotary tool, changing the rotary tool to a burr removal tool that removes burrs on the workpiece, and treating the surface treatment area with the burr removal tool Then, in the next processing by the rotary tool, the rotary tool different from the rotary tool used immediately after the processing by the deburring tool is selected and the processing by the rotary tool is executed. To do.
[0007]
The surface treatment apparatus of the present invention inserts a rotary tool removably supported on a tool support means of a machine tool into a work surface, and stirs the work surface without melting it by frictional heat generated by the rotation of the rotary tool. A surface treatment device for reforming, A plurality of rotary tools are supported on the tool support means, Rotating tool driving means for stirring the surface treatment area of the workpiece by the rotating tool, and the rotating tool Or Deburring tool for removing burrs on the workpiece choose Tool change means to in front Burr removal tool driving means for treating the surface treatment region with the burr removal tool And after the rotary tool driving means agitates the surface treatment area of the workpiece with one rotary tool of the plurality of rotary tools, the tool changing means selects the deburring tool, and then The deburring tool driving means processes the surface treatment area with the deburring tool, and in the next processing with the rotating tool, the tool changing means rotates differently from the rotating tool used immediately after the processing with the deburring tool. Select a tool, and the rotary tool drive means executes the process with the rotary tool To do.
[0008]
【The invention's effect】
As described above, claim 1, 2 According to the invention, when a rotating tool supported detachably on the tool support means of the machine tool is inserted into the surface of the workpiece and surface-treated by friction stirring, the surface treatment area of the workpiece is stirred by the rotating tool and rotated. By changing the tool to a deburring tool that removes burrs on the workpiece and treating the surface treatment area with the deburring tool, friction stirring and deburring can be performed using the same machine tool, and the heat of the rotating tool can be reduced. Variations in processing depth due to expansion can be suppressed, and unfilled defects can be prevented.
[0009]
According to the second aspect of the present invention, a rotary tool that has a plurality of rotary tools and that is different from the rotary tool used immediately after the processing by the deburring tool is sufficient for the rotary tool used immediately before. A cooling period can be given.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
[0011]
The embodiment described below is an example as means for realizing the present invention, and the present invention can be applied to a modified or modified embodiment described below without departing from the spirit of the present invention.
[0012]
FIG. 1 is a schematic view of a friction stirrer for carrying out a surface treatment method according to an embodiment of the present invention. FIG. 2 is an enlarged view of the vicinity of the rotary tool of FIG. FIG. 3 is a detailed view of the tip portion of the rotary tool.
[0013]
The surface treatment by friction agitation in this embodiment is directed to an aluminum alloy casting as an example of a surface treatment member (hereinafter referred to as a workpiece), and particularly between adjacent ports (valve portions) formed in a cylinder head of an automobile. It is used for surface modification treatment for the purpose of improving the thermal fatigue strength of pistons, brake disks, etc., and the surface modification region of an aluminum alloy casting is agitated in the atmosphere without being melted by frictional heat, resulting in a fine metal structure. To improve the uniformity of eutectic silicon (Si) particles, reduce casting defects, and obtain material properties such as thermal fatigue (low cycle fatigue) life, elongation, impact resistance, etc. that exceed conventional remelt treatment. Can do.
[0014]
Here, the state of stirring without melting is to stir by softening the metal with frictional heat at a temperature lower than the lowest melting point of each component or eutectic compound contained in the base material. Means.
[0015]
As shown in FIGS. 1 to 3, the friction stirrer 1 is a non-consumable type in which a thread is formed on an outer peripheral surface having a diameter smaller than that of the shoulder portion 3 on a flat shoulder portion 3 at one end of a cylindrical shaft body. A rotating tool 4 in which the projecting portion 2 is integrally formed or mounted, and the projecting portion 2 is inserted into the surface modification region of the work by rotating the rotating tool 4 to rotate the projecting portion 2 and driving the shoulder portion. 3 includes a tool driving means 5 for relatively moving the workpiece surface while pressing the workpiece surface, and a jig (not shown) for positioning and holding the workpiece.
[0016]
The tool driving means 5 is a device in which the rotary tool 4 can be rotated by a motor or the like, and the rotary tool 4 can be moved in all directions up, down, left and right by a feed screw mechanism, a robot arm or the like. The number, the feed speed, and the pressing force (processing depth) that can be variably controlled are used. As another form of the tool driving means 5, the rotary tool 4 is rotatably supported on a spindle of a machine tool such as a machining center which will be described later, and the work is moved in the vertical direction and the horizontal direction relative to the rotary tool 4. It may be moved two-dimensionally or three-dimensionally.
