A bimetallic wear-resistant roller sleeve for MPS medium-speed mill and a composite overlay manufacturing method thereof

Abstract

The application discloses a MPS medium-speed mill double-metal wear-resistant roller sleeve and a composite overlay manufacturing method thereof, wherein the MPS medium-speed mill double-metal wear-resistant roller sleeve comprises a roller sleeve base body which is a casting part made of ZG20SiMn or ZG270-500 material; an overlay curved surface is arranged on the outer surface of the roller sleeve base body; a base transition layer and a wear-resistant overlay layer are sequentially arranged on the overlay curved surface; and the wear-resistant overlay layer comprises an inner overlay intermediate layer and an outer overlay cover layer. The application can be repeatedly used and can meet the use requirements of low cost and high wear resistance.

Description

Technical Field

[0001] This invention relates to a weld overlay roller sleeve for medium-speed coal mills and its manufacturing method, particularly a bimetallic wear-resistant roller sleeve for MPS medium-speed mills and its composite weld overlay manufacturing method, belonging to the technical field of medium-speed coal mill parts application. Background Technology

[0002] Currently, medium-speed coal mills are widely recognized as the preferred choice for large-scale thermal power units due to their low initial investment cost, low power consumption during coal grinding, and minimal increase in unit power consumption during low-load operation. In my country, 81% of thermal power units with a capacity of 500MW and above are equipped with medium-speed coal mills. The MPS type medium-speed coal mill is a roller-disc type medium-speed coal mill designed and manufactured by Babcock GmbH in Germany. In large-scale thermal power plant coal pulverizing systems, the MPS coal mill is mainly used in direct-fired pulverizing systems for grinding bituminous coal, high-moisture bituminous coal, and lignite.

[0003] Raw coal enters the mill through the coal inlet pipe. The centrifugal force generated by the rotation of the mill disc causes the coal to evenly enter the mill disc track. The rotation of three evenly distributed grinding rollers driven by the mill disc crushes the coal into fine powder between the rollers and the mill disc. Under centrifugal force, the powder overflows from the mill disc. Hot air enters the mill at a speed of 70-90 m / s through rotating nozzle rings driven by the mill disc, drying the raw coal and simultaneously conveying the ground coal powder to a separator. Qualified coal powder enters the furnace for combustion, while coarse powder is returned to the mill for re-grinding. Stones, iron blocks, and other impurities in the coal fall through the nozzle rings onto the lower frame and are scraped into the slag box by scrapers, thus being discarded outside the mill.

[0004] As can be seen from the above, the roller sleeve is a key component of the MPS medium-speed mill.

[0005] In recent years, China has been vigorously researching composite surfacing roller sleeve technology. The goal is to manufacture a new type of composite roller sleeve that allows the roller sleeve substrate and working surface to meet the requirements of impact resistance and wear resistance during coal grinding. Surfacing roller sleeve has become a major development direction and means for manufacturing, repairing, and improving the service life of roller sleeves in China.

[0006] When considering the service life of MPS medium-speed grinding roller sleeves, there are nearly 20 types of welding wires for wear-resistant welded roller sleeves, with significant cost differences. When considering both low cost and high wear resistance, existing niobium-containing and ceramic welded series are extremely expensive to manufacture. Therefore, there is an urgent need for a long-life, low-cost composite roller sleeve and its manufacturing method to address the short wear life of existing roller sleeves. Summary of the Invention

[0007] In order to overcome the above-mentioned shortcomings of related technologies, the present invention provides a bimetallic wear-resistant roller sleeve for MPS medium-speed mill and a composite welding manufacturing method thereof, which can be reused and can meet the requirements of low cost and high wear resistance.

[0008] One technical solution adopted by the present invention to solve its technical problem is:

[0009] A bimetallic wear-resistant roller sleeve for MPS medium-speed mill includes a roller sleeve base, which is a casting made of ZG20SiMn or ZG270-500 material; the outer surface of the roller sleeve base is provided with a weld overlay curved surface, and a base transition layer and a weld overlay wear-resistant layer are sequentially provided on the weld overlay curved surface, and the weld overlay wear-resistant layer further includes an inner and outer weld overlay intermediate layer and a weld overlay cover layer.

