JP2014184465A - Joint method for cast iron material and joint member obtained thereby - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a joint method for cast iron and a joint member capable of applying to a joint target material whose cross section is not a circular shape, particularly, to provide a friction agitation joint method for cast iron and a joint member for friction agitation in which a black lead deformation layer and a chill structure which reduce mechanical properties of a joint are not formed.SOLUTION: Provided is the joint method for joint target materials, in which at least one of the joint target materials includes a cast iron material. The joint method comprises the following steps of: a first step of forming a decarbonization layer on the cast iron material; and a second step of contacting the joint target materials each other via the decarbonization layer and performing friction agitation joint to the joint target area including the decarbonization layer.

Description

  TECHNICAL FIELD The present invention relates to a method for joining cast iron materials and a joining member obtained thereby, and more specifically, a friction stir welding method and friction stir welding for cast iron materials that do not form a graphite deformed layer and a chill structure that lower mechanical properties of the joint. The present invention relates to a joining member.

  Melting welding of cast iron materials is extremely difficult compared to melting welding of steel materials, and there are many cases where practical application is abandoned both for joining cast iron materials and for dissimilar joining of cast iron materials and other metal materials. . This is because when a cast iron material is rapidly solidified from a molten state, a hard and brittle cementite-type eutectic or martensite structure is formed, which causes cracks and the like and deteriorates joint characteristics.

  On the other hand, in recent years, solid-phase bonding that does not involve melting of materials has attracted attention, and solid-phase bonding has also been studied for the joining of cast iron materials. For example, Patent Document 1 (Japanese Patent Laid-Open No. 2000-246466) proposes a method for joining graphite cast iron materials. Specifically, at least one of the materials to be joined is made of various cast iron materials having graphite, and the other is made of the same or different types of graphite cast iron, non-cast iron-type various steel materials or non-ferrous materials, and at least one of them. A cross section of the joining surface of one of the materials to be joined is formed with a concave groove that is inclined in the circumferential direction with the center of the rotation axis as an apex, and an identical void void is formed between the joining surface of the other material to be joined. In other words, one of the materials to be joined is fixed, the other is coaxially rotated at high speed, the graphite deformation layer generated by the mutual frictional force is discharged out of the joining surface, and friction welding is described.

  And in the joining method of the graphite-type cast iron material described in the said patent document 1, the strength of a joining surface exceeds the intensity | strength of a base material or its heat-affected zone at least by discharging | emitting a graphite deformation layer out of a joining surface. The joint can be adjusted to be formed with a sound and defect-free tough structure.

  Further, in Non-Patent Document 1 (Journal of the Japan Welding Society Vol. 27, No. 3, p. 176-182 (2009)), a spheroidal graphite cast iron material is preheated to 573K and 773K, and friction stir is applied to the preheated spheroidal graphite cast iron material. There has been proposed a method for joining spheroidal graphite cast iron materials characterized by performing joining.

  In the joining method of the spheroidal graphite cast iron material described in Patent Document 1, the preheating temperature and joining speed are changed to change the chilling (formation of cementite eutectic) and martensite of the spheroidal graphite cast iron material. In addition, it is said that a good joint can be obtained by suppressing the influence of the graphite deformation layer formed by the plastic flow accompanying the friction stir welding on the mechanical properties.

JP 2000-246466 A

Welding Society Proceedings Vol. 27, No. 3, p. 176-182 (2009)

  However, the method for joining graphite cast iron materials disclosed in Patent Document 1 can be applied only to a material to be joined having a circular cross-section from the principle of the friction welding method. There are limitations. In addition, the spheroidal graphite cast iron material joining method disclosed in Non-Patent Document 1 requires preheating at a high temperature of, for example, 773K, and in addition to a graphite deformation layer and a chill that cause mechanical properties to deteriorate. An organization cannot be completely excluded.

