Method for rapid tlp diffusion bonding of steel using a non-metallic interlayer

Abstract

A rapid TLP diffusion welding method for steel using a non-metallic interlayer includes: grinding and wiping to clean the surface of the steel to be welded; pre-placing a graphite interlayer between the cleaned interfaces of the steel to be welded and applying pressure to ensure close contact between the interfaces of the first steel to be welded, the graphite interlayer, and the second steel to be welded; heating the interfaces at a temperature above the Fe-C eutectic temperature and below the melting point of the steel to be welded; during heating, an inert gas or CO2 gas can be used to form a locally sealed cavity, or a protective method can be used by wrapping with QJ102 flux powder or heat-resistant material; based on the Fe-C eutectic reaction, the Fe-C eutectic liquid phase is extruded and isothermally solidified until the carbon content in the weld is reduced from 100% before welding to the same level as the higher carbon content in the base material of the steel; grinding away the extruded Fe-C eutectic solidified weld beads to make the appearance smooth; this invention can be used for welding and repairing the same type of steel, and can also be used for large-area composite, repair, and welding between various types of steel with different carbon contents.

Description

Technical Field

[0001] This invention relates to the field of welding technology, and specifically to a rapid TLP diffusion welding method for steel with a small atomic radius non-metallic interlayer when any base material is medium carbon steel or high carbon steel with poor arc welding weldability. Background Technology

[0002] Steels with high carbon content or high carbon equivalent, including medium carbon steel, medium carbon alloy steel, cast iron, cast steel, high carbon steel, and some low alloy high-strength steels with high carbon equivalent, have poor weldability for arc welding. This is mainly manifested in the fact that both the weld (WM) and the heat-affected zone (HAZ) are prone to hardened structures and cold cracks. Even when using low-matching welding wire, i.e., the strength of the welding wire is lower than that of the base metal, the risk of cold cracking in the HAZ due to hardened structures, thermal stress, and diffusing hydrogen is still very high. Taking 35 steel and 45 steel as examples, both cold cracking and hot cracking are prone to occur when using high-efficiency CO2 welding (Mikami Akihiro: Q&A on welding, Welding Technology, 2001, 49(7):93-96). As a countermeasure against cold cracking, although CO2 welding has the ability to suppress hydrogen dissolution into the weld than shielded metal arc welding, preheating and post-heating are still required. Hot cracking occurs because CO2 welding causes significant melting of the base metal, leading to carbon accumulation towards the weld center. This carbon is distributed along the central solidification line and easily forms hot cracks under shrinkage stress. This type of hot cracking cannot be prevented by preheating or post-heating. As a countermeasure to hot cracking, to reduce the penetration and width of the base metal, low-current, short-arc welding should be used. This requires a complex welding process involving preheating, low-current, short-arc welding, and post-heating, as well as multi-layer, multi-pass welding. It is evident that for arc welding applications where one of the base materials is medium-carbon steel or high-carbon steel with poor weldability, including medium-carbon steel / medium-carbon steel arc welding, high-carbon steel / high-carbon steel arc welding of the same type of steel, and low-carbon steel / medium-carbon steel and low-carbon steel / high-carbon steel dissimilar steel arc welding, especially for large-area welding of medium-carbon steel, such as the arc welding repair of corroded and thinned medium-carbon steel claws (diameter range of 50mm to 170mm) used in electrolytic aluminum, there are problems such as high risk of cold cracking, very low efficiency (preheating + slow cooling), arc spatter, and extremely hot operating conditions. There is an urgent need to find new, efficient and simple welding methods to replace arc welding.

[0003] On the other hand, to improve the surface hardness and wear resistance of low-carbon steel, it is often necessary to first perform carburizing at high temperatures in the austenitic state for several hours, followed by quenching or quenching and tempering. The carburizing process, a critical control step, suffers from high energy consumption, long processing time, and low efficiency. To eliminate the energy-intensive and time-consuming carburizing step in the surface hardening process of low-carbon steel, commercially available medium-carbon steel with good wear resistance and high hardness is used as the outer surface material. This involves directly combining commercially available medium-carbon steel as the cladding material with low-carbon steel as the base material, and then using welding technology to create a layered composite material of "low-carbon steel / medium-carbon steel." This quickly solves the problems of low surface hardness and poor wear resistance in low-carbon steel.

[0004] The fabrication of layered composite materials is essentially a lap welding process between dissimilar base materials, requiring welding techniques suitable for large-area lap welding. Arc welding, due to its poor accessibility and low efficiency, is only suitable for butt joining and not for large-area lap joining, thus making it unsuitable for composite material fabrication. Arc welding is even less suitable for composite plates where one of the base materials is medium carbon steel. Regarding large-area composite welding techniques for low-carbon / medium carbon steel, available welding methods include brazing (besides fusion welding) and solid-state welding (diffusion welding, explosive welding, rolling welding, etc.).

[0005] It is evident that both the welding of medium carbon steel / medium carbon steel and the preparation of composite plates of low carbon steel / medium carbon steel require high-strength and high-efficiency welding methods other than fusion welding. These high-strength and high-efficiency welding methods, besides fusion welding, mainly include three solid-state welding methods: explosive welding, rolling welding, and transition liquid phase bonding (TLP). Among these, the first two (explosive welding and rolling welding) are currently the main methods used in the industry for preparing large-area composite plates. Explosive welding composites are subject to some limitations in terms of workpiece size and shape: due to the edge effect of explosive welding, the dimensional accuracy of the edges and the interface bonding are difficult to guarantee, making it unsuitable for composites of thin, long, narrow, and thin parts; unsuitable for excessively thin substrates or substrate / cladding thickness ratios that are too small (resulting in poorer relative deformation of the interface between the substrate and cladding, affecting interface film removal); unsuitable for composites of columnar workpiece end faces with other columnar workpiece end faces or circular pieces; and the poor plastic deformation capacity of medium and high carbon steels themselves poses a risk of cracking due to work hardening.

[0006] The rolling-welding composite technology suffers from high energy consumption and large investment.

[0007] The Transient Liquid Phase Diffusion (TLP) welding method was initially developed in the United States to eliminate hot cracking in the fusion welding of Ni-based high-temperature alloys. The Transient Liquid Phase Diffusion (TLP) welding technology for steel was introduced in the 1990s (Zhang Guifeng, Zhang Jianxun. Instantaneous liquid phase diffusion welding technology for pipes with amorphous metal foil as intermediate layer. Welding, 2002, (2): 35-37). It was initially developed by Yuichi Komizo of Sumitomo Metal Industries, Ltd. of Japan. This technology won the "Tanaka Kamehito Award" from the Japan Welding Society (Yuichi Komizo, Fumito Kashimoto. High-speed joining of steel pipes. Welding Technology, 1990, 38(7): 72-75). Its advantages are that it eliminates the need for beveling, especially the short welding time (2-3 min; commonly used standard 1200℃-3 min), high efficiency, and satisfactory joint tensile strength and bending performance. Japan has replaced manual shielded metal arc welding with TLP diffusion welding technology in the maintenance of boiler steel pipes in power plants, which can significantly save manpower and time costs.

