Solid core welding wire, high wear resistance composite step plate and their manufacturing method

Abstract

The application discloses a kind of solid core welding wire, high wear-resistant composite step plate and their manufacturing method, belong to composite step plate technical field.The high wear-resistant composite step plate of the application is composed of base body part and wear-resistant composite surfacing face, and the solid core welding wire containing nano rare earth oxide particles is used for wear-resistant face, the solid core welding wire is combined on base material by surfacing welding, to form the composite structure of "flexible and rigid combination".The application aims at the problem of high welding difficulty of high alloying element content, high carbon equivalent and high sensitivity, by modifying welding wire, selecting appropriate welding mode, controlling welding parameter, to prepare wear-resistant face meeting the requirement of comprehensive performance.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of composite step plate, more particularly, relates to a solid core welding wire, a high wear-resistant composite step plate and their manufacturing methods. BACKGROUND

[0002] With the increasing demand for product quality and the continuous development of the steel industry, the steel rolling technology is constantly updated and upgraded, and the performance of the step plate is also increasingly required.

[0003] In the process of strip rolling, the energy generated by dynamic pressure, static pressure and impact is transmitted to the roll neck through the roll body, then transmitted to the bearing seat by the roll neck, and then transmitted to the rolling mill step plate by the bearing seat; due to the size limitation of the supporting roll bearing box, the contact area between the step plate and the lower circular arc pad of the supporting roll bearing seat is small, the stress is large, the impact force is large, and the contact stress is large; in addition, the corrosion of cooling water and the abrasive wear friction caused by the oxide scale on the surface of the steel plate make the step plate work in the process of sliding friction of the bearing seat and the impact from the bearing seat, which will cause the surface of the step plate to appear pits, edge pressure and cracks, and even breakage. The deterioration of the surface of the step plate, such as pits and cracks, will cause the rigidity value of the rolling mill on both sides to exceed the standard, and under the action of a certain rolling pressure, the elastic deformation of the rolling mill is not the same, causing a certain deviation of the roll gap on both sides, which affects the intermediate plate shape. Therefore, the safety and stability of the step plate plays a decisive role in the stability of the four-roll mill and the quality of the intermediate plate shape.

[0004] After searching, patent CN105149810A discloses a welding method for preventing high-carbon equivalent strip weld breakage, the welding of the weld between the strips is carried out by laser welding, and the composition of the welding wire used in the laser welding is as follows: C 0.08-0.09%, Si 0.7-0.88%, Mn 1.3-1.47%, P≤0.011%, S≤0.008%, Cu 0.11-0.14%, Ni 0.004-0.007%, Cr 0.040-0.046%, and the balance is Fe; the welding machine power is 9000-11000W, the welding speed of the welding machine is 2-6m / min, the wire feeding speed is 2-7m / min, the annealing current is 100-160A, and the annealing temperature is 500-900℃. The laser welding method provided by the present application for preventing high-carbon equivalent strip weld breakage solves the technical problem that the weld of high-carbon equivalent strip with a carbon equivalent greater than 0.5% is prone to breakage. The present application is used for connecting and welding between strips, uses a high-energy-density laser beam as a heat source for welding, and uses a high-energy-density welding wire for surfacing, which is prone to uneven distribution of welding materials.

[0005] Patent CN104923935A discloses a welding method for high-alloy content and large-thickness continuous casting slab, comprising the following steps: a, taking at least two high-alloy content continuous casting slabs as raw materials, removing the oxidation layer on the joint surface of the continuous casting slab by mechanical milling, and processing an L-shaped step on the edge of the joint surface of the continuous casting slab; b, using stainless steel strip surfacing to surfacing a stainless steel transition layer on the L-shaped step, and using mechanical milling to process the continuous casting slab into a cuboid with the same size; c, aligning and stacking the continuous casting slabs, and using arc welding to position and weld the continuous casting slabs; d, placing the continuous casting slabs in a vacuum chamber, and using an electron beam to weld the edge seams between the continuous casting slabs under high vacuum. The continuous casting slab of the patent uses stainless steel welding material with low welding crack tendency for submerged arc welding bottoming transition, and then performs spot welding positioning and vacuum electron beam welding.

[0006] Patent CN109868342A discloses a method for improving the toughness of the weld heat-affected zone of high-carbon-equivalent steel plate by using rare earth. The method comprises the following steps in sequence: converter smelting step, LF refining step, RH refining step, continuous casting step, hot rolling step and heat treatment step. A certain amount of rare earth Ce alloy is added to the molten steel during the RH refining process, the inclusions in the molten steel are modified by rare earth to form rare earth inclusions, and fine newly-formed rare earth inclusions are generated in the molten steel, and the dispersion distribution of the rare earth inclusions is controlled. The newly-formed fine and dispersed rare earth Ce-containing inclusions in the molten steel and the original inclusions modified by rare earth inhibit the growth of the original austenite grains in the heat-affected zone during welding, and the addition of rare earth also delays the bainite transformation in the weld heat-affected zone, thereby inhibiting the formation of upper bainite, thereby greatly improving the toughness of the weld heat-affected zone of the high-carbon-equivalent thick plate. The patent adds rare earth alloy to the smelting raw material to form original inclusions, but the rare earth original inclusions in the molten steel have problems such as small specific gravity, easy floating, poor wettability, small particle size and easy agglomeration, which affect the uniformity of the distribution of inclusions and the quality stability of the weld heat-affected zone. SUMMARY

[0007] 1. Problems to be solved

[0008] In view of the problem that the base material with high alloy element content and high carbon equivalent has high welding difficulty, the present application provides a manufacturing method of a composite step plate. By modifying the solid core welding wire, selecting a suitable welding method, and adjusting the welding parameters, a wear-resistant surface meeting the comprehensive performance requirements is prepared. The prepared composite step plate forms a "rigid-flexible combined" composite structure, effectively improving the performance of the step plate during use.

[0009] The solid core welding wire for welding is modified by nano rare earth oxides, which is beneficial to improve the comprehensive mechanical properties of the solid core welding wire and the wear-resistant surface.

