Method for manufacturing hard-face lining plate needing screw hole and deep hole machining

Abstract

The invention discloses a method for manufacturing a hard-surface lining plate needing screw hole and deep hole machining, which comprises the following steps of: forging the hard-surface lining plate by using 42CrMo steel, sequentially forging, normalizing, rough machining, flaw detection, quenching, semi-finishing, flaw detection, stabilizing heat treatment, finishing and checking to obtain the hard-surface lining plate, and manufacturing a hard-surface layer by using the hardenability and hardness gradient distribution of the steel. The finish machining allowance is reserved on the deep hole side of the lining plate, a high-hardness quenched-tempered heat treatment decarburized layer is machined on the hard face working side of the lining plate, then it is guaranteed that the surface hardness of the lining plate is high, the hardness of the deep hole side is low, the use performance can be guaranteed, and the machining manufacturability can be guaranteed. According to the method, the defects of traditional hard-surface lining plate screw hole and deep hole machining are overcome, the machining allowance is reasonably arranged through the hardenability and hardness gradient distribution change of steel to avoid a hard-surface layer, hard-surface lining plate screw hole and deep hole machining is achieved, and it is ensured that machining of the hard-surface lining plate meets the technological requirements.

Description

Technical Field

[0001] This invention relates to the field of workpiece manufacturing technology, and in particular to a method for manufacturing a hard-faced liner plate that requires screw hole and deep hole machining. Background Technology

[0002] Hardface liners possess high wear resistance, corrosion resistance, impact resistance, and self-lubrication properties, making them widely used in various types of mechanical equipment. Hardface liners are very common in machining, and maintaining the hardness of the hardface layer is crucial throughout the entire manufacturing process, ensuring the liner's performance. The hardface layer is obtained through quenching or quenching followed by low-temperature tempering. However, this brings new challenges. Due to the high hardness of the hardface layer, it poses difficulties not only for milling but also for drilling deep holes and tapping threads. Balancing the liner's hardness with ease of machining becomes a key focus and challenge in the manufacturing process. Traditional machining methods utilize extremely high-hardness thread and deep-hole cutting tools to achieve threading and deep-hole machining of hardface liners, but this is difficult and costly. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a method for manufacturing a hard-faced liner plate that requires screw hole and deep hole machining. This method overcomes the defects of traditional hard-faced liner plate screw hole and deep hole machining, and makes reasonable arrangement of machining allowance by utilizing the hardenability of steel and the hardness gradient distribution to avoid the hard surface layer, thereby realizing the machining of screw holes and deep holes in the hard-faced liner plate and ensuring that the machining of the hard-faced liner plate meets the process requirements.

[0004] To solve the above-mentioned technical problems, the present invention provides a method for manufacturing a hard-faced liner plate requiring screw hole and deep hole machining, comprising the following steps: Step 1: Select 42CrMo steel for hardface liner forging. The forging is delivered in annealed condition and undergoes ultrasonic testing. Step 2: Normalize the forgings to improve their machinability and refine their grain structure. Step 3: Roughly machine the forging, rough mill the entire part, and mill out the shape of the hardened liner, leaving a 5mm allowance on each side. If there is a stress concentration at the root of the forging, round the corner of the root. Step 4: Perform ultrasonic testing on the rough-machined workpiece to ensure there are no cracks or defects. Step 5: Quenching treatment to achieve a workpiece hardness of HRC40-45. The quenching process involves holding the workpiece at 860℃ for 2 hours, followed by oil cooling and holding at 360℃ for 4 hours, and then cooling at room temperature. Step 6: After quenching, the hardness of the semi-martensitic structure of the 42CrMo steel reaches HRC43. The critical diameter for oil cooling is 40mm, the effective hardened layer depth is 20mm on each side, and the hardness of the workpiece cross section is distributed in a U-shape. After tempering at 360℃, the hardness of the workpiece 18mm away from the surface of the hardened layer is HRC38, which is the location for drilling deep holes and tapping threaded holes. Step 7: Perform semi-finishing on the workpiece. The working surface should be smooth to ensure hardness. For deep holes and threaded holes, use the hardenability and hardness gradient distribution of the steel to process them, leaving a 1.5mm allowance on each side. Step 8: Perform dye penetrant testing on the workpiece surface to ensure there are no cracks or defects. Then, perform stabilization heat treatment on the workpiece to reduce residual stress and deformation. The stabilization heat treatment temperature should be lower than the tempering temperature of the quenching treatment. Step 9: Perform finishing on the workpiece. Finish the entire part and leave a grinding allowance on the hard surface layer. Select to leave the finishing allowance on the deep hole side, and remove the high hardness heat-treated decarburized layer on the working side of the hard surface layer. This ensures that the surface hardness of the hard surface liner is high and the hardness on the deep hole side is low, which can ensure both performance and machinability. Step 10: Perform dye penetrant testing on the workpiece surface to ensure there are no cracks or defects. Grind the workpiece working surface to the dimensional tolerances. Inspect the workpiece dimensions and tolerances to complete the manufacturing of the hardened liner.