In view of the above problems in the prior art, an object of the present invention is to provide a cast iron material joining method applicable to a material to be joined having a cross-sectional shape other than circular, and a joining member obtained thereby, and more specifically Specifically, it is intended to provide a friction stir welding method for a cast iron material that does not require preheating and that does not form a graphite deformed layer and a chill structure that lower the mechanical properties of the joint, and a friction stir welding member obtained thereby. .

  In order to achieve the above object, the present inventor conducted extensive research on the friction stir welding conditions and the pretreatment method of the cast iron material for the friction stir welding, and as a result, the friction stir welding can be performed on the cast iron material that has been decarburized. The inventors have found that the present invention is extremely effective, and have reached the present invention.

That is, the present invention
It is a method for joining materials to be joined that include cast iron material at least in one of the following:
A first step of forming a decarburized layer on the cast iron material;
A second step of bringing the bonding materials into contact with each other via the decarburized layer, and applying friction stir welding to the bonded region including the decarburized layer;
Provided is a method for joining materials to be joined, including a cast iron material having the following.

  In the cast iron material joining method of the present invention, in the second step, the depth or width of the stirring portion of the cast iron material formed by friction stir welding is substantially the same as the depth or width of the decarburized layer. Is preferred.

  In the cast iron material joining method of the present invention, the other material to be joined is a metal material other than the cast iron material, and in the second step, the metal material is stacked on the cast iron material, and the metal material It is preferable that the rotary tool for friction stir welding is inserted from the side to perform overlap welding.

  In the method for joining cast iron materials of the present invention, it is preferable to use a vacuum decarburization treatment for forming the decarburized layer in the first step, and the other material to be joined is a stainless steel material. preferable.

The joining member of the present invention is characterized by having no graphite deformation layer and chill structure in the friction stir welding region of the cast iron material, and can be manufactured by a method for joining materials to be joined including the cast iron material of the present invention. preferable.

  ADVANTAGE OF THE INVENTION According to this invention, the cross-sectional shape provides the joining method of the cast iron material applicable also to to-be-joined materials other than circular, and the joining member obtained by it, More specifically, it does not require preheating and is a coupling. It is possible to provide a friction stir welding method for a cast iron material that does not form a graphite deformed layer and a chill structure that lower the mechanical properties of the steel, and a friction stir welding member obtained thereby.

It is process drawing of the joining method of the to-be-joined materials containing the cast iron material of this invention. It is the schematic which shows the relationship between a stirring part and a decarburization layer (butt joining). It is the schematic which shows the relationship between a stirring part and a decarburization layer (lamination joining). It is sectional drawing which shows 1st embodiment (butt joining) of the joining member containing a cast iron material. It is sectional drawing which shows 2nd embodiment (lamination joining) of the joining member containing a cast iron material. It is a cross-sectional photograph of the spheroidal graphite cast iron plate which has a decarburized layer by having performed the decarburization process. It is the surface appearance photograph of the coupling 1-coupling 4 and the comparative coupling 1-the comparative coupling 3 which were obtained in the Example and the comparative example. 3 is a cross-sectional photograph showing the structure in the vicinity of the joint interface of the joint 1. 3 is a cross-sectional photograph showing a structure in a stirring portion of a comparative joint 4. 3 is a cross-sectional photograph showing the structure in the vicinity of the joint interface of the comparative joint 1. 4 is a cross-sectional photograph showing a structure in the vicinity of a joint interface of a joint 4. It is a schematic perspective view which shows the structure of the test piece used for the tensile shear test. It is a graph which shows the test result of the tensile shear strength of each test piece. It is a photograph which shows the external appearance of the test piece after a tensile shear test.

  Hereinafter, a representative embodiment of a method for joining materials to be joined including the cast iron material of the present invention and a joining member obtained thereby will be described in detail with reference to the drawings, but the present invention is limited only to these. It is not a thing. In the following description, the same or corresponding parts are denoted by the same reference numerals, and redundant description may be omitted. Further, since the drawings are for conceptually explaining the present invention, the dimensions and ratios of the components shown may be different from the actual ones.