[0010] 2. Technical scheme

[0011] To solve the above problems, the technical scheme adopted by the present application is as follows:

[0012] A manufacturing method of a composite stepping plate, the specific steps are as follows:

[0013] S1, making a stepping plate base part: making the base part through forging and rough machining;

[0014] S2, heat treating the base part: improving the organization and mechanical properties of the base part through heat treatment, facilitating welding and machining;

[0015] S3, opening a wear-resistant surface groove of the stepping plate: processing the wear-resistant surface groove through numerical control milling;

[0016] S4, welding a wear-resistant composite overlay: welding the solid core welding wire to the wear-resistant surface welding groove, and then performing post-weld heat treatment;

[0017] S5, finishing: machining the welded stepping plate to the finished product size through milling and grinding;

[0018] S6, detection: detecting the hardness and metallographic structure of the finished composite stepping plate.

[0019] Further, the composition and weight percentage of the base part in step S1 are as follows: C: 0.18%-0.24%, Si: 0.10%-0.50%, Mn: 0.40%-0.90%, Cr: 11.00%-12.50%, Mo: 0.80%-1.20%, Ni: 0.30%-0.80%, V: 0.25%-0.35%, S≤0.025%, P≤0.025%, and the rest is Fe.

[0020] Further, in step S2, after the base part is made, the base part is heat treated, the heat treatment process adopts quenching and tempering, and is used to adjust the hardness of the base part, so that the hardness of the base part reaches HB240-260.

[0021] The specific process of heat treatment is as follows:

[0022] Quenching: slowly heated to quenching temperature 1010-1040℃, then put into oil pool for quenching treatment, and quenched to below 200℃;

[0023] Tempering: after quenching, it needs to be put into the furnace again within 20-30min and heated to 670-690℃, and then kept for 10-12 hours, then oil-cooled to 200℃, and then air-cooled to room temperature, so that the hardness of the treated base part reaches HB240-260.

[0024] Further, the wear-resistant surface build-up welding area in step S3 is a groove with a size of 810mmx210mmx10mm to ensure that enough wear-resistant surface material can be built up.

[0025] Further, in step S4, the solid core wire used is a modified solid core wire treated with a modifier, and the diameter of the solid core wire is 1.2mm, which is built up in the build-up welding groove opened in step S3.

[0026] The build-up welding method is tungsten inert gas welding.

[0027] During post-weld heat treatment, the built-up stepping plate is loaded into the furnace, the furnace temperature is ensured to be 200℃ or above, then heated uniformly to 380±10℃ at a speed of ≤200℃ / h, and then cooled to ≤100℃ at a speed of ≤50℃ / h.

[0028] The step of building up the wear-resistant composite surface in step S4 specifically includes:

[0029] S4.1. Preheating: using a preheating furnace to preheat the stepping plate body, the preheating temperature is 200-250℃, and the temperature is maintained during the build-up welding process;

[0030] S4.2. Preparing the base layer: high-chromium stainless steel solid core wire containing nano rare earth oxide particles is built up into the wear-resistant composite surface build-up welding groove by tungsten inert gas welding, in order to avoid welding cracks, a smaller heat input is used, the first layer base layer parameter current is 120-150A, the arc voltage is 13-17V, pure argon gas is used, and the flow rate is 12-16L / min;

[0031] S4.3. Preparing the filler layer: the filler layer parameter current is 130-160A, the arc voltage is 14-19V, and the gas flow rate is 12-16L / min;

[0032] S4.4. Preparing the cover layer: in order to ensure the appearance quality and surface flatness for subsequent processing, the cover layer parameter current is 110-150A, the arc voltage is 12-17V, the gas flow rate is 12-15L / min, and a 3mm machining allowance is left for the build-up welding height, then post-weld heat treatment is performed to eliminate welding residual stress, remove diffusion hydrogen in the joint, and also improve the microstructure and performance of the joint.

[0033] The higher the base material alloy element content and carbon equivalent, the greater the crack sensitivity and the greater the welding difficulty. The welding performance of the steel can be determined by the carbon equivalent, and the greater the carbon equivalent, the worse the welding performance. When the carbon equivalent is less than 0.4%, the weldability is good; when the carbon equivalent is 0.4%-0.6%, the hardening tendency of the strip steel gradually increases, the weldability is poor, and preheating and other measures need to be taken to prevent cracks during welding; if the carbon equivalent is greater than 0.6%, a higher preheating temperature (or annealing temperature) and strict process measures are required during welding. The present application is directed to the welding of a base with a carbon equivalent greater than 0.6%, preferably the carbon equivalent of the base is greater than 2.0%.

[0034] The base material is selected from different materials, the carbon equivalent is different, and the treatment method is different. First, the heat treatment process parameters are different. The reason is that the base material is different, the carbon equivalent is different, the control difficulty of the welding quality is different, the base material with high carbon equivalent has high control difficulty of welding quality, high alloy element content, and high hardening tendency, which leads to the decrease of the toughness of the weld metal and the easy production of cracks. Generally, the preheating temperature before welding needs to be improved, and low heat input welding method and parameters are used for welding. The base material with low carbon equivalent has low control difficulty of welding quality and good welding performance.

[0035] Secondly, the surfacing method is different. The carbon equivalent of the X22CrMoV12-1 base is high, and the welding temperature requirement is high. It is difficult to maintain in actual production, so the tungsten inert gas welding process with good welding stability, strong material adaptability and high weld purity is selected for welding.

[0036] Further, the welding process parameters of the high chromium stainless steel solid wire are different. The reason is that the base material high temperature stainless steel X22CrMoV12-1 has good high temperature performance, better oxidation resistance, ductility and mechanical strength at high temperature, but its alloy element content and carbon equivalent are high, which causes its crack sensitivity to be large, and the tungsten inert gas welding method with high welding quality, stable process and small heat input needs to be used for welding. The welding protection gas is pure argon, which can effectively reduce the burning loss of alloy elements and oxide particles in the weld, and fully ensure the comprehensive performance of the deposited metal.

