JP4590014B2 - Method for joining steel members and method for strengthening joining force in joined body comprising steel members - Google Patents

Description

  The present invention relates to a method for joining steel members and a method for strengthening a joining force in a joined body made of steel members.

  FIG. 13 is a flowchart shown for explaining a conventional method of joining steel members. FIG. 14 is a figure shown in order to demonstrate the joining method of the conventional steel member.

  As shown in FIG. 13 and FIG. 14, the conventional steel member joining method includes two steel members in a state in which the steel member preparation step S <b> 910 for preparing two steel members and the surfaces to be joined in the two steel members face each other. A joined body forming step S920 for joining the two steel members to each other to form a joined body by heating the two steel members to a first temperature at which the two steel members can be joined while pressing the members under a predetermined pressure condition, and a joined body. Is subjected to a heat treatment under a predetermined temperature condition, and a joining force strengthening step S930 for strengthening the joining force in the joined body is included (see, for example, Patent Document 1).

For this reason, according to the conventional joining method of steel members, it becomes possible to join a plurality of steel members without using any welding auxiliary material. Moreover, according to the conventional method for joining steel members, it is possible to reinforce the joining force in the joined body by performing the joining force enhancing step S930 after forming the joined body.
As a result, according to the conventional method for joining steel members, a joined body (steel product) suitable for a resin molding die such as a plastic gear can be manufactured.

JP 2002-59270 A

  However, in the conventional method for joining steel members, it has been found that there is a problem that a sufficiently high joining force cannot be obtained when two steel members containing Cr are joined together to produce a joined body. .

  Therefore, the present invention has been made to solve the above-described problems, and it is possible to obtain a sufficiently high joining force even when two steel members containing Cr are joined together to produce a joined body. An object of the present invention is to provide a method for joining steel members. Moreover, it aims at providing the joining force reinforcement | strengthening method in the joined body which consists of a steel member which can fully raise the joining force of the joined body by which the two steel members containing Cr were joined mutually.

  In addition, the joining method of the steel member of this invention is not limited only when joining two steel members, It is possible to apply also when joining three or more steel members. When three or more steel members are to be joined, the method for joining steel members of the present invention will be implemented by paying attention to two steel members to be joined to each other among the three or more steel members. The same applies to the method for strengthening the joining force in the joined body made of the steel member of the present invention.

  In order to achieve the above object, the inventors of the present invention have a sufficiently high joining force when a joined body is manufactured by joining two steel members containing Cr to each other in a conventional steel member joining method. As a result of investigating the cause that cannot be obtained, the inventors have found that the cause is the presence of a Cr-containing passive layer and voids on the joint surface. Therefore, based on these findings, the inventors of the present invention can sufficiently increase the bonding force of the bonded body if the Cr-containing passive layer and voids present on the bonding surface can be dissipated. The inventor came up with the idea that the problem could be solved and completed the present invention.

(1) That is, the method for joining steel members of the present invention includes a steel member preparation step for preparing two steel members containing Cr, and a state in which the planned joining surfaces of the two steel members are butted. A joined body forming step of joining the two steel members to each other to form a joined body by heating to the first temperature at which the two steel members can be joined while pressing the steel members under a predetermined pressure condition; at a temperature range of less than the a ₁ transformation point at 520 ° C. or higher and the steel member, characterized in that it comprises a conjugate standing step of standing for more than 30 minutes the conjugates in this order.

(2) In the method for joining steel members of the present invention, the steel member preparation step for preparing steel members for joining two steel members containing Cr to each other, and the joining scheduled surfaces of the two steel members are in contact with each other. A joined body that joins the two steel members together to form a joined body by heating the two steel members to a first temperature at which the two steel members can be joined while pressing the two steel members under a predetermined pressure condition. It includes a forming step and a joined body stationary step of standing the joined body for 30 minutes or more in a temperature range of 520 ° C. or higher and lower than 820 ° C. in this order.

Therefore, according to the joining method of the steel members according to the above (1) or (2), the conjugate formed by conjugate formation step, a temperature range of less than the A ₁ transformation point at 520 ° C. or higher and the steel member or Since it is supposed to be left for 30 minutes or more in a temperature range of 520 ° C. or more and less than 820 ° C., most of the Cr-containing passivating layer and voids existing on the joint surface dissolve in the steel material of the parent phase, and finally It becomes possible to dissipate most of the Cr-containing passive layer and voids present on the joint surface. As a result, the bonding force of the bonded body can be sufficiently increased depending on the application.

  Therefore, the method for joining steel members according to the above (1) or (2) can obtain a sufficiently high joining force even when two steel members containing Cr are joined together to produce a joined body. This is a possible method for joining steel members.

  Moreover, the joining method of the steel member as described in said (1) or (2) makes the joining force in the joined body formed by the joined body formation process high by leaving still in such a comparatively low temperature range. Therefore, it becomes possible to cool the joined body with a strengthened joining force relatively quickly, and it becomes a highly productive joining method for steel members.

The above (1) or (2) The joining method of the steel members according to the assembly formed by the bonding body forming step, A ₁ transformation in such a relatively low temperature range (520 ° C. or higher and the steel member Temperature range of less than the point or a temperature range of 520 ° C. or more and less than 820 ° C. for 30 minutes or more. The details of whether or not it dissolves in the steel material is unknown, but it is speculated that the crystal grains of the steel member can move in submicron units even in the relatively low temperature range as described above. .

  From the viewpoint of increasing the bonding strength of the bonded body, it is more preferable to leave the bonded body for 1 hour or more, and still more preferable to leave it for 2 hours or more.

(3) In the method for joining steel members described in (1) or (2) above, it is preferable to perform the joined body stationary step a plurality of times after performing the joined body forming step.

  By setting it as such a method, it becomes possible to obtain a higher joining force.

(4) In the method for joining steel members according to any one of the above (1) to (3), the joined body is cooled in an inert gas atmosphere after performing the joined body stationary step. preferable.

  By setting it as such a method, it becomes possible to suppress that the surface of a joined body oxidizes and a quality deteriorates in the cooling process.

(5) In the joining method of the steel member in any one of said (1)-(4), it is preferable that said 1st temperature exists in the range of 850 degreeC-1150 degreeC.