[0010] Optionally, the chemical composition of the ZG20SiMn is: 0.12%-0.22% C, 1.0%-1.3% Mn, 0.6%-0.8% Si, ≤0.020% P, and ≤0.020% S.

[0011] Optionally, the chemical composition of the ZG270-500 is: ≤0.35% C, ≤0.5% Si, ≤0.8% Mn, ≤0.020% P, and ≤0.020% S.

[0012] Optionally, the underlay transition layer is formed by welding the underlay wire onto the weld overlay surface; the number of weld overlay layers in the underlay transition layer is 1-2 layers.

[0013] Optionally, the chemical composition of the root pass welding wire is: 0.05%-0.10% C, 18.0%-20.0% Cr, 6.0%-7.0% Mn, 0.6%-1.2% Si, and 9.0%-10.0% Ni.

[0014] Optionally, both the intermediate weld overlay layer and the weld overlay cover layer are welded using high-alloy high-chromium cast iron welding materials.

[0015] Optionally, the chemical composition of the first high-alloy high-chromium cast iron welding material for the overlay intermediate layer is as follows:

[0016] 4.5%-5.5% C, 25.0%-30.0% Cr, 0.8%-1.5% Mn, 0.6%-1.0% Si; metallographic structure is ≥50.0% carbides.

[0017] Optionally, the chemical composition of the second high-alloy high-chromium cast iron welding material for the overlay layer is as follows:

[0018] 4.5%-5.5% C, 25.0%-33.0% Cr, 0.8%-1.5% Mn, 0.6%-1.0% Si, 0.8%-1.5% Mo, 2% Ti+V+W; the metallographic structure is ≥55.0% carbides.

[0019] With the above technical solution, the MPS medium-speed mill bimetallic wear-resistant roller sleeve of the present invention achieves a significant improvement in wear resistance by setting a composite structure of a casting of ZG20SiMn or ZG270-500 material + a base transition layer + a welded intermediate layer + a welded cover layer on the welded surface, which greatly improves the overall service life. At the same time, based on the reasonable setting of the welded surface and multiple cyclic welds, the weld weight and weld cost can be greatly reduced.

[0020] Another technical solution adopted by the present invention to solve its technical problem is:

[0021] A composite welding manufacturing method for the bimetallic wear-resistant roller sleeve of the MPS medium-speed mill includes casting the roller sleeve substrate, welding the underlying transition layer, and welding the wear-resistant layer.

[0022] Specifically, a weld overlay surface is drawn based on the on-site wear curve, and a root transition layer is welded onto the weld overlay surface. The thickness of the weld overlay layer composed of the root transition layer and the wear-resistant layer is determined according to the actual wear location. The root transition layer and the wear-resistant layer are respectively selected with corresponding chemical compositions of the root welding wire, the first high-alloy high-chromium cast iron welding material, and the second high-alloy high-chromium cast iron welding material, and all adopt the open arc offline automatic wear-resistant weld overlay method.

[0023] Optionally, it also includes setting process parameters for the welding process and controlling the welding process;

[0024] The process parameters for the welding process include the welding process parameters for the underlay transition layer and the welding process parameters for the wear-resistant layer.

[0025] The welding process parameters for the root transition layer are: current 320-350A, voltage 32-34V, wire extension 20-35mm, and welding speed 1200mm / min.

[0026] The welding process parameters for the wear-resistant overlay are: voltage 28-32V, current 420-450A, distance between the contact tip and the roller sleeve 20-30mm, and welding line speed 1200mm / min.

[0027] The welding process control includes controlling the interpass temperature to be below 80°C, cooling of the weld overlay, and the process control of subsequent welds pressing against previous welds.

[0028] By employing the above technical solution, the composite overlay welding manufacturing method for the bimetallic wear-resistant roller sleeve of the MPS medium-speed mill of the present invention has at least the following advantages:

[0029] The composite surfacing manufacturing method of this invention involves drawing a surfacing surface based on the actual wear conditions on site, and then surfacing a base layer and a wear-resistant layer on this surface. The overall thickness of the surfacing layer is determined according to the actual wear location, which greatly saves on surfacing weight, welding materials, and labor costs. This invention also achieves low-cost, high-wear-resistance requirements by optimizing the chemical composition of the base welding wire, the first high-alloy high-chromium cast iron welding material, and the second high-alloy high-chromium cast iron welding material. By using different materials for the roller sleeve substrate and the surfacing wear-resistant layer, this invention achieves a bimetallic effect: the roller sleeve substrate meets impact resistance and crack prevention requirements, while the surfacing wear-resistant layer has high wear resistance and can be repeatedly surfacing for repair. Attached Figure Description

[0030] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0031] Figure 1 This is a schematic diagram of the main structure of the roller sleeve substrate in an embodiment of the MPS medium-speed mill bimetallic wear-resistant roller sleeve according to the present invention.