(A) Cast Iron Joining Method FIG. 1 is a process diagram of a joining method between workpieces including the cast iron material of the present invention. The joining method of the to-be-joined materials containing the cast iron material of this invention is in the to-be-joined area | region containing the decarburized layer formed in the 1st process (S01) and the 1st process (S01) which form a decarburized layer in cast iron material. And a second step (S02) for performing friction stir welding. The cast iron used in the cast iron joining method of the present invention is not particularly limited, but spheroidal graphite cast iron is preferably used.

≪First step: decarburization treatment≫
About the decarburization processing method to a cast iron material, the conventionally well-known various decarburization processing methods can be used in the range which does not impair the effect of this invention. For example, decarburization can be achieved by using sand iron or a scale piece as an atmosphere for decarburization, sealing it in an iron box together with a cast iron member, and heating the iron box in a furnace. Generally, after decarburizing by heating at a temperature of about 1070 ° C. for 60 to 100 hours, it is gradually cooled to 500 to 600 ° C. and then left to cool.

In the decarburization method described above, for example, about 80 hours are required to obtain a decarburized layer having a depth of 2 mm, but the viewpoint that the decarburization process can be efficiently performed by reducing the processing time. Therefore, it is preferable to use a fluidized bed heat treatment furnace in which an atmospheric gas containing carbon monoxide and carbon dioxide is circulated. In this case, the amount of decarburization can be adjusted by adding one or more kinds of gases arbitrarily selected from nitrogen, hydrogen, hydrocarbons, and air to the atmospheric gas. In order to generate carbon monoxide, carbon particles such as graphite and activated carbon may be placed in the furnace.

  Moreover, the above-mentioned decarburization speed can be increased by using a conventionally known decarburizing agent. As the decarburizing agent, for example, iron oxide, sodium carbonate, potassium carbonate, calcium carbonate, or the like can be used.

  Here, from the viewpoints of decarburization efficiency, homogeneity of decarburization, and the like, it is preferable to use a vacuum decarburization process using a vacuum heating furnace in the bonding method of the material to be bonded including the cast iron material of the present invention. By performing decarburization treatment under reduced pressure in the presence of oxygen using a vacuum heating furnace, the reaction atmosphere formed in the vicinity of the cast iron material surface can be prevented from stagnation for a long time, so that decarburization treatment can be performed efficiently. Can do. In addition, the pressure in a vacuum furnace is not specifically limited, What is necessary is just to set suitably according to a to-be-processed material, the processing time required, etc.

  The depth of the decarburized layer to be formed by the decarburization treatment can be set in various ranges depending on the friction stir welding conditions in the second step (S02), but is preferably about 100 to 1000 μm. If the decarburized layer is 100 μm or more, it is easy to optimize the friction stirring conditions. If the decarburized layer is 1000 μm or less, the characteristics of the joint and cast iron material (mechanical characteristics) even if voids are formed by the decarburization process. In other words, corrosion resistance and covering properties can be maintained and secured to some extent. Furthermore, about 500-800 micrometers is more preferable from a viewpoint of optimizing friction stirring conditions more reliably and maintaining and ensuring the characteristic of a joint and cast iron material.

  In the cast iron material, when decarburization is not preferable except in a bonded region, decarburization can be suppressed by masking the region. That is, in the first step (S01), it is possible to leave a region that is not decarburized by masking.

≪Second process: Friction stir welding≫
The second step (S02) is a step of performing friction stir welding on the bonded region including the decarburized layer formed in the first step (S01). That is, a cast iron material having a decarburized layer is used as one material to be joined, the material to be joined and the other material to be joined are brought into contact with each other via the decarburized layer, and both are friction stir welded.

  Friction stir welding is referred to as FSW (Friction Stir Welding), where the ends of the materials to be joined made of two metal materials to be joined are brought into contact with each other, and a protrusion (probe) provided at the tip of the rotary tool is used. It is a method of joining two metal members by inserting between both ends and moving the rotating tool along the longitudinal direction of these ends while rotating.

