A rail transition welding material resistant to stress corrosion damage, a preparation method and its application in rail welding

Abstract

The invention discloses a track transition welding material resistant to stress corrosion damage, a preparation method and an application thereof in track welding, and belongs to the technical field of welding materials. The track transition welding material resistant to stress corrosion damage has the following components, by mass percentage: C 0.02-0.04%, Si≤0.20%, Mn6.5-7.0%, Ni 11.0-11.5%, Cr 17.6-18.0%, Mo 2.1-2.4%, N 0.02-0.04%, Nb0.05-0.15%, V 0.05-0.15%, P≤0.015%, S≤0.010%, and the balance is Fe. The track transition welding material of the invention has excellent strength and plastic toughness, a small tendency to form carbides, a fine grain size, and can still ensure that there is no carbide precipitation at the grain boundary under the influence of flash welding heat, and resists stress corrosion cracking.

Description

Technical Field

[0001] The invention relates to the technical field of welding materials, and in particular to a rail transition welding material capable of resisting stress corrosion damage, a preparation method and application thereof in rail welding. Background Art

[0002] Rail transition welding materials are the key to achieving high-quality welding of high-carbon steel rails and high-manganese steel frogs. In order to improve the service safety and stability of high manganese steel frog welding joints, many explorations have been carried out at home and abroad on track transition welding materials and flash welding processes. For example, CrMnNiMo austenite-ferrite dual-phase steel is used as the medium material. The high manganese steel frog and carbon steel rail are connected together by flash welding, which can solve the problem of stress corrosion cracking. However, the morphology of ferrite in the dual-phase steel is significantly affected by deformation and is difficult to control. Under the action of welding residual stress, cracks are easily extended along the dual-phase interface, causing failure of the welded joint. By using low-carbon chromium-nickel austenitic steel stabilized with niobium or / and titanium as the connecting material, the formation of grain boundary carbides can be effectively prevented, thereby inhibiting stress corrosion cracking, but it is easy to cause the problem of low strength and also easy to cause fracture failure of the welding material. When high-strength single-phase austenitic steel with a high carbon content is used as the connecting material, although it can ensure high strength performance, the carbon content is high, and carbides are easily generated at the austenite grain boundary under the influence of welding heat, which is very likely to cause stress corrosion cracking in a corrosive environment. It can be seen that the current intermediate welding materials have problems such as low strength and easy fracture, high carbon content and easy precipitation of grain boundary carbides, and cannot be well used in high axle weight, high humidity and severe corrosion environment. Therefore, it is urgent to develop an intermediate welding material with stable structure, moderate strength and resistance to stress corrosion damage. Summary of the invention

[0003] The purpose of the present invention is to provide a rail transition welding material resistant to stress corrosion damage, a preparation method and application thereof in rail welding, so as to solve the problems existing in the above-mentioned prior art.

[0004] To achieve the above object, the present invention provides the following solutions:

[0005] One of the technical solutions of the present invention: a rail transition welding material for resisting stress corrosion damage, the components of which are as follows, in mass percentage: C 0.02-0.04%, Si≤0.20%, Mn 6.5-7.0%, Ni 11.0-11.5%, Cr17.6-18.0%, Mo 2.1-2.4%, N 0.02-0.04%, Nb 0.05-0.15%, V 0.05-0.15%, P≤0.015%, S≤0.010%, and the balance is Fe.

[0006] The second technical solution of the present invention is a method for preparing the above-mentioned track transition welding material, comprising the following steps:

[0007] The component raw materials are mixed, smelted and then cast to obtain a steel ingot;

[0008] The steel ingot is homogenized and then pre-forged to obtain a forging blank; the forging blank is rapidly water-cooled after being thermally deformed to obtain the track transition welding material.

[0009] Furthermore, the temperature of the homogenization treatment is 1200° C., and the insulation time is 10 to 13 hours.

[0010] Furthermore, the forging ratio of the pre-forging is greater than 4.

[0011] Furthermore, the thermal deformation includes hot extrusion or hot rolling.

[0012] Furthermore, the temperature of the hot extrusion is 1050-1120°C.

[0013] Furthermore, the initial rolling temperature of the hot rolling is 1000-1120°C, and the final rolling temperature is not less than 1000°C.

[0014] Furthermore, the forging blank obtained by the forging is a cylindrical extruded ingot or a square elongated forging blank;

[0015] When the forging blank is a cylindrical extruded ingot, hot deformation is performed by hot extrusion; when the forging blank is a square elongated forging blank, hot deformation is performed by hot rolling.