  By setting it as such a method, it becomes possible to join two steel members and to form a joined body, pressing on predetermined pressure conditions.

(6) In the method for joining steel members according to any one of the above (1) to (5), the joined body is inserted between the joined body forming step and the joined body stationary step. It is preferable to further include a metal structure homogenization step of heating to a second temperature that can make the structure of the metal layer more uniform.

  By adopting such a method, it becomes possible to make the metal structure that has been in a non-uniform state through the joined body forming step more uniform, so it is possible to form a joined body with higher homogeneity. It becomes.

(7) In the joining method of the steel member as described in said (6), it is preferable that said 2nd temperature exists in the range of 850 degreeC-1150 degreeC.

  By setting it as such a method, it becomes possible to make more uniform the metal structure which is in the non-uniform | heterogenous state through the conjugate | zygote formation process.

(8) In the method for joining steel members according to the above (6) or (7), after performing the metal structure homogenization step, the joined body is rapidly cooled to the Ms point, and then the joined body is gradually cooled. It is preferable to do.

  By adopting such a method, it is possible to form a high-quality bonded body with high mechanical strength by increasing the hardness of the bonded body due to the quenching effect.

(9) In the method for joining steel members according to any one of the above (1) to (8), it is preferable that the planned joining surfaces of the two steel members are flat surfaces.

  By adopting such a method, it is possible to increase the degree of adhesion between the steel members when the two steel members are abutted by processing the planned joining surfaces with high accuracy, and to obtain a sufficiently high joining force. It becomes.

(10) In the method for joining steel members described in (9) above, the arithmetic average roughness Ra on the planned joining surface is preferably 0.2 μm or less.

  By adopting such a method, the joined body forming step is performed in a state where the interval between the planned joining surfaces of the two steel members is 0.4 μm or less on average, and the planned joining surfaces of the two steel members Performing a bonding force strengthening step on a bonded body (in other words, a bonded body having a very small gap that may remain on the bonded surface) formed in a state where the distance between them is 0.4 μm or less on average. As a result, a sufficiently high joining force can be obtained.

(11) In the method for joining steel members according to any one of (1) to (10) above, the joined body forming step and the joined body stationary step are performed in a vacuum or in an inert gas atmosphere. Is preferred.

  By adopting such a method, it is possible to suppress adverse effects caused by the presence of an active gas such as oxygen in each heat treatment step.

(12) In the method for joining steel members according to any one of (1) to (11), the steel member is particularly effective when the steel member is a steel member made of stainless steel.

  Thus, especially when the steel member is a steel member made of stainless steel, it becomes possible to dissipate most of the Cr-containing passive layer and voids present on the joint surface by performing the joined body stationary step. Therefore, it becomes possible to sufficiently increase the bonding force of the bonded body. This is clear from the test examples described later.

  Examples of the stainless steel include SUS420J2 stainless steel and SUS440C stainless steel. Examples of the SUS420J2 stainless steel include STAVAX (registered trademark of Woodeholm), HPM38, S-STAR, and the like. Examples of the SUS440C stainless steel include ELMAX.

(13) In the method for joining steel members according to any one of (1) to (11), the steel member is a steel for hot molds, steel for cold molds, steel for mechanical structures, or high It is preferably a steel member made of speed tool steel.

  By setting it as such a method, it becomes possible to manufacture the conjugate | zygote which can be used for various uses.

(14) The joining force strengthening method for a joined body made of a steel member according to the present invention reinforces the joining force of a joined body in which two steel members containing Cr are joined to each other. a strengthening method, as the conjugate, the conjugate preparation step of the two steel members containing Cr is prepared mutually bonded conjugate, a temperature lower than the a ₁ transformation point at 520 ° C. or higher and the steel members It is characterized by including a joined body stationary step of standing the joined body for 30 minutes or more in this order.

(15) The joining force strengthening method for a joined body made of a steel member of the present invention is a joining force for a joined body made of a steel member that reinforces the joining force of the joined body in which two steel members containing Cr are joined together. In the strengthening method, a joined body preparing step of preparing a joined body in which two steel members containing Cr are joined together as the joined body, and the joined body in a temperature range of 520 ° C. or more and less than 820 ° C. And a joined body stationary step of standing for 30 minutes or more in this order.

For this reason, according to the joining force strengthening method in the joined body which consists of the steel member as described in said (14) or (15), the joined body by which two steel members were joined mutually is 520 degreeC or more, and A in a steel member. Because it is allowed to stand for 30 minutes or more in a temperature range of less than _one transformation point or in a temperature range of 520 ° C. or more and less than 820 ° C., most of the Cr-containing passivating layer and voids present on the joining surface are the parent phase steel material It is possible to dissipate many of the Cr-containing passive layers and voids present in the bonding surface and finally in the bonding surface. As a result, the bonding force of the bonded body can be sufficiently increased depending on the application.

  Therefore, the method for strengthening the joining force in the joined body composed of the steel member according to (14) or (15) described above sufficiently increases the joining force of the joined body in which the two steel members containing Cr are joined together. This is a method for strengthening the joining force in a joined body made of steel members.

  Further, the method for strengthening the joining force in the joined body composed of the steel member according to the above (14) or (15), the joining force of the joined body in which the two steel members are joined to each other, in such a relatively low temperature range. Therefore, it is possible to cool the bonded body with a strengthened bonding force relatively rapidly, and this is a highly productive method.

  From the viewpoint of increasing the bonding strength of the bonded body, it is more preferable to leave the bonded body for 1 hour or more, and still more preferable to leave it for 2 hours or more.

(16) In the joining force strengthening method in the joined body composed of the steel member according to (14) or (15), the joined body stationary step is performed a plurality of times after the joined body preparing step is performed. preferable.

  By setting it as such a method, it becomes possible to make the joining force of a joined body higher.

(17) The steel product of the present invention is the joined body joined by the joining method of steel members according to any one of (1) to (13) or any one of (14) to (16) above. It is a steel product manufactured using a joined body whose joining force is strengthened by a joining force strengthening method in a joined body made of steel members.

  For this reason, the steel product of the present invention becomes a steel product joined with a sufficiently high joining force, and can be used for various applications.

