Linear friction joining method for stainless steel materials, linear friction joining joint and joining structure

Abstract

To provide a joining method which easily and effectively inhibits sensitization in a weld zone of a stainless steel material, a joint in which sensitization of a junction has been inhibited, and a joined structure including the joint.SOLUTION: A linear friction joining method for a stainless steel material includes: a first step of forming an interface 6 to be joined by making one member abut on the other member; a second step of discharging burrs 8 from the interface to be joined by making one member 2 and the other member 4 repeatedly slide on the same trajectory in a state that pressure is applied almost vertically to the interface to be joined; and a third step of stopping the sliding to form a joined surface. In the linear friction joining method, at least one member is a stainless steel material, and the pressure is set to a yield stress or higher and to a tensile strength or lower of the stainless steel material at a desired joining temperature. Further, in the method, a temperature history during joining is controlled according to the pressure and a sliding frequency and / or an amplitude, so that a temperature during joining does not fall into a grain boundary corrosion region of a TTS curve obtained according to The Strauss Test of a stainless steel plate.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a linear friction welding method for stainless steel materials, a linear friction welding joint obtained by said linear friction welding method, and a welded structure having said linear friction welding joint. [Background technology]

[0002] Stainless steel has excellent properties such as corrosion resistance, mechanical properties, workability, and heat resistance, and is therefore used in a very wide range of fields, including chemical industry equipment parts, automobile parts, aircraft parts, building materials, machine structural parts, and medical equipment.

[0003] However, when stainless steel materials are welded, the temperature history caused by the welding causes chromium carbides to precipitate at the grain boundaries, which reduces the chromium concentration along the grain boundaries and makes them susceptible to intergranular corrosion. This phenomenon, known as "sensitization of stainless steel," is essentially unavoidable in conventional fusion welding, and it is extremely difficult to completely prevent this phenomenon even when solid-state welding, which uses lower joining temperatures, is used.

[0004] In contrast, for example, Patent Document 1 (JP 2017-61748 A) discloses "a ferritic stainless steel for tubes containing, by mass%, C: 0.030% or less, Si: 1.00% or less, Mn: 1.00% or less, Cr: 16 to 20%, Ni: 0.6% or less, N: 0.025% or less, and further containing one or more of Nb: 8(C+N) to 0.8% and Ti: 8(C+N) to 0.8%, with the balance being Fe and unavoidable impurities, and having excellent corrosion resistance that allows post-weld heat treatment to be omitted."

[0005] The ferritic stainless steel for tubes described in Patent Document 1 uses ferritic stainless steel to which one or more of Nb and Ti have been added to reduce the C and N contents to below a specified range. This prevents sensitization of the ferritic stainless steel even if post-weld heat treatment is omitted, and it is said that a tube with corrosion resistance equal to or greater than that of conventional SUS430 can be provided.

[0006] Furthermore, Patent Document 2 (Japanese Patent Laid-Open Publication No. 58-205687) discloses "a method for welding austenitic stainless steel, characterized in that, when welding austenitic stainless steel, after the weld has solidified, the weld metal portion and the vicinity of the metal portion are heated to a temperature range of 850°C to 1200°C, and then the weld metal portion and the vicinity of the metal portion are rapidly cooled with running water."

[0007] The welding method described in Patent Document 2 above is a method for welding austenitic stainless steel, and is said to suppress sensitization of the heat-affected zone of the austenitic stainless steel weld by rapidly cooling the weld metal with running water when the temperature is in the range of 1200°C to 850°C during solidification and cooling, thereby significantly improving the reliability of austenitic stainless steel welded structures in corrosive environments. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-61748 [Patent Document 2] Japanese Patent Publication No. 58-205687 Summary of the Invention [Problem to be solved by the invention]

[0009] However, the ferritic stainless steel for tubes described in Patent Document 1 is limited in its material properties, making it essential to use this ferritic stainless steel for tubes. In other words, it lacks versatility and cannot be used for structural members other than tubes.