[0008] Intermediate layers used in TLP diffusion welding of steel at home and abroad can be divided into two categories: one is commercially available Ni-based intermediate layers, such as BNi-2 of Ni-Si-B system and MBF-60 of Ni-P system; the other is various Fe-based intermediate layers developed by users themselves. There are two categories of reported Fe-based intermediate layers: one is the patent application document with publication number CN1394978A, which discloses an iron-based amorphous intermediate layer alloy for instantaneous liquid phase diffusion welding, whose main components are 46Fe-40Ni-5.5Cr-5.5Si-3B, with a melting range of 1050~1150℃; the other is Fe-33Ni-3Cr-5Si-3B, with a melting range of 1190-1120℃ (Wang Xuegang, Yan Qian, Li Xingeng. Instantaneous liquid phase diffusion bonding of 45MnMoB geological drill pipe using dual-temperature process. Journal of Welding, 2007, 28(5):53-56). ; Subsequently, there were reports by Chen Sijie on Fe-9Si-13B and Fe-46Ni-5Cr-7Si-7B intermediate layers (Chen Sijie, Jing Xiaotian, Li Xingeng. Microstructure and properties of T91 steel pipes with different intermediate layers TLP connection. Journal of Welding, 2006, 27(2):77-80), and reports by Yu Jianrong et al. on Fe-30Ni-5Si-6B-5Cr-1Mn, with a melting range of 1100~1130℃ (Wang Lei, Yu Jianrong, Yue Long. Study on microstructure and mechanical properties of instantaneous liquid phase diffusion welded joint of X70 pipeline steel. Electric Welding Machine, 2005, 107-109). Second, there is the high-Cr Fe-based brazing alloy developed by Tokyo Brazing Alloy Co., Ltd. in Japan: Fe-42Ni-20Cr-(10-12)(Si,B)(Toshi-Taka Ikeshoji, Tatsuya Tokunaga, Akio Suzumura, Takahisa Yamazaki. Brazing of C / C composite and Ni-based alloy using interlayer. Proceeding of IJST, 2013, 49-50, Osaka, Japan.).

[0009] In theory, given a sufficiently long holding time, both commercially available Ni-based and reported Fe-based interlayers used in TLP diffusion welding of steel can ultimately achieve isothermal solidification, resulting in a solid solution weld. However, existing Ni-based or Fe-based interlayers exhibit high brittleness due to their high content of melting point degrading elements Si and B (especially Si with large atomic radii, which tends to remain in the weld center due to slow diffusion). Therefore, the disadvantages of existing TLP diffusion welding of steel lie in its sensitivity to gaps and stringent requirements for end-face flatness and the perpendicularity of assembly and pressurization, affecting its practicality. Its high efficiency can only be realized under the premise of flat end faces and straight assembly. Otherwise, if the local gap is too large, incomplete isothermal solidification will occur in the larger gap area, resulting in residual brittle phases, poor joint plasticity, and susceptibility to brittle fracture. Summary of the Invention

[0010] To overcome the shortcomings of the aforementioned low-carbon steel carburizing process, medium-carbon steel arc welding, Fe-based intermediate layer (TLP) for steel, and Ni-based intermediate layer (TLP) for steel, this invention proposes a rapid TLP diffusion welding method for steel using a non-metallic intermediate layer with a small atomic radius. Graphite is used as the intermediate layer, and its rapid and significant dissolution of steel facilitates quick interface film removal and densification. Simultaneously, leveraging the small atomic radius, rapid inter-aperture diffusion, and short isothermal solidification time of carbon atoms, this method solves the problems of strict requirements for end-face surface finish preparation, sensitivity to assembly gaps, slow diffusion, and high brittleness associated with existing TLP diffusion welding methods using Ni-based and Fe-based intermediate layers. This method features simple processing, rapid and efficient operation, and the ability to complete welding between the same type of steel and composite welding of dissimilar low / medium carbon steels within minutes, achieving metallurgical bonding. It also has low requirements for steel surface processing and assembly precision, strong practicality on construction sites, and wide applicability.

[0011] A rapid TLP diffusion welding method for steel using a non-metallic interlayer includes the following steps:

[0012] Step 1: Grind and wipe to clean the surfaces of the first steel material 1 and the second steel material 2 to be welded. Place the graphite intermediate layer 3 between the cleaned interfaces of the first steel material 1 and the second steel material 2 to be welded, and apply pressure of 0.2 to 3 MPa to ensure close contact between the interfaces of the first steel material 1, the graphite intermediate layer 3, and the second steel material 2 to be welded.

[0013] Step 2: Heat the interface between the graphite intermediate layer 3 and the first steel material to be welded 1 and the second steel material to be welded 2. The heating temperature is above the Fe-C eutectic temperature and below the melting point of the first steel material to be welded 1 and the second steel material to be welded 2, i.e., between 1170-1300℃. During heating, an inert gas or CO2 gas can be used to form a locally sealed cavity, or a protective method can be adopted by wrapping with flux QJ102 powder or heat-resistant material.

[0014] Step 3: After the rapid reaction in Step 2, the Fe-C eutectic liquid phase is extruded and kept at a temperature for 3-20 minutes to achieve isothermal solidification until the carbon content in the weld is reduced from 100% before welding to the same level as the higher carbon content in either the first steel to be welded 1 or the second steel to be welded 2.

[0015] Step 4: Grind away the Fe-C eutectic solidified weld beads that have been extruded from the weld seam to make the appearance smooth.

[0016] In step 1, the graphite intermediate layer 3 can be graphite paper or graphite powder, or a mixture of graphite powder, metallic iron powder and flux powder, a mixture of graphite powder, metallic iron powder, wear-resistant ceramic powder and flux powder, or a mixture of graphite powder, metallic iron powder and alloy powder, or a mixture of graphite powder, metallic iron powder and ceramic powder. The mass ratio of graphite powder to metallic iron powder is maintained at 0.05 to 0.1, and the remaining wear-resistant ceramic powder and metallic powder can be added in any amount.

[0017] In step 1, the thickness of the graphite intermediate layer 3 can be adjusted according to the gap size to ensure that the steel and graphite can be in close contact.

[0018] In step 2, the heating method can be selected from induction heating, furnace heating, or graphite block heating element heating.

[0019] In step 3, the isothermal solidification process can be omitted for cast iron steel to be welded, base materials that bear static pressure loads and have low plasticity and toughness.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] (1) The transition liquid phase diffusion welding (TLP) method, which uses non-metallic graphite paper and graphite + metal mixed powder as the intermediate layer, replaces the arc welding method, which has a large amount of work for groove filling and has spatter and arc light. It has strong adaptability to gap size and can complete the efficient composite welding between low carbon steel and other dissimilar steels in 3 to 10 minutes. It has the advantages of high welding efficiency, excellent film removal and wettability, low requirements for end face preparation and convenient cooling rate control. It can solve the problem of strong hardening and cold cracking tendency in arc welding of medium carbon steel and high carbon steel.