  Examples of steel products include various molding dies, various tools, and various structural materials.

(18) In the steel product described in (17) above, it is preferable that a portion exposed to the outside of the joint surface of the joined body is removed.

  The part exposed to the outside of the joined surface in the joined body is compared with the other part (the part that is not exposed to the outside of the joined surface in the joined body, for example, the central part of the joined surface in the joined body). However, by configuring as described above, a high-quality steel product from which a portion having a relatively low bonding force is removed is obtained.

(19) In the steel product of the present invention, the steel product is preferably subjected to a surface treatment for increasing the surface height.

  By comprising in this way, it becomes possible to improve the abrasion resistance of steel products. In addition, when the steel product is a molding die such as a resin molding die, it is possible to improve the releasability.

(20) The steel product of the present invention is particularly effective when it is a resin molding die.

By the way, as a resin molding die, there is a demand for a resin molding die having a structure including a medium channel for heat exchange inside, but a single resin molding die having such a structure is required. It is extremely difficult to manufacture using this steel member.
On the other hand, according to the steel product (mold for resin molding) of the present invention, by the joining force strengthening method in the joined body joined by the joining method of the steel member of the present invention or the joined body made of the steel member of the present invention. Because it is a steel product (resin molding die) manufactured using a joined body with enhanced bonding strength, it is relatively easy to make a resin molding die having a structure including a medium channel for heat exchange inside. It can be realized.
Moreover, since the steel product (resin molding die) of the present invention is joined with a sufficiently high joining force, it becomes a highly reliable and long-life resin molding die.

(21) The resin product of the present invention is a resin product produced using the resin molding die described in (20) above.

  Therefore, as described above, the resin product of the present invention is a resin molding die having a structure including a heat exchange medium flow path therein, and is a highly reliable and long-life resin molding die. Since it is a resin product manufactured by using, it becomes a high-quality resin product.

It is a flowchart shown in order to demonstrate the joining method of the steel member which concerns on Embodiment 1. FIG. It is a figure for demonstrating the joining method of the steel member which concerns on Embodiment 1. FIG. It is a figure shown in order to demonstrate the joining method of the steel member concerning Embodiment 1. FIG. It is a figure shown in order to demonstrate a test procedure. It is a cross-sectional electron micrograph of the junction part in each conjugate | zygote. It is a cross-sectional electron micrograph of the junction part in each conjugate | zygote. It is a cross-sectional electron micrograph of the junction part in each conjugate | zygote. It is a cross-sectional electron micrograph of the junction part in each conjugate | zygote. It is a cross-sectional electron micrograph of the junction part in each conjugate | zygote. It is a photograph of the test piece after performing a fracture test. It is a figure in order to explain the joining method of the steel member concerning Embodiment 2. It is a figure shown in order to demonstrate the joining method of the steel member which concerns on Embodiment 3. FIG. It is a flowchart shown in order to demonstrate the joining method of the conventional steel member. It is a figure shown in order to demonstrate the joining method of the conventional steel member.

  Hereinafter, the joining method of the steel member of the present invention, the joining force strengthening method in the joined body made of the steel member, the steel product, and the resin product will be described based on the embodiments shown in the drawings.

[Embodiment 1]
Embodiment 1 is an embodiment for explaining a method for joining steel members of the present invention.

  FIG. 1 is a flowchart shown for explaining a method for joining steel members according to the first embodiment. FIG. 2 is a view for explaining the method of joining steel members according to the first embodiment. In FIG. 2, the horizontal axis indicates time, and the vertical axis indicates temperature.

  FIG. 3 is a view for explaining the method for joining steel members according to the first embodiment. FIG. 3 (a1) is a view for explaining the steel member preparation step S110, FIG. 3 (b1) is a view for explaining the joined body forming step S120, and FIG. 3 (c1) is a metallographic structure. FIGS. 3 (d1) and 3 (e1) are diagrams for explaining the bonded body stationary step S140, and FIGS. 3 (a2) to 3 (a) to 3 (c). (E2) is the elements on larger scale of the area | region R in FIG.3 (a1)-FIG.3 (e1).

  The Cr-containing passive layer is not visible with a normal cross-sectional electron microscope, but in order to facilitate understanding, the Cr-containing passive layer 142 is not shown in FIGS. 3 (b2) and 3 (c2). It will be shown shaded.

  As shown in FIG. 1, the method for joining steel members according to Embodiment 1 includes a steel member preparation step S110, a joined body forming step S120, a metal structure homogenizing step S130, and a joined body stationary step S140. Include in order.

1. Steel Member Preparation Step Steel member preparation step S110 is a step of preparing two steel members 110 and 120 containing Cr (see FIG. 3A).

  As the steel members 110 and 120, SUS420J2-based stainless steel (for example, HPM38) is used. The shapes of the steel members 110 and 120 are each cylindrical (20 mmφ × 20 mmL). The planned joining surfaces 112 and 122 of the two steel members 110 and 120 are flat surfaces, and the arithmetic average roughness Ra of the scheduled joining surfaces 112 and 122 is, for example, 0.1 μm.

2. Bonded body forming step In the bonded body forming step S120, the two steel members 110, 120 are pressed against each other under a predetermined pressure condition in a state where the planned joining surfaces 112, 122 of the two steel members 110, 120 are in contact with each other. By heating the steel members 110 and 120 to a first temperature T ₁ that can be joined (for example, 850 ° C. to 1150 ° C. (1070 ° C. in FIG. 2)), the two steel members 110 and 120 are joined to each other and joined. This is a step of forming the body 100 (see FIG. 3B1).

In the joined body forming step S120, a pulsed current joining apparatus (for example, see Japanese Patent No. 3548509) that applies a pulse current to a plurality of joining target members to join the plurality of joining target members. Form. The pressing of the two steel members 110 and 120 is performed under a pressure condition of 10 MPa, for example, using hydraulic pressure. The two steel members 110 and 120 are heated by applying a pulse current to the two steel members 110 and 120. The holding time (first heat treatment time t ₁ ) at the first temperature T ₁ is 30 minutes (see FIG. 2). After the joined body forming step S120, the joined body 100 is gradually cooled to room temperature.

