Manufacturing method of high-fatigue-resistance vertical chain connecting ring

Abstract

The invention belongs to the field of coal mine machinery chain connecting rings, and particularly relates to a manufacturing method of a high-fatigue-resistance vertical chain connecting ring. The vertical chain connecting ring comprises the following chemical components: 0.20-0.26% of C; si < = 0.25%; 1.00 to 1.40 percent of Mn; less than or equal to 0.010% of P; s is less than or equal to 0.010%; 0.40 to 0.60 percent of Cr; 0.90 to 1.10 percent of Ni; 0.50 to 0.60 percent of Mo; 0.02 to 0.05 percent of Al; cu < = 0.25%; 0.05% to 0.10% of V; the content of Nb is 0.025 to 0.045 percent; the manufacturing method comprises the steps of material smelting and blank manufacturing. Forging and heat treatment; and machining and heat treatment. Through alloy component optimization and machining process improvement, the vertical chain connecting ring obtains excellent surface quality and dimensional precision, and meanwhile, the fatigue performance of the vertical chain connecting ring is greatly improved under the condition that other performance indexes such as the strength and the wear resistance of the vertical chain connecting ring are not reduced.

Description

Technical Field

[0001] The invention belongs to the field of coal mine machinery chain connecting rings, and in particular relates to a manufacturing method of a high fatigue resistance vertical chain connecting ring. Background Art

[0002] The vertical chain link is an important component of coal conveying equipment such as scraper conveyors and transfer machines. Its main function is to connect mining compact chains or ultra-flat chains to form a closed chain loop to ensure the continuous operation of the entire conveying system.

[0003] During the operation of the vertical connecting link, the main failure form is fatigue fracture. Due to the harsh underground production conditions and more complex working conditions, once the connecting link breaks, it not only threatens the safety of personnel, but also requires great labor intensity and time-consuming to replace, which seriously affects production efficiency. At present, the national standard "MT / T 99-1997 Flat connecting link for round link chain for mining" has not yet stipulated the fatigue times of the vertical connecting link, but only stipulates that the fatigue times of the flat connecting link is greater than or equal to 40,000 times. The German "DIN22258-3:2016-12" standard stipulates that the fatigue times of the vertical connecting link is greater than or equal to 70,000 times. As the scraper conveyor continues to develop towards large capacity, long distance, high power, long life and high reliability, higher requirements are put forward for the fatigue life of the vertical connecting link. Currently, the raw materials for vertical connecting links are generally traditional 23MnNiMoCr54 alloy steel produced by steel mills, which is the same raw material as the chain production. However, due to the differences in structural form and production process, the fatigue life of the connecting link is lower than that of the chain. The fatigue times of those with better performance are only close to or reach the DIN standard requirements. Especially for heavy and ultra-heavy scraper conveyors, their fatigue life is difficult to meet the working conditions.

[0004] After searching, the applicant found that the Chinese patent disclosed "a high-strength wear-resistant and corrosion-resistant stainless steel connecting ring and manufacturing method", with the publication number CN117867392A. This invention is aimed at flat connecting rings, vertical connecting rings, flat connecting rings, arc tooth connecting rings and open connecting rings, and further improves the 23MnNiMoCr54 alloy steel. Specifically, it includes the following components by mass: C: 0.1-0.24; Si: 0.25-1; Mn: 0.8-1; Ni: 2-4; Cr: 14-17; Mo: 0.7-0.8; V: 2-4; Cu: 2-4; Al: 0.02-0.05; W: 0.2-0.4, mainly through alloy composition design and surface strengthening process to improve the corrosion resistance and wear resistance of the connecting ring. However, too much Cr content will affect the toughness and plasticity of the material, thereby reducing the fatigue life of the material. Summary of the invention

[0005] In view of the shortcomings of the prior art, the present invention provides a method for manufacturing a vertical link ring with high fatigue resistance. The chemical composition of the vertical link ring is: C 0.20-0.26%; Si ≤0.25%; Mn 1.00-1.40%; P ≤0.010%; S ≤0.010%; Cr 0.40-0.60%; Ni 0.90-1.10%; Mo 0.50-0.60%; Al 0.02-0.05%; Cu ≤0.25%; V 0.05-0.10%; Nb 0.025-0.045%; the remainder is Fe and unavoidable impurity elements. The method for manufacturing the vertical link ring comprises the following steps: S1 material smelting and blanking; S2 forging and heat treatment; S3 machining and heat treatment.