  “Friction stir welding” in the present invention refers to friction stir welding in which the rotating tool is rotated and moved in the joining direction, spot friction stir welding in which the rotating tool is not rotated and moved at the joining site, and the materials to be joined are joined together. Any one of four modes of friction stir welding to be abutted at a part and friction stir welding in which a rotating tool is inserted from the side of one of the members to be joined together by overlapping the parts to be joined, and these are arbitrarily selected Are combined with each other.

  Further, the materials to be joined may be cast iron materials, or a combination of cast iron materials and other metal materials. Here, in order to prevent the formation of the graphite deformation layer and the chill structure in the joining region, at least the joined region of the cast iron material needs to be decarburized. In addition, in this application, a graphite deformation layer means what is formed by the 2nd process (S02) which performs friction stir welding, and the thing which has in a base material before a 2nd process (S02) is not included.

  Here, the relationship between the stirrer formed by friction stir welding (region formed by plastic flow resulting from insertion of a rotating tool) and the decarburized layer will be described with reference to FIGS. 2 and 3. FIG. 2 shows the relationship between the stirring unit 6 and the decarburized layer 4 in the case of butt joining, and FIG. 3 shows the relationship between the stirring unit 6 and the decarburized layer 4 in the case of lap joining. In the present invention, the depth or width of the stirring portion formed by friction stir welding is preferably approximately the same as the depth of the decarburized layer. Here, since the pores existing in the decarburized layer 4 are crushed to some extent during the friction stir welding, the stirrer 6 is smaller than the decarburized layer 4 as long as the influence of the pores on various mechanical characteristics and the like is allowed. Also good. In general, the base material crystal grains of the stirring unit 6 are often refined, and the strength and the like are improved as compared with the untreated part.

  2 and 3, it is assumed that the entire cast iron plate 2 is decarburized, and the decarburized layer 4 is formed on the entire outer peripheral surface of the cast iron material 2 (easy to understand). Therefore, the ratio of the decarburized layer 4 is shown larger than the actual). FIG. 3 shows a case where the cast iron plate 2 and the metal plate 8 other than the cast iron plate 2 are joined.

  In the case of the butt joint shown in FIG. 2, it is preferable to insert a rotating tool into the decarburized layer 4 existing on the butt surface to form the stirring unit 6 having the same width as the decarburized layer 4. When the stirrer 6 extends outside the decarburized layer 4, a graphite deformation layer is formed due to the influence of plastic flow. On the other hand, when the stirrer 6 is smaller than the width of the decarburized layer 4, pores present in the decarburized layer 4 are present. This is because the joint strength is lowered. In addition, the void | hole which exists in the decarburization layer 4 is lose | disappeared by the plastic flow accompanying friction stir welding.

  In the case of lap joining shown in FIG. 3, it is preferable to form a stirring portion 6 having the same degree as the depth of the decarburized layer 4 existing on the lap surface of the cast iron plate 2 and the metal plate 8. When the stirrer 6 extends outside the decarburized layer 4, a graphite deformation layer is formed due to the influence of plastic flow. On the other hand, when the stirrer 6 is smaller than the depth of the decarburized layer 4, voids present in the decarburized layer 4 are present. This is because the joint strength is lowered. In addition, the void | hole which exists in the decarburization layer 4 is lose | disappeared by the plastic flow accompanying friction stir welding.

  As described above, the joining method of the material to be joined including the cast iron material of the present invention can be applied to various joining modes, but the other material to be joined is a metal material other than the cast iron material, and is on the cast iron material. It is preferable that metal materials other than the cast iron material are stacked, and a rotary tool is inserted from the metal material side other than the cast iron material to perform the overlap bonding. In particular, the other material to be joined is preferably a stainless steel material. For stainless steel, it is not necessary to consider the formation of a graphite deformed layer and a chill structure, and in addition, corrosion resistance and the like can be imparted to the cast iron member by joining the cast iron material and the stainless steel material.