3. Metal structure homogenization metal structure homogenizing step S130 is a conjugate 100, conjugate 100 of the tissue more evenly to the second temperature can be _{T 2} (e.g., 850 ° C. to 1150 ° C. (in FIG. 2 1040 ° C.)) (see FIG. 3C1).

In the metal structure homogenization step S130, the bonded body 100 is heated using a vacuum furnace. The holding time (second heat treatment time t ₂ ) at the second temperature T ₂ is 1 hour (see FIG. 2). After the metal structure homogenization step S130, the joined body 100 is rapidly cooled to the Ms point, and then the joined body 100 is gradually cooled.

4). Conjugate standing step assembly stand step S140 is carried out at a temperature range of less than _{the A 1} transformation point (about 820 ° C.) at 520 ° C. or higher and steel members 110 and 120, the assembly 100 in the step of stand 30 minutes or more is there.

In the bonded body stationary step S140, the bonded body 100 is heated using a vacuum furnace. The temperature T ₃ when the joined body 100 is allowed to stand is, for example, 650 ° C. as a guide, and the standing time t ₃ is 2 hours (see FIG. 2). After performing the bonded body stationary step S140, the bonded body 100 is cooled in an inert gas atmosphere (for example, in an N ₂ gas atmosphere).

  In each process described above, when measuring the temperature of the joined body, the temperature of the outermost peripheral portion of the joined body is measured using a thermocouple or a radiation thermometer.

According to the joining method of the steel members according to the first embodiment including the above steps, the bonded body 100 was formed by the bonding body forming step S120, it is less than the A ₁ transformation point at 520 ° C. or higher and steel members 110 and 120 Since it is supposed that it is allowed to stand for 30 minutes or more in the temperature range, most of the Cr-containing passive layer 142 and voids 144 existing on the joint surface 140 are dissolved in the steel material of the parent phase (FIG. 3 (c2) and FIG. 3 ( d2).) Finally, it is possible to dissipate most of the Cr-containing passive layer 142 and the voids 144 present on the bonding surface 140 (see FIG. 3 (e2)). As a result, the joining force of the joined body 100 can be made sufficiently high depending on the application.

  Therefore, the method for joining steel members according to the first embodiment is a method for joining steel members that can obtain a sufficiently high joining force even when two steel members containing Cr are joined together to produce a joined body. Become a method.

  Moreover, the joining method of the steel member which concerns on Embodiment 1 makes the joining force in the joined body 100 formed by joined body formation process S120 high by leaving still for 30 minutes or more in such a comparatively low temperature range. Therefore, it becomes possible to cool the joined body 100 having a strengthened joining force relatively rapidly, and it becomes a highly productive joining method for steel members.

  Moreover, in the joining method of the steel member which concerns on Embodiment 1, the steel members 110 and 120 are steel members which consist of stainless steel. For this reason, since it becomes clear also from the test example mentioned later, since it becomes possible to dissipate many of the Cr containing passive layer 142 and the space | gap 144 which exist in the joint surface 140 by performing joined body stationary process S140. In addition, the bonding force of the bonded body 100 can be sufficiently increased.

  In the method for joining steel members according to Embodiment 1, since the joined body 100 is cooled in an inert gas atmosphere after performing the joined body stationary step S140, the surface of the joined body 100 is cooled during the cooling process. It is possible to suppress the deterioration of quality due to oxidation.

In the method of bonding steel members according to the first embodiment, the first temperature _{T 1} of, since in the range of 850 ° C. to 1150 ° C., joining two steel members 110 and 120 while being pressed at a predetermined pressure condition Thus, the joined body 100 can be formed.

  In the method for joining steel members according to the first embodiment, the metal structure homogenizing step S130 is performed between the joined body forming step S120 and the joined body stationary step S140. It becomes possible to make the metal structure in a uniform state more uniform, and to form a bonded body 100 with higher homogeneity.

In the method of bonding steel members according to the first embodiment, the second temperature T _2, because in the range of 850 ° C. to 1150 ° C., the metal structure via a bonded body forming step S120 has a non-uniform state Furthermore, it becomes possible to make it uniform.

  In the method for joining steel members according to the first embodiment, after the metal structure homogenization step S130 is performed, the joined body 100 is rapidly cooled to the Ms point, and then the joined body 100 is gradually cooled. By increasing the hardness of the bonded body 100, it is possible to form a bonded body with high mechanical strength and high quality.

  In the method for joining steel members according to the first embodiment, the joining planned surfaces 112 and 122 of the two steel members 110 and 120 are flat surfaces. It becomes possible to obtain a sufficiently high joining force by increasing the degree of adhesion between the steel members when the steel members 110 and 120 are abutted against each other.

  In the method for joining steel members according to the first embodiment, the arithmetic average roughness Ra of the joining planned surfaces 112 and 122 is 0.2 μm or less, and therefore the interval between the joining scheduled surfaces of the two steel members 110 and 120 is the same. The joined body forming step S120 is performed in an average state of 0.4 μm or less, and the two steel members 110 and 120 are formed in a state in which the interval between the planned joining surfaces is 0.4 μm or less on average. Since the bonding force strengthening step S120 is performed on the bonded body 100 (in other words, a bonded body having a very small gap that may remain on the bonded surface 140), a sufficiently high bonding force can be obtained. It becomes.

  In the method for joining steel members according to the first embodiment, the joined body forming step S120 and the joined body stationary step S140 are performed in a vacuum, which is caused by the presence of an active gas such as oxygen in each heat treatment step. It is possible to suppress the adverse effects that occur.

[Test example]
A test was conducted to confirm the effect of the steel member joining method according to the first embodiment. The test is performed on each of the joined bodies A1 to A5 obtained by the steel member joining method according to the first embodiment and the joined bodies B1 to B5 obtained by the steel member joining method according to the comparative example of the first embodiment. While evaluating the joining state, each joined body was evaluated by a fracture test.

  The method for joining steel members according to the comparative example of the first embodiment basically includes the same steps as the method for joining steel members according to the first embodiment, but the embodiment is that the joined body stationary step is not performed. 1 is different from the method for joining steel members according to No. 1.

  That is, the method for joining steel members according to the comparative example includes a steel member preparation step, a joined body forming step, and a metal structure homogenizing step in this order. Since the contents of these steps are the same as those described in the first embodiment, detailed description thereof is omitted.