[0037] Therefore, by selecting appropriate welding methods and adjusting welding parameters, the comprehensive performance of the wear-resistant surface can be effectively improved. The solid core welding wire is layered and stacked on the surface of the base in the form of surfacing to form a wear-resistant surface. The lower weld layer is heated again during the surfacing process, and the near-seam area is likely to have grain growth and form harmful structures such as widmanstatten structure, which leads to the performance degradation of the second layer heat affected zone (the first layer of weld).

[0038] This invention further modifies the solid welding wire. The modified solid welding wire includes an iron-based material and a modifier. The chemical composition of the iron-based material is: C: 0.47%-0.55%, Si: 0.30%-0.50%, Mn: 0.50%-0.80%, Cr: 12.00%-14.00%, S≤0.03%, P≤0.03%, with the remainder being Fe. The modifier is a nano-rare earth oxide, wherein the nano-rare earth oxide includes one or more of CeO2 and La2O3, and the particle size of the nano-rare earth oxide is 50-1100 nm, preferably with an average particle size of 50 nm. The ratio of the modifier to the iron-based material is (2-3):(15-20).

[0039] The method for preparing the above-mentioned solid welding wire includes the following steps:

[0040] a. A homogenized ceramic phase powder is obtained by mechanically grinding the modifier with iron powder; the size of the modifier is 50-1100 nm.

[0041] b. Ball mill the ceramic phase powder obtained in step a for 8115 hours to obtain a ceramic phase toughening agent;

[0042] c. Add sodium silicate binder to the ceramic phase toughening agent obtained in step b, and roll it into a spherical material;

[0043] d. Finally, according to the raw material ratio of solid welding wire, the raw materials of the required elements are added to the melting furnace, and the spherical material obtained in step c is added at the same time. After forging, rolling and cold drawing, solid welding wire is obtained. The ratio of the modifier to the iron base material is (2-3):(15-20).

[0044] The method for preparing solid welding wire in this application is applicable to multiple steel grades, such as 5Cr13 and H13.

[0045] The wear-resistant surface is constructed by layering solid welding wires onto the substrate surface using a welding process. The underlying weld layer is continuously heated and cured during the welding process. The addition of rare earth oxides can improve the crystal phase structure during the secondary curing of the coating, producing a eutectic and enhancing the adhesion and wear resistance of the wear-resistant layer. The added rare earth oxides can also act as "anchors," anchoring the heat-affected zone (HAZ) and effectively inhibiting abnormal grain growth, thereby ensuring the mechanical properties of the HAZ (weld layer).

[0046] Furthermore, the modifier's fine-grain strengthening of the weld metal is beneficial to improving the overall mechanical properties of the solid welding wire and the wear-resistant surface.

[0047] Compared to adding rare earth alloys to the raw materials during smelting to form original inclusions for modification, this patent adds rare earth alloy synthetic oxide modifiers to the molten steel, avoiding the problems of low specific gravity, easy floating, poor wettability, and small particle size of the original rare earth inclusions in the molten steel. Furthermore, appropriate welding methods and processes are adopted according to product requirements, effectively improving the performance of solid welding wire and wear-resistant surface.

[0048] In this application, solid welding wire is deposited in the groove on the surface of the stepper plate. Traditional stepper plates generally adopt an integral structure, which makes them prone to pitting, edge crushing, cracking, and even breakage during use. This application uses a composite stepper plate, forming a wear-resistant layer with higher hardness on the substrate of the stepper plate, forming a composite structure that combines rigidity and flexibility. This composite structure greatly improves the wear resistance, corrosion resistance, impact resistance, and fatigue resistance of the stepper plate during use.

[0049] The present invention also discloses a composite stepper plate prepared by the above method. The composite stepper plate includes a substrate with grooves formed thereon, and a wear-resistant layer is formed by welding solid wire into the grooves.

[0050] The wear-resistant surface contains 85% to 90% martensite and has a hardness of HRC50-57.

[0051] The matrix metallographic structure is tempered sorbite;

[0052] There is a 2-4mm heat-affected zone between the wear-resistant surface and the substrate. The metallographic structure of the heat-affected zone is bainite, and there is no embrittlement caused by MA components, upper bainite, or coarse Widmanstätten structure.

[0053] The matrix is ​​selected from materials with a hardness of HB240-260 and an impact energy Akv(J)≥34, such as X22CrMoV12-1. In addition, other materials that meet the comprehensive mechanical properties can also be used in the composite stepper plate of this application.

[0054] 3. Beneficial effects

[0055] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0056] (1) A method for preparing a composite stepper plate according to the present invention addresses the problem of high welding difficulty due to high alloy element content, high carbon equivalent, and high texture sensitivity of the substrate. By modifying the welding wire, selecting a suitable welding method, and adjusting the welding parameters, a wear-resistant surface that meets the comprehensive performance requirements can be prepared.

[0057] (2) The solid welding wire used in the welding of the present invention is modified by using nano-rare earth oxides as modifiers. Nano-rare earth oxides have a low melting point and nucleate earlier than ordinary ceramic oxides during solidification and crystallization. They also have more heterogeneous nucleation cores with a more uniform distribution. Furthermore, the modifier strengthens the fine grains of the weld metal, which is beneficial to improving the comprehensive mechanical properties of the solid welding wire and the wear-resistant surface.

[0058] (3) The solid core welding wire of the present invention has a more uniform nucleation distribution during the solidification and crystallization of nano-rare earth oxides, which is conducive to forming a more uniform solid core welding wire during the cold drawing process and improving the drawing performance of the solid core welding wire.

[0059] (4) A composite stepper plate of the present invention uses modified solid welding wire to build up a wear-resistant surface, forming a "rigid and flexible" composite structure with the substrate. The composite stepper plate has both the impact resistance of the substrate material and the wear resistance of the welding material, which solves the problems of pits, edge pressure and cracks, and even breakage on the surface of traditional stepper plates, and improves the service life of the stepper plate. Attached Figure Description

[0060] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. However, it should be understood that these drawings are designed for illustrative purposes only and are not intended to limit the scope of the present invention. Furthermore, unless specifically indicated, these drawings are intended only to conceptually illustrate the structural construction described herein and are not necessarily drawn to scale.