[0022] (2) Using non-metallic graphite as an intermediate layer, the Fe-C eutectic liquid phase is generated through a transition liquid phase diffusion welding method. This process is easy to achieve and has good repeatability. The Fe-C eutectic liquid phase is generated quickly and fills all interfacial gaps. After the oxide film is extruded and carried away by the Fe-C eutectic liquid phase, the film removal, wetting and interface densification are quickly achieved. Then, taking advantage of the small radius of carbon atoms, their rapid diffusion into the base material and short time required for isothermal solidification, the carbon content in the weld is reduced to the carbon content level of one of the base materials after isothermal solidification. This quickly solves a series of problems such as film removal, wetting, interface densification, excessive carbon content in the weld, weld embrittlement, and joint embrittlement. It also reduces the stringent requirements for surface finish and assembly perpendicularity, making it highly practical on the construction site.

[0023] (3) Compared with Fe-based interlayer, graphite interlayer is more economical than Fe-based interlayer, does not require commissioned processing, and is readily available; it significantly dissolves Fe matrix and has excellent film removal and wetting capabilities; carbon atoms, as the only melting point reducing element, diffuse faster than Si atoms, and the isothermal solidification time is shorter, which can significantly reduce the brittle phase in the weld in a short time, and the plasticity reaches a level close to that of the base material.

[0024] (4) It has a wide range of applications in various industries, including:

[0025] TLP rapid repair of medium carbon cast steel anode claws for electrolytic aluminum using a graphite interlayer; repair of high Mn cast steel tracks for vehicles; TLP technology with graphite as the interlayer for bonding medium carbon steel layers to low carbon steel surfaces, eliminating the time-consuming and energy-intensive carburizing process and improving the wear resistance of low carbon steel surfaces; TLP repair of worn steel surfaces; upgrading and replacement of agricultural machinery (welding or large-area composite of low carbon steel / high Mn steel) or fracture repair, TLP rapid repair of worn agricultural machinery; TLP butt welding of high carbon and high manganese steel rails; TLP repair of medium carbon alloy steel landing gear.

[0026] (5) Compared with commercially available Ni-based interlayers, the advantages of graphite interlayers are as follows:

[0027] Graphite interlayers are less expensive than Ni-based interlayers. Graphite interlayers exhibit more significant dissolution, superior interfacial film removal, and wetting capabilities: Utilizing the Fe-C eutectic reaction to generate a eutectic liquid phase, the steel surface is liquefied, and the eutectic liquid phase is extruded. This allows the oxide film on the hard base material surface to be easily removed with the extrusion of the liquid phase, resulting in strong dissolution of the steel matrix and excellent interfacial film removal and wetting capabilities. Furthermore, in special cases where joint pressure requirements are lower, a certain amount of residual C atoms is permissible, and even heat preservation after liquid phase extrusion is not allowed. Because the composition of the residual liquid phase is close to that of cast iron, its hardness and brittleness are lower than that of Ni-Si-B interlayers, thus allowing for a certain amount of liquid phase residue. Even with liquid phase residue, the weld structure is close to that of "cast iron," still possessing certain properties.

[0028] (6) Advantages of graphite paper interlayer material: Graphite paper is easy to pre-place and has uniform thickness; it does not oxidize and does not require polishing; graphite powder is easy to add other metal powders, suitable for large gaps and surface repair; the joint composition and structure are close to the base material: according to the TLP principle, after eutectic reaction, isothermal solidification, and composition homogenization, the joint composition and structure are close to the base material. This avoids local hardening of the welding area; online adjustment of cooling rate and structure minimizes the proportion of high-carbon martensite. Appropriate heating or setting of a cooling platform can be used during the cooling process, and the t8 / 5, t8 / 3, and t100 can be extended according to the carbon content of the steel, making online control of the structure easy.

[0029] In summary, this invention, on the one hand, replaces arc welding of medium carbon steel / medium carbon steel to eliminate the preheating and post-heating processes; on the other hand, it utilizes the composite of medium carbon steel on the surface of low carbon steel to prepare a "low carbon steel / medium carbon steel composite plate," eliminating the lengthy carburizing process required for surface hardening of low carbon steel. Employing a non-metallic interlayer graphite method, including graphite paper and graphite powder, for rapid TLP diffusion welding of steel, this invention can not only be used for welding and repairing the same type of steel, especially for welding medium carbon steel and high carbon steel, but also for large-area composite, repair, and welding of various steels with different carbon contents. The TLP diffusion welding technology for steel with non-metallic graphite as the intermediate layer proposed in this invention is suitable for various structural steels, cast steels, and cast irons with low, medium, and high carbon contents. It solves the problems of existing TLP diffusion welding of steel using Ni-based and Fe-based intermediate layers, which have strict requirements for end face surface finish preparation, sensitivity to assembly gaps (i.e., the maximum local gap exceeding the critical gap will lead to residual brittle phases, slow diffusion, and high brittleness). It has the characteristics of simple processing, fast and efficient processing, and the ability to complete the composite welding between the two in a few minutes to achieve metallurgical bonding, and has a wide range of applications. Attached Figure Description

[0030] Figure 1 This is a rod transition liquid phase diffusion welding (TLP) method with graphite paper as the intermediate layer.

[0031] Figure 2 This is a transition liquid phase diffusion welding (TLP) method for pipes with graphite paper as the intermediate layer.

[0032] Figure 3 The macroscopic morphology of the Q235 / 35 steel dissimilar steel transition liquid phase diffusion weld joint with graphite powder as the intermediate layer is shown.

[0033] Figure 4 The results show the shear test results of the Q235 / 35 steel dissimilar steel transition liquid phase diffusion weld joint with graphite powder as the intermediate layer.

[0034] Figure 5 The optical microstructure of the Q235 / 35 steel dissimilar steel transition liquid phase diffusion welded joint with graphite powder as the intermediate layer is shown in the figure. Figure 5 (a) is a macroscopic continuous shot of the connector (100×). Figure 5 (b) is a magnified photograph (500×) of a portion of the low-carbon steel base material (area b). Figure 5 (c) is a magnified (500×) photo of a portion of the interface c. Figure 5 (d) Enlarged partial photograph (200×) of medium carbon steel base material (area d).

[0035] Figure 6 The macroscopic morphology of a Q235 / 35 steel bar (Φ20mm) transition liquid phase diffusion welded joint with graphite paper as the intermediate layer.

[0036] Figure 7The location of tensile fracture of a Q235 / 35 steel bar (Φ20mm) transition liquid phase diffusion welded joint sample with graphite paper as the intermediate layer.

[0037] Figure 8 The tensile stress-strain curves of a Q235 / 35 steel bar (Φ20mm) transition liquid phase diffusion welded joint sample with graphite paper as the intermediate layer are shown. Figure 8 (a) is the tensile stress-strain curve of the joint of sample 1. Figure 8 (b) shows the tensile stress-strain curve of the joint in sample 2. Figure 8 (c) shows the tensile stress-strain curve of the joint of sample 3.