[0032] Figure 2 yes Figure 1 A schematic diagram of the cross-sectional structure at point AA.

[0033] Figure 3 This is a partially enlarged schematic diagram of the roller sleeve substrate at point B in an embodiment of the MPS medium-speed grinding bimetallic wear-resistant roller sleeve of the present invention.

[0034] Figure 4 This is a partially enlarged schematic diagram of point B in the bimetallic wear-resistant roller sleeve of the MPS medium-speed grinding mill, according to an embodiment of the present invention.

[0035] Figure 5 This is an image showing the volume percentage of metallographic carbides on a weld overlay test block according to an embodiment of the present invention.

[0036] Figure 6 This is a comprehensive analysis chart of a welding test block according to an embodiment of the present invention.

[0037] The following are the annotations in the figure: 1-Roller sleeve base; 11-Weld overlay curved surface; 2-Underlay transition layer; 3-Weld overlay wear-resistant layer; 31-Weld overlay intermediate layer; 32-Weld overlay cover layer. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0039] Figures 1 to 4 The diagram shows a preferred embodiment of the present invention. A bimetallic wear-resistant roller sleeve for an MPS medium-speed mill includes a roller sleeve base 1, which is a casting made of ZG20SiMn or ZG270-500 material. The outer surface of the roller sleeve base 1 is provided with a weld overlay curved surface 11. A base transition layer 2 and a weld overlay wear-resistant layer 3 are sequentially provided on the weld overlay curved surface 11. The weld overlay wear-resistant layer 3 further includes a weld overlay intermediate layer 31 and a weld overlay cover layer 32 arranged inside and outside.

[0040] Choosing ZG20SiMn or ZG270-500 castings as the roller sleeve base 1 can increase the number of weld overlays and extend the service life. The roller sleeve base 1 needs to ensure its impact resistance and resistance to deformation, as well as ease of welding. Therefore, ZG20SiMn or ZG270-500 with low carbon content are selected, and the content of harmful elements S and P must be strictly controlled to ≤0.02%. These two materials have a tensile strength ≥500MPa and a yield strength of 270-300MPa, and their comprehensive performance can meet the impact requirements of the roller sleeve.

[0041] After establishing the weld overlay surface 11 on the roller sleeve substrate 1, a base transition layer 2 and a weld overlay wear-resistant layer 3 are formed. The base transition layer 2 effectively fixes the weld overlay wear-resistant layer 3 onto the welded surface and also serves to level the surface of the roller sleeve substrate 1. The weld overlay intermediate layer 31 and the weld overlay cover layer 32 together form the wear-resistant hard surface layer of the roller sleeve. The wear resistance of this hard surface layer can reach the international advanced level, and the service life of a single weld overlay is twice that of a cast roller. In terms of cost, the cost of the first weld overlay of this invention is similar to that of casting, but the service life is 1.3-1.8 times that of a cast roller. Furthermore, cast rollers cannot be reused and have a low service life. The bimetallic wear-resistant roller sleeve of this invention can be repeatedly welded after the first wear. The cost of the second weld overlay is 20-30% of that of a cast roller. It can be cyclically welded 3-5 times, greatly improving the overall service life and significantly reducing the comprehensive cost.

[0042] In a specific embodiment of the present invention, the chemical composition of the ZG20SiMn is: 0.12%-0.22% C, 1.0%-1.3% Mn, 0.6%-0.8% Si, ≤0.020% P, and ≤0.020% S.

[0043] In a specific embodiment of the present invention, the chemical composition of the ZG270-500 is: ≤0.35% C, ≤0.5% Si, ≤0.8% Mn, ≤0.020% P, and ≤0.020% S.

[0044] In a specific embodiment of the present invention, the underlay transition layer 2 is formed by underlay welding wire on the weld overlay surface 11; the number of weld overlay layers 2 is 1-2 layers.