[0006] Preferably, the step S1 is specifically as follows: S11. Preparation of steel ingots: The raw materials are smelted in an electric furnace, refined by LF, vacuum treated, and electroslag remelted to form steel ingots; S12, preparing a bar blank: the steel ingot is cut, forged multiple times, and turned into a bar blank with a certain diameter, and the diameter of the bar blank is determined according to the specifications of the vertical connecting link; Preferably, in the step S12, the two end caps of the steel ingot are cut off before each forging and after the last forging, and the amount of each end cap cut off is not less than 5% of the billet length.

[0007] Preferably, in the step S12, the turning amount is not less than 8% of the diameter of the blank.

[0008] Preferably, the step S2 is specifically as follows: S21, forging: heating the bar blank to the forging temperature, and then pre-flattening and then die forging to form a vertical link forging blank; S22, Dimension and surface quality inspection: Grind and dephosphorize the vertical link forging blank, and inspect the dimension and surface quality; S23. Heat treatment and surface treatment: The vertical link forging blank is heat treated by normalizing + tempering, and shot blasting and flaw detection are performed after heat treatment.

[0009] Preferably, the rod blank is heated by electromagnetic induction, and the forging temperature is 1180-1200°C.

[0010] Preferably, in the step S21, after die forging, in order to control the deformation and crack generation of the blank, the blank is reheated and kept warm before blanking, and the keeping temperature is 800°C.

[0011] Preferably, in the step S23, the normalizing temperature is 880°C, air cooling, the tempering temperature is 600-650°C, air cooling, the surface hardness after tempering is ≤270 HBW, and the depth of the decarburized layer does not exceed 0.50 mm. Preferably, in the step S2, the overall forging ratio from the steel ingot to the vertical link forging blank is not less than 30:1.

[0012] Preferably, the process S3 specifically includes: clamping and positioning, rough machining, fine machining, assembly, drilling, heat treatment, pre-stretching, shot blasting, and painting.

[0013] Preferably, in the step S3, the clamping jaws are designed according to the structural dimensions of the vertical link to ensure the maximum clamping surface and clamping force.

[0014] Preferably, in the process S3, the cutting parameters of low speed and large feed are adopted during rough machining, specifically, the speed is 280-320r / min, the cutting depth is 2-3mm, and the feed speed is 30-40mm / min; the cutting parameters of high speed and small feed are adopted during fine machining, specifically, the speed is 1000-1300r / min, the cutting depth is 0.4-0.6mm, and the feed speed is 15-20mm / min.

[0015] Preferably, in the step S3, the heat treatment process includes quenching + tempering, the quenching adopts a controlled atmosphere rotary hearth furnace, the quenching temperature is 860~890℃, the carbon potential is 0.25~0.3%, and the process is water-cooled; the tempering adopts a pit-type tempering furnace, the tempering temperature is 400~430℃, and the process is air-cooled; the surface hardness after tempering is HRC38~42.

[0016] The beneficial effects achieved by the present invention are: 1. V and Nb elements are added to 23MnNiMoCr54 alloy steel. V has a significant strengthening effect in steel, mainly by refining grains and forming carbides or nitrides to improve the strength and hardness of steel. V can also inhibit the growth of steel grains, thereby improving its impact toughness and wear resistance; trace amounts of Nb also have the effect of refining grains, which can improve the strength and impact toughness of steel without affecting its plasticity, and reduce its brittle transition temperature.

[0017] 2. The steel ingots are made by electric furnace smelting, LF refining, vacuum treatment and electroslag remelting. Compared with ordinary steel ingots, electroslag remelting ingots have the characteristics of high metal purity, dense structure, uniform composition, few non-metallic inclusions, small metal anisotropy, smooth surface and high yield rate, which further improves the performance of raw materials.

[0018] 3. Reheat the blank to 800℃ before blanking, which can easily control the deformation and cracks of the blank and improve the dimensional accuracy of the forging blank of the link ring.

[0019] 4. The overall forging ratio from the steel ingot to the vertical link forging blank is not less than 30:1. A larger forging ratio can break up the dendritic crystals and coarse columnar crystals, refine them and distribute them along the main elongation direction; and forge the defects such as looseness, pores, shrinkage holes in the ingot to make the structure dense, fully reduce segregation and broken inclusions, make the structure uniform, and improve the performance of the steel.