[0005] Furthermore, the semi-martensitic structure of the 42CrMo steel is composed of 1 / 2 martensite and 1 / 2 pearlite. The present invention employs the above-mentioned technical solution in its method for manufacturing hardface liners requiring screw hole and deep hole machining. Specifically, this method uses 42CrMo steel for forging the hardface liner, sequentially undergoing forging, normalizing, rough machining, flaw detection, quenching, semi-finishing, flaw detection, stabilization heat treatment, finish machining, and inspection to obtain the hardface liner. The hardening properties and hardness gradient distribution of the steel are utilized to create the hard surface layer. The finishing allowance is left on the deep hole side of the liner, while the high-hardness decarburized layer from the tempering heat treatment is removed from the working side of the hard surface. This ensures high surface hardness and low hardness on the deep hole side, guaranteeing both performance and machinability. This method overcomes the shortcomings of traditional hardface liner screw hole and deep hole machining methods by rationally arranging the machining allowance using the hardening properties and hardness gradient distribution of the steel to avoid the hard surface layer, thus achieving screw hole and deep hole machining of the hardface liner and ensuring that the machining of the hardface liner meets process requirements. Attached Figure Description

[0006] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments: Figure 1 This is a schematic diagram showing the cross-section of the hardened liner plate and the machining locations of the screw holes and deep holes according to this method; Figure 2 This is a schematic diagram of the workpiece quenching process in this method; Figure 3 This is a schematic diagram of the U-shaped gradient distribution of workpiece cross-section hardness in this method. Detailed Implementation

[0007] Implementation, for example Figure 1 , Figure 2 and Figure 3 As shown, the manufacturing method of the hardface liner plate requiring screw hole and deep hole machining according to the present invention includes the following steps: Step 1: Select 42CrMo steel for hardface liner forging. The forging is delivered in annealed condition and undergoes ultrasonic testing. 42CrMo steel has the characteristics of high strength, high hardenability, good toughness, small deformation during quenching, and high creep strength and endurance strength at high temperature. The heat treatment process produces tempered troostite structure, and its cementite is granular. Compared with ordinary troostite, tempered troostite has higher strength, plasticity and toughness. After tempering, the residual internal stress generated by quenching can be eliminated, the plasticity and toughness of the material can be improved, good comprehensive mechanical properties can be obtained, and the workpiece dimensions can be stabilized, so that the steel structure does not change during the use of the workpiece. Therefore, 42CrMo is the preferred material for manufacturing hardface liner 1. Step 2: Normalize the forgings to improve their machinability and refine their grain structure. Step 3: Roughly machine the forging, rough mill the entire part, and mill out the shape of the hardened liner plate, leaving a 5mm allowance on each side. If there is a stress concentration root 11 in the forging, then fillet the root 11. Step 4: Perform ultrasonic testing on the rough-machined workpiece to ensure there are no cracks or defects. Step 5, as follows Figure 2 As shown, the quenching process is carried out to make the workpiece hardness reach HRC40~45. The quenching process is carried out at 860℃ for 2 hours, followed by oil cooling and holding at 360℃ for 4 hours, and then cooling at room temperature. Step Six, as Figure 3 As shown, the hardness of the semi-martensitic structure of 42CrMo steel after quenching reaches HRC43, the critical diameter for oil cooling is 40mm, the effective hardened layer depth is 20mm on one side, the hardness of the workpiece cross section is distributed in a U-shape, and the hardness of the workpiece 18mm away from the surface of the hardened layer after tempering at 360℃ is HRC38, which is the position for drilling deep holes and tapping threaded holes. Figure 3 The dashed U-shaped curve represents the hardness distribution of 42CrMo oil quenching. The hardness of the semi-martensitic structure is HRC43. The solid line obtained by analogy based on the dashed line represents the hardness distribution gradient of the workpiece after quenching and tempering at 360ºC. The curve obtained by analogy can be used to calculate that the hardness at 18mm away from the surface of the quenched layer is HRC38, which is the location for drilling deep holes and tapping screw holes. Step 7: Perform semi-finishing on the workpiece. The working surface should be smooth to ensure hardness. For deep holes and threaded holes, use the hardenability and hardness gradient distribution of the steel to process them, leaving a 1.5mm allowance on each side. Step 8: Perform dye penetrant testing on the workpiece surface to ensure there are no cracks or defects. Then, perform stabilization heat treatment on the workpiece to reduce residual stress and deformation. The stabilization heat treatment temperature should be lower than the tempering temperature of the quenching treatment. Step 9: Perform finishing on the workpiece. Finish the entire part and leave a grinding allowance on the hard surface layer. Select to leave the finishing allowance on the deep hole side, and remove the high hardness heat-treated decarburized layer on the working side of the hard surface layer. This ensures that the surface hardness of the hard surface liner is high and the hardness on the deep hole side is low, which can ensure both performance and machinability. Step 10: Perform dye penetrant testing on the workpiece surface to ensure there are no cracks or defects. Grind the workpiece working surface to the dimensional tolerances. Inspect the workpiece dimensions and tolerances to complete the manufacturing of the hardened liner.