[0045] In a specific embodiment of the present invention, the chemical composition of the root pass welding wire is: 0.05%-0.10% C, 18.0%-20.0% Cr, 6.0%-7.0% Mn, 0.6%-1.2% Si, and 9.0%-10.0% Ni.

[0046] In a specific embodiment of the present invention, the intermediate layer 31 and the cover layer 32 are both welded together using high-alloy high-chromium cast iron welding materials.

[0047] In a specific embodiment of the present invention, the chemical composition of the first high-alloy high-chromium cast iron welding material of the weld overlay intermediate layer 31 is as follows:

[0048] 4.5%-5.5% C, 25.0%-30.0% Cr, 0.8%-1.5% Mn, 0.6%-1.0% Si, with a metallographic structure of ≥50.0% carbides.

[0049] In a specific embodiment of the present invention, the chemical composition of the second high-alloy high-chromium cast iron welding material of the overlay layer 32 is as follows:

[0050] 4.5%-5.5% C, 25.0%-33.0% Cr, 0.8%-1.5% Mn, 0.6%-1.0% Si, 0.8%-1.5% Mo, 2% Ti+V+W, with a metallographic structure of ≥55.0% carbides.

[0051] Another technical solution adopted by the present invention to solve its technical problem is:

[0052] A composite welding manufacturing method for the bimetallic wear-resistant roller sleeve of the MPS medium-speed mill includes casting a roller sleeve substrate 1, welding a base transition layer 2, and welding a wear-resistant layer 3.

[0053] Specifically, a weld overlay surface 11 is drawn based on the on-site wear curve, and a root transition layer 2 is welded onto the weld overlay surface 11. The thickness of the weld overlay layer composed of the root transition layer 2 and the wear-resistant layer 3 is determined according to the actual wear location. The root transition layer 2 and the wear-resistant layer 3 are respectively selected with corresponding chemical compositions of root welding wire, first high alloy high chromium cast iron welding material, and second high alloy high chromium cast iron welding material, and all adopt the open arc offline automatic wear-resistant weld overlay method.

[0054] As a further optional embodiment of the present invention, it also includes setting process parameters for the welding process and controlling the welding process;

[0055] The process parameters for the welding process include the welding process parameters for the underlay transition layer 2 and the welding process parameters for the wear-resistant layer 3.

[0056] The welding process parameters for the underlay transition layer 2 are: current 320-350A, voltage 32-34V, wire extension 20-35mm, and welding speed 1200mm / min.

[0057] The welding process parameters for the wear-resistant overlay layer 3 are: voltage 28-32V, current 420-450A, distance between the contact tip and the roller sleeve 20-30mm, and welding line speed 1200mm / min.

[0058] The welding process control includes controlling the interpass temperature to be below 80°C, cooling of the weld overlay, and the process control of subsequent welds pressing against previous welds.

[0059] This invention determines the optimal process parameters for overlay welding through experiments on the process and process parameters, strengthens process control of interlayer temperature, interlayer cleaning, spray cooling, and the process control of subsequent welds pressing against previous welds, so that the overlay layer produces more carbides and a refined grain structure, achieving a high wear-resistant service life for the composite roller sleeve.

[0060] The detailed steps of the composite overlay welding manufacturing method of the present invention are as follows:

[0061] 1) Casting of roller sleeve base 1

[0062] 1.1) Cast steel ZG20SiMn or ZG270-500 casting blanks are selected; the weld overlay surface 11 is drawn based on the on-site wear curve. The thickness of the weld overlay layer is determined according to the actual wear location, which can save weld overlay costs. See [reference needed]. Figure 3 .

[0063] 1.2) The chemical composition of the above-mentioned cast blanks shall meet the requirements of the relevant national standards for steel grades. In addition, there are special requirements for the content of S and P, which shall be controlled below 0.020%.