[0061] Figure 1 and Figure 2 This is a schematic diagram of the composite stepper plate substrate of the present invention;

[0062] Figure 3 This is a schematic diagram of the wear-resistant surface overlay welding of the present invention;

[0063] Figure 4 This is a diagram illustrating the post-weld heat treatment process of the composite stepper plate of the present invention. Detailed Implementation

[0064] The following detailed description of exemplary embodiments of the invention is taken with reference to the accompanying drawings, which form part of the description and illustrate exemplary embodiments in which the invention may be practiced. While these exemplary embodiments have been described in sufficient detail to enable those skilled in the art to practice the invention, it should be understood that other embodiments may be implemented and various changes may be made to the invention without departing from the spirit and scope thereof. The more detailed description of embodiments of the invention below is not intended to limit the scope of the claimed invention, but is merely illustrative and not restrictive of the description of the features and characteristics of the invention, to suggest the best mode for carrying out the invention, and is sufficient to enable those skilled in the art to practice the invention. Therefore, the scope of the invention is defined only by the appended claims.

[0065] The wear resistance of each sample in the examples was characterized by wear tests conducted using a UMT Tribolab high-load reciprocating friction tester. The wear material was an Al2O3 ball with a diameter of 6.35 mm.

[0066] The wear test specimens were first pre-fabricated using wire cutting, and then the surface to be worn was polished to a mirror finish using a metallographic polishing machine. During the wear process, the wear specimen was in direct contact with the Al2O3 balls being worn. The wear time was 30 minutes, the testing machine speed was set to 150 r / min, and the load was 50 N. An analytical balance with a sensitivity of 0.00001 g was used for weighing. After the wear process was completed, the specimens were purged and weighed again. The weight loss characterized the wear resistance, and the coefficients of friction of each specimen were compared. The test results are shown in Table 1.

[0067] The formula for calculating carbon equivalent is CE=[C+Mn / 6+(Cu+Ni) / 15+(Cr+Mo+V) / 5]×100%.

[0068] Example 1

[0069] This embodiment describes a method for manufacturing a composite stepper plate, using high-temperature resistant stainless steel X22CrMoV12-1 as the substrate. The carbon equivalent of this substrate is 2.94. The specific steps are as follows:

[0070] Step S1: Fabrication of the base material: High-temperature resistant stainless steel X22CrMoV12-1 is fabricated. The composition and weight percentage of X22CrMoV12-1 are: C: 0.20%, Si: 0.45%, Mn: 0.78%, Cr: 11.5%, Mo: 1.06%, V: 0.31%, Ni: 0.55%, S≤0.035%, P≤0.035%, with the remainder being Fe. Square steel ingots or continuously cast billets are used for forging. Sufficient cut-off ends and machining allowances are left at both ends of the billet to avoid harmful defects in the forging. The forging is formed using an 8-ton hammer or higher, ensuring the entire cross-section is forged through and the microstructure is uniform, with a forging ratio ≥3. The forged billet is placed in a gas furnace according to process or specification requirements to ensure uniform heating, and the holding time must not be less than the minimum holding time required for each forging pass. The initial forging temperature is 1220℃-1250℃, and the final forging temperature is ≥880℃. Forgings are subjected to rapid solution treatment after forging.

[0071] Step S2, heat treatment of the substrate:

[0072] Quenching: Slowly heat to the quenching temperature of 1030℃ and then put it into an oil bath for quenching treatment. Cool the quenched temperature to below 200℃.

[0073] Tempering: After quenching, the material needs to be reheated to 680℃ in the furnace within 30 minutes and held for 10 hours. Then, it is oil-cooled to 200℃ and air-cooled to room temperature. This ensures that the hardness of the X22CrMoV12-1 matrix reaches HB240-260. The microstructure of the X22CrMoV12-1 forging blank is coarse martensite + alloy carbides + retained austenite. After quenching and tempering, the microstructure is tempered sorbite. The mechanical properties are tensile strength σb (MPa) ≥800, yield strength σs (MPa) ≥600, elongation δ5 (%) ≥14, and impact energy Akv (J) ≥34.

[0074] Step S3: Fabricate the wear-resistant composite surface weld groove of the stepper plate:

[0075] A groove with dimensions of 810mm × 210mm × 10mm is milled according to the contour, such as... Figure 1 and Figure 2 As shown;

[0076] Step S4: Welding a wear-resistant composite weld overlay surface:

[0077] like Figure 3 As shown, the wear-resistant composite surface is deposited by tungsten inert gas welding, which specifically includes the following steps:

[0078] S4.1 Preheating: The main body of the stepper plate is preheated in a preheating furnace at a temperature of 280°C and kept warm during the welding process;

[0079] S4.2 Overlay welding: High-chromium stainless steel solid welding wire containing nano-rare earth oxide particles is overlaid into the wear-resistant composite surface overlay groove by tungsten inert gas welding.

[0080] The solid welding wire in this embodiment includes an iron-based material and a modifier. The iron-based material has the following composition: C: 0.49%, Si: 0.45%, Mn: 0.60%, Cr: 12.51%, S: 0.003%, P: 0.003%, with the remainder being Fe. The modifier is a nano-rare earth oxide including CeO2, the average particle size of which is 50 mm, and the mass ratio of CeO2 to the iron-based material is 2:15.

[0081] The method for preparing the above-mentioned solid welding wire includes the following steps:

[0082] a. By mechanically grinding the modifier with iron powder, a homogenized ceramic phase powder is obtained;

[0083] b. Ball mill the ceramic phase powder obtained in step a for 9 hours to obtain a ceramic phase toughening agent;

[0084] c. Add sodium silicate binder to the ceramic phase toughening agent obtained in step b, and roll it into a spherical material;

[0085] d. Finally, according to the raw material ratio of solid welding wire, the required elements are added to the melting furnace, and the spherical material obtained in step c is added at the same time. After forging, rolling and cold drawing, solid welding wire is obtained.