[0038] Figure 9 The macroscopic morphology of a rapid transition liquid phase diffusion welded joint of 35 steel / 35 steel plates with graphite paper as the intermediate layer.

[0039] Figure 10 The results show the shear strength test results of the rapid transition liquid phase diffusion welded joint of 35 steel / 35 steel plate with graphite paper as the intermediate layer.

[0040] Figure 11 Microscopic images of the transition liquid phase diffusion weld joint of 35 steel / 35 steel plates with graphite paper as the intermediate layer. Figure 11 (a) is a macroscopic continuous shot of the connector (100×). Figure 11 (b) is a magnified photograph (500×) of a portion of region b. Figure 11 (c) is a magnified photograph of area c (500×).

[0041] Figure 12 Macroscopic morphology of a small-diameter (Φ20mm) 35 steel / 35 steel bar transition liquid phase diffusion weld joint with graphite paper as the intermediate layer.

[0042] Figure 13 The location of macroscopic tensile fracture of a small-diameter (Φ20mm) 35 steel / 35 steel bar transition liquid phase diffusion weld joint with graphite paper as the intermediate layer.

[0043] Figure 14 The tensile stress-strain curves are shown for a small-diameter (Φ20mm) 35 steel / 35 steel bar transition liquid phase diffusion welded joint with graphite paper as the intermediate layer. Figure 14 (a) is the tensile stress-strain curve of the joint of sample 1. Figure 14 (b) shows the tensile stress-strain curve of the joint in sample 2. Figure 14 (c) shows the tensile stress-strain curve of the joint of sample 3.

[0044] Figure 15 Macroscopic morphology of a large-diameter (Φ50mm) 35 steel / 35 steel bar transition liquid phase diffusion weld joint with graphite paper as the intermediate layer.

[0045] In the diagram, 1. First steel material to be welded; 2. Second steel material to be welded; 3. Graphite intermediate layer; 4. High-temperature cotton; 5. Ceramic tube; 6. Induction coil. Detailed Implementation

[0046] The present invention will now be described in further detail with reference to the accompanying drawings.

[0047] like Figure 1 , Figure 2 As shown, the rapid TLP diffusion welding method for steel using a non-metallic interlayer includes the following steps:

[0048] Step 1: Pre-welding preparation: First, grind and wipe the surface of the same type of steel to be welded or repaired, or the dissimilar type of steel to be composited. Apply pressure of 0.2-3 MPa to ensure close contact between the interfaces of the first steel to be welded 1, the graphite intermediate layer 3, and the second steel to be welded 2. This creates conditions for achieving film removal and metallurgical bonding through the Fe-C eutectic reaction. The thickness of the graphite intermediate layer 3 can be adjusted according to the gap size (if the gap is too large, a mixture of graphite powder and iron powder can be used; the mass ratio of graphite powder to iron powder should be maintained at 0.05-0.1) to ensure close contact between the steel and graphite.

[0049] Step 2: Use induction coil 6 to heat the steel to be welded and the graphite intermediate layer; use high-temperature cotton 4 and ceramic tube 5 to form a local sealed space, and introduce protective gas to avoid severe oxidation of the interface and surface at high temperature;

[0050] Heating the graphite intermediate layer and the interface of the steel to be welded can be achieved by induction heating, furnace heating, or heating with a graphite block heating element. The heating temperature is above the Fe-C eutectic temperature and below the melting point of the first steel to be welded 1 and the second steel to be welded 2, i.e., between 1170-1300℃. During heating, a locally sealed cavity filled with inert gas or CO2 gas can be used, or the steel can be protected by wrapping with flux QJ102 powder or heat-resistant material. The liquid phase produced by the Fe-C eutectic reaction has a large liquid yield. On the one hand, the oxide film is brought out with the extrusion of the eutectic liquid phase, realizing the wetting of the steel by the eutectic liquid phase. On the other hand, the flow of the eutectic liquid phase and the subsequent Fe-C eutectic reaction are used to fill and dissolve the film in the large gaps, and finally achieve the cleaning and densification of the entire welding interface.

[0051] Step 3: Extrude the Fe-C eutectic liquid phase and hold at a temperature for 3-20 minutes to achieve isothermal solidification until the carbon content in the weld is reduced from 100% before welding to the higher carbon content in either the first steel to be welded 1 or the second steel to be welded 2. For base materials that bear static pressure loads and have low plasticity and toughness, such as cast iron, medium carbon steel or high carbon steel base materials, the isothermal solidification process can be omitted. In this case, even without isothermal solidification, the weld can achieve a strength close to that of cast iron, which greatly reduces the requirements for surface assembly perpendicularity.

[0052] Step 4: Use an angle grinder to grind away the Fe-C eutectic solidified weld beads that have been extruded from the weld seam to ensure a smooth appearance; at the same time, eliminate the potential for crack propagation caused by the cracking of high-carbon brittle weld beads under large deformation load conditions.

[0053] The graphite intermediate layer 3 can be graphite paper or graphite powder, or it can be a mixture of graphite powder, metallic iron powder and QJ102 powder, or it can be graphite powder, metallic iron powder, wear-resistant ceramic powder + flux powder. The latter two types of mixed powder welding materials are mainly used to improve the wear resistance of low carbon steel surfaces under non-standard curved surface conditions or to repair the wear of low carbon steel surfaces through high carbonization and composite materials.

[0054] The mass ratio of graphite powder to metallic iron powder is C: 4±2%; Fe: 96±3%; the flux powder is applied to the outer surface of the Fe-C mixed powder exposed to the atmosphere.

[0055] It is also possible to configure mixed powders with different combinations such as graphite powder + metallic Fe powder + alloy powder, graphite powder + metallic Fe powder + ceramic powder, etc., as the graphite intermediate layer 3 for large gap welding and surface wear-resistant repair.

[0056] Example 1: TLP composite of low-carbon steel / medium-carbon steel "dissimilar steel" with graphite powder as the intermediate layer and shear strength test

[0057] To improve the wear resistance of low-carbon steel, a medium-carbon steel 35 layer was welded onto the surface of a commercially available low-carbon steel Q235 plate as a cladding layer, achieving a low-carbon steel / medium-carbon steel composite. A 20μm thick layer of graphite powder was pre-placed between the Q235 and 35 steel base materials. Induction heating was performed under Ar argon protection at 1200℃ for 5 min at 0.5 MPa to achieve efficient and rapid TLP composite bonding of the Q235 low-carbon steel and 35 medium-carbon steel. The macroscopic appearance and shear strength test results of the resulting TLP joint are shown below. Figure 3 and Figure 4 As shown, the interface is fully filled and the bond is dense; the average shear strength of the joint reaches 357MPa (364; 354; 353MPa), the shear performance of the joint has good repeatability and low dispersion; moreover, the joint has good deformation capacity, and the shear displacement before fracture can reach 2mm.

[0058] A rapid TLP diffusion welding method for steel using a non-metallic interlayer includes the following steps:

[0059] Step 1: Grind and wipe to clean the surfaces of low-carbon steel Q235 and medium-carbon steel 35. Place 20μm thick graphite powder between the cleaned interfaces of low-carbon steel Q235 and medium-carbon steel 35, and apply a pressure of 0.5MPa to ensure tight contact between the interfaces of low-carbon steel Q235, graphite powder, and medium-carbon steel 35.