  The size and shape of the stirring unit 6 can be appropriately adjusted depending on the friction stir welding conditions in addition to the size and shape of the rotary tool. When performing friction stir welding, the tool position is basically defined by an arbitrary set value, but it rotates under conditions where the heat input during welding is low (the rotating tool has a low rotational speed and a high moving speed). The tool tends to rise. Further, when the friction stir welding is performed by a load control method that is controlled by a load applied to the tool or a torque control method that is controlled by a torque applied to the motor, the tool position is a balance between the tool rotation speed and the tool movement speed and the set load.

  In addition, the width of the stirring unit 6 is large when the heat input accompanying the friction stir welding is large (high load, high rotation and low moving speed), and when the heat input is small (low load, low rotation and high moving speed). Get smaller. By utilizing these relationships, the size and shape of the stirring unit 6 can be controlled by appropriately setting the size and shape of the rotary tool used for friction stir welding and the joining conditions.

(B) Joining Member Containing Cast Iron Material FIG. 4 is a cross-sectional view showing a first embodiment (butt joint) of a joining member containing a cast iron material of the present invention. Moreover, FIG. 5 is sectional drawing which showed 2nd embodiment (lamination joining) of the joining member containing the cast iron material of this invention. In addition, about FIG. 5, it has shown about the case where a cast iron material and metal materials other than a cast iron material are joined.

The joining member including the cast iron material of the present invention has a stirring portion 6, and is characterized in that a graphite deformed layer and a chill structure do not exist in the stirring portion 6. In addition, although the cast iron material used for the joining member containing the cast iron of the present invention is not particularly limited, it is preferable to use spheroidal graphite cast iron. Moreover, in this invention, a graphite deformation layer means what is formed by the 2nd process (S02) which performs friction stir welding, and the thing which has in a base material before a 2nd process (S02) is not included.

  It is preferable that the decarburized layer 4 completely disappears and becomes the stirring unit 6 at the joint, but the decarburized layer 4 remains to the extent that mechanical properties such as tensile strength and fatigue strength are not greatly affected. It may be. In addition, about the decarburized layer 4 other than a junction part, it may remain | survive or may lose | disappear, and it is not specifically limited.

  The joining member may be composed of cast iron materials or a combination of a cast iron material and a metal material other than the cast iron material, but is preferably composed of a cast iron material and a stainless steel material. The cast iron joining member of the present invention can be manufactured using the cast iron joining method of the present invention.

  In addition, the friction stir welding mode includes a friction stir welding in which the rotating tool is rotated and moved in the joining direction, a spot friction stir welding in which the rotating tool is rotated and not moved at the joining site, and the materials to be joined are joined to each other. 4, friction stir welding to be brought into contact with each other, friction stir welding in which the members to be joined are overlapped and the rotary tool is inserted from the side of one of the materials to be joined to each other, and combinations thereof are included.

  As mentioned above, although typical embodiment of this invention was described, this invention is not limited only to these, Various design changes are possible and these design changes are all contained in the technical scope of this invention. It is.

Example 1
Using a vacuum heating furnace, decarburization treatment was performed on a spheroidal graphite cast iron (FCD450-10) plate having a thickness of 3 mm. Table 1 shows the composition of the spheroidal graphite cast iron plate used. By performing decarburization treatment for 24 hours in a furnace at 970 ° C., a spheroidal graphite cast iron plate having a decarburized layer shown in FIG. 6 was obtained. It can be seen that small black spherical regions observed near the surface of the spheroidal graphite cast iron plate are pores formed by decarburization, and a decarburized layer having a depth of about 700 μm is formed.

  A stainless steel (SUS304) plate having a thickness of 1.5 mm is overlaid on the spheroidal graphite cast iron plate subjected to the above decarburization treatment, and a rotating tool is inserted from above the stainless steel plate, and friction stir welding (line joining) is performed. Was given. Table 2 shows the composition of the stainless steel plate used.