[0086] By incorporating a ceramic phase into the iron-based material, the problems of low specific gravity, easy floating, poor wettability, and easy agglomeration of nano-ceramic phase powder in molten steel are solved. When added to the molten steel, it acts as a heterogeneous nucleation core, providing fine-grain strengthening, and as a fine second phase, providing dispersion strengthening, thereby improving the material's toughness and ductility. However, in existing technologies, the addition of SiO2, MgO, and CaO to form a ceramic phase (CN116021191A) results in a high melting point and low specific gravity. This leads to a short diffusion time during welding, causing the ceramic phase to float and resulting in uneven distribution in the weld, thus affecting performance stability.

[0087] Compared to the addition of general ceramic phase oxides, the addition of rare earth oxides in the steel smelting process has the following additional effects: 1. Purifying molten steel: Rare earth elements can react with oxygen and sulfur in inclusions such as manganese sulfide, alumina, and aluminosilicates in steel to generate high-melting-point non-metallic compounds. These compounds float to the slag layer, thereby reducing the content of inclusions in the steel and producing solid welding wire with higher purity. 2. Microalloying effect: Rare earth elements can refine grains, improve the microstructure of steel, affect the phase transformation process of steel, change the composition and structure of phase transformation products, and thus improve the physical and mechanical properties of steel. 3. Improving resistance to hydrogen embrittlement and stress corrosion: Rare earth elements can effectively absorb and diffuse hydrogen atoms, reducing the hydrogen content in steel, thereby improving the steel's resistance to hydrogen embrittlement and corrosion. 4. Refining grains and improving steel performance: The addition of rare earth elements can improve the strength, toughness, and plasticity of steel, while also improving its wear resistance and corrosion resistance. 5. Controlling inclusion morphology. Rare earth elements can control the morphology of inclusions in steel, avoiding or overcoming the anisotropy of properties caused by the extension and deformation of other types of inclusions during hot pressure processing.

[0088] To ensure sufficient diffusion of oxides during welding, it is necessary to increase heat input and prolong the molten pool's melting time. This results in a larger heat-affected zone, generating thermal and residual stresses, leading to significant weld joint deformation and a coarse weld joint microstructure, affecting its mechanical and corrosion resistance properties. Therefore, this application incorporates nano-rare earth oxides. Rare earth oxides have lower melting points than general ceramic oxides, allowing for more sufficient time to diffuse into the molten steel or weld pool during both material smelting and welding processes. Their distribution is more uniform, and they nucleate earlier during solidification and crystallization compared to general ceramic oxides. Furthermore, rare earth oxides exhibit a greater number and more uniform distribution of heterogeneous nucleation cores, which facilitates the formation of a fine-grained strengthening mechanism, promotes material toughening, and results in a more uniform solid core welding wire during cold drawing. This improves the tensile properties of the solid core welding wire, enabling it to be drawn into a welding wire with a diameter of 1.2 mm.

[0089] During the welding process, the parameters for the first root pass are: current 130±10A, arc voltage 15±1V, and gas flow rate 15L / min; the parameters for the fill pass are: current 150±10A, arc voltage 16±2V, and gas flow rate 16L / min; and the parameters for the cover pass are: current 130±10A, arc voltage 14±1V, and gas flow rate 15L / min. A machining allowance of 3mm should be left for the welding height.

[0090] S4.3 Post-weld heat treatment: Post-weld heat treatment is used to eliminate residual welding stress, remove diffusible hydrogen from the joint, and improve the microstructure and properties of the joint. Post-weld heat treatment is carried out according to... Figure 4The heat treatment process shown is as follows: the weld-overlayed stepper plate is loaded into the furnace, the furnace temperature is ensured to be above 200℃, and then it is uniformly heated to 380±10℃ at a rate of ≤200℃ / hour, held for 4 hours, and then cooled to ≤100℃ at a rate of ≤50℃ / hour before being removed from the furnace.

[0091] The composition of the wear-resistant surface after welding is the same as that of the solid welding wire.

[0092] Step S5, Finishing: The weld-overlay stepper board is machined to the finished size through rough grinding, fine grinding, milling, and clamping.

[0093] Step S6, Detection:

[0094] The finished product was tested for hardness and metallographic structure.

[0095] The hardness test results were 52-56 HRC. The metallographic structure of the wear-resistant surface was martensite + δ-ferrite, with martensite accounting for approximately 85-88%. The hardness of the area with 85% martensite was HRC52, and the hardness of the area with 88% martensite was HRC56. The matrix metallographic structure was sorbite + bainite, which ensures that no embrittlement will occur after welding. The thickness of the heat-affected zone was 2 mm, and the metallographic structure of the heat-affected zone was bainite. No embrittlement caused by MA components, upper bainite, or coarse Widmanstätten structure was observed. The test results met the technical requirements.

[0096] The friction properties of the obtained wear-resistant surface are shown in Table 1.

[0097] Example 2

[0098] This embodiment describes a method for manufacturing a composite stepper plate, using high-temperature resistant stainless steel X22CrMoV12-1 as the substrate. The carbon equivalent of this substrate is 3.21. The specific steps are as follows:

[0099] Step S1: Fabrication of the base material: Fabricate high-temperature resistant stainless steel X22CrMoV12-1. The composition and weight percentage of X22CrMoV12-1 are: C: 0.24%, Si: 0.48%, Mn: 0.80%, Cr: 12.5%, Mo: 1.20%, V: 0.28%, Ni: 0.68%, S≤0.035%, P≤0.035%, with the remainder being Fe. Forging is performed using square steel ingots or continuously cast billets. Sufficient cut-off ends and machining allowances are left at both ends of the billet to avoid harmful defects in the forging. The forging is formed using an 8-ton hammer or higher, ensuring the entire cross-section is forged through and the microstructure is uniform, with a forging ratio ≥3. The forged billet is placed in a gas-fired furnace according to process or specification requirements to ensure uniform heating. The holding time must not be less than the minimum holding time required for each forging pass. The initial forging temperature is 1220℃-1250℃, and the final forging temperature is ≥880℃. Forgings are subjected to rapid solution treatment after forging.