[0017]
The protrusion 2 and the shoulder 3 of the rotary tool 4 are made of steel such as tool steel or stainless steel having a hardness higher than that of an aluminum alloy, and the shape of the protrusion 2 is formed in a thread shape with a predetermined pitch. .
[0018]
In this embodiment, as shown in FIG. 4, AC4D, which is an aluminum alloy standardized by JIS, is used as an example of the surface treatment member, but the magnesium (Mg) content of the aluminum alloy is 0.2-1. The composition ratio can be changed in the range of 5 wt% and silicon (Si) content of 1 to 24 wt%, preferably 4 to 13 wt%. In addition, AC4B, AC2B, AC8A used for the piston, and the like can be used. The reason why the upper limit of the silicon content is set to 24% is that even if silicon is further increased, the material characteristics and castability are saturated and the stirring property is deteriorated.
[0019]
Aluminum alloy castings containing magnesium are treated with ₂ Si is deposited to increase the strength. However, when the metal structure is refined by melting as in the remelt process, the low melting point (650 ° C.) magnesium may evaporate and the content may be reduced. And if magnesium content falls, even if it heat-processes, hardness and intensity | strength will fall and a desired material characteristic will not be acquired.
[0020]
On the other hand, in the surface treatment by friction stirring, since the metal structure is not melted, magnesium does not evaporate. ₂ Si is deposited to increase the strength.
[0021]
By adding silicon to the aluminum alloy, castability (melt fluidity, shrinkage characteristics, hot cracking resistance) is improved, but eutectic silicon acts as a kind of defect and mechanical properties (elongation) are reduced. To do.
[0022]
Eutectic silicon is hard and brittle, and its elongation decreases because it becomes the starting point and propagation path of cracks. In addition, the fatigue life of a portion such as a valve portion that is repeatedly subjected to thermal stress is reduced. In the metal structure, eutectic silicon is formed along dendrites, but the eutectic silicon is refined and dispersed uniformly to suppress the generation of cracks due to stress concentration and the propagation of the generated cracks. It becomes possible to do.
[0023]
FIG. 5A is a diagram showing the processing depth according to the protrusion length, FIG. 5B is a diagram showing the protrusion length PL, and FIG. 5C shows the maximum processing depth Dmax. FIG. FIG. 6 is a diagram showing the processing depth according to the rotational speed and feed speed of the rotary tool.
[0024]
In the present embodiment, the protruding portion length PL is set to 80 to 90% of the required depth. The required depth is 1.1 to 1.2 times the length of the protrusion, and can be set to about (0) to 10 mm. Further, as shown in FIG. 5A, the maximum processing depth Dmax increases in proportion to the protruding portion length PL (1.1 to 1.2 times the protruding portion length), and the maximum processing width also increases the protruding portion diameter. Increases in proportion to Further, as shown in FIG. 5 (b), the maximum processing depth Dmax is determined by the protrusion length PL, and it can be said that the influence of the rotation speed and the feed speed is small. Further, the variation is smaller than the maximum processing depth by the remelt processing illustrated in FIG. 6, and the reliability can be improved.
[0025]
FIG. 7 is a diagram showing a basic shape in the vicinity of a port of a cylinder head material for a diesel engine before finishing that performs a surface treatment by friction stirring according to the present embodiment. 8 is a cross-sectional view taken along the line II of FIG. FIG. 9 is a diagram showing a characteristic shape in the vicinity of a port of a cylinder head material for a diesel engine before finishing that performs a surface treatment by friction stirring according to the present embodiment. 10 is a cross-sectional view taken along the line II-II in FIG.
[0026]
The inter-valve portion 16 having the port openings on both side surfaces repeats volume expansion due to engine combustion and volume contraction due to cooling, and thus cracks due to thermal fatigue are likely to occur. For this reason, surface treatment is performed on the inter-valve portion 16 by friction stir to realize a refinement of the metal structure and a reduction in the void area ratio, thereby increasing the resistance to crack generation and propagation due to thermal fatigue and thermal fatigue. The strength can be improved.
[0027]
However, the inter-valve portion 16 has low work rigidity due to the presence of the port openings 14 and 15, and the base metal structure on the side surfaces of the openings 14 and 15 is plastically deformed in the vertical and horizontal directions by the pressing force and rotational moment of the rotary tool 4. The shape of the port openings 14 and 15 changes.
[0028]
When the shape of the port openings 14 and 15 is changed, the material plastically flowed by the friction stirrer is also moved to the port opening side, and the material filled in the exhaust port opening 15 side of the projecting portion 2 is reduced to improve the surface. Tunnel-like unfilled defects are likely to occur along the movement trajectory Q inside the region.