[0064] Except for sulfur (S) and phosphorus (P), the remaining chemical composition complies with the requirements of JB / T6402 standard. ZG20SiMn is equivalent to ZG20Mn; the carbon content in ZG270-500 is reduced to lower the carbon equivalent value, making it easier to weld. Carbon has the greatest impact on the weldability of steel. The higher the carbon content, the greater the hardening tendency of the heat-affected zone, the greater the sensitivity to weld cracks, and the worse the weldability. Impurities in steel, such as sulfur and phosphorus, as well as commonly used alloying elements like manganese, chromium, cobalt, copper, silicon, molybdenum, titanium, niobium, vanadium, and boron, all increase the hardening tendency of steel to varying degrees, thus worsening weldability. The influence of material factors on weldability is mainly reflected in the crack sensitivity of the weld or heat-affected zone. Impurity elements such as phosphorus and sulfur tend to dissolve into the liquid metal at grain boundaries rather than the solid metal within the grains. Therefore, when the size of the liquid metal decreases, the content of these elements will increase at the grain boundaries, promoting the formation of solidification cracks.

[0065] 1.3) Machining of roller sleeve blanks before welding

[0066] The upper and lower planes and conical surfaces of the roller sleeve blank are rough machined, with a 3mm machining allowance on each side. The weld overlay curved surface is machined, and any defects found during the machining process are dealt with promptly.

[0067] 1.4) Mounting and positioning before roller sleeve welding

[0068] Align the roller sleeve with the center of the inner cone opening and clamp it on the worktable. Adjust the end face of the roller sleeve blank to be parallel to the plane of the positioner turntable, and adjust the concentricity of the center of the roller sleeve blank cone opening with the turntable.

[0069] 2) Pre-welding work

[0070] 2.1) Use a coloring agent to color the upper and lower planes, conical surface and weld overlay surface of the roller sleeve, and check for cracks and casting defects. Repair any defects in time.

[0071] 2.2) Thoroughly clean and grind before welding to remove dirt from the roller sleeve surface and expose the metallic luster.

[0072] 2.3) Weigh the weld overlay and welding wire before welding.

[0073] 2.4) Use templates to inspect the external dimensions of the weld overlay and record them.

[0074] 3) Welding materials and welding process for the underlay of the roller sleeve

[0075] 3.1) Welding method: The open arc offline automatic wear-resistant welding method is adopted.

[0076] 3.2) Chemical composition of the root pass welding material: The root pass is the key layer of the weld overlay. The roller sleeve substrate 1 and the wear-resistant weld overlay are made of ordinary cast steel and high-alloy high-chromium cast iron, respectively, which have particularly poor weldability. A transition layer is required to achieve weld overlay of the two materials. The chemical composition of the root pass welding wire is shown in the table below:

[0077]

[0078] 3.3) Process parameters for the underlay and transition layer 2:

[0079] 3.3.1) Specifications: Ф2.8mm flux-cored welding wire

[0080] 3.3.2) Welding process parameters: Current: 320-350A; Voltage: 32-34V; Welding wire extension: 20-35mm; Welding line speed: 1000-1600mm / min, optimal control: 1200mm / min.

[0081] 4) Welding materials and welding process for wear-resistant surfacing of roller sleeves

[0082] 4.1) Welding material for wear-resistant overlay layer 3: Based on the hardness, chemical composition, metallographic and abrasive wear test analysis of the overlay test blocks, the composition of the low-cost and high-wear-resistant overlay welding wire was determined as follows:

[0083]

[0084] 4.2) Weld overlay process parameters:

[0085] 4.2.1) Specifications: Ф2.8mm flux-cored welding wire.

[0086] 4.2.2) Welding method: The open arc offline automatic wear-resistant overlay welding method is adopted.

[0087] 4.2.3) Welding process parameters: Voltage: 28-32V; Current: 350-450A, optimal current control 420A; Distance between contact tip and roller sleeve: 20-30mm; Welding line speed 1000-1600mm / min, optimal control 1200mm / min.

[0088] 4.2.4) When overlaying the surface, use a new contact tip and a low current: 320-380A. Overlay a thickness of 15-20mm on the top surface.

[0089] 4.2.5) Wire feeding speed: 3.5-6.0m / min; Deposited metal amount: 5-8KG / hour.

[0090] 4.2.6) The weld bead shape should be a narrow weld bead with a width of 10-13mm and a height of 2-3mm. The subsequent weld bead of the same weld layer should cover 30%-40% of the previous weld bead, and the weld bead of the next weld layer should be arranged in the middle of the two weld beads of the previous weld layer.