[0008] Preferably, the semi-martensite structure of the 42CrMo steel is 1 / 2 martensite and 1 / 2 pearlite.

[0009] Figure 1 The diagram shows a cross-sectional view of the hardened liner plate 1 produced by the waste edge briquetting machine in a cold-rolled galvanizing unit. The surface hardness of this liner plate 1 reaches approximately HRC43, and a deep hole 2 (Φ6, 275mm) needs to be drilled on the side of the workpiece, with G1 / 4 threaded holes tapped at the opening. This method utilizes the hardenability of steel and the variation in hardness gradient to rationally arrange machining allowances, avoiding the manufacture of a hardened liner plate with a hardened surface layer. Furthermore, this process flow is also applicable to the manufacture of various hardened liner plates requiring threaded holes or deep hole machining.

Claims

1. A method for manufacturing a hardface liner plate requiring screw holes and deep hole machining, characterized in that... Includes the following steps: Step 1: Select 42CrMo steel for hardface liner forging. The forging is delivered in annealed condition and undergoes ultrasonic testing. Step 2: Normalize the forgings to improve their machinability and refine their grain structure. Step 3: Roughly machine the forging, rough mill the entire part, and mill out the shape of the hardened liner, leaving a 5mm allowance on each side. If there is a stress concentration at the root of the forging, round the corner of the root. Step 4: Perform ultrasonic testing on the rough-machined workpiece to ensure there are no cracks or defects. Step 5: Quenching treatment to achieve a workpiece hardness of HRC40-45. The quenching process involves holding the workpiece at 860℃ for 2 hours, followed by oil cooling and holding at 360℃ for 4 hours, and then cooling at room temperature. Step 6: After quenching, the hardness of the semi-martensitic structure of the 42CrMo steel reaches HRC43. The critical diameter for oil cooling is 40mm, the effective hardened layer depth is 20mm on each side, and the hardness of the workpiece cross section is distributed in a U-shape. After tempering at 360℃, the hardness of the workpiece 18mm away from the surface of the hardened layer is HRC38, which is the location for drilling deep holes and tapping threaded holes. Step 7: Perform semi-finishing on the workpiece. The working surface should be smooth to ensure hardness. For deep holes and threaded holes, use the hardenability and hardness gradient distribution of the steel to process them, leaving a 1.5mm allowance on each side. Step 8: Perform dye penetrant testing on the workpiece surface to ensure there are no cracks or defects. Then, perform stabilization heat treatment on the workpiece to reduce residual stress and deformation. The stabilization heat treatment temperature should be lower than the tempering temperature of the quenching treatment. Step 9: Perform finishing on the workpiece. Finish the entire part and leave a grinding allowance on the hard surface layer. Select to leave the finishing allowance on the deep hole side, and remove the high hardness heat-treated decarburized layer on the working side of the hard surface layer. This ensures that the surface hardness of the hard surface liner is high and the hardness on the deep hole side is low, which can ensure both performance and machinability. Step 10: Perform dye penetrant testing on the workpiece surface to ensure there are no cracks or defects. Grind the workpiece working surface to the dimensional tolerances. Inspect the workpiece dimensions and tolerances to complete the manufacturing of the hardened liner.

2. The method for manufacturing a hardface liner requiring threaded holes and deep hole machining according to claim 1, characterized in that: The semi-martensite structure of the 42CrMo steel is 1 / 2 martensite and 1 / 2 pearlite.

Images