[0029]
As shown in FIG. 7 and FIG. 8, the surface reforming region includes the contour of the shoulder portion 3 of the rotary tool 4 and between the intake port openings 14 indicated by the movement trajectory Q to the exhaust port openings 15 and the intake port openings. It is set between the portion 14 and the exhaust port opening 15. Further, the shape of the edge portions 14a, 14b, 15a, 15b of the port openings 14, 15 adjacent to the surface modification region is such that the shoulder portion 3 of the rotary tool 4 contacts the workpiece surface throughout the surface treatment process. It is formed linearly along the movement trajectory of the rotary tool 4.
[0030]
Thus, by forming the edge portions 14a, 14b, 15a, and 15b of the port openings 14 and 15 linearly, the apparent width of the inter-valve portion 16 is the same over the entire surface modification region. However, as shown in FIG. 8, the cross-sectional shape (thickness) of the inter-valve portion 16 is smaller in the intake port opening 14 than the exhaust port opening 15 due to the restriction of the port shape of the part that is not machined. . Due to the difference in workpiece rigidity due to the difference in cross-sectional shape, the vertical plastic deformation of the base material structure due to the pushing of the rotary tool 4 and the horizontal plastic deformation due to the rotational moment are more than the exhaust port opening 15. This easily occurs in the intake port opening 14.
[0031]
As a result, the material that has plastically flowed due to the surface treatment by friction stirring is easily filled on the intake port opening 14 side where the base material is deformed, and the material filled on the exhaust port opening 15 side of the protrusion 2 is reduced. As a result, tunnel-like unfilled defects are likely to occur along the movement locus Q inside the surface modification region.
[0032]
This unfilled defect usually occurs in a tunnel shape along the movement trajectory Q of the rotary tool 4 and has a larger area (volume) than the cast hole of the base material. Increases and the desired thermal fatigue strength cannot be obtained.
[0033]
Therefore, in the present embodiment, the port shown in FIGS. 7 and 8 is a basic shape, and as shown in FIGS. 9 and 10, the intake port opening 14 is orthogonal to the movement locus Q having a width of about 4 mm and a height of about 5 mm. The two beams 17 and 18 are formed as surplus portions that prevent deformation due to softening of the material of the opening 14.
[0034]
The beams 17 and 18 are provided with a transfer portion for forming a beam in a work casting mold, and this mold is arranged at the upper position and is formed at the time of casting the work. Therefore, the beams 17 and 18 can be formed without increasing the manufacturing process.
[0035]
Due to the presence of the beams 17 and 18, the lateral deformation resistance of the side surface of the intake port opening 14 is greatly increased, and the vertical deformation resistance is also increased because the cantilever structure is a double-supported beam structure. Thus, the deformation of the port opening and the occurrence of unfilled defects accompanying this deformation can be suppressed.
[0036]
Further, since these beams 17 and 18 are removed together with the linear shape portion in the finishing process, there is no adverse effect on the intake efficiency.
[0037]
In the above example, the beam is provided only at the intake port opening 14 having relatively low work rigidity, but may be provided at the exhaust port opening 15 according to the port shape. Further, the width and height of the beams 17 and 18 may be changed as necessary in consideration of the thickness of the port opening, or may be formed in a T shape instead of an orthogonal shape.
[0038]
Further, if there is little influence on the productivity reduction in the finishing process, the port opening is completely closed at the time of workpiece casting, or the port opening diameter φ1 shown in FIG. A shape satisfying φ1 ≦ φ2 / 2 may be satisfied with respect to the inner diameter φ2, and in this case, the shape of the port opening is circular and there is no straight portion, so that deformation can be reduced.
[0039]
[Manufacturing method of cylinder head]
Next, the manufacturing process of the cylinder head for diesel engines by this embodiment is demonstrated.
[0040]
FIG. 11 is a flowchart illustrating a manufacturing process of the cylinder head for a diesel engine according to the present embodiment.
[0041]
As shown in FIG. 11, in step S1, a cylinder head as an intermediate is cast from an aluminum alloy. In step S2, the casting is removed from the casting mold and the gate is deleted. In step S3, the casting taken out from the casting mold is subjected to T6 heat treatment mainly for sand removal. In step S4, a surface treatment is performed on the valve portion of the casting by friction stirring. In step S5, the casting is again subjected to T6 heat treatment to increase the hardness and strength. In step S6, finishing is performed.
[0042]
[Surface treatment by friction stirring]
Next, the friction stirring process in step S4 of FIG. 11 will be described.