[0060] Step 2: Using induction heating, heat the interface between graphite powder and low carbon steel Q235 steel plate and medium carbon steel 35 steel plate at a heating temperature of 1200℃. During heating, Ar can be used to form a local sealed cavity for protection.

[0061] Step 3: After the rapid reaction in Step 2, the Fe-C eutectic liquid phase is extruded and kept at a temperature for 5 minutes to achieve isothermal solidification until the carbon content in the weld is reduced from 100% before welding to the same level as the carbon content in the medium carbon steel 35 plate.

[0062] Step 4: Grind away the Fe-C eutectic solidified weld beads that have been extruded from the weld seam to make the appearance smooth.

[0063] The microstructure of the cross-section of the TLP diffusion weld was observed, and the results are as follows: Figure 5 As shown, only a few pore defects exist on the medium carbon steel 35 steel side in the weld center area, which can be eliminated by increasing pressure and graphite thickness. The weld interface exhibits excellent wetting, with no defects indicating poor wetting. The graphite layer has completely disappeared and been metallized, and the microstructure of the weld zone is nearly identical to that of the high-carbon base metal, i.e., the medium carbon steel 35 steel. The location of the pores indicates that the graphite paper significantly dissolves the low carbon steel, while on the medium carbon steel 35 steel side, the original interface has disappeared and is almost indistinguishable. From left to right, the joint microstructure shows a decrease in ferrite and an increase in pearlite. At the low carbon steel / weld interface, ferrite spans both sides, achieving metallurgical bonding. The low carbon steel base metal microstructure maintains a predominance of equiaxed ferrite, while the medium carbon steel base metal maintains a predominance of pearlite, avoiding feathery upper bainite and acicular martensite. Therefore, the joint possesses a certain degree of deformation capacity.

[0064] Example 2: TLP welding of solid low-carbon / medium-carbon steel "dissimilar steel" bars with graphite paper as the intermediate layer

[0065] To visually confirm the fracture location of dissimilar steel joints, low-carbon steel bars (Q235) and medium-carbon steel bars (35) with a diameter of 20 mm were used as base materials, with 20 μm thick graphite paper as the intermediate layer. Induction heating was performed under Ar protection, and TLP welding tests were conducted on solid Q235 / 35 dissimilar steel bars at 1200℃×5min×0.5MPa.

[0066] A rapid TLP diffusion welding method for steel using a non-metallic interlayer includes the following steps:

[0067] Step 1: Grind and wipe to clean the surfaces of low-carbon steel Q235 steel bars and medium-carbon steel 35 steel bars, both with a diameter of 20mm. Place a 20μm thick graphite paper between the cleaned interfaces of the low-carbon steel Q235 steel bars and medium-carbon steel 35 steel bars, and apply a pressure of 0.5MPa to ensure tight contact between the interfaces of the low-carbon steel Q235 steel bars, graphite paper, and medium-carbon steel 35 steel bars.

[0068] Step 2: Using induction heating, heat the interface between the graphite paper and the low-carbon steel Q235 steel bar and the medium-carbon steel 35 steel bar at a temperature of 1200℃. During heating, a protective method of internal argon filling to form a locally sealed cavity can be adopted.

[0069] Step 3: After the rapid reaction in Step 2, the Fe-C eutectic liquid phase is extruded and kept at a temperature for 5 minutes to achieve isothermal solidification until the carbon content in the weld is reduced from 100% before welding to the same level as the carbon content of medium carbon steel 35 bar.

[0070] Step 4: Grind away the Fe-C eutectic solidified weld beads that have been extruded from the weld seam to make the appearance smooth.

[0071] like Figure 6 , Figure 7 and Figure 8 The image shows the macroscopic morphology, tensile fracture location, and tensile strength test results of a small-diameter (Φ20mm) low-carbon steel / medium-carbon steel dissimilar TLP diffusion weld joint using graphite paper as the interlayer. Macroscopic photographs of the joint show a small amount of liquid phase extrusion at the joint, indicating a dense interfacial bond. During tensile testing, fractures occurred within the low-carbon steel (Q235 steel) base material, not at the interface. Figure 8 (a) Sample 1 has a tensile strength of 483 MPa and an elongation of 18.6%. Figure 8 (b) Sample 2 has a tensile strength of 498.4 MPa and an elongation of 18.8%. Figure 8 (c) The tensile strength of sample 3 is 483 MPa and the elongation is 18.4%. The tensile strength of the joint is above 483 MPa and the average elongation is 18.6%, indicating that the joint has high tensile strength and good plasticity, and can realize rapid TLP composite of Q235 steel / 35 steel.

[0072] Example 3: Forming, microstructure and properties of medium carbon steel / medium carbon steel plate by TLP diffusion welding

[0073] Commercially available medium carbon steel (35 steel) was used as the base material in the experiment. A 20 μm thick layer of graphite paper was pre-placed between the 35 steel and 35 steel base materials. Temperature was measured using a type K thermocouple, and induction heating and Ar gas protection were employed to perform rapid and efficient TLP bonding of 35 steel / 35 steel under conditions of 1200℃ × 5 min × 0.5 MPa. The macroscopic appearance and shear strength test results of the resulting TLP joint are shown below. Figure 9 and Figure 10 As shown, the brazing interface is fully filled and the bond is dense; three samples were tested respectively, and the shear strength of the joint was 583MPa, 585MPa and 549MPa respectively, with an average shear strength of 572MPa.

[0074] A rapid TLP diffusion welding method for steel using a non-metallic interlayer includes the following steps:

[0075] Step 1: Grind and wipe to clean the surfaces of the first and second medium carbon steel 35 plates. Place a 20μm thick graphite paper between the cleaned interfaces of the first and second medium carbon steel 35 plates and apply a pressure of 0.5MPa to ensure tight contact between the interfaces of the first medium carbon steel 35 plate, the graphite paper, and the second medium carbon steel 35 plate.

[0076] Step 2: Using induction heating, heat the graphite paper and the interface between the first medium carbon steel 35 steel plate and the second medium carbon steel 35 steel plate at a heating temperature of 1200℃. During heating, a protective method of internal argon filling to form a locally sealed cavity can be adopted.

[0077] Step 3: After the rapid reaction in Step 2, the Fe-C eutectic liquid phase is extruded and kept at a temperature for 5 minutes to achieve isothermal solidification until the carbon content in the weld is reduced from 100% before welding to the same level as the carbon content in the medium carbon steel 35 plate.

[0078] Step 4: Grind away the Fe-C eutectic solidified weld beads that have been extruded from the weld seam to make the appearance smooth.