[0016] Single-phase austenite short rails with a grain size of 8 to 9 and no carbides at the grain boundaries were obtained by both hot extrusion and hot rolling.

[0017] The third technical solution of the present invention: an application of the above-mentioned orbital transition welding material in orbital welding.

[0018] The present invention discloses the following technical effects:

[0019] (1) The rail transition welding material of the present invention adopts a low-carbon design and utilizes a carbon-nitrogen synergistic strengthening method to strengthen austenitic stainless steel. At the same time, the total amount of carbon and nitrogen is not greater than 0.08, which reduces the tendency of carbide formation while exerting a strengthening effect.

[0020] (2) The present invention ensures corrosion resistance in a corrosive environment by controlling the chromium content in the track transition welding material (appropriately increasing the chromium content in the material); and reduces the manufacturing cost of the material while ensuring a single-phase austenite structure by controlling the manganese content (increasing the manganese content in the material) and replacing nickel with manganese.

[0021] (3) The present invention reduces the temperature of thermal deformation by adjusting the composition, and suppresses the static recrystallization growth process after forming by rapid water cooling during thermal deformation, thereby obtaining finer austenite grains.

[0022] The lower the heat deformation temperature, the slower the growth rate of recrystallized grains, and it is easier to obtain fine grains. At present, the extrusion temperature (heat deformation temperature) is generally 1150-1200°C, and the extrusion temperature cannot be further reduced, which is easy to cause accidents. The present invention reduces the C content by adjusting the component types and component amounts. The lower the C content, the lower the high-temperature strength of the steel. When the extrusion force or rolling force is constant, heat deformation can be achieved at a lower temperature, thereby achieving grain refinement.

[0023] (4) The rail transition welding material of the present invention has both excellent strength and plastic toughness.

[0024] (5) The track transition welding material of the present invention has a small tendency to form carbides and a fine grain size. Under the influence of flash welding heat, it can still ensure that there is no carbide precipitation at the grain boundary and resist stress corrosion cracking. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0026] Figure 1 This is a metallographic photograph of the track transition welding material prepared in Example 1 of the present invention;

[0027] Figure 2 This is a metallographic photograph of the track transition welding material prepared in Example 2 of the present invention;

[0028] Figure 3 This is a metallographic photograph of the track transition welding material prepared in Example 3 of the present invention;

[0029] Figure 4 This is a metallographic photograph of the track transition welding material prepared in Comparative Example 1 of the present invention;

[0030] Figure 5 This is a metallographic photograph of the orbital transition welding material substrate after flash welding using the orbital transition welding material prepared in Example 1 of the present invention;

[0031] Figure 6 This is a metallographic photograph of the orbital transition welding material substrate after flash welding using the orbital transition welding material prepared in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0032] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0033] It should be understood that the terms described in the present invention are only for describing special embodiments and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0034] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0035] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to the skilled artisan. The present invention description and examples are exemplary only.

[0036] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0037] Example 1

[0038] A method for preparing a track transition welding material that resists stress corrosion damage:

[0039] (1) Rail transition welding material, the composition, in mass percentage, is as follows: C 0.02%, Si 0.10%, Mn 6.8%, Ni 11.5%, Cr 17.7%, Mo 2.1%, N 0.04%, Nb 0.09%, V 0.09%, P 0.013%, S 0.006%, and the balance is Fe.

[0040] (2) The component raw materials are smelted using an electric arc furnace + a refining furnace to obtain molten steel, which is then cast to obtain a steel ingot.

[0041] (3) The steel ingot is homogenized at 1200°C for 11 hours to obtain a homogenized steel ingot.

[0042] (4) The homogenized steel ingot is pre-forged (roughening and drawing process, forging ratio is 6) to obtain a cylindrical extruded ingot, which is a cylindrical ingot with a diameter of 365 mm and a length of 650 mm.

[0043] (5) The cylindrical extruded ingot is heated to 1100°C (uniform temperature) by induction heating, and then the extruded ingot is extruded into a UIC54 short rail by a horizontal hot extruder. After the extrusion process is completed, it is quickly cooled in water (the water temperature is 1080°C) to obtain the rail transition welding material.

[0044] The structure of the rail head of the rail transition welding material prepared in this embodiment and the performance of the rail transition welding material were tested, and the results are shown in Figure 1 and Table 1.