[0100] Step S2, heat treatment of the substrate:

[0101] Quenching: Slowly heat to the quenching temperature of 1030℃ and then put it into an oil bath for quenching treatment. Cool the quenched temperature to below 200℃.

[0102] Tempering: After quenching, the material needs to be reheated to 680℃ in the furnace within 30 minutes and held for 10 hours. Then, it is oil-cooled to 200℃ and air-cooled to room temperature. This ensures that the hardness of the X22CrMoV12-1 matrix reaches HB240-260. The microstructure of the X22CrMoV12-1 forging blank is coarse martensite + alloy carbides + retained austenite. After quenching and tempering, the microstructure is tempered sorbite. The mechanical properties are tensile strength σb (MPa) ≥800, yield strength σs (MPa) ≥600, elongation δ5 (%) ≥14, and impact energy Akv (J) ≥34.

[0103] Step S3: Fabricate the wear-resistant composite surface weld groove of the stepper plate:

[0104] A groove with dimensions of 810mm × 210mm × 10mm is milled according to the contour, such as... Figure 1 and Figure 2 As shown;

[0105] Step S4: Welding a wear-resistant composite weld overlay surface:

[0106] like Figure 3 As shown, the wear-resistant composite surface is deposited by tungsten inert gas welding, which specifically includes the following steps:

[0107] S4.1 Preheating: The main body of the stepper plate is preheated in a preheating furnace at a temperature of 280°C and kept warm during the welding process;

[0108] S4.2 Overlay welding: High-chromium stainless steel solid welding wire containing nano-rare earth oxide particles is overlaid into the wear-resistant composite surface overlay groove by tungsten inert gas welding.

[0109] The solid welding wire in this embodiment includes an iron-based material and a modifier. The iron-based material has the following composition: C: 0.49%, Si: 0.45%, Mn: 0.60%, Cr: 12.51%, S: 0.003%, P: 0.003%, with the remainder being Fe. The modifier is a nano-rare earth oxide including CeO2, the average particle size of which is 50 mm, and the mass ratio of CeO2 to the iron-based material is 2:20.

[0110] The method for preparing the above-mentioned solid welding wire includes the following steps:

[0111] a. By mechanically grinding the modifier with iron powder, a homogenized ceramic phase powder is obtained;

[0112] b. Ball mill the ceramic phase powder obtained in step a for 9 hours to obtain a ceramic phase toughening agent;

[0113] c. Add sodium silicate binder to the ceramic phase toughening agent obtained in step b, and roll it into a spherical material;

[0114] d. Finally, according to the raw material ratio of solid welding wire, the required elements are added to the melting furnace, and the spherical material obtained in step c is added at the same time. After forging, rolling and cold drawing, solid welding wire is obtained.

[0115] During the welding process, the parameters for the first root pass are: current 140±10A, arc voltage 15±1V, pure argon gas, and flow rate 15L / min; the parameters for the fill pass are: current 150±10A, arc voltage 17±1V, and gas flow rate 18L / min; the parameters for the cover pass are: current 140±10A, arc voltage 15±1V, and gas flow rate 14L / min. A machining allowance of 3mm should be left for the welding height.

[0116] S4.3 Post-weld heat treatment: Post-weld heat treatment is used to eliminate residual welding stress, remove diffusible hydrogen from the joint, and improve the microstructure and properties of the joint. Post-weld heat treatment is carried out according to... Figure 4 The heat treatment process shown is as follows: the weld-overlayed stepper plate is loaded into the furnace, the furnace temperature is ensured to be above 200℃, and then it is uniformly heated to 380±10℃ at a rate of ≤200℃ / hour, held for 4 hours, and then cooled to ≤100℃ at a rate of ≤50℃ / hour before being removed from the furnace.

[0117] The composition of the wear-resistant surface after welding is the same as that of the solid welding wire.

[0118] Step S5, Finishing: The weld-overlay stepper board is machined to the finished size through rough grinding, fine grinding, milling, and clamping.

[0119] Step S6, Detection:

[0120] The finished product was tested for hardness and metallographic structure.

[0121] The hardness test results were 52-57 HRC. The metallographic structure of the wear-resistant surface was martensite + δ-ferrite, with martensite accounting for approximately 86-90%. The hardness of the area with 86% martensite was HRC52, and the hardness of the area with 90% martensite was HRC57. The matrix metallographic structure was sorbite + bainite, which ensures that no embrittlement will occur after welding. The thickness of the heat-affected zone was 2 mm, and the metallographic structure of the heat-affected zone was bainite. No embrittlement caused by MA components, upper bainite, or coarse Widmanstätten structure was observed. The test results met the technical requirements.

[0122] The friction properties of the obtained wear-resistant surface are shown in Table 1.

[0123] Example 3

[0124] This embodiment describes a method for manufacturing a composite stepper plate, using high-temperature resistant stainless steel X22CrMoV12-1 as the substrate. The carbon equivalent of this substrate is 2.70. The specific steps are as follows:

[0125] Step S1: Fabrication of the base material: High-temperature resistant stainless steel X22CrMoV12-1 is fabricated. The composition and weight percentage of X22CrMoV12-1 are: C: 0.18%, Si: 0.10%, Mn: 0.41%, Cr: 11.05%, Mo: 0.82%, Ni: 0.35%, V: 0.25%, S≤0.025%, P≤0.025%, with the remainder being Fe. Square steel ingots or continuously cast billets are used for forging. Sufficient cut-off ends and machining allowances are left at both ends of the billet to avoid harmful defects in the forging. The forging is formed using an 8-ton hammer or higher, ensuring the entire cross-section is forged through and the microstructure is uniform, with a forging ratio ≥3. The forged billet is placed in a gas-fired furnace according to process or specification requirements to ensure uniform heating. The holding time must not be less than the minimum holding time required for each forging pass. The initial forging temperature is 1220℃-1250℃, and the final forging temperature is ≥880℃. Forgings are subjected to rapid solution treatment after forging.