[0079] The above-mentioned sample was cut along the cross-section of the weld, and its microstructure was observed using an optical microscope. The results are as follows: Figure 11 As shown. By Figure 11 (a) It can be seen that both the original graphite paper interlayer and the weld have disappeared. The weld microstructure is similar to that of the base materials on both sides. Therefore, based on the microstructure characteristics, the joint microstructure under this process condition has achieved homogenization and meets the microstructure conditions of a classic TLP diffusion welded joint. To further determine the weld microstructure composition, the location of the weld center region is magnified, as shown in Figure 1. Figure 11 (b) Figure 11 As shown in (c), the two regions have similar structures, both consisting of relatively coarse pearlite and ferrite.

[0080] Example 4: TLP diffusion welding formation, microstructure and properties of small-diameter medium carbon steel / medium carbon steel bars

[0081] To apply this invention to the repair of anode steel claws in electrolytic aluminum, replacing existing arc welding technology and solving problems such as the need for beveling, large workload of beveling and filling, and arc light and spatter in existing arc welding repair technology, TLP diffusion welding tests were conducted on small-diameter (Φ20mm) medium carbon steel / medium carbon steel (35 steel) bars. TLP diffusion welding of small-diameter (Φ20mm) medium carbon steel / medium carbon steel (35 steel) bars was performed under the conditions of 1180℃×5min×0.5MPa, 1200℃×3min×0.5MPa, and 1250℃×3min×0.3MPa, respectively. Induction heating, furnace heating, and graphite block heating elements were used for heating, with Ar gas protection fixtures.

[0082] Sample 1: A rapid TLP diffusion bonding method for steel using a non-metallic interlayer, comprising the following steps:

[0083] Step 1: Grind and wipe to clean the surfaces of the first and second smallest diameter (Φ20mm) medium carbon steel 35 bars. Place a 20μm thick graphite paper between the cleaned interfaces of the first and second smallest diameter (Φ20mm) medium carbon steel 35 bars and apply a pressure of 0.5MPa to ensure tight contact between the interfaces of the first and second smallest diameter (Φ20mm) medium carbon steel 35 bars, the graphite paper, and the second smallest diameter (Φ20mm) medium carbon steel 35 bars.

[0084] Step 2: Using induction heating, heat the graphite paper and the interface between the first small diameter (Φ20mm) medium carbon steel 35 bar and the second small diameter (Φ20mm) medium carbon steel 35 bar at a heating temperature of 1180℃. During heating, a protective method of internal Ar argon filling to form a locally sealed cavity can be adopted.

[0085] Step 3: After the rapid reaction in Step 2, the Fe-C eutectic liquid phase is extruded and kept at a temperature for 5 minutes to achieve isothermal solidification until the carbon content in the weld is reduced from 100% before welding to the same level as the carbon content of medium carbon steel 35 bar.

[0086] Step 4: Grind away the Fe-C eutectic solidified weld beads that have been extruded from the weld seam to make the appearance smooth.

[0087] Sample 2: A rapid TLP diffusion welding method for steel using a non-metallic interlayer, comprising the following steps:

[0088] Step 1: Grind and wipe to clean the surfaces of the first and second smallest diameter (Φ20mm) medium carbon steel 35 bars. Place a 30μm thick graphite paper between the cleaned interfaces of the first and second smallest diameter (Φ20mm) medium carbon steel 35 bars and apply a pressure of 0.5MPa to ensure tight contact between the interfaces of the first and second smallest diameter (Φ20mm) medium carbon steel 35 bars, the graphite paper, and the second smallest diameter (Φ20mm) medium carbon steel 35 bars.

[0089] Step 2: Using induction heating, heat the graphite paper and the interface between the first small diameter (Φ20mm) medium carbon steel 35 bar and the second small diameter (Φ20mm) medium carbon steel 35 bar at a heating temperature of 1200℃. During heating, a protective method of internal Ar argon filling to form a locally sealed cavity can be adopted.

[0090] Step 3: After the rapid reaction in Step 2, the Fe-C eutectic liquid phase is extruded and kept at a temperature for 3 minutes to achieve isothermal solidification until the carbon content in the weld is reduced from 100% before welding to the same level as the carbon content of medium carbon steel 35 bar.

[0091] Step 4: Grind away the Fe-C eutectic solidified weld beads that have been extruded from the weld seam to make the appearance smooth.

[0092] Sample 3, using a rapid TLP diffusion bonding method for steel with a non-metallic interlayer, includes the following steps:

[0093] Step 1: Grind and wipe to clean the surfaces of the first and second smallest diameter (Φ20mm) medium carbon steel 35 bars. Place a 40μm thick graphite paper between the cleaned interfaces of the first and second smallest diameter (Φ20mm) medium carbon steel 35 bars and apply a pressure of 0.3MPa to ensure tight contact between the interfaces of the first and second smallest diameter (Φ20mm) medium carbon steel 35 bars, the graphite paper, and the second smallest diameter (Φ20mm) medium carbon steel 35 bars.

[0094] Step 2: Use a graphite block heating element to heat the graphite paper and the interface between the first small diameter (Φ20mm) medium carbon steel 35 bar and the second small diameter (Φ20mm) medium carbon steel 35 bar. The heating temperature is 1250℃. During heating, an internal Ar argon filling method can be used to form a locally sealed cavity for protection.

[0095] Step 3: After the rapid reaction in Step 2, the Fe-C eutectic liquid phase is extruded and kept at a temperature for 3 minutes to achieve isothermal solidification until the carbon content in the weld is reduced from 100% before welding to the same level as the carbon content of medium carbon steel 35 bar.

[0096] Step 4: Grind away the Fe-C eutectic solidified weld beads that have been extruded from the weld seam to make the appearance smooth.

[0097] like Figure 12 , Figure 13 and Figure 14 The image shows the macroscopic morphology, macroscopic tensile fracture results, and tensile strength test results of a small-diameter (Φ20mm) medium carbon steel bar TLP joint using graphite paper as the intermediate layer. The macroscopic photograph of the joint shows a small amount of liquid phase extrusion at the joint, indicating a dense interfacial bond. The tensile test results indicate that fracture occurred within the 35 steel base material rather than at the interface during tensile testing. Figure 14 (a) Sample 1 has a tensile strength of 829.5 MPa and an elongation of 12.6%. Figure 14 (b) Sample 2 has a tensile strength of 820.5 MPa and an elongation of 13.5%. Figure 14(c) Sample 3 has a tensile strength of 808.7 MPa and an elongation of 12.9%. The average tensile strength of the joint is 820 MPa, which is not lower than the nominal strength of the base material. The average elongation is 13%, indicating that the joint has high tensile strength and good plasticity, and can achieve rapid TLP composite of 35 steel / 35 steel.

[0098] Example 5: Forming, microstructure and properties of large-diameter medium carbon steel / medium carbon steel bars by TLP diffusion welding

[0099] To apply this invention to the repair of anode steel claws in electrolytic aluminum, replacing existing arc welding technology and solving problems such as the need for beveling, large workload of beveling and filling, and arc light and spatter associated with existing arc welding repair techniques, a larger diameter (50mm) 35 steel bar was selected. Using 20μm thick graphite paper, a TLP connection was performed on the 50mm diameter 35 steel bar under Ar gas protection at 1250℃×10min×0.5MPa. The macroscopic morphology of the 35 steel / C / 35 steel joint is shown below. Figure 15 As shown, a large amount of liquid phase is extruded at the weld, indicating good joint quality.