[0010] Furthermore, the welding method described in Patent Document 2 suppresses sensitization of the welded portion by rapid cooling using flowing water, but the welded portion to which rapid cooling using flowing water can be applied is limited, and it is necessary to consider the effects of flowing water on properties other than sensitization of the welded portion. Furthermore, effective cooling by flowing water is limited to the vicinity of the surface of the welded portion, and the effect obtained is limited when the welded materials are thick plates.

[0011] In view of the above-mentioned problems in the prior art, an object of the present invention is to provide a joining method that can simply and effectively suppress sensitization in welded parts of stainless steel materials, and that can be applied regardless of plate thickness or composition. Another object of the present invention is to provide a joint obtained by the joining method of the present invention, in which sensitization in the welded part is suppressed, and a welded structure having such a joint. [Means for solving the problem]

[0012] In order to achieve the above object, the present inventors have conducted extensive research into methods for joining stainless steel materials, and as a result have discovered that it is extremely effective to strictly control the temperature history of linear friction joining, which is a solid-state joining method, in relation to the intergranular corrosion region of the TTS (Time-Temperature-Sensitization) curve of the stainless steel materials being joined, and have arrived at this invention.

[0013] That is, the present invention provides: a first step of bringing one member into contact with another member to form a joining interface; a second step of repeatedly sliding the one member and the other member on the same trajectory while applying pressure substantially perpendicular to the interface to be joined, thereby removing burrs from the interface to be joined; a third step of stopping the sliding and forming a joining surface, At least one of the one member and the other member is made of stainless steel, The pressure is set to be equal to or greater than the yield stress and equal to or less than the tensile strength of the stainless steel material at a desired joining temperature; controlling the temperature history during bonding by the pressure and the frequency and / or amplitude of the sliding; the temperature during the joining is kept out of the intergranular corrosion region of the TTS (Time-Temperature-Sensitization) curve obtained by a Strauss test (sulfuric acid / copper sulfate corrosion test) of the stainless steel plate; The present invention provides a linear friction joining method for stainless steel materials, characterized by the following.

[0014] The linear friction welding method for stainless steel materials of the present invention is characterized by controlling the temperature history during welding by adjusting the welding pressure of the linear friction welding and the frequency and / or amplitude of the sliding. Here, the relationship between these welding conditions in linear friction welding and the temperature history during welding was not known until now, but the inventors have conducted extensive experiments and have clarified a clear relationship.

[0015] The greatest feature of controlling the temperature history during linear friction welding in this invention is that the maximum temperature of the weld can be controlled by the welding pressure. More specifically, the maximum temperature of the weld during linear friction welding (welding temperature) can be determined by the welding pressure, and the welding temperature can be reduced by increasing the welding pressure.

[0016] Increasing the joining pressure increases the amount of frictional heat generated by the sliding of the workpieces, but if the area softened by this frictional heat is continuously expelled as a burr, the temperature of the joint does not increase. In other words, by applying a joining pressure that corresponds to the strength of the workpieces at the desired joining temperature, this joining pressure acts as a trigger, and the moment the desired joining temperature is reached, the burr is expelled and the joining is complete. Based on this relationship, by understanding the temperature dependence of the strength of the workpieces in advance, the maximum temperature reached during linear friction joining can be accurately determined.

[0017] In addition, increasing the frequency or amplitude of the linear sliding in linear friction welding increases the heating rate, while decreasing the frequency or amplitude decreases the heating rate. As mentioned above, the maximum temperature of the weld can basically be determined by the welding pressure, but if the welding temperature exceeds the desired value due to overshoot caused by an excessively high heating rate, it is preferable to decrease the frequency and / or amplitude.

[0018] On the other hand, increasing the cooling rate is preferable to increase the frequency and / or amplitude to prevent the temperature during joining from entering the intergranular corrosion region of the TTS curve obtained by the Strauss test of stainless steel sheets. Increasing the frequency and / or amplitude increases the heating rate and shortens the joining time. As a result, the temperature rise near the joint due to heat conduction from the joining surface (friction surface) can be suppressed, and the cooling rate can be increased.