[0043]
In the surface treatment by friction stirrer, the end hole where the protrusion shape is transferred remains at the end of the process, but if the part to be drilled in the subsequent process is set as the end hole position, it is possible to avoid the end hole remaining. it can. However, the diameter of the protrusion needs to be less than the diameter of the post-machined hole, and depending on the work shape specifications and surface treatment specifications of the work, it is necessary to reciprocate the movement trajectory Q of the rotary tool 4 with respect to each other and process it twice or more. There is.
[0044]
At this time, as described with reference to FIGS. 7 to 10, the cross-sectional shape (thickness) of the inter-valve portion 16 is thicker at the intake port opening 14 than at the exhaust port opening 15 due to the restriction of the port shape of the part that is not machined. Is getting smaller. Due to the difference in workpiece rigidity due to the difference in cross-sectional shape, the vertical plastic deformation of the base material structure due to the pushing of the rotary tool 4 and the horizontal plastic deformation due to the rotational moment are more than the exhaust port opening 15. This easily occurs in the intake port opening 14.
[0045]
The second return path treatment area conducts frictional heat due to the first forward path process, so the Young's modulus decreases as the temperature rises and easily deforms, and the machining allowance in the subsequent process increases. When the amount is excessive, the flow of the material is promoted in the deformed direction, so that the material filled on the opposite side to the deformed direction is reduced, and the tunnel-like unshaped portion along the movement locus Q is formed inside the surface modification region. Filling defects are likely to occur.
[0046]
Therefore, in the present embodiment, a highly rigid portion (exhaust port opening side) due to the shape of the inter-valve portion is set as a processing region for the second return path to reduce the adverse effect of Young's modulus reduction due to temperature rise, The amount of deformation is reduced and the occurrence of unfilled defects is prevented.
[0047]
As shown in FIG. 13, when the processing path P2 of the second return path is set to a part with low work rigidity (on the intake port opening 14 side), the exhaust port opening 15 at the part with high work rigidity has the original shape. In contrast to this, the part with low work rigidity is greatly deformed, and the material flow caused by the deformation causes unfilled defects in the surface modified region.
[0048]
On the other hand, as shown in FIG. 12, when the processing path P2 of the second return path is set on the exhaust port opening 15 side of the part with high work rigidity, both the part with high work rigidity and the low part have port openings 14 and 15. In general, the original shape can be maintained, and the occurrence of unfilled defects inside the surface modified region can be suppressed.
[0049]
A drawback of the surface treatment using the rotary tool 4 having the protruding portion 2 as in the present embodiment is that the terminal hole of the protruding portion 2 remains at the end point of the processing path. Furthermore, defects are likely to occur even at the processing start point, and in order to solve this, a processing path is set so as to pass through the start point. In addition, when processing the surface of a casting that is subjected to drilling of a bolt such as a cylinder head in a later process, the end point of the processing path is drilled using a protrusion having a diameter smaller than the hole diameter in the drilling process. Set to position. Thereby, it can prevent that a terminal hole remains in a product.
[0050]
FIG. 14 is a diagram for explaining the surface treatment of the cylinder head of the in-line multi-cylinder diesel engine using the friction stir processing of the present embodiment.
[0051]
As shown in FIG. 14, the cylinder head material H has a plurality of tensions for fastening to a pair of intake port openings 14, a pair of exhaust port openings 15, and a cylinder block (not shown) corresponding to a plurality of cylinders. It has a bolt hole 21. Here, since there is a demand for the intake port opening 14 to be as large as possible in order to increase the intake amount, the space between adjacent intake ports becomes narrower and thinner.
[0052]
Therefore, in the present embodiment, as an example of the processing path, one end portion in the longitudinal direction of the cylinder head material H passes between a pair of the exhaust port opening 15 and the intake port opening 14 facing each other with respect to one cylinder. The first forward path Q1 which is continuously processed from the first end to the other end and the tension bolt hole 21 is the end point, and is folded back at the other end of the cylinder head material H and offset in the opposite direction to the first forward path Q1. The tension bolt hole 21 is the end point by continuously processing from the other end in the longitudinal direction of the cylinder head material H to one end so as to pass between the pair of the exhaust port opening 15 and the intake port opening 14 in parallel. After the processing of the first return path Q2 and the first return path Q2, a pair of exhaust ports 15 and a pair of cylinders facing each other from the cylinder adjacent to the return position to the first return path Q2 Stirring is performed without melting the surface of the cylinder head material H by the heat of the rotary tool through the second reciprocating passes Q3 to Q6 which are sequentially processed while reciprocating between the air ports 14 and end at the tension bolt hole 21. To improve.