[0091] 4.2.7) Cooling of the weld overlay on the roller sleeve

[0092] In summer, water spray cooling is used; in winter, cold air cooling is used. The spray system should be positioned 150-300mm above the welding torch on the weld bead, and the water volume should be adjusted based on the dryness of the weld surface after the workpiece has rotated half a revolution. Cooling water spray must be stopped when the roller stops rotating. For excessively high interlayer temperatures, internal water cooling can be added to the roller sleeve.

[0093] 4.2.8) The interlayer temperature of all roller sleeves needs to be controlled below 80℃. During the welding process, the construction personnel use a thermometer to monitor the temperature at irregular intervals.

[0094] 4.2.9) The thickness of each weld bead is 1.2-1.5mm. The weld bead should be flat but without depressions. The two sides of the weld bead should be straight and well fused. There should be no weld beads on the two sides. The surface flatness after welding should be ≤3mm.

[0095] 4.2.10) The area in front of the weld bead should be thoroughly cleaned to prevent large particles from splattering. During the welding process, use a grinding wheel to remove dust and flux residue from each layer.

[0096] 4.2.11) The welding sequence for each layer is from the large end to the small end of the roller sleeve.

[0097] 4.2.12) During the surfacing process, the welding procedure must be strictly followed. Temperature should be measured every 15 minutes, and the results recorded along with welding parameters such as welding current and voltage. The welding angle should be adjusted promptly. The weld bead should be observed regularly to detect and address welding defects early, preventing porosity, slag inclusions, and bridging or incomplete penetration caused by molten metal flowing to other areas. Hidden welding defects, cracks, and potential detachment (discontinuous metallic sound) can be detected early by gently tapping the weld with a hammer.

[0098] 5) Temperature control during the welding process

[0099] 5.1) Preheating

[0100] The ambient temperature must not be lower than 5℃; otherwise, appropriate measures should be taken. The purpose of preheating is to prevent the formation of cracks under the weld bead, which could lead to large-area detachment of the weld overlay on the roller sleeve.

[0101] 5.2) Post-weld insulation treatment

[0102] Newly welded roller sleeves should be placed under wooden blocks or inside insulation material. Roller sleeves should not be placed directly on concrete surfaces (especially in winter).

[0103] 5.3) During the welding process, monitor the overall temperature of the weld overlay components to ensure that it does not exceed 80°C.

[0104] 6) Welding records:

[0105] Welding records must be kept for each roller sleeve welded together, and the roller sleeve must be numbered and an archive established.

[0106] 7) After welding, the conical surface and the upper and lower planes are precision machined to meet the dimensions and surface roughness requirements of the drawings.

[0107] 8) After the welding is completed, the following inspections shall be performed on the weld overlay of the roller sleeve:

[0108] 8.1) Weld visual inspection

[0109] The weld overlay surface should be free of obvious slag, arc craters, weld beads, and spatter; areas with pores larger than φ5 and large-particle spatter are not allowed. Uniformly distributed transverse stress-relief cracks are permitted in the weld overlay, but transverse cracks exceeding 100mm in length and densely packed pores are not allowed. The weld bead should be smooth, fine, and uniform, transitioning smoothly to the base material.

[0110] 8.2) Hardness inspection of weld overlay surface

[0111] For HRC58-63, it is best to use an ultrasonic hardness tester.

[0112] 8.3) Finished product dimensional inspection

[0113] The welded roller sleeves are then inspected for shape and dimensions. The weld shape is checked using a template, and the diameter is checked using calipers or a self-made measuring tool. The radial dimension deviation should not exceed ±3mm, and the circumferential dimension deviation should be ±5mm.

[0114] 8.4) Metallographic examination of test blocks

[0115] Before hardfacing, take samples of the hard-base hardfacing test block, prepare metallographic films, and examine its metallographic structure. The metallographic structure should contain initial carbides + eutectic carbides + secondary carbides, and the volume fraction of carbides should reach more than 55%.

[0116] Reference Figure 5 and Figure 6 The images shown are the metallographic carbide volume percentage images and comprehensive analysis charts of the weld overlay test blocks. The test data for the weld overlay test blocks shown in the table below can be obtained from this.

[0117]

[0118] In considering low cost and high wear resistance, refer to Figure 5 and Figure 6The inventors of this invention conducted hardness, chemical composition, metallographic and abrasive wear tests on six welding wires with different chemical compositions at low cost. Through comprehensive data analysis, following the principle that composition determines structure and structure determines performance, the correlation between hardness value, chemical composition, metallographic and wear resistance was clarified. This solved the problem of determining whether the roller sleeve can meet the wear resistance requirements for field use by checking the hardness value, chemical composition and metallographic data of the weld overlay test block, thus achieving the requirement of low cost and high wear resistance.