[0019] The TTS curve of the stainless steel plate used as the material to be joined may be obtained in advance by a Strauss test (sulfuric acid / copper sulfate corrosion test), and a publicly known TTS curve may be used.

[0020] In the linear friction joining method for stainless steel materials of the present invention, the joining temperature is preferably set to 600°C or less. Linear friction joining is a joining method that uses localized frictional heat on the sliding surfaces as a heat source, and has a higher heating rate and cooling rate than general fusion welding, etc. Therefore, by setting the joining temperature (maximum temperature reached) to 600°C or less, the intergranular corrosion region of the TTS curve can be avoided for essentially all stainless steels. As a result, even ferritic stainless steel materials, which are extremely difficult to avoid sensitization, can be suitably used as welded materials.

[0021] Furthermore, in the linear friction joining method for stainless steel materials of the present invention, it is preferable to have a sensitization behavior evaluation step in which a corrosion test is performed on a cross section of the obtained weld to confirm the presence or absence of sensitization, and if intergranular corrosion is found in the sensitization behavior evaluation step, to change the joining conditions based on the following (1) and / or (2): (1) The increase in pressure reduces the bonding temperature. (2) By increasing the frequency and / or the amplitude, the cooling rate after the bonding temperature is reached is increased.

[0022] As described above, the temperature history during linear friction welding can be controlled by the welding pressure, frequency, and amplitude, so a sensitization behavior evaluation step can be provided in which the presence or absence of sensitization is confirmed by a corrosion test on the cross section of the weld, and if sensitization is detected, the welding temperature (maximum temperature reached) can be lowered and / or the cooling rate can be increased, thereby obtaining a weld that is reliably free of sensitization. Here, the linear friction welding conditions can be changed multiple times based on the sensitization behavior evaluation step until sensitization is no longer observed.

[0023] The present invention also provides A linear friction welded portion is formed by joining one member and another member together via a linear friction welded interface, At least one of the one member and the other member is made of stainless steel, In an evaluation using JIS-G0571 (oxalic acid etching test method for stainless steel), no sensitization was observed in the stainless steel material of the linear friction welded portion. Also provided is a linear friction-bonded joint characterized by:

[0024] The linear friction-welded joint of the present invention can be suitably obtained by the linear friction-welding method of stainless steel materials of the present invention.

[0025] Furthermore, the present invention also provides a welded structure having the linear friction welded joint of the present invention. The welded structure of the present invention has excellent corrosion resistance and mechanical properties, and therefore can be suitably used in applications requiring reliability in corrosive environments. [Effects of the Invention]

[0026] According to the present invention, it is possible to provide a joining method that can simply and effectively suppress sensitization in a welded portion of a stainless steel material, and that can be applied regardless of the plate thickness or composition. Furthermore, according to the present invention, it is also possible to provide a joint in which sensitization of the welded portion obtained by the joining method of the present invention is suppressed, and a welded structure having such a joint. [Brief explanation of the drawings]

[0027] [Figure 1] 1 is a schematic diagram showing one embodiment of the linear friction joining method for stainless steel materials of the present invention. FIG. [Figure 2] 1 is a graph showing the tensile strength of various stainless steel materials at each temperature. [Figure 3] This is the TTS curve for stainless steel. [Figure 4] 1 is a schematic cross-sectional view showing an example of a linear friction-welded joint of the present invention. [Figure 5] 1 is a cross-sectional macrophotograph of the joint obtained in Example 1. [Figure 6] 1A and 1B are optical microscope photographs of the joint obtained in Example 1 before and after oxalic acid electrolytic etching. [Figure 7] 1 is a cross-sectional macrophotograph of the joint obtained in Example 2. [Figure 8] 10A and 10B are optical microscope photographs of the joint obtained in Example 2 before and after oxalic acid electrolytic etching. [Figure 9] 1 is a graph showing the relationship between the temperature history during bonding and the TTS curve in an example. DETAILED DESCRIPTION OF THE INVENTION