[0053]
In the second reciprocating paths Q3 to Q6, the processing path offset toward the intake port opening 14 which is a part having a low work rigidity is defined as an outward path, and the path offset to the exhaust port opening 15 which is a part having a high work rigidity is defined as a return path. As a continuous round trip path, and the processing areas of the forward path and the backward path overlap each other.
[0054]
By setting the processing path of the second return path to the exhaust port opening 15 side, which is a part with high work rigidity, as in the second reciprocating path Q3 to Q6, not only the part with high work rigidity but also the work Deformation does not occur even in the intake port opening having low rigidity, and the occurrence of unfilled defects inside the surface modification region can be suppressed.
[0055]
In the surface treatment of the cylinder head, the rotational speed of the rotary tool is 700 to 1100 rpm, the feed speed is 400 to 550 mm / min, the protrusion length is 5 to 6 mm, the protrusion diameter is 7 ± 1 mm, and the shoulder diameter is 15 ± 1 mm. It is desirable to set so that the total processing width of the first pass and the second pass is equal to or less than the inter-valve width of the material -2 mm. Note that the projecting portion diameter and the shoulder portion diameter are set such that 2 ≦ shoulder portion / projecting portion <4. The pushing amount of the shoulder portion with respect to the material processing surface is set to 0.3 mm or more.
[0056]
[Machine tools as tool drive means]
When performing surface treatment by continuous friction stirring using a single rotating tool, the higher the actual operation rate of the surface treatment equipment, the more easily heat generated by friction between the workpiece and the rotating tool is accumulated in the rotating tool. The amount of thermal expansion of the tool itself and the spindle to which the tool is attached increases, and the position of the protrusion with respect to the workpiece surface changes.
[0057]
Due to the influence of this change, although the NC control data is the same, the pushing amount of the rotary tool with respect to the workpiece surface becomes larger in the warmer time than in the colder time. As a result, the depth of the surface modification region varies, and the generation of unfilled defects is affected.
[0058]
On the other hand, in the case of surface treatment by friction stirring, since the shoulder portion of the rotary tool is moved while being pressed against the workpiece surface, burrs are generated on the workpiece surface corresponding to the outer peripheral edge of the shoulder portion. Removal processing is also required.
[0059]
Therefore, in this embodiment, a machine tool having a tool changer is used, or a tool changer is provided in the machine tool, and at least two rotary tools having the same shape are held on the tool changer, and at least one deburring tool is provided. The rotary tool different from the rotary tool used immediately before the processing by the burr removal tool is selected, and the surface treatment by friction stirring and the burr removal processing generated by this surface treatment are alternately executed. .
[0060]
By this method, the waiting time per rotating tool can be extended from the burr removal processing time by the surface treatment time x the number of rotating tools held, and the temperature of the rotating tool can be lowered during the waiting time. Variation in the depth of the surface modification region due to thermal expansion can be suppressed.
[0061]
FIG. 15 is a schematic front view of a machine tool as tool driving means.
[0062]
As shown in FIG. 15, the machine tool 100 selects a tool changer 101 that removably supports the rotary tool 4 and the burr removal tool T, and selects the rotary tool 4 or the burr removal tool T according to the NC control program, and then selects the tool center axis. A spindle 102 that rotates around and that can move in the vertical direction; and an XY table 103 that holds the workpiece facing the tool and moves the workpiece two-dimensionally relative to the tool. Numerical control is performed according to the NC control program stored in the controller shown in the figure. The workpiece is positioned and held with respect to the XY table 103 by the machining reference hole 22 (see FIG. 14).
[0063]
As a first processing example of the present embodiment, the tool changer 101 is held with five rotary tools 4A-4E having the same shape and a milling cutter T1 as one burr removing tool, and the processing time per workpiece. Is about 1 minute 20 seconds for workpiece exchange, 4 minutes for surface treatment, 1 minute 20 seconds for deburring, and after using the first rotating tool 4A, the procedure shown in FIG. The tools are sequentially changed to process 31 workpieces continuously.
[0064]
The number of rotating tools attached to the tool changer 101 is preferably a time that can be sufficiently cooled after using a certain rotating tool until the next use of the rotating tool is at least 20 minutes.
[0065]
Then, the surface temperature of the rotary tool is directly measured using a thermometer for each of the first, eleventh, twenty-first, and thirty-first workpieces processed using the first rotary tool 4A. did.
[0066]
Further, as a second processing example of the present embodiment, each tool changer 101 holds one rotary tool 4 and a milling cutter T1, and the processing time per work and its breakdown are the same as in the first processing example. As a condition, 31 workpieces are continuously processed by exchanging tools alternately in the procedure shown in FIG.