[0126] Step S2, heat treatment of the substrate:

[0127] Quenching: Slowly heat to the quenching temperature of 1030℃ and then put it into an oil bath for quenching treatment. Cool the quenched temperature to below 200℃.

[0128] Tempering: After quenching, the material needs to be reheated to 680℃ in the furnace within 30 minutes and held for 10 hours. Then, it is oil-cooled to 200℃ and air-cooled to room temperature. This ensures that the hardness of the X22CrMoV12-1 matrix reaches HB240-260. The microstructure of the X22CrMoV12-1 forging blank is coarse martensite + alloy carbides + retained austenite. After quenching and tempering, the microstructure is tempered sorbite. The mechanical properties are tensile strength σb (MPa) ≥800, yield strength σs (MPa) ≥600, elongation δ5 (%) ≥14, and impact energy Akv (J) ≥34.

[0129] Step S3: Fabricate the wear-resistant composite surface weld groove of the stepper plate:

[0130] A groove with dimensions of 810mm × 210mm × 10mm is milled according to the contour, such as... Figure 1 and Figure 2 As shown;

[0131] Step S4: Welding a wear-resistant composite weld overlay surface:

[0132] like Figure 3 As shown, the wear-resistant composite surface is deposited by tungsten inert gas welding, which specifically includes the following steps:

[0133] S4.1 Preheating: The main body of the stepper plate is preheated in a preheating furnace at a temperature of 280°C and kept warm during the welding process;

[0134] S4.2 Overlay welding: High-chromium stainless steel solid welding wire containing nano-rare earth oxide particles is overlaid into the wear-resistant composite surface overlay groove by tungsten inert gas welding.

[0135] The solid welding wire in this embodiment includes an iron-based material and a modifier. The iron-based material has the following composition: C: 0.49%, Si: 0.45%, Mn: 0.60%, Cr: 12.51%, S: 0.003%, P: 0.003%, with the remainder being Fe. The modifier is a nano-rare earth oxide including La2O3, the average particle size of which is 50 mm, and the mass ratio of La2O3 to the iron-based material is 2:20.

[0136] The method for preparing the above-mentioned solid welding wire includes the following steps:

[0137] a. By mechanically grinding the modifier with iron powder, a homogenized ceramic phase powder is obtained;

[0138] b. Ball mill the ceramic phase powder obtained in step a for 9 hours to obtain a ceramic phase toughening agent;

[0139] c. Add sodium silicate binder to the ceramic phase toughening agent obtained in step b, and roll it into a spherical material;

[0140] d. Finally, according to the raw material ratio of solid welding wire, the required elements are added to the melting furnace, and the spherical material obtained in step c is added at the same time. After forging, rolling and cold drawing, solid welding wire is obtained.

[0141] During the welding process, the parameters for the first root pass are: current 135±10A, arc voltage 14±1V, pure argon gas, and flow rate 15L / min; the parameters for the fill pass are: current 140±10A, arc voltage 15.5±1V, and gas flow rate 16L / min; the parameters for the cover pass are: current 125±10A, arc voltage 14±1V, and gas flow rate 13L / min. A machining allowance of 3mm should be left for the weld height.

[0142] S4.3 Post-weld heat treatment: Post-weld heat treatment is used to eliminate residual welding stress, remove diffusible hydrogen from the joint, and improve the microstructure and properties of the joint. Post-weld heat treatment is carried out according to... Figure 4 The heat treatment process shown is as follows: the weld-overlayed stepper plate is loaded into the furnace, the furnace temperature is ensured to be above 200℃, and then it is uniformly heated to 380-310℃ at a rate of ≤200℃ / hour, held for 4 hours, and then cooled to ≤100℃ at a rate of ≤50℃ / hour before being removed from the furnace.

[0143] The composition of the wear-resistant surface after welding is the same as that of the solid welding wire.

[0144] Step S5, Finishing: The weld-overlay stepper board is machined to the finished size through rough grinding, fine grinding, milling, and clamping.

[0145] Step S6, Detection:

[0146] The finished product was tested for hardness and metallographic structure.

[0147] The hardness test results are 50-55 HRC. The metallographic structure of the wear-resistant surface is martensite + δ-ferrite, with martensite accounting for approximately 85-187%. The hardness of the area with 85% martensite content is HRC50, and the hardness of the area with 87% martensite content is HRC55. The matrix metallographic structure is sorbite + bainite, which ensures that no embrittlement will occur after welding. The thickness of the heat-affected zone is 2 mm, and the metallographic structure of the heat-affected zone is bainite. No embrittlement caused by MA components, upper bainite, or coarse Widmanstätten structure is observed. The test results meet the technical requirements.

[0148] The friction properties of the obtained wear-resistant surface are shown in Table 1.

[0149] Table 1. Wear loss data of each material in Examples 1-3

[0150] Example Hardness / HRC original weight M0 / g weight M1 / g after grinding Weight loss AM / g Average coefficient of friction 1 52-56 2083.52 2083.48 0.04 0.8525 2 52-57 2136.17 2136.09 0.08 0.8402 3 50-55 2163.90 2163.82 0.08 0.8482

[0151] The modified solid welding wire used in this application forms a wear-resistant surface with higher wear resistance, creating a "rigid-flexible" composite structure with the substrate. This composite stepper plate combines the impact resistance of the substrate material with the wear resistance of the welding material, greatly improving the wear resistance, corrosion resistance, impact resistance, and fatigue resistance of the stepper plate during use.

[0152] The above description is merely a preferred embodiment of this application and an explanation of the technical principles used. Those skilled in the art should understand that the scope involved in this application is not limited to the technical solutions formed by a specific combination of the above-mentioned technical features, but should also cover other technical solutions formed by any combination of the above-mentioned technical features or their equivalent features without departing from the inventive concept. For example, technical solutions formed by replacing the above-mentioned features with technical features with similar functions disclosed in this application (but not limited to) each other.

[0153] Apart from the technical features described in the specification, the other technical features are known to those skilled in the art. To highlight the innovative features of this invention, the other technical features will not be described in detail here.