[0028] Representative embodiments of the linear friction welding method for stainless steel materials, the linear friction welding joint, and the welded structure of the present invention will be described in detail below with reference to the drawings, but the present invention is not limited to these. In the following description, the same or equivalent parts will be given the same reference numerals, and duplicate explanations may be omitted. Furthermore, since the drawings are intended to conceptually explain the present invention, the dimensions of the components shown and their ratios may differ from the actual ones.

[0029] (1) Linear friction welding method for stainless steel materials 1 is a schematic diagram showing the joining steps of the linear friction joining method for stainless steel materials of the present invention. The linear friction joining method for stainless steel materials of the present invention comprises a first step of bringing one member 2 into contact with another member 4 to form a welded interface 6, a second step of repeatedly sliding the one member 2 and the other member 4 on the same trajectory while applying pressure substantially perpendicular to the welded interface 6, and expelling burrs 8 from the welded interface substantially parallel and perpendicular to the sliding direction, and a third step of stopping the sliding to form a welded surface. Each step will be described in detail below.

[0030] (1-1) First step The first step is a step of bringing one member 2 into contact with the other member 4 to form the bonded interface 6. The one member 2 and / or the other member 4 are moved to the location where it is desired to form a bond, and the surfaces to be bonded are brought into contact with each other to form the bonded interface 6.

[0031] At least one of the first member 2 and the second member 4 is made of a stainless steel material. The type of stainless steel material is not particularly limited as long as it does not impair the effects of the present invention, and various conventionally known stainless steel materials can be used. Stainless steel materials include all stainless steel materials specified in the JIS standard, such as austenitic stainless steel, martensitic stainless steel, ferritic stainless steel, duplex stainless steel, and precipitation hardening stainless steel. However, even ferritic stainless steel materials, which are extremely difficult to suppress from sensitizing, can be suitably used as the welded material.

[0032] Furthermore, the size and shape of the stainless steel material are not particularly limited as long as they do not impair the effects of the present invention, and can be any size and shape conventionally known for stainless steel material. However, when controlling the joining temperature by forced cooling from the outside, such as water cooling, it is difficult to achieve this effect inside the thick plate. In contrast, in the linear friction joining method of stainless steel materials of the present invention, the temperature of the joining portion is controlled by joining conditions such as the joining pressure, so that it can be suitably used even for thick plates with a plate thickness of 6 mm or more.

[0033] (1-2) Second process The second step is a step in which one member 2 and the other member 4 are repeatedly slid along the same trajectory while applying pressure P approximately perpendicular to the joined interface 6, and burrs 8 are expelled from the joined interface 6 approximately parallel to and approximately perpendicular to the sliding direction.

[0034] The method of repeatedly sliding one member 2 and the other member 4 on the same trajectory is not particularly limited as long as it does not impair the effects of the present invention, and both members may be vibrated together, or one may be fixed and the other may be vibrated.

[0035] Here, the joining temperature can be controlled by setting the pressure P during linear friction joining to a value equal to or greater than the yield stress and equal to or less than the tensile strength of one member and / or the other member at the desired joining temperature. In the friction joining method of the present invention, the pressure P is set to a value equal to or greater than the yield stress and equal to or less than the tensile strength of the stainless steel material at the desired joining temperature, allowing the joining temperature to be determined based on the stainless steel material. Setting the pressure P to a value equal to or greater than the yield stress of the stainless steel material starts the removal of burrs 8 from the joined interface 6, and increasing the pressure P until the tensile strength is reached accelerates the removal of burrs 8. Similar to the yield stress, the tensile strength at a specific temperature is also approximately constant depending on the materials being joined, so the joining temperature corresponding to the set pressure P can be achieved. From the viewpoint of suppressing an increase in the joining temperature, it is preferable to set the pressure P equal to or less than the tensile strength.