  FIG. 4 is a diagram for explaining the test procedure. 4 (a) is a perspective view showing two steel members 10 and 20 before joining, FIG. 4 (b) is a perspective view showing joined body A1 after joining, and FIG. 4 (c) is a joined body. FIG. 4 (d) is a perspective view showing a test piece a1 and FIG. 4 (e) is a view showing a state in which the test piece a1 is fixed with a vise V. FIG. is there.

  The test procedure will be described taking the case of the joined body A1 as an example. First, two steel members 10 and 20 were prepared (see FIG. 4A). The size of each steel member 10 and 20 is 50 mm x 50 mm x 10 mm thickness. Next, two steel members 10 and 20 were joined to form a joined body A1 (see FIG. 4B). In the case of joined bodies A1 to A5, a joined body forming process, a metal structure homogenizing process, and a joined body stationary process are performed. In the case of joined bodies B1 to B5, a joined body forming process and a metal structure homogenizing process are performed. went.

  Next, the joined body A1 was divided into four to create four block pieces 30 to 36 (see FIG. 4C). One of the four block pieces 30 to 36 (for example, the block piece 30) is used for evaluating the joined state of the joined body, and the other block piece (for example, the block piece 32) is used for performing a break test. Used for.

  In evaluating the bonded state of the bonded body, the bonded portion and its peripheral portion of the block piece 30 were polished and etched, and then the bonded portion was observed using an SEM (scanning electron microscope).

  In performing the rupture test, a test piece a1 is prepared from the block piece 32 as shown in FIG. 4D, and the test piece a1 is fixed with a vise V as shown in FIG. A predetermined impact was applied to the piece a1 with a hammer, and the fracture state and the like of the test piece a1 were observed. The size of the test piece a1 is 10 mm × 20 mm × 2 mm thick.

  In accordance with such a test procedure, the evaluation of the bonding state of each of the bonded bodies A1 to A5 (the one that performed the bonded body stationary step) and the bonded bodies B1 to B5 (the one that does not perform the bonded body stationary step) and Evaluation by a break test was performed, and comprehensive evaluation of each joined body was performed based on the evaluation results.

Note that the joined bodies A1 to A5 and B1 to B5 are different from each other in the types of two steel members constituting the joined body. That is, the joined bodies A1 and B1 use HPM38 (manufactured by Hitachi Metals) as two steel members, and the joined bodies A2 and B2 use S-STAR (manufactured by Daido Steel) as two steel members. The joined bodies A3 and B3 use STAVAX (manufactured by Woodeholm) as two steel members, and the joined bodies A4 and B4 use ELMAX (manufactured by Woodeholm) as two steel members. The bodies A5 and B5 use SKD61 as two steel members.
HPM38, S-STAR and STAVAX are SUS420J2 stainless steel. ELMAX is a SUS440C stainless steel. SKD61 is a steel for hot die.

  5 to 9 are cross-sectional electron micrographs of the bonded portion in each bonded body. FIG. 5A is a cross-sectional electron micrograph of the joined portion in the joined body A1, FIG. 5B is a cross-sectional electron micrograph of the joined portion in the joined body B1, and FIG. 6A is the joined body A2. Fig. 6 (b) is a cross-sectional electron micrograph of the bonded portion in the bonded body B2, Fig. 7 (a) is a cross-sectional electron micrograph of the bonded portion in the bonded body A3, FIG. 7B is a cross-sectional electron micrograph of the bonded portion in the bonded body B3, FIG. 8A is a cross-sectional electron micrograph of the bonded portion in the bonded body A4, and FIG. 8B is the bonded body B4. FIG. 9A is a cross-sectional electron micrograph of the bonded portion, FIG. 9A is a cross-sectional electron micrograph of the bonded portion in the bonded body A5, and FIG. 9B is a cross-sectional electron micrograph of the bonded portion in the bonded body B5.

  FIG. 10 is a photograph of the test piece after the break test. FIG. 10A is a photograph showing a state in which the test piece is broken in the base material, and FIG. 10B is a photograph showing a state in which the test piece is broken in the vicinity of the joint surface without breaking the base material. In addition, the joint surface exists in the position of the code | symbol P shown in Fig.10 (a) and FIG.10 (b).

Table 1 is a table | surface which shows the test result about each joined body.
In addition, in the column for evaluation of the bonding state in Table 1, “◎” indicates that the bonding surface cannot be confirmed at all, “◯” indicates that the bonding surface is hardly confirmed, and “Δ” indicates that the bonding surface is visually recognized. The case where it is possible is represented, and “x” represents the case where the joint surface is clearly visible. Also, in the column of evaluation by break test in Table 1, “○” represents the case where the base material breaks, and “△” represents breakage at the joint surface, but relatively strong force is required for breakage. “×” represents a case where the joint surface is broken even with a relatively weak force. In addition, the column of comprehensive evaluation in Table 1 is a comprehensive evaluation based on the evaluation of the bonding state and the evaluation by the fracture test, and “◎” represents a considerably excellent bonded body, “○” Represents an excellent bonded body, and “x” represents a bad bonded body.

  As is apparent from FIGS. 5 to 9 and Table 1, the joined state of the joined bodies B1 to B5 joined by the steel member joining method according to the comparative example (without performing the joined body stationary step) ), In the joined bodies A1 to A5 joined by the joining method of steel members according to Embodiment 1 (those subjected to the joined body stationary step), there are voids on the joined surfaces. The presence of voids on the joint surface could hardly be confirmed. In particular, in the joined bodies A1, A2 and A3, it was impossible to confirm the presence of voids on the joined surfaces. From this, in the joined bodies A1 to A5 joined by the steel member joining method according to the first embodiment (the one subjected to the joined body stationary step), it is confirmed that voids existing on the joined surface are dissipated. did it.