[0045] Table 1 Mechanical properties of rail transition welding materials

[0046] state Tensile strength / MPa Elongation / % Impact energy / J Hardness / HB Example 1 635 72 348 172 Standard requirements ≥580 ≥40 ≥160 ≥160

[0047] from Figure 1 As can be seen from Table 1, the orbital transition welding material prepared in this embodiment is a single-phase austenite structure, with an average grain size of 18.5 μm, a grain size grade of 8.5, and various mechanical performance indicators are far higher than the standard requirements of transition welding materials.

[0048] Example 2

[0049] A method for preparing a track transition welding material that resists stress corrosion damage:

[0050] (1) Orbital transition welding material, the composition, in mass percentage, is as follows: C 0.04%, Si 0.13%, Mn 6.6%, Ni 11.1%, Cr 17.9%, Mo 2.3%, N 0.03%, Nb 0.11%, V 0.11%, P 0.012%, S 0.006%, and the balance is Fe.

[0051] (2) The component raw materials are smelted using an electric arc furnace + a refining furnace to obtain molten steel, which is then cast to obtain a steel ingot.

[0052] (3) The steel ingot is homogenized at 1200°C for 11 hours to obtain a homogenized steel ingot.

[0053] (4) The homogenized steel ingot is pre-forged (roughening and drawing process, forging ratio is 6) to obtain a square slender forging blank.

[0054] (5) The square slender forging billet is heated to 1105°C (average temperature) using a walking-beam heating furnace, and then rolled using a rail forming rolling mill. After three passes of rolling, the forging billet is formed into a UIC54 short rail with an initial rolling temperature of 1080°C and a final rolling temperature of 1035°C. After rolling, it is quickly cooled in water to obtain a rail transition welding material.

[0055] The structure of the rail head of the rail transition welding material prepared in this embodiment and the performance of the rail transition welding material were tested, and the results are shown in Figure 2 and Table 2.

[0056] Table 2 Mechanical properties of rail transition welding materials

[0057] state Tensile strength / MPa Elongation / % Impact energy / J Hardness / HB Example 1 642 70 328 175 Standard requirements ≥580 ≥40 ≥160 ≥160

[0058] from Figure 2 As can be seen from Table 2, the orbital transition welding material prepared in this embodiment is a single-phase austenite structure, with an average grain size of 15.5 μm, a grain size grade of 9.0, and various mechanical properties are far higher than the standard requirements of transition welding materials.

[0059] Example 3

[0060] A method for preparing a track transition welding material that resists stress corrosion damage:

[0061] (1) Rail transition welding material, in terms of mass percentage, has the following composition: C 0.03%, Si 0.13%, Mn 6.8%, Ni 11.2%, Cr 17.9%, Mo 2.4%, N 0.03%, Nb 0.13%, V 0.13%, P 0.011%, S 0.008%, and the balance is Fe.

[0062] (2) The component raw materials are smelted using an electric arc furnace + a refining furnace to obtain molten steel, which is then cast to obtain a steel ingot.

[0063] (3) The steel ingot is homogenized at 1200°C for 11 hours to obtain a homogenized steel ingot.

[0064] (4) The homogenized steel ingot is pre-forged (roughening and drawing process, forging ratio is 6) to obtain a cylindrical extruded ingot, which is a cylindrical ingot with a diameter of 365 mm and a length of 650 mm.

[0065] (5) The cylindrical extruded ingot is heated to 1080°C (average temperature) by induction heating, and then extruded into a UIC54 short rail by a horizontal hot extruder. After the extrusion process is completed, it is quickly cooled in water (the water temperature is 1069°C) to obtain the rail transition welding material.

[0066] The structure of the rail head of the rail transition welding material prepared in this embodiment and the performance of the rail transition welding material were tested, and the results are shown in Figure 3 and Table 3.

[0067] Table 3 Mechanical properties of orbital transition welding materials

[0068] state Tensile strength / MPa Elongation / % Impact energy / J Hardness / HB Example 3 641 69 337 176 Standard requirements ≥580 ≥40 ≥160 ≥160

[0069] from Figure 3 As can be seen from Table 3, the orbital transition welding material prepared in this embodiment is a single-phase austenite structure, with an average grain size of 16.5 μm, a grain size grade of 8.5, and various mechanical properties are far higher than the standard requirements of transition welding materials.

[0070] Comparative Example 1

[0071] (1) Rail transition welding material, in terms of mass percentage, has the following composition: C 0.12%, Si 0.10%, Mn 6.9%, Ni 11.8%, Cr 17.5%, Mo 2.3%, P 0.012%, S 0.008%, and the balance is Fe.