[0036] As a specific example, Figure 2 shows the tensile strength of various stainless steel materials at each temperature. Note that Figure 2 is a graph published in "Sanyo Technical Report Vol. 21 (2014) No. 1." As shown in Figure 2, the tensile strength at a specific temperature is roughly constant depending on the material. In other words, by creating a database of such data for the materials to be joined, it is possible to efficiently and easily perform joining at any temperature.

[0037] If the joining pressure P is set high, the joined materials (stainless steel materials) with higher yield strength and tensile strength can be removed as burrs, and the joining temperature can be reduced. Also, as shown in Figure 2, the tensile strength (and yield stress) at a specific temperature is approximately constant depending on the material, so by setting the joining pressure P based on the temperature dependency of the strength of the stainless steel material, the joining temperature (maximum temperature reached) of the stainless steel material can be controlled very accurately.

[0038] In linear friction welding, it is necessary to set welding parameters other than the pressure P (such as the frequency and amplitude of vibration of the workpieces, welding time and distance), but these values ​​are not limited as long as they do not impair the effects of the present invention, and may be set appropriately depending on the material, shape, size, etc. of the workpieces. Here, by increasing the amplitude and frequency of sliding the workpieces, the temperature rise rate and the cooling rate after welding increase, but the maximum temperature (welding temperature) remains unchanged.

[0039] The maximum temperature of the bonded portion can be determined essentially by the bonding pressure. However, if the bonding temperature exceeds the desired value due to overshoot caused by an excessively high heating rate, it is preferable to reduce the frequency and / or amplitude.

[0040] The commonly known TTS curves for ferritic stainless steel and austenitic stainless steel are shown in Figure 3 (Nishimoto Kazutoshi, Natsume Shogo, Ogawa Kazuhiro, Matsumoto Cho, Welding and Joining Selection, Stainless Steel Welding, (2001) p. 53). The intergranular corrosion region in the lower left of the figure corresponds to ferritic stainless steel, and the intergranular corrosion region in the upper right corresponds to austenitic stainless steel.

[0041] For example, when the workpiece is a ferritic stainless steel material having the TTS curve shown in Figure 3, the line showing the temperature change during linear friction welding and the curve showing the boundary of the intergranular corrosion region should not intersect. Here, the temperature at the tip of the nose of the curve showing the boundary of the intergranular corrosion region is approximately 600°C, and in linear friction welding, cooling occurs quickly after welding is completed. Therefore, by setting the welding temperature (maximum temperature reached) to 600°C or less, the formation of the intersection can be suppressed extremely effectively. Furthermore, it is easier to suppress the formation of the intersection in austenitic stainless steel materials than in ferritic stainless steel materials.

[0042] In addition, the reduction in joining temperature also suppresses softening of the heat-affected zone of the stainless steel material. In other words, by using the linear friction joining of stainless steel materials of the present invention, a joint having both excellent corrosion resistance and mechanical properties can be obtained.

[0043] (1-3) Third step The third step is a step in which the sliding in the second step is stopped to form a weld surface. In the linear friction joining method for stainless steel materials of the present invention, a good weld can be obtained by stopping the sliding after burrs 8 have been removed from the entire surface of the weld interface 6. The pressure P applied to the welded materials in the second step can be maintained as is, or it can be increased to remove burrs 8 and to bring the newly formed surfaces into stronger contact. As the weld area increases during the joining process, the pressure P decreases, which can sometimes result in an unintended rise in the joining temperature; however, this phenomenon can be suppressed by increasing the pressure P.

[0044] Here, the timing for stopping the sliding is not limited as long as burrs 8 are discharged from the entire surface of the joined interface 6, but by observing the joined interface 6 from a direction approximately perpendicular to the sliding direction and stopping the sliding the moment the burrs 8 are discharged approximately parallel to the sliding direction, it is possible to form a good joint while minimizing the amount of burrs 8 discharged (minimizing the consumption of the joined materials). Note that "a direction approximately perpendicular to the sliding direction" and "a direction approximately parallel to the sliding direction" both refer to directions approximately perpendicular to the applied pressure.