  As is apparent from Table 1 regarding the fracture test results, all of the joined bodies B1 to B5 joined by the steel member joining method according to the comparative example (without performing the joined body stationary step) are fractured at the joined surfaces. In contrast, of the joined bodies A1 to A5 joined by the steel member joining method according to the first embodiment (the joined body stationary step was performed), the joined bodies A1 to A3 caused the base material fracture. . In addition, the joined bodies A4 and A5 did not reach the base material breakage, but did not break at the joined surface unless a considerably strong force was applied compared to the joined bodies B1 to B5. From this, it joined by the joining method of the steel member which concerns on Embodiment 1 compared with joined body B1-B5 (thing which does not perform a joined body stationary process) joined by the joining method of the steel member which concerns on a comparative example. It was found that the bonded bodies A1 to A5 (those subjected to the bonded body stationary step) had higher bonding strength. In particular, it has been found that the joined bodies A1, A2, and A3 have such a high joining strength that the base material breaks.

  If each joined body is evaluated comprehensively based on these evaluations, as shown in Table 1, joined bodies B1 to B5 joined by the steel member joining method according to the comparative example (the joined body stationary step is not performed). Are low in joining force, whereas joined bodies A1 to A5 joined by the steel member joining method according to Embodiment 1 (the one subjected to the joined body stationary step) have a relatively high joining force. ing. In particular, for the joined bodies A1, A2, and A3, since the joining surface cannot be confirmed and the joining strength is high enough to cause the base material to break, from the viewpoint of joining quality, From the viewpoint of the bonding force, it can be seen that the bonded body is very excellent.

  As described above, the effect of the method for joining steel members according to the first embodiment by the test in this test example (a sufficiently high joining force can be obtained even when two steel members containing Cr are joined together to produce a joined body. The effect that it becomes possible to obtain.) Was able to be confirmed.

[Embodiment 2]
Embodiment 2 is an embodiment for explaining a method for joining steel members of the present invention.

  FIG. 11 is a diagram for explaining a method of joining steel members according to the second embodiment. In FIG. 11, the horizontal axis indicates time, and the vertical axis indicates temperature.

  The method for joining steel members according to the second embodiment basically includes the same steps as the method for joining steel members according to the first embodiment, but the number of times that the joined body stationary step is performed is the steel according to the first embodiment. It is different from the joining method of members.

  That is, the method for joining steel members according to the second embodiment includes a steel member preparation step S210, a joined body forming step S220, a metal structure homogenizing step S230, and a joined body stationary step S240 in this order. The bonded body stationary step S240 is performed twice.

  Note that the steel member preparation step S210, the joined body forming step S220, and the metallographic structure homogenizing step S230 in the method for joining steel members according to the second embodiment are the same as the steps described in the first embodiment, and thus detailed description thereof. Is omitted.

Conjugate standing step S240, similar to the assembly stand step S140 described in Embodiment 1, at a temperature range of less than the A ₁ transformation point at 520 ° C. or higher and the steel member, to stand the assembly for 30 minutes or more It is a process.

In the joined body stationary step S240, the joined body is heated using a vacuum furnace. The temperature T ₃ at the time of standing conjugate, for example, a guideline 650 ° C., standing between t ₃ is respectively 2 hours (see Figure 11.). After performing the bonded body stationary step S240, the bonded body is cooled in an inert gas atmosphere (for example, in an N ₂ gas atmosphere).

Thus, although the joining method of the steel member which concerns on Embodiment 2 differs from the joining method of the steel member which concerns on Embodiment 1 in the frequency | count of performing a joined body stationary process, joining of the steel member which concerns on Embodiment 1 as with the method, the bonded body formed by bonding body forming step S220, since you are allowed to stand for 30 minutes or more in a temperature range of less than the a ₁ transformation point at 520 ° C. or higher and the steel member, bonding conjugate The force can be made sufficiently high depending on the application.

  Therefore, the method for joining steel members according to the second embodiment is a method for joining steel members that can obtain a sufficiently high joining force even when two steel members containing Cr are joined together to produce a joined body. Become a method.

  In the method for joining steel members according to the second embodiment, after the metal structure homogenization step S230 is performed, the joined body stationary step S240 is performed twice, so that a higher joining force can be obtained. .

  The method for joining steel members according to Embodiment 2 includes the same steps as the method for joining steel members according to Embodiment 1 except that the number of times of performing the joined body stationary step is different. It has the effect applicable as it is among the effects which the joining method of the steel member which concerns has.

[Embodiment 3]
Embodiment 3 is an embodiment shown for explaining a method for joining steel members of the present invention and a steel product manufactured by the method. In the third embodiment, a resin molding die (resin molding die according to the third embodiment) will be described as an example of steel products.

  FIG. 12 is a view for explaining the method for joining steel members according to the third embodiment. FIG. 12 (a) is a view for explaining the steel member preparation step S310, FIG. 12 (b) is a view for explaining the joined body forming step S320, and FIG. 12 (c) is a metallographic structure. It is a figure shown in order to demonstrate the equalization process S330, FIG.12 (d) is a figure shown in order to demonstrate joining body stationary process S340, FIG.12 (e) is in order to demonstrate cutting process S350. FIG.

  The method for joining steel members according to the third embodiment basically includes the same method as the method for joining steel members according to the first embodiment, but the joining target is different from the method for joining steel members according to the first embodiment. . Further, in the method for joining steel members according to the third embodiment, the surface hardness of the joined body after performing the cutting process for cutting the joined body after performing the joined body stationary step, and after performing the cutting process. It differs from the joining method of the steel member which concerns on Embodiment 1 by the point which performs the surface treatment process which makes high.

  In the method for joining steel members according to the third embodiment, as shown in FIG. 12A, heat exchange medium flow path forming grooves 314 and 324 are formed on the planned joining surfaces 312 and 322 as joining objects. Steel members 310 and 320 are used. As the steel members 310 and 320, SUS420J2 stainless steel (for example, HPM38) is used as in the case of the steel member joining method according to the first embodiment.

  In the method for joining steel members according to Embodiment 3, nitriding (for example, ion nitriding) is performed as the surface treatment process. In addition to the nitriding treatment, other surface treatment methods (for example, multi-knight treatment, carburizing treatment, various coating treatments (eg, titanium coating or ceramic coating)) may be used.