[0100] A rapid TLP diffusion welding method for steel using a non-metallic interlayer includes the following steps:

[0101] Step 1: Grind and wipe to clean the surfaces of the first and second largest diameter (Φ50mm) medium carbon steel 35 bars. Place a 20μm thick graphite paper between the cleaned interfaces of the first and second largest diameter (Φ50mm) medium carbon steel 35 bars and apply a pressure of 0.5MPa to ensure tight contact between the interfaces of the first and second largest diameter (Φ50mm) medium carbon steel 35 bars, the graphite paper, and the second largest diameter (Φ50mm) medium carbon steel 35 bars.

[0102] Step 2: Using induction heating, heat the graphite paper and the interface between the first large diameter (Φ50mm) medium carbon steel 35 bar and the second large diameter (Φ50mm) medium carbon steel 35 bar at a heating temperature of 1250℃. During heating, a protective method of internal Ar argon filling to form a locally sealed cavity can be adopted.

[0103] Step 3: After the rapid reaction in Step 2, the Fe-C eutectic liquid phase is extruded and kept at a temperature for 10 minutes to achieve isothermal solidification until the carbon content in the weld is reduced from 100% before welding to the same level as the carbon content of medium carbon steel 35 bar.

[0104] Step 4: Grind away the Fe-C eutectic solidified weld beads that have been extruded from the weld seam to make the appearance smooth.

[0105] The small and large diameters provided in Examples 4 and 5 are only for distinguishing the embodiments in this invention. When this invention is used to repair electrolytic aluminum anode steel claws, it is not limited to the 20mm and 50mm provided in the embodiments. Electrolytic aluminum anode steel claws with diameters ranging from 30 to 200mm can achieve TLP rapid repair.

[0106] In summary, the small atomic radius non-metallic graphite interlayer proposed in this invention is more economical and easier to store than Fe-based and Ni-based interlayers (i.e., it does not rust, requires no pre-welding grinding, diffuses quickly, and does not form brittle intermetallic compounds). In particular, it can utilize the Fe-C eutectic reaction to obtain a liquid phase with good repeatability. After the oxide film is extruded with the liquid phase, it can quickly achieve film removal, wetting, and densification. Furthermore, by utilizing the rapid diffusion of carbon atoms as interstitial atoms, it can quickly achieve isothermal solidification. Therefore, it not only has good repeatability and high efficiency, but also greatly reduces the requirements for the flatness of the original workpiece surface and the parallelism or perpendicularity of the assembly. It is highly practical and suitable for industrial production.

[0107] The TLP (Transfer-Lift) process for steel, using rapidly diffusing graphite (with a small carbon atomic radius and fast diffusion) as an intermediate layer, has wide applications. It can be used not only for composite welding of dissimilar steels with any carbon content, but also for welding of homogeneous steels with any carbon content (including high-carbon cast iron). For example, it can be used for large-area rapid welding between medium-carbon steel / medium-carbon steel, high-carbon steel / high-carbon steel, low-carbon steel / low-carbon steel, and cast iron / cast iron homogeneous steels. Especially for rod and tubular cross-sections, TLP is more easily achieved using induction heating, replacing existing inefficient (requiring multiple layers and passes), spatter-prone, and complex arc welding processes.

[0108] By utilizing readily available medium-carbon steel plates or powders, high-carbon steel plates or powders, high-strength steel plates or powders, alloy steel plates or powders, or mixed powders of different steel grades to replace the carburizing layer, a "low-carbon steel / medium-carbon steel, low-carbon steel / high-carbon steel, low-carbon steel / high-strength steel, low-carbon steel / alloy steel dissimilar steel layered composite material" product can be manufactured to improve the wear resistance, corrosion resistance, and oxidation resistance of the low-carbon steel surface. The wear-resistant layer of the composite plate composed of low-carbon steel / medium-carbon steel or low-carbon steel / high-carbon steel is made of medium-carbon steel plate or high-carbon steel plate, with a thickness of at least mm, far exceeding the micron-level thickness of the carburizing layer, resulting in a longer wear-resistant life. Even if the wear-resistant layer is locally worn down to below the required thickness during use, it can be quickly repaired by transition liquid phase diffusion welding with graphite as the intermediate layer, restoring the original thickness of the wear-resistant layer.

[0109] Compared to traditional carburizing technology, which can only improve the mechanical property of hardness, the idea of ​​directly bonding high-strength steel or alloy steel to the surface of low-carbon steel can also endow low-carbon steel with other special properties in addition to its advantages of high hardness and long wear life, such as impact resistance, fatigue resistance, corrosion resistance, and oxidation resistance. However, these alloying elements (such as Mn, Cr, Mo, Ni, and W) that can improve the surface strength, corrosion resistance, and oxidation resistance of low-carbon steel are difficult to penetrate into the surface of low-carbon steel through a similar carburizing process due to their easy oxidation and large atomic radius.

Claims

1. A rapid TLP diffusion welding method for steel using a non-metallic interlayer, characterized in that, Includes the following steps: Step 1: Grind and wipe to clean the surfaces of the first steel material (1) and the second steel material (2) to be welded. Place the graphite intermediate layer (3) between the cleaned interfaces of the first steel material (1) and the second steel material (2) to be welded, and apply pressure of 0.2~3MPa to ensure close contact between the interfaces of the first steel material (1), the graphite intermediate layer (3), and the second steel material (2). Step 2: Heat the interface between the graphite intermediate layer (3) and the first steel to be welded (1) and the second steel to be welded (2). The heating temperature is above the Fe-C eutectic temperature and below the melting point of the first steel to be welded (1) and the second steel to be welded (2), i.e., between 1170-1300℃. During heating, an inert gas or CO2 gas can be used to form a locally sealed cavity, or a protective method can be adopted by wrapping with flux QJ102 powder or heat-resistant material. Step 3: After the rapid reaction in step 2, the Fe-C eutectic liquid phase is extruded and kept at a temperature for 3-20 minutes to achieve isothermal solidification until the carbon content in the weld is reduced from 100% before welding to the same as the higher carbon content in the first steel to be welded (1) or the second steel to be welded (2). Step 4: Grind away the Fe-C eutectic solidified weld beads that have been extruded from the weld seam to make the appearance smooth; In step 1, the graphite intermediate layer (3) can be graphite paper or graphite powder, or a mixture of graphite powder, metallic iron powder and flux powder, or a mixture of graphite powder, metallic iron powder, wear-resistant ceramic powder and flux powder, or a mixture of graphite powder, metallic iron powder and alloy powder or a mixture of graphite powder, metallic iron powder and wear-resistant ceramic powder, wherein the mass ratio of graphite powder to metallic iron powder is maintained at 0.05~0.

1.

2. The rapid TLP diffusion welding method for steel using a non-metallic interlayer as described in claim 1, characterized in that, In step 1, the thickness of the graphite intermediate layer (3) can be adjusted according to the gap size to ensure that the steel and graphite can be in close contact.