[0045] Furthermore, if the cooling rate needs to be increased so that the line showing the temperature change during linear friction welding does not intersect with the curve showing the boundary of the intergranular corrosion region, it is preferable to increase the frequency and / or amplitude of the linear friction welding. Increasing the frequency and / or amplitude increases the heating rate and shortens the welding time. As a result, the temperature rise near the joint due to heat conduction from the joining surface (friction surface) can be suppressed, and the cooling rate can be increased.

[0046] Furthermore, after the third step, a sensitization behavior evaluation step is provided in which a corrosion test is performed on the cross section of the obtained joint to confirm the presence or absence of sensitization, and if intergranular corrosion is recognized in the sensitization behavior evaluation step, it is preferable to change the joining conditions based on the following (1) and / or (2). (1) Increasing the bonding pressure reduces the bonding temperature. (2) Increasing the frequency and / or amplitude increases the cooling rate after the joining temperature is reached.

[0047] Since the temperature history during linear friction welding can be controlled by the welding pressure, frequency, and amplitude, a sensitization behavior evaluation process is provided in which the presence or absence of sensitization is confirmed by a corrosion test on the cross section of the weld, and if sensitization is detected, the welding temperature (maximum temperature reached) is lowered and / or the cooling rate is increased, thereby ensuring the production of a weld that is free of sensitization. Here, the linear friction welding conditions can be changed multiple times based on the sensitization behavior evaluation process until sensitization is no longer observed.

[0048] (2) Linear friction joint 4 is a schematic cross-sectional view showing an example of a linear friction-welded joint of the present invention. A linear friction-welded joint 10 is formed by linearly friction welding one member 2 to another member 4, and at least one of the one member 2 and the other member 4 is made of stainless steel.

[0049] The greatest feature of the linear friction welded joint 10 is that no sensitization is observed in the linear friction welded portion 12 of the stainless steel material when evaluated using JIS-G0571 (oxalic acid etching test method for stainless steel).

[0050] 4 is a butt joint, the joint shape is not limited to this and various conventionally known joint shapes such as a cross joint or a lap joint can be used. The size and shape of the workpieces are also not particularly limited as long as they do not impair the effects of the present invention.

[0051] (3) Jointed structure The welded structure of the present invention is a welded structure having a linear friction welded joint 10, and because it combines excellent corrosion resistance and mechanical properties, it can be suitably used in applications requiring high reliability in corrosive environments.

[0052] The bonded structure of the present invention is not particularly limited as long as the effects of the present invention are not impaired, and can be any of various conventionally known bonded structures that can use various stainless steel materials. Examples of such bonded structures include automobile parts, railway vehicle parts, ship parts, aircraft parts, kitchenware, architectural structures, mechanical structural parts, medical equipment and devices, and chemical industry facility parts.

[0053] Representative embodiments of the present invention have been described above, but the present invention is not limited to these, and various design modifications are possible, all of which are included in the technical scope of the present invention. [Example]

[0054] Example 1 Ferritic stainless steel (SUS430), which is extremely difficult to prevent sensitization at the joint, was butted together at the end faces of 5mm x 25mm and subjected to linear friction welding.

[0055] Based on the graph of the temperature dependence of the strength of SUS430 shown in Figure 3, the joining pressure was set to 200 MPa so that the joining temperature (maximum temperature reached at the joining portion) would be approximately 600°C. This joining pressure was applied in all of the first to third steps shown in Figure 1. The frequency was 15 Hz and the amplitude was 2 mm. A thermocouple was used to measure the temperature history during linear friction joining in the immediate vicinity of the joining interface, and the maximum temperature reached was 600°C. The joining time was 1.3 seconds.