[0067]
Similarly, for each of the first, eleventh, twenty-first, and thirty-first workpieces processed using the first rotary tool 4A, the surface temperature of the rotary tool is directly measured using a thermometer immediately before the start of processing. It was measured.
[0068]
FIG. 18 shows the measured temperatures and processing depths for the first, eleventh, twenty-first, and thirty-first workpieces after the 31st continuous processing in the first processing example and the second processing example is completed. According to the first processing example, the processing depth was substantially constant for all the workpieces, no internal unfilled defects were generated, and the surface temperature of the rotary tool did not change greatly, and good results were obtained.
[0069]
On the other hand, in the second processing example, the surface temperature of the rotary tool from the first to the eleventh and from the eleventh to the twenty-first tool suddenly rises, and the processing depth gradually increases accordingly, and the twenty-first and thirty-first tools. An internal unfilled defect occurred in the first workpiece.
[0070]
As in the first processing example, the processing time per rotating tool is set as processing time per work × number of rotating tools (about 30 minutes), and the substantial waiting time of the rotating tool is secured for about 6 minutes. In this case, the frictional heat accumulated in the rotary tool is dissipated within the waiting time, and the 11th and subsequent workpieces have a substantially constant temperature, and the variation width of the processing depth is 0.15 mm. And no correlation with the cumulative number of treatments.
[0071]
On the other hand, in the second processing example, since the waiting time of the rotary tool is only about 2 minutes, the next process is started before the frictional heat accumulated in the rotary tool is dissipated. Until the number of treatments reaches the 21st, the surface temperature and treatment depth of the tool tend to increase with time. The reason why the processing depth increases with time is that the amount of indentation of the tool has increased due to thermal expansion, and unfilled defects have occurred only in the 21st and 31st pieces. This is because it increased.
[0072]
In the case of the second processing example, good results cannot be obtained under the same conditions as in the first processing example, but the movement trajectory of the rotary tool is long (processing time is long), and the required processing depth is When the thickness is large and the workpiece thickness is large in the surface modification region, it can be an effective processing procedure. Further, the rotary tool may be forcibly cooled by blowing air or the like.
[0073]
[Other processing examples]
As another processing example other than the surface treatment by the tool changer, the surface temperature of the rotary tool is measured using a temperature sensor or the like immediately before the surface treatment by friction stirring is started, or the thermal expansion amount of the rotary tool is obtained using a touch sensor or the like. And correct the push amount of the rotary tool according to these measured values, or prepare a plurality of NC control programs in advance and select the appropriate NC control program corresponding to the measured value for each workpiece. A surface treatment may be performed.
[0074]
By this method, even when the rotary tool is thermally expanded due to frictional heat, the amount of tool push-in can be controlled to be substantially constant, and the variation in the depth of the surface modification region and the occurrence of unfilled defects can be suppressed.
[0075]
As a specific processing example, the processing time per workpiece is about 7 minutes, and the breakdown is as follows: (i) 1 minute 20 seconds for workpiece replacement, (ii) 1 minute 10 seconds for surface temperature measurement of rotating tool , (Iii) 30 seconds for measuring the thermal expansion amount of the rotary tool, (iv) 4 minutes for the surface treatment, and processing procedures in the order of (i) → (iv).
[0076]
And the surface temperature measurement of said (ii) is performed using a contact thermometer etc. by making the axial direction center part 3a of the shoulder part 3 outer peripheral side surface of the rotary tool 4 shown in FIG. Further, the measurement of the thermal expansion amount of the rotary tool 4 in (iii) is performed using a dial gauge or the like with the displacement amount of the step portion 3b formed on the outer peripheral side surface of the shoulder portion 3 of the rotary tool 4 shown in FIG. . The step portion 3b is formed by grinding a portion that is as close as possible to the tip of the rotary tool 4 and that is not inserted into the workpiece. The reason why the tip of the projecting portion 2 and the end of the shoulder portion 3 of the rotary tool 4 are not used as the measurement sites is that the materials stirred by the surface treatment adhere to these sites and the film thickness of the material is added to the thermal expansion amount. This is because is measured.
[0077]
FIG. 20 shows tool position measurement data based on the tool surface temperature and thermal expansion when 10 workpieces according to the above processing procedure are continuously processed with one rotating tool, and rotates as the cumulative number of processing increases. It can be seen that as the surface temperature of the tool rises, the tool expands in the axial direction due to thermal expansion due to the temperature rise. Therefore, if the NC control program is the same, the amount of push-in of the tool changes due to the thermal expansion of the rotary tool, resulting in variations in processing depth and internal unfilled defects.