Thus, although the joining method of the steel member which concerns on Embodiment 3 differs in the joining object from the joining method of the steel member which concerns on Embodiment 1, it further includes the cutting process and the surface treatment process, Embodiment 1 as with the method of bonding steel members according to the assembly formed by the bonding body forming step S320, and the allowed to stand for 30 minutes or more in a temperature range of less than the a ₁ transformation point at 520 ° C. or higher and the steel member Therefore, it is possible to sufficiently increase the bonding force of the bonded body 300.

  Therefore, the joining method of the steel member which concerns on Embodiment 3 joins the steel member which can obtain a sufficiently high joining force, even when manufacturing the joined body by joining two steel members containing Cr mutually. Become a method.

  In the method for joining steel members according to Embodiment 3, as shown in FIG. 12 (e), a medium for heat exchange is obtained by cutting the joined body 300 so as to have a desired shape. It becomes possible to manufacture the resin molding die 350 (the resin molding die according to the third embodiment) including the flow path 360 therein.

  In the method for joining steel members according to the third embodiment, by performing the surface treatment step, even if the hardness of the mold 350 for resin molding may be reduced by performing the joined body stationary step. The surface hardness of the resin molding die 350 can be increased. For this reason, it is possible to improve the durability (wear resistance) of the resin molding die 350 and to improve the mold release property.

  Since the resin molding die 350 according to the third embodiment is joined with a sufficiently high joining force, it becomes a highly reliable and long-life resin molding die (in the experiment, the life is extended 100 times or more). Has been confirmed.) For this reason, the resin product manufactured using the resin molding die 350 is a resin product with high quality and low manufacturing cost.

  In addition, in the resin molding die 350 according to the third embodiment, although a description with illustration is omitted here, a portion exposed to the outside of the bonding surface 340 in the bonded body 300 is removed. Specifically, at least 2 mm inner portion of the end surface of the bonded body 300 where the bonding surface 340 is exposed is removed from the end surface. The part exposed to the outside of the joint surface 340 in the joined body 300 is the other part (the part that is not exposed to the outside of the joint surface 340 in the joined body 300, for example, the part of the joint surface 340 in the joined body 300. The bonding force may be lower than the center portion), but according to the resin molding die 350 according to the third embodiment, the portion exposed to the outside of the bonding surface 340 is removed. It becomes a high-quality resin molding die from which a relatively low bonding force is removed.

  The method for joining steel members according to the third embodiment includes the same steps as the method for joining steel members according to the first embodiment, except that the joining target is different and further includes a cutting step and a surface treatment step. And it has an applicable effect as it is among the effects which the joining method of the steel member concerning Embodiment 1 has.

  As mentioned above, although the joining method of the steel member, steel product, and resin product of this invention were demonstrated based on said each embodiment, this invention is not limited to said each embodiment, and does not deviate from the summary. The present invention can be implemented in various modes within the scope, and for example, the following modifications are possible.

(1) In each of the above embodiments, a method for joining steel members including a steel member preparation step, a joined body forming step, a metal structure homogenizing step, and a joined body stationary step in this order has been described. The present invention is not limited to this. The assembly of two steel members which contains are bonded together Cr, in a temperature range or 520 ° C. or higher and a temperature range below 820 ° C. of less than the A ₁ transformation point at 520 ° C. or higher and the steel member, 30 minutes conjugate It also includes a method for strengthening the joining force in a joined body made of a steel member that dissipates the Cr-containing passivating layer and voids present on the joining surface and thereby strengthens the joining force of the joined body. Also in this case, it is possible to sufficiently increase the joining force of the joined body in which the two steel members containing Cr are joined to each other.

(2) In each of the above embodiments, the HPM 38, which is a SUS420J2-based stainless steel, is used as the steel member, but the present invention is not limited to this. For example, the same SUS420J2 stainless steel STAVAX (registered trademark of Woodeholm), S-STAR, SUS440C stainless steel ELMAX, or the like may be used. Further, martensitic stainless steel other than these may be used as the steel member, or hot mold steel, cold mold steel, machine structural steel, or high-speed tool steel may be used. Even when such a steel member is used, it is possible to join with a sufficiently high joining force.

(3) In each of the above embodiments, the case where the planned joining surface is a plane has been described, but the present invention is not limited to this. As long as the surfaces to be bonded can be brought into close contact with each other, the surfaces to be bonded may be curved surfaces or have steps.

(4) In each of the above embodiments, the case where the arithmetic average roughness Ra of the planned joining surface in the steel member is 0.1 μm has been described as an example, but the present invention is not limited to this, and the joining is performed. The arithmetic average roughness Ra of the planned surface may be 0.2 μm or less.

(5) In each of the above-described embodiments, the bonded body forming step is performed by pulse current heating using a pulse current heating apparatus, but the present invention is not limited to this. For example, it can be performed by external heating or magnetic heating. Among these, in the case of magnetic heating, it is possible to heat a plurality of steel members uniformly at high speed, and as a result, it is possible to manufacture a high-quality joined body with low stress strain with high productivity.
In addition, the method of performing a joined body formation process by magnetic heating is applicable also to the joining method of the steel member which mutually joins the several steel member which consists of steel materials which do not contain Cr.

(6) In each of the above embodiments, the plurality of steel members are heated while pressing the plurality of steel members by hydraulic pressure, but the present invention is not limited to this. For example, a some steel member can also be heated, pressing a some steel member on predetermined pressure conditions using a servomotor. Thereby, it becomes possible to press a some steel member on fixed pressure conditions, As a result, it becomes possible to manufacture a high quality joined body with small stress distortion.
In addition, the method of pressing a steel member using a servo motor in the joined body forming step can also be applied to a method of joining steel members that join together a plurality of steel members made of a steel material not containing Cr.

(7) In the above embodiments, a temperature range of less than the A ₁ transformation point at 520 ° C. or higher and the steel member has been described with reference to the case of standing conjugates, the present invention is not limited thereto Instead, the joined body may be allowed to stand in a temperature range of 520 ° C. or more and less than 820 ° C.

(8) In the above embodiment 1 has been described as an example the case of the standing between t ₃ of the joint body and two hours, the present invention is not limited thereto. Although it depends on the size of the joined body, the standing time of the joined body in the joined body standing step may be 30 minutes or more.

(9) In Embodiment 2 described above, the bonded body stationary step is performed twice, but the present invention is not limited to this, and the bonded body stationary step may be performed three or more times.