[0020] 6. The present invention optimizes the alloy composition and improves the processing technology, thereby greatly improving the fatigue performance of the vertical link ring without reducing other performance indicators such as the strength and wear resistance of the vertical link ring. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 A three-dimensional diagram of the semi-vertical link before assembly; Figure 2 This is a three-dimensional diagram of the vertical chain link after assembly. DETAILED DESCRIPTION

[0022] The present invention will be further described in detail below in conjunction with specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Example

[0023] Taking the vertical link chain with the specification of Φ48×152mm as an example, its structure is as follows Figure 2 As shown, it is assembled from two semi-vertical link rings. Figure 1 The chemical composition of the vertical link ring is: C 0.22%; Si 0.18%; Mn 1.20%; P 0.008%; S 0.003%; Cr 0.52%; Ni 0.97%; Mo 0.52%; Al 0.03%; Cu 0.14%; V 0.08%; Nb 0.036%; the balance is Fe and unavoidable impurity elements. The vertical link ring manufacturing method includes the following steps: S1 Material smelting and billet making; S2 Forging and heat treatment; S3 Machining and heat treatment.

[0024] S1 is specifically: S11. Preparation of steel ingot: The raw materials are subjected to electric furnace smelting, LF refining, vacuum treatment, and electroslag remelting to form a steel ingot with a diameter of Φ500mm; S12. Preparation of bar blanks: Cut off the end of each end of the Φ500mm steel ingot, and forge it into a Φ180mm blank for the first time after cutting. Cut off the end of each end of the Φ180mm blank, and forge it into a Φ85mm blank for the second time after cutting. Cut off the end of each end of the Φ85mm blank and turn it into a Φ75mm bar blank. In the above process, the amount of end cut off at each end is 5% of the billet length.

[0025] S2 is specifically: S21, forging: the Φ75mm bar blank is heated to 1200℃ by electromagnetic induction, and then pre-flattened and die-forged to form a Φ48×152mm vertical link forging blank. After die-forging, in order to control the deformation of the blank, the blank is reheated and kept warm before blanking, and the holding temperature is 800℃; S22, Dimension and surface quality inspection: Grind and dephosphorize the Φ48mm×152mm vertical link forging blank, and inspect its dimension and surface quality; S23, heat treatment and surface treatment: Φ48mm×152mm vertical link forging blank is heat treated by normalizing + tempering, wherein the normalizing temperature is 880℃, air cooling, the tempering temperature is 620℃, air cooling, the surface hardness after tempering is 252HBW, the decarburization layer depth is 0.38mm, and shot blasting and flaw detection are carried out after heat treatment; The overall forging ratio from Φ500mm steel ingot to Φ48×152mm vertical link forging blank is 108.5:1.

[0026] Step S3 is specifically as follows: The Φ48×152mm vertical link ring forging blank is clamped and positioned, wherein the clamping jaws are designed according to the structural dimensions of the vertical link ring to ensure the maximum clamping surface and clamping force, and then the semi-link ring is made through rough machining and fine machining, wherein the rough machining adopts the cutting parameters of low speed and large feed, specifically, the speed is 300r / min, the cutting depth is 3mm, and the feed speed is 40mm / min, and the fine machining adopts the cutting parameters of high speed and small feed, specifically, the speed is 1200r / min, the cutting depth is 0.4mm, and the feed speed is 15mm / min; The Φ48×152mm half-jointed link is assembled, drilled, heat treated, pre-stretched, shot blasted and painted to be made into a finished product. The heat treatment process includes quenching + tempering. The quenching adopts a controlled atmosphere rotary hearth furnace with a quenching temperature of 880℃, a carbon potential of 0.25%, and water cooling. The tempering adopts a pit tempering furnace with a tempering temperature of 420℃ and air cooling. The surface hardness after tempering is HRC41.

[0027] The fatigue performance test of the prepared Φ48×152mm chain link was carried out. The results are shown in Table 1. The number of cycles is greater than 100,000 times without fracture. At the same time, the tested breaking load is 3011 kN.

[0028] Table 1 Fatigue performance test results of Φ48×152mm link.