[0078]
Based on the above results, (1) A rotary tool is attached to the spindle of the machine tool, and the vertical position of the thermal expansion measurement site is measured using a touch sensor or the like immediately before the surface treatment by friction stirring is started. The tool push-in amount is corrected, or an appropriate NC control program is selected and changed to control the tool push-in amount constant.
[0079]
(2) Between the surface temperature of the tool shown in FIG. 20 and the amount of thermal expansion, the correlation shown in the following functional equation is recognized, so that the surface temperature of the tool is expressed as a surrogate characteristic of the amount of thermal expansion of the tool. Measurement is performed before the start of processing, and the tool push-in amount is controlled to be constant by correcting the tool push-in amount or selecting / changing an appropriate NC control program according to the measured value.
[0080]
(ΔT−T) × α × L = ΔL
Where T: initial surface temperature of the rotary tool, ΔT: surface temperature after the temperature rise of the rotary tool, L: initial length of the rotary tool, ΔL: length of the rotary tool after the temperature ΔT rises (after thermal expansion), α: Coefficient of linear expansion of rotating tool
Since a correlation coefficient R≈0.975 is recognized between the surface temperature of the tool and the thermal expansion amount shown in FIG. 20, the surface temperature of the tool is used as a substitute characteristic of the thermal expansion amount of the tool. Measurement may be performed before the surface treatment is started, and the tool push-in amount may be controlled to be constant by correcting the tool push-in amount according to the measured value and the correlation coefficient, or selecting / changing an appropriate NC control program.
[0081]
By using one or both of the above (1) and (2) together, the processing depth can be stabilized even if the spindle of the tool or machine tool is thermally expanded due to the temperature rise of the rotary tool. Can do.
[0082]
[Defect inspection method for surface treated members]
Defects occurring in the surface modification region are generally detected by human visual observation. However, when the size of the defect becomes small, visual detection becomes difficult. Further, in the case of the surface treatment by friction stirring as in the present embodiment, since burrs are generated on the work surface, it becomes more difficult to visually detect defects in the portion covered with burrs.
[0083]
Therefore, in this embodiment, during the surface treatment by friction stirring, the spindle power waveform of the machine tool is monitored using a power meter, a frequency measuring device, etc., and the rotating tool comes into contact with the workpiece surface by a computing device such as a personal computer. The amount of power consumption until it is pulled out from the surface is calculated, or the workpiece surface temperature before the start of surface treatment is measured in advance by a temperature sensor or the like.
[0084]
Then, immediately after the processing, the relationship between the work temperature and the power consumption is analyzed using a personal computer or the like, and when the power consumption shows an abnormally high value, it is considered that a defect has occurred and a warning is issued.
[0085]
Specifically, an aluminum alloy casting having a predetermined dimension (for example, length 150 mm × width 35 mm × thickness 20 mm) is used as a workpiece, and a rotary tool is attached to the spindle of an NC machine tool, and the rotary tool is attached to the workpiece surface. The surface treatment by friction stirring is performed according to the treatment conditions shown in FIG.
[0086]
In addition, if the processing is performed continuously under the above conditions, the generated frictional heat is transferred to the jig holding the workpiece, and the heat of the jig is conducted to the next workpiece. Is measured with a contact thermometer.
[0087]
Further, a power meter is attached to a power supply line to the spindle motor, and the measured value is transferred to a personal computer, whereby the spindle power waveform shown in FIG. 22 is obtained. Furthermore, the power consumption amount during spindle idling (no load) is calculated in advance, and the main shaft power consumption amount required for the surface treatment is calculated by integrating the main shaft power waveform with the value as a reference value.
[0088]
FIG. 23 shows the relationship between the measured value of the workpiece surface temperature before the start of the surface treatment for each workpiece and the power consumption of the spindle. Defects were found in the workpiece corresponding to the position of 113.18 KWs.
[0089]
Therefore, when it is confirmed whether or not there is a correlation between the visual inspection result and the result shown in FIG. 24, the measurement of the work whose power consumption is higher than the work surface temperature as shown in FIG. A high correlation is observed between the results.
[0090]
Therefore, using the substantially linear correlation between the workpiece temperature and the spindle power consumption in FIG. 24, when each measurement value of the workpiece temperature and the power consumption exceeds a predetermined threshold value, By issuing a warning by assuming that the workpiece in the corresponding process has a defect, it is possible to save the labor by visual inspection, and it is possible to judge the quality of the workpiece by online remote operation on the assembly line. .