Claims

1. A method for manufacturing a composite stepper plate, characterized in that, The process includes the following steps: creating wear-resistant grooves on the surface of the stepper plate substrate, and depositing solid welding wire into the wear-resistant grooves to form a wear-resistant surface. The solid welding wire comprises an iron-based material and a modifier. The chemical composition of the iron-based material is: C: 0.47%-0.55%, Si: 0.30%-0.50%, Mn: 0.50%-0.80%, Cr: 12.00%-14.00%, S≤0.03%, P≤0.03%, with the remainder being Fe. The modifier is a nano-rare earth oxide. The components and weight percentages of the matrix are as follows: C: 0.18%-0.24%, Si: 0.10%-0.50%, Mn: 0.40%-0.90%, Cr: 11.00%-12.50%, Mo: 0.80%-1.20%, Ni: 0.30%-0.80%, V: 0.25%-0.35%, S≤0.025%, P≤0.025%, with the remainder being Fe; The carbon equivalent of the matrix portion is greater than 2.0%; The specific steps involved in depositing solid welding wire into the wear-resistant groove to form the wear-resistant surface include: S4.

1. Preheating: The preheating temperature is 200-250℃, and the temperature is maintained during the welding process; S4.

2. Preparation of the root layer: Solid welding wire with a diameter of 1.2 mm containing nano-rare earth oxides is deposited into the groove of the wear-resistant composite surface. The parameters for the first root layer are: current of 120-150A, arc voltage of 13-17V, pure argon gas, and flow rate of 12-16L / min. S4.

3. Preparation of the filling layer: The filling layer parameters are: current 130-160A, arc voltage 14-19V, and gas flow rate 12-16L / min; S4.

4. Preparation of the capping layer: The capping layer parameters are: current 110-150A, arc voltage 12-17V, and gas flow rate 12-15L / min.

2. The manufacturing method according to claim 1, characterized in that, The ratio of the modifier to the iron-based material is (2-3):(15-20).

3. The manufacturing method according to claim 2, characterized in that, The nano-rare earth oxides include one or more of CeO2 and La2O3.

4. The manufacturing method according to claim 3, characterized in that, The welding method is tungsten inert gas (TIG) shielded welding.

5. The manufacturing method according to claim 4, characterized in that, Including the following steps: S1. Fabricate the stepper plate base; S2, Heat-treated substrate portion; S3. Create wear-resistant grooves on the stepper plate: The wear-resistant grooves are machined by CNC milling. S4. Wear-resistant composite weld overlay: Solid welding wire is welded to the groove of the wear-resistant surface, and then post-weld heat treatment is performed; S5. Finishing: The welded stepper plate is machined to the finished size through milling and grinding.

6. The manufacturing method according to claim 5, characterized in that, The heat treatment substrate step in step S2 includes: Quenching: Slowly heat to the quenching temperature of 1010~1040℃ and then put it into the oil bath for quenching treatment. Cool the quenched temperature to below 200℃. Tempering: After quenching, the furnace needs to be reheated to 670-690℃ within 20-30 minutes and held for 10-12 hours. Then, it should be oil-cooled to 200℃ and air-cooled to room temperature.

7. A composite stepper plate, manufactured using the manufacturing method according to any one of claims 1-6, characterized in that, The material includes a substrate with grooves formed thereon. Solid welding wire is used to deposit the material in the grooves to form a wear-resistant layer. The carbon equivalent of the substrate is greater than 2.0%. The solid welding wire comprises an iron-based material and a modifier. The chemical composition of the iron-based material is: C: 0.47%-0.55%, Si: 0.30%-0.50%, Mn: 0.50%-0.80%, Cr: 12.00%-14.00%, S≤0.03%, P≤0.03%, with the remainder being Fe. The modifier is a nano-rare earth oxide. The components and weight percentages of the matrix are as follows: C: 0.18%-0.24%, Si: 0.10%-0.50%, Mn: 0.40%-0.90%, Cr: 11.00%-12.50%, Mo: 0.80%-1.20%, Ni: 0.30%-0.80%, V: 0.25%-0.35%, S≤0.025%, P≤0.025%, with the remainder being Fe.

8. The composite stepper plate according to claim 7, characterized in that, The wear-resistant surface contains 85% to 90% martensite and has a hardness of HRC50-57.

9. The composite stepper plate according to claim 8, characterized in that, The matrix metallographic structure is tempered sorbite, the matrix hardness is HB240-260, and the impact energy Akv(J)≥34.

10. The composite stepper plate according to claim 9, characterized in that, It also includes a heat-affected zone, located between the wear-resistant surface and the substrate, the thickness of which is 2-4 mm, and the metallographic structure of which is bainite.

11. A solid welding wire for welding the composite stepper plate according to any one of claims 7-10, characterized in that, It includes an iron-based material and a modifier. The chemical composition of the iron-based material is: C: 0.47%-0.55%, Si: 0.30%-0.50%, Mn: 0.50%-0.80%, Cr: 12.00%-14.00%, S≤0.03%, P≤0.03%, with the remainder being Fe. The modifier is a nano-rare earth oxide.

12. The solid welding wire according to claim 11, characterized in that, The ratio of the modifier to the iron-based material is (2-3):(15-20).

13. The solid welding wire according to claim 12, characterized in that, The nano-rare earth oxides include one or more of CeO2 and La2O3.

14. A method for manufacturing the solid welding wire according to any one of claims 11-13, characterized in that, Including the following steps: a. By mechanically grinding the modifier with iron powder, a homogenized ceramic phase powder is obtained; b. Ball mill the ceramic phase powder obtained in step a for 8-15 hours to obtain a ceramic phase toughening agent; c. Add sodium silicate binder to the ceramic phase toughening agent obtained in step b, and roll it into a spherical material. d. Finally, according to the raw material ratio of solid welding wire, the required elements are added to the melting furnace, and the spherical material obtained in step c is added at the same time. After forging, rolling and cold drawing, solid welding wire is obtained.

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