  A rotating tool made of cemented carbide (shoulder diameter: 15 mm, probe diameter: 6 mm, probe length: 1.6 mm) was used, the tool rotation speed was 300 rpm, the tool movement speed was 100 mm / min, and the load was 1.6 tonf. As a result, friction stir welding was performed by a load control method to obtain a joint 1. The tool advance angle was 3 °, and the friction stir welding was performed in an Ar atmosphere.

<< Example 2 >>
A joint 2 was obtained in the same manner as in Example 1 except that the tool rotation speed in friction stir welding was 400 rpm and the tool moving speed was 80 mm / min.

Example 3
A joint 3 was obtained in the same manner as in Example 1 except that the tool rotation speed in friction stir welding was 400 rpm and the tool moving speed was 150 mm / min.

Example 4
A joint 4 was obtained in the same manner as in Example 1 except that the probe length of the rotary tool was 2.0 mm, the tool rotation speed in friction stir welding was 400 rpm, and the tool movement speed was 180 mm / min.

≪Comparative example 1≫
Comparative joint 1 was obtained in the same manner as in Example 1 except that the probe length of the rotary tool was set to 2.0 mm.

≪Comparative example 2≫
A comparative joint 2 was obtained in the same manner as in Example 1 except that the probe length of the rotary tool was 2.0 mm, the tool rotation speed in friction stir welding was 400 rpm, and the tool movement speed was 100 mm / min.

«Comparative Example 3»
Comparative joint 3 was obtained in the same manner as in Example 1 except that the probe length of the rotary tool was 2.0 mm, the tool rotation speed in friction stir welding was 400 rpm, and the tool movement speed was 150 mm / min.

<< Comparative Example 4 >>
Comparative joint 4 was obtained in the same manner as in Example 1 except that the spheroidal graphite cast iron plate was not subjected to decarburization treatment.

<< Comparative Example 5 >>
Comparative joint 5 was obtained in the same manner as in Example 1 except that the spheroidal graphite cast iron plate was not decarburized, the tool rotation speed in friction stir welding was 400 rpm, and the tool movement speed was 50 mm / min.

<< Comparative Example 6 >>
Comparative joint 6 was obtained in the same manner as in Example 1 except that the spheroidal graphite cast iron plate was not decarburized, the tool rotation speed in friction stir welding was 400 rpm, and the tool movement speed was 100 mm / min.

<< Comparative Example 7 >>
Comparative joint 7 was obtained in the same manner as in Example 1 except that the spheroidal graphite cast iron plate was not decarburized, the tool rotation speed in friction stir welding was 400 rpm, and the tool movement speed was 150 mm / min.

  Surface appearance photographs of the joint 1 to the joint 4 and the comparative joint 1 to the comparative joint 3 are shown in FIG. In any of the joints, no significant burrs or surface defects are observed, and it can be seen that a good joint is obtained in appearance.

  A structure photograph in the vicinity of the joint interface of the joint 1 is shown in FIG. The graphite deformation layer and the chill structure are not observed in all regions (center, right end, and left end) of the joint. Moreover, the void | hole formed by the decarburization process has lose | disappeared completely by plastic flow, and it can confirm that a very favorable joint is obtained.

  A structural photograph in the stirring portion of the comparative joint 4 is shown in FIG. Since the comparative joint 4 is not decarburized, a graphite deformation layer is observed in the entire stirring portion. In particular, a graphite deformed layer that is significantly deformed is formed in the vicinity of the plate surface having a strong plastic flow.

  A structural photograph in the vicinity of the joint interface of the comparative joint 1 is shown in FIG. In particular, the formation of a graphite deformation layer can be confirmed remarkably at the center of the joint. This is because a rotating tool having a probe length of 2.0 mm was used, so that plastic flow penetrated the decarburized layer during friction stir welding and reached a region where spherical graphite was present.

  A structural photograph in the vicinity of the joint interface of the joint 4 is shown in FIG. In the joint 4, the graphite deformation layer is not confirmed although a rotating tool having a probe length of 2.0 mm is used. This is because the rotational pitch of friction stir welding (tool moving speed / tool rotating speed) is relatively large and the heat input during welding is small, so the position of the tool changes slightly upward due to the reaction force from the materials to be joined. It is thought that the plastic flow was stored in the decarburized bed. Moreover, the void | hole formed by the chill structure | tissue and the decarburization process does not exist, and it can confirm that a very favorable joint is obtained.