[Brief description of the drawings]
FIG. 1 is a schematic view of a friction stirrer for carrying out a surface treatment method according to an embodiment of the present invention.
FIG. 2 is an enlarged view of the vicinity of the rotary tool in FIG.
FIG. 3 is a detailed view of the tip portion of the rotary tool.
FIG. 4 is a diagram showing a component ratio of the aluminum alloy of the present embodiment.
5A is a diagram showing a processing depth according to a tip pin length, FIG. 5B is a diagram showing a tip pin length PL, and FIG. 5C is a diagram showing a maximum processing depth Dmax.
FIG. 6 is a diagram showing a processing depth according to the rotational speed and feed speed of a pin-shaped tool.
FIG. 7 is a diagram showing a basic shape in the vicinity of a port of a cylinder head material for a diesel engine before finishing, which is subjected to surface treatment by friction stirring according to the present embodiment.
8 is a cross-sectional view taken along the line II of FIG.
FIG. 9 is a view showing a characteristic shape in the vicinity of a port of a cylinder head material for a diesel engine before finishing that performs a surface treatment by friction stirring according to the present embodiment.
10 is a cross-sectional view taken along the line II-II in FIG.
FIG. 11 is a flowchart illustrating a manufacturing process of a cylinder head for a diesel engine according to the present embodiment.
FIG. 12 is a cross-sectional view of a valve portion showing a surface treatment example of the present embodiment.
FIG. 13 is a cross-sectional view of a valve portion showing a comparative example for the surface treatment of the present embodiment.
FIG. 14 is a diagram for explaining the surface treatment of the cylinder head of the in-line multi-cylinder diesel engine using the friction stir processing of the present embodiment.
FIG. 15 is a schematic front view of a machine tool as tool driving means.
FIG. 16 is a diagram illustrating a first processing example of surface processing by a tool changer.
FIG. 17 is a diagram illustrating a second processing example of surface processing by a tool changer.
FIG. 18 is a diagram comparing the tool temperature and the processing depth over time in the first processing example and the second processing example.
FIG. 19 is a diagram showing a temperature measurement part and a position measurement part of the rotary tool.
FIG. 20 is a diagram showing tool position measurement data based on the tool surface temperature and thermal expansion when 10 workpieces are continuously processed with one rotary tool.
FIG. 21 is a diagram showing surface treatment conditions by friction stirring.
FIG. 22 is a diagram showing a main shaft power waveform at the time of surface treatment by friction stirring.
FIG. 23 is a diagram showing a visual defect inspection result after the friction stir processing.
FIG. 24 is a diagram showing a correlation between the workpiece temperature immediately before the friction stir processing and the integral value of the spindle power waveform.
[Explanation of symbols]
1 Friction stirrer
2 Protrusion
3 Shoulder Club
4 Rotary tools
5 Tool drive means
14 Inlet port opening
15 Exhaust port opening
16 Interval
17, 18 beams
H Cylinder head material

Claims (2)

A surface treatment method in which a rotating tool removably supported by a tool support means of a machine tool is inserted into a work surface, and the work surface is stirred and reformed without melting by frictional heat generated by the rotation of the rotating tool. There,
A plurality of rotary tools are supported on the tool support means,
Stir the surface treatment area of the workpiece with one rotary tool of the plurality of rotary tools ,
Change the rotary tool to a deburring tool that removes burrs on the workpiece,
Treating the surface treatment region with the deburring tool ;
In the next processing by a rotating tool , a surface processing method characterized by selecting a rotating tool different from the rotating tool used immediately after the processing by the burr removing tool and executing the processing by the rotating tool . A surface treatment device that inserts a rotary tool removably supported by a tool support means of a machine tool into a work surface and stirs and modifies the work surface without melting by the frictional heat generated by the rotation of the rotary tool. There,
A plurality of rotary tools are supported on the tool support means,
Rotary tool driving means for stirring the surface treatment region of the workpiece by the rotary tool;
Tool changing means for selecting the burr removal tool for removing the burr of the rotating tool or the workpiece;
The pre-SL surface treatment areas are provided with a burr removal tool driving means for processing by the burr removal tool,
After the rotary tool driving means agitates the surface treatment area of the workpiece with one rotary tool of the plurality of rotary tools,
The tool changing means selects the deburring tool,
Thereafter, the deburring tool driving means processes the surface treatment region with the deburring tool,
In the next processing by the rotary tool, the tool changing unit selects a rotary tool different from the rotary tool used immediately after the processing by the deburring tool, and the rotary tool driving unit executes the processing by the rotary tool. The surface treatment apparatus characterized by the above-mentioned.

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