[0029] Chain ring specifications Frequency times / minute Pulsating load lower limit kN Upper limit of pulsating load kN Cycle times state Φ48×152mm 240 181 905 105159 Unbroken

Claims

1. A method for manufacturing a high fatigue resistance vertical link chain, characterized in that: The chemical composition of the vertical connecting link is: C 0.20-0.26%; Si ≤0.25%; Mn 1.00-1.40%; P ≤0.010%; S ≤0.010%; Cr 0.40-0.60%; Ni0.90-1.10%; Mo 0.50-0.60%; Al 0.02-0.05%; Cu ≤0.25%; V 0.05-0.10%; Nb 0.025-0.045%; the remainder is Fe and unavoidable impurity elements. The manufacturing method of the vertical connecting link includes the following steps: S1 material smelting and blanking; S2 forging and heat treatment; S3 machining and heat treatment.

2. The method for manufacturing a vertical link according to claim 1, characterized in that: The process S1 is specifically as follows: S11. Preparation of steel ingots: The raw materials are smelted in an electric furnace, refined by LF, vacuum treated, and electroslag remelted to form steel ingots; S12. Preparation of rod blanks: The steel ingot is cut, forged multiple times, and turned into a rod blank of a certain diameter. The diameter of the rod blank is determined according to the specifications of the vertical connecting link.

3. The manufacturing method according to claim 2, characterized in that: In the process S12, the ends of the steel ingot are cut off before each forging and after the last forging, and the amount of each end cut off is not less than 5% of the length of the billet.

4. The manufacturing method according to claim 2, characterized in that: In the process S12, the turning amount is not less than 8% of the diameter of the blank.

5. The method for manufacturing a vertical link according to claim 1, characterized in that: The process S2 is specifically as follows: S21, forging: heating the bar blank to the forging temperature, and then pre-flattening and then die forging to form a vertical link forging blank; S22, Dimension and surface quality inspection: Grind and dephosphorize the vertical link forging blank, and inspect the dimension and surface quality; S23. Heat treatment and surface treatment: The vertical link forging blank is heat treated by normalizing and tempering, and then shot blasting and flaw detection are performed after heat treatment.

6. The method for manufacturing a vertical link according to claim 5, characterized in that: In the step S21, the rod blank is heated by electromagnetic induction, and the forging temperature is 1180-1200°C.

7. The method for manufacturing a vertical link according to claim 5, characterized in that: In the process S21, after die forging, in order to control the deformation of the blank, the blank is reheated and kept warm before blanking, and the keeping temperature is 800°C.

8. The method for manufacturing a vertical link according to claim 5, characterized in that: In the process S23, the normalizing temperature is 880°C, air cooling, the tempering temperature is 600-650°C, air cooling, the surface hardness after tempering is ≤270HBW, and the depth of the decarburized layer does not exceed 0.50mm.

9. The method for manufacturing a vertical link according to claim 1, characterized in that: In the step S2, the overall forging ratio from the steel ingot to the vertical link forging blank is not less than 30:

1.

10. The method for preparing a vertical linking ring according to claim 1, characterized in that: The process S3 specifically includes: clamping and positioning, rough machining, fine machining, assembly, drilling, heat treatment, pre-stretching, shot blasting, and painting.

11. The method for preparing a vertical linking ring according to claim 10, characterized in that: In the step S3, the clamping jaws are designed according to the structural dimensions of the vertical link to ensure the maximum clamping surface and clamping force.

12. The method for preparing a vertical link according to claim 10, characterized in that: In the process S3, the cutting parameters of low speed and large feed are adopted for rough machining, specifically, the speed is 280-320r / min, the cutting depth is 2-3mm, and the feed speed is 30-40mm / min; the cutting parameters of high speed and small feed are adopted for fine machining, specifically, the speed is 1000-1300r / min, the cutting depth is 0.4-0.6mm, and the feed speed is 15-20mm / min.

13. The method for preparing a vertical linking ring according to claim 10, characterized in that: In the step S3, the heat treatment process includes quenching + tempering. The quenching adopts a controlled atmosphere rotary hearth furnace with a quenching temperature of 860~890℃, a carbon potential of 0.25~0.3%, and water cooling. The tempering adopts a pit tempering furnace with a tempering temperature of 400~430℃ and air cooling. The surface hardness after tempering is HRC38~42.

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