(10) In each of the above embodiments, the case where the joined body is cooled in an inert gas atmosphere (for example, under an N ₂ gas atmosphere) after the joined body stationary step has been described as an example. It is not limited to this. The joined body after performing the joined body stationary step may be taken out of the furnace and left as it is in the atmosphere.

(11) In each of the above embodiments, the bonded body forming step, the metal structure homogenizing step, and the bonded body stationary step are performed in a vacuum, but the present invention is not limited to this. For example, these steps can also be performed in an inert gas atmosphere such as N ₂ gas or Ar gas. Also by adopting such a method, it is possible to suppress an adverse effect due to a reactive gas such as oxygen in each heat treatment step.

(12) In each of the above embodiments, a resin mold is manufactured as a steel product, but the present invention is not limited to this. Examples of steel products include various molding dies, various tools, and various structural materials.

Explanation of symbols

10, 20, 110, 120, 310, 320 ... steel member, 30, 32, 34, 36 ... block piece, 100, 300, A1 ... joined body, 140, 340 ... joined surface, 142 ... Cr-containing passive layer, 144 ... Gap, 312,322 ... Scheduled surfaces to join, 314,324 ... Heat exchange medium flow path forming groove, 350 ... Resin molding die, 360 ... Heat exchange medium flow path, 42,44 ... Heat exchange Medium flow path forming groove, a1 ... test piece, T ₁ ... first temperature, T ₂ ... second temperature, T ₃ ... third temperature, T _A1 ... A ₁ transformation point, t ₁ ... first heat treatment time, t ₂ ... second heat treatment time, t ₂ ... standing time, t ₄ ... fourth heat treatment time, V ... vise

Claims (16)

A steel member preparation step of preparing two steel members containing Cr;
By heating the two steel members to a first temperature at which the two steel members can be joined while pressing the two steel members under a predetermined pressure condition in a state in which the surfaces to be joined in the two steel members are abutted, A joined body forming step of joining steel members to each other to form a joined body;
At a temperature range of less than the A ₁ transformation point at 520 ° C. or higher and the steel members, the joining method of the steel member, characterized in that it comprises a conjugate standing step of standing for more than 30 minutes the conjugates in this order. A steel member preparation step of preparing two steel members containing Cr;
By heating the two steel members to a first temperature at which the two steel members can be joined while pressing the two steel members under a predetermined pressure condition in a state in which the surfaces to be joined in the two steel members are abutted, A joined body forming step of joining steel members to each other to form a joined body;
The joining method of the steel member characterized by including the joined body stationary process which leaves the said joined body still for 30 minutes or more in the temperature range of 520 degreeC or more and less than 820 degreeC. In the joining method of the steel member according to claim 1 or 2,
After performing the said joined_body | zygote formation process, the said joined body stationary process is performed in multiple times, The joining method of the steel member characterized by the above-mentioned. In the joining method of the steel member in any one of Claims 1-3,
After performing the said joined body stationary process, the said joined body is cooled in inert gas atmosphere, The joining method of the steel member characterized by the above-mentioned. In the joining method of the steel member in any one of Claims 1-4,
Said 1st temperature exists in the range of 850 degreeC-1150 degreeC, The joining method of the steel member characterized by the above-mentioned. In the joining method of the steel member in any one of Claims 1-5,
The method further includes a metal structure homogenization step of heating the joined body to a second temperature capable of making the structure of the joined body more uniform between the joined body forming step and the joined body standing step. The joining method of the steel member characterized by the above-mentioned. In the joining method of the steel member according to claim 6,
Said 2nd temperature exists in the range of 850 degreeC-1150 degreeC, The joining method of the steel member characterized by the above-mentioned. In the joining method of the steel member according to claim 6 or 7,
A steel member joining method comprising: performing the metallographic structure homogenizing step, rapidly cooling the joined body to an Ms point, and then gradually cooling the joined body. In the joining method of the steel member in any one of Claims 1-8,
The method for joining steel members, wherein the planned joining surfaces of the two steel members are flat surfaces. In the method for joining steel members according to claim 9,
The arithmetic average roughness Ra on the planned joining surface is 0.2 μm or less, and the joining method of steel members, In the joining method of the steel member in any one of Claims 1-10,
A method for joining steel members, wherein the joined body forming step and the joined body stationary step are performed in a vacuum or in an inert gas atmosphere. In the joining method of the steel member in any one of Claims 1-11,
The method for joining steel members, wherein the steel member is a steel member made of stainless steel. In the joining method of the steel member in any one of Claims 1-11,
The steel member is a steel member made of hot die steel, cold die steel, machine structural steel or high-speed tool steel. A method for strengthening a joining force in a joined body made of a steel member, which reinforces the joining force of a joined body in which two steel members containing Cr are joined together,
As the joined body, in a state in which the planned joining surfaces of the two steel members containing Cr are in contact with each other, the first steel member is brought to a first temperature at which the two steel members can be joined while pressing the two steel members under a predetermined pressure condition. A joined body preparation step of preparing a joined body formed by joining the two steel members by heating,
At a temperature range of less than the A ₁ transformation point at 520 ° C. or higher and the steel member, characterized in that it comprises a conjugate standing step of standing for more than 30 minutes the conjugates in this order, bonding consisting of steel members A method for strengthening bonding strength in the body. A method for strengthening a joining force in a joined body made of a steel member, which reinforces the joining force of a joined body in which two steel members containing Cr are joined together,
As the joined body, in a state in which the planned joining surfaces of the two steel members containing Cr are in contact with each other, the first steel member is brought to a first temperature at which the two steel members can be joined while pressing the two steel members under a predetermined pressure condition. A joined body preparation step of preparing a joined body formed by joining the two steel members by heating,
And a joined body stationary step of standing the joined body for 30 minutes or more in a temperature range of 520 ° C. or more and less than 820 ° C. in this order. . In the joining force strengthening method in the joined body which consists of a steel member according to claim 14 or 15,
After performing the said conjugate | zygote preparation process, the said conjugate | zygote stationary process is performed in multiple times, The joining force reinforcement | strengthening method in the conjugate | zygote consisting of a steel member characterized by the above-mentioned.

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