[0119] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications and equivalent changes made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A bimetallic wear-resistant roller sleeve for MPS medium-speed mills, comprising a roller sleeve substrate, characterized in that: The roller sleeve substrate is a casting made of ZG20SiMn or ZG270-500 material; the outer surface of the roller sleeve substrate is provided with a weld overlay curved surface, and a base transition layer and a weld overlay wear-resistant layer are provided in sequence on the weld overlay curved surface, and the weld overlay wear-resistant layer includes an inner and outer weld overlay intermediate layer and a weld overlay cover layer. The chemical composition of ZG20SiMn is as follows: 0.12%-0.22% C, 1.0%-1.3% Mn, 0.6%-0.8% Si, ≤0.020% P, and ≤0.020% S. The chemical composition of ZG270-500 is: ≤0.35% C, ≤0.5% Si, ≤0.8% Mn, ≤0.020% P, ≤0.020% S; Both the intermediate layer and the cover layer of the weld overlay are welded together using high-alloy high-chromium cast iron welding materials. The chemical composition of the first high-alloy high-chromium cast iron welding material in the intermediate layer of the weld overlay is as follows: 4.5%-5.5% C, 25.0%-30.0% Cr, 0.8%-1.5% Mn, 0.6%-1.0% Si; metallographic structure is ≥50.0% carbides; The chemical composition of the second high-alloy high-chromium cast iron welding material for the overlay layer is as follows: 4.5%-5.5% C, 25.0%-33.0% Cr, 0.8%-1.5% Mn, 0.6%-1.0% Si, 0.8%-1.5% Mo, 2% Ti+V+W; the metallographic structure is ≥55.0% carbides; A weld overlay surface is drawn based on the on-site wear curve, and a base transition layer is welded onto the weld overlay surface. The thickness of the weld overlay layer, consisting of the base transition layer and the wear-resistant layer, is determined according to the actual wear location.

2. The bimetallic wear-resistant roller sleeve for MPS medium-speed mill according to claim 1, characterized in that: The underlay transition layer is formed by welding the underlay welding wire onto the weld overlay surface; the number of weld overlay layers in the underlay transition layer is 1-2 layers.

3. The bimetallic wear-resistant roller sleeve for MPS medium-speed mill according to claim 2, characterized in that: The chemical composition of the root pass welding wire is: 0.05%-0.10% C, 18.0%-20.0% Cr, 6.0%-7.0% Mn, 0.6%-1.2% Si, and 9.0%-10.0% Ni.

4. A composite overlay welding manufacturing method applicable to the bimetallic wear-resistant roller sleeve of the MPS medium-speed mill according to any one of claims 1 to 3, characterized in that: This includes casting the roller sleeve substrate, welding the underlying transition layer, and then welding the wear-resistant layer. Specifically, a weld overlay surface is drawn based on the on-site wear curve, and a root transition layer is welded onto the weld overlay surface. The thickness of the weld overlay layer composed of the root transition layer and the wear-resistant layer is determined according to the actual wear location. The root transition layer and the wear-resistant layer are respectively selected with corresponding chemical compositions of the root welding wire, the first high-alloy high-chromium cast iron welding material, and the second high-alloy high-chromium cast iron welding material, and all adopt the open arc offline automatic wear-resistant weld overlay method.

5. The composite overlay welding manufacturing method for a bimetallic wear-resistant roller sleeve of an MPS medium-speed mill according to claim 4, characterized in that: It also includes setting process parameters for welding overlay and controlling the welding process; The process parameters for the welding process include the welding process parameters for the underlay transition layer and the welding process parameters for the wear-resistant layer. The welding process parameters for the root transition layer are: current 320-350A, voltage 32-34V, wire extension 20-35mm, and welding speed 1200mm / min. The welding process parameters for the wear-resistant overlay are: voltage 28-32V, current 420-450A, distance between the contact tip and the roller sleeve 20-30mm, and welding line speed 1200mm / min. The welding process control includes controlling the interpass temperature to be below 80°C, cooling of the weld overlay, and the process control of subsequent welds pressing against previous welds.

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