Machining method of pin bush for caterpillar track

Abstract

The invention relates to a processing method of a pin bush for a caterpillar track, which relates to the technical field of pin bush processing, and comprises the following steps: normalizing: heating a seamless steel tube in a trolley furnace to 920-950 DEG C, preserving heat, cooling in air, performing integral normalizing treatment, turning, reserving 0.8 mm of outer circle single edge for the whole normalized seamless steel tube, sawing, reserving 1 mm of the saw-cut pin bush length single edge, and cutting the saw-cut pin bush length single edge by the saw-cut pin bush length single edge by the saw-cut pin bush length single edge by the saw-cut pin bush length single edge by the saw-cut pin bush length single edge. The method comprises the steps of rough turning, rough turning of the end face of the pin bush, rough turning of the end face of the pin bush, rough turning of the end face of the pin bush, rough turning of the outer circle, chamfering of an inner hole, carburizing, carburizing treatment through a carburizing furnace, quenching, after carburizing treatment, after the temperature is reduced to a certain temperature, afterheat quenching and tempering are adopted, after quenching, tempering, finish turning and outer circle finish turning are completed within 2 hours, it is guaranteed that the concentricity tolerance of the outer circles on the two sides is smaller than 0.05 mm, and grinding is conducted. And grinding the two end surfaces to obtain the required pin bush finished product. The device has the advantages of high efficiency and low energy consumption.

Description

Technical Field

[0001] The present application relates to the technical field of pin sleeve processing, and in particular to a method for processing a pin sleeve for a chain track. Background Art

[0002] The service conditions of the chain rail pin bushings of construction machinery are various and the working environment is quite harsh, so high requirements are placed on their wear resistance and impact resistance.

[0003] There are two processing technologies for traditional pin bushings: 1. Cutting with band saw → drilling inner hole with radial drill → rough turning → carburizing → tempering → medium frequency → tempering → fine turning → grinding end face. 2. Cutting with band saw → medium frequency heating, hot forging → rough turning → carburizing → tempering → medium frequency → tempering → fine turning → grinding end face. The above two processing methods are widely used because they can ensure product quality. The characteristics of their machining process are: large rough turning and drilling processing allowance, long processing time, low overall efficiency; more heat treatment processes increase energy consumption. Summary of the invention

[0004] In view of the shortcomings of the prior art, one of the purposes of the present application is to provide a method for processing a pin sleeve for a chain rail, which has the advantages of high efficiency and low energy consumption.

[0005] The above-mentioned purpose of the present application is achieved through the following technical solutions: A pin sleeve processing method for a chain track comprises the following steps: a normalizing step, placing a 20CrMnTi seamless steel pipe in a trolley furnace, heating it to 920-950°C, keeping it warm, air cooling it, and performing overall normalizing treatment; a turning step, turning the entire 20CrMnTi seamless steel pipe after normalizing on a centerless lathe with a single side reserved for 0.8mm of the outer circle; a sawing step, sawing the pin sleeve on a disc high-speed saw with a single side reserved for 1mm; a rough turning step, rough turning the end face, outer circle, and inner hole chamfer of the pin sleeve; a carburizing step, performing carburizing treatment in a carburizing furnace; a quenching step, after the carburizing treatment, performing residual temperature quenching after the temperature drops to a certain temperature; a tempering step, completing tempering within 2 hours after quenching; a fine turning step, fine turning the outer circle, ensuring that the concentricity tolerance of the outer circles on both sides is less than 0.05mm; and a grinding step, grinding the two end faces to obtain the required pin sleeve finished product.

[0