  Table 3 shows the relationship between the probe length and rotation pitch of the rotary tool used in the friction stir welding and the presence or absence of the graphite deformation layer. When the probe length is 1.6 mm, the graphite deformation layer is not formed in all the joints. This has shown that the probe length which can be used suitably is 1.6 mm with respect to arrangement | positioning of the to-be-joined material used this time, and the thickness of a decarburization layer.

Since the thickness of the stainless steel plate disposed on the upper side of the spheroidal graphite cast iron plate is 1.5 mm, and the thickness of the decarburized layer formed on the spheroidal graphite cast iron plate is about 700 μm, the total thickness is about 2.2 mm. Here, considering the plastic flow directly under the probe, it is considered that when the tool having a probe length of 1.6 mm is used, the thickness of the stirring region is substantially equal to the above-described about 2.2 mm.

On the other hand, when the probe length is 2.0 mm, the graphite deformation layer is formed except when the rotation pitch is 0.45. When the probe length is 2.0 mm, the influence of plastic flow is outside the decarburized layer and a graphite deformed layer is formed, but by increasing the rotation pitch to 0.45, the rotating tool slightly floats, resulting in It is considered that plastic flow occurred within a suitable range.

[Tensile shear test]
Using the joints obtained in the above Examples and Comparative Examples, a test piece shown in FIG. 12 was prepared, and the tensile shear strength was measured. In addition, the said test piece cut | disconnected the joint to the width | variety 10mm perpendicular | vertical with respect to the joining direction. The tensile shear strength of each test piece is shown in FIG.

  Regarding the comparative joint 1 to the comparative joint 7 formed with the graphite deformation layer, the tensile shear strength remains at about 6 kN at the maximum. On the other hand, with regard to the joints 1 to 4, it can be seen that the tensile shear strength reaches about twice that of the comparative joints 1 to 7.

  The appearance of the test piece after the tensile shear test is shown in FIG. In the joint 1 obtained in Example 1, the base material is broken not by the joining portion but by the stainless steel plate, so that the joint can sufficiently utilize the mechanical properties of the materials to be joined. In contrast, in the comparative joint 1 obtained in Comparative Example 1, the joint (stirring portion) is broken along the graphite deformation layer.

2 ... Cast iron plate 4 ... Decarburized layer 6 ... Stirrer 8 ... Metal plate

Claims (6)

It is a method for joining materials to be joined that include cast iron material at least in one of the following:
A first step of forming a decarburized layer on the cast iron material;
A second step of bringing the bonding materials into contact with each other via the decarburized layer, and applying friction stir welding to the bonded region including the decarburized layer;
The joining method of the to-be-joined materials containing the cast iron material which has this. In the second step,
The depth or width of the stirring portion of the cast iron material formed by friction stir welding is substantially the same as the depth or width of the decarburized layer;
The joining method of the to-be-joined materials containing the cast iron material of Claim 1 characterized by these. The other material to be joined is a metal material other than cast iron material,
In the second step, the metal material is overlaid on the cast iron material, and the rotary tool for friction stir welding is inserted from the metal material side to perform overlap bonding,
The joining method of the to-be-joined materials containing the cast iron material of Claim 1 or 2 characterized by these. In the first step, a vacuum decarburization treatment is used to form the decarburization layer,
The joining method of the to-be-joined materials containing the cast iron material in any one of Claims 1-3 characterized by these. The other material to be joined is a stainless steel material,
The joining method of the to-be-joined materials containing the cast iron material in any one of Claims 1-4 characterized by these. Not having a graphite deformation layer and a chill structure in the friction stir welding region of the cast iron material,
The joining member formed by the joining method of the to-be-joined materials containing the cast iron material in any one of Claims 1-5 characterized by these.