[0056] Figure 5 shows a cross-sectional macrophotograph of the resulting joint, which shows that a good, defect-free joint has been formed. Furthermore, to confirm the presence or absence of sensitization at the joint, an evaluation was carried out using JIS-G0571 (oxalic acid etching test method for stainless steel). Figure 6 shows optical microscope images of the joint before and after oxalic acid electrolytic etching. Absolutely no intergranular corrosion due to etching was observed at the joint, confirming that sensitization had been completely suppressed.

[0057] <Example 2> The materials to be welded were ferritic stainless steel (SUS430LX), and the ferritic stainless steel materials were butted together at their 5 mm x 25 mm end faces and subjected to linear friction welding, in the same manner as in Example 1. The maximum temperature of the welded joint was 600°C, and the welding time was 1.4 seconds.

[0058] A cross-sectional macrophotograph of the resulting joint is shown in Figure 7, and it can be seen that a good joint without defects was formed. Furthermore, to check for the presence or absence of sensitization in the joint, oxalic acid electrolytic etching was performed in the same manner as in Example 1. Optical microscope photographs of the joint before and after oxalic acid electrolytic etching are shown in Figure 8. No intergranular corrosion due to etching was observed in the joint, confirming that sensitization had been completely suppressed.

[0059] The relationship between the temperature history during welding and the TTS curves of the ferritic stainless steel material in Examples 1 and 2 is shown in Figure 9. The nose end of the intergranular corrosion region of the ferritic stainless steel material is located at a position on the vertical axis at 600°C and on the horizontal axis at 20 to 30 seconds. In contrast, the maximum temperature reached during linear friction welding is 600°C, and the welding time is less than 1.5 seconds, so the line showing the temperature change during linear friction welding and the curve showing the boundary of the intergranular corrosion region are reliably prevented from forming an intersection. [Explanation of symbols]

[0060] 2. One of the members, 4. The other member, 6... bonded interface, 8. Bali, 10. Linear friction welded joints, 12...Linear friction joint.

Claims

1. a first step of bringing one member into contact with another member to form a joining interface; a second step of repeatedly sliding the one member and the other member on the same trajectory while applying pressure substantially perpendicular to the interface to be joined, thereby removing burrs from the interface to be joined; a third step of stopping the sliding and forming a joining surface, At least one of the one member and the other member is made of stainless steel, The pressure is set to be equal to or greater than the yield stress and equal to or less than the tensile strength of the stainless steel material at a desired joining temperature; controlling the temperature history during bonding by the pressure and the frequency and / or amplitude of the sliding; The temperature during the joining is kept out of the intergranular corrosion region of the TTS (Time-Temperature-Sensitization) curve obtained by a Strauss test (sulfuric acid / copper sulfate corrosion test) of the stainless steel material; A linear friction joining method for stainless steel materials, characterized by:

2. The bonding temperature is set to 600°C or less.

2. The method for linear friction joining of stainless steel members according to claim 1, wherein

3. The stainless steel material is a ferritic stainless steel material; 3. The method for linear friction joining of stainless steel materials according to claim 1 or 2, characterized in that:

4. a sensitization behavior evaluation step of conducting a corrosion test on the cross section of the obtained joint to confirm whether or not sensitization has occurred; If intergranular corrosion is observed in the sensitization behavior evaluation step, changing the joining conditions based on the following (1) and / or (2):

4. The method for linear friction joining of stainless steel materials according to claim 1, wherein (1) The increase in pressure reduces the bonding temperature. (2) Increasing the frequency and / or amplitude increases the cooling rate after the bonding temperature is reached.

5. A linear friction welded portion is formed by joining one member and another member together via a linear friction welded interface, At least one of the one member and the other member is made of stainless steel, In an evaluation using JIS-G0571 (oxalic acid etching test method for stainless steel), no sensitization is observed in the stainless steel material of the linear friction welded portion. A linear friction welded joint characterized by:

6. A welded structure having the linear friction welded joint according to claim 5.

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