[0072] (2) The component raw materials are smelted using an electric arc furnace + a refining furnace to obtain molten steel, which is then cast to obtain a steel ingot.

[0073] (3) The steel ingot is homogenized at 1200°C for 11 hours to obtain a homogenized steel ingot.

[0074] (4) The homogenized steel ingot is pre-forged (roughening and drawing process, forging ratio is 6) to obtain a cylindrical extruded ingot, which is a cylindrical ingot with a diameter of 365 mm and a length of 650 mm.

[0075] (5) The cylindrical extruded ingot is heated to 1150°C (average temperature) by induction heating, and then the extruded ingot is extruded into a UIC54 short rail using a horizontal hot extruder. After the extrusion process is completed, it is quickly cooled in water (the water temperature is 1136°C) to obtain the rail transition welding material.

[0076] The structure of the rail head of the rail transition welding material prepared in this comparative example and the performance of the rail transition welding material were tested, and the results are shown in Figure 4 and Table 4.

[0077] Table 4 Mechanical properties of orbital transition welding materials

[0078] state Tensile strength / MPa Elongation / % Impact energy / J Hardness / HB Comparative Example 1 642 62 246 180 Standard requirements ≥580 ≥40 ≥160 ≥160

[0079] It can be seen from Table 4 that the performance indicators of the transition welding material in this comparative example can meet the standard requirements, but compared with the embodiment, the plasticity and toughness are significantly lower.

[0080] from Figure 4 It can be seen that there are some carbides precipitated on the grain boundaries of the transition welding material, the average grain size is 35μm, and the grain size grade is 6.5.

[0081] Effect Example 1

[0082] The rail transition welding materials prepared in Example 1 and Comparative Example 1 were used as transition welding materials for high manganese steel frogs and high carbon steel rails, and flash welding was performed. The microstructure of the welded material was then observed. The results were as follows: Figure 5 and Figure 6 .

[0083] from Figure 5 and Figure 6 It can be seen that under the action of welding thermal cycle, the grain boundary of the track transition welding material prepared in Example 1 of the present invention is still very clean, and no carbide is produced, thereby avoiding the stress corrosion cracking problem caused by chromium depletion near the grain boundary. However, the transition welding material prepared in Comparative Example 1 produces a more serious grain boundary carbide problem under the action of welding thermal cycle.

[0084] The transition welding materials after welding of Example 1 and Comparative Example 1 were subjected to a slow strain rate tensile test under 3.5wt.% NaCl conditions. The results are shown in Table 5.

[0085] It can be seen from Table 5 that the material of Example 1 has higher strength and plasticity and has a more excellent ability to resist stress corrosion cracking.

[0086] Table 5 Slow strain rate tensile properties of transition welding materials after welding thermal cycle

[0087] state Tensile strength / MPa Elongation / % Example 1 359 27 Comparative Example 1 263 16

[0088] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A rail transition welding material resistant to stress corrosion damage, characterized in that: In terms of mass percentage, the components are as follows: C 0.02-0.04%, Si≤0.20%, Mn 6.5-7.0%, Ni 11.0-11.5%, Cr17.6-18.0%, Mo2.1-2.4%, N 0.02-0.04%, Nb 0.05-0.15%, V 0.05-0.15%, P≤0.015%, S≤0.010%, and the balance is Fe.

2. A method for preparing the track transition welding material according to claim 1, characterized in that: The following steps are involved: The component raw materials are mixed, smelted and then cast to obtain a steel ingot; The steel ingot is homogenized and then pre-forged to obtain a forging blank; the forging blank is rapidly water-cooled after being thermally deformed to obtain the track transition welding material.

3. The preparation method according to claim 2, characterized in that: The temperature of the homogenization treatment is 1200° C., and the insulation time is 10 to 13 hours.

4. The preparation method according to claim 2, characterized in that: The forging ratio of the pre-forging is greater than 4.

5. The preparation method according to claim 2, characterized in that: The thermal deformation includes hot extrusion or hot rolling.

6. The preparation method according to claim 5, characterized in that: The temperature of the hot extrusion is 1050-1120°C.

7. The preparation method according to claim 5, characterized in that: The initial rolling temperature of the hot rolling is 1000-1120°C, and the final rolling temperature is not less than 1000°C.

8. Use of the orbital transition welding material according to claim 1 in orbital welding.

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