3. The rapid TLP diffusion welding method for steel using a non-metallic interlayer as described in claim 1, characterized in that, In step 2, the heating method can be selected from induction heating, furnace heating, or graphite block heating element heating.

4. The rapid TLP diffusion welding method for steel using a non-metallic interlayer as described in claim 1, characterized in that, In step 3, the isothermal solidification process can be omitted for cast iron steel to be welded, steel to be welded that is subjected to static pressure load and has low plasticity and toughness.

5. The rapid TLP diffusion welding method for steel using a non-metallic interlayer as described in claim 1, characterized in that, Includes the following steps: Step 1: Grind and wipe to clean the surfaces of low-carbon steel Q235 and medium-carbon steel 35. Place 20μm thick graphite powder between the cleaned interfaces of low-carbon steel Q235 and medium-carbon steel 35, and apply a pressure of 0.5MPa to ensure tight contact between the interfaces of low-carbon steel Q235, graphite powder, and medium-carbon steel 35. Step 2: Using induction heating, heat the interface between graphite powder and low carbon steel Q235 steel plate and medium carbon steel 35 steel plate at a heating temperature of 1200℃. During heating, Ar can be used to form a local sealed cavity for protection. Step 3: After the rapid reaction in Step 2, the Fe-C eutectic liquid phase is extruded and kept at a temperature for 5 minutes to achieve isothermal solidification until the carbon content in the weld is reduced from 100% before welding to the same level as the carbon content in the medium carbon steel 35 plate. Step 4: Grind away the Fe-C eutectic solidified weld beads that have been extruded from the weld seam to make the appearance smooth.

6. The rapid TLP diffusion welding method for steel using a non-metallic interlayer as described in claim 1, characterized in that, Includes the following steps: Step 1: Grind and wipe to clean the surfaces of the first and second medium carbon steel 35 plates. Place a 20μm thick graphite paper between the cleaned interfaces of the first and second medium carbon steel 35 plates and apply a pressure of 0.5MPa to ensure tight contact between the interfaces of the first medium carbon steel 35 plate, the graphite intermediate layer, and the second medium carbon steel 35 plate. Step 2: Using induction heating, heat the graphite intermediate layer and the interface between the first medium carbon steel 35 steel plate and the second medium carbon steel 35 steel plate at a heating temperature of 1200℃. During heating, a protective method of internal argon filling to form a locally sealed cavity can be adopted. Step 3: After the rapid reaction in Step 2, the Fe-C eutectic liquid phase is extruded and kept at a temperature for 5 minutes to achieve isothermal solidification until the carbon content in the weld is reduced from 100% before welding to the same level as the carbon content in the medium carbon steel 35 plate. Step 4: Grind away the Fe-C eutectic solidified weld beads that have been extruded from the weld seam to make the appearance smooth.

7. The rapid TLP diffusion welding method for steel using a non-metallic interlayer as described in claim 1, characterized in that, Includes the following steps: Step 1: Grinding and wiping to clean the first small diameter. 20mm medium carbon steel 35 bar and second smallest diameter On the surface of a 20mm medium carbon steel 35 bar, a 20μm thick graphite paper is pre-placed on the cleaned first small diameter section. 20mm medium carbon steel 35 bar and second smallest diameter Between the interfaces of 20mm medium carbon steel 35 bars, a pressure of 0.5MPa is applied to ensure the first small diameter 20mm medium carbon steel 35 bar, graphite paper, second smallest diameter The interfaces of the 20mm medium carbon steel 35 bar are in close contact. Step 2: Use induction heating to heat the graphite paper and the first small diameter... 20mm medium carbon steel 35 bar and second smallest diameter The interface of 20mm medium carbon steel 35 bar is heated to 1180℃. During heating, the protection method of forming a local closed cavity by internal argon filling can be adopted. Step 3: After the rapid reaction in Step 2, the Fe-C eutectic liquid phase is extruded and kept at a temperature for 5 minutes to achieve isothermal solidification until the carbon content in the weld is reduced from 100% before welding to the same level as that of medium carbon steel 35 bar. Step 4: Grind away the Fe-C eutectic solidified weld beads that have been extruded from the weld seam to make the appearance smooth.

8. The rapid TLP diffusion welding method for steel using a non-metallic interlayer as described in claim 1, characterized in that, Includes the following steps: Step 1: Grinding and wiping to clean the first small diameter. 20mm medium carbon steel 35 bar and second smallest diameter On the surface of a 20mm medium carbon steel 35 bar, a 40μm thick graphite paper is pre-placed on the cleaned first small diameter section. 20mm medium carbon steel 35 bar and second smallest diameter Between the interfaces of 20mm medium carbon steel 35 bars, a pressure of 0.3MPa is applied to ensure the first small diameter 20mm medium carbon steel 35 bar, graphite paper, second smallest diameter The interfaces of the 20mm medium carbon steel 35 bar are in close contact. Step 2: Use a graphite block heating element to heat the graphite paper and the first small diameter... 20mm medium carbon steel 35 bar and second smallest diameter The interface of 20mm medium carbon steel 35 bar is heated to 1250℃. During heating, the protection method of forming a local closed cavity by internal argon filling can be adopted. Step 3: After the rapid reaction in Step 2, the Fe-C eutectic liquid phase is extruded and kept at a temperature for 3 minutes to achieve isothermal solidification until the carbon content in the weld is reduced from 100% before welding to the same level as the carbon content of medium carbon steel 35 bar. Step 4: Grind away the Fe-C eutectic solidified weld beads that have been extruded from the weld seam to make the appearance smooth.

9. The rapid TLP diffusion welding method for steel using a non-metallic interlayer as described in claim 1, characterized in that, Includes the following steps: Step 1: Grinding and wiping to clean the first large diameter. 50mm medium carbon steel 35 bar and the second largest diameter On the surface of a 50mm medium carbon steel 35 bar, a 20μm thick graphite paper is pre-placed on the cleaned first large diameter section. 50mm medium carbon steel 35 bar and the second largest diameter Between the interfaces of 50mm medium carbon steel 35 bars, a pressure of 0.5MPa is applied to ensure the first largest diameter 50mm medium carbon steel 35 bar, graphite interlayer, second largest diameter The interfaces of the 50mm medium carbon steel 35 bar are in close contact. Step 2: Using induction heating, heat the graphite intermediate layer and the first large diameter layer. 50mm medium carbon steel 35 bar and the second largest diameter The interface of 50mm medium carbon steel 35 bar is heated to 1250℃. During heating, the protection method of forming a local closed cavity by internal argon filling can be adopted. Step 3: After the rapid reaction in Step 2, the Fe-C eutectic liquid phase is extruded and kept at a temperature for 10 minutes to achieve isothermal solidification until the carbon content in the weld is reduced from 100% before welding to the same level as the carbon content of medium carbon steel 35 bar. Step 4: Grind away the Fe-C eutectic solidified weld beads that have been extruded from the weld seam to make the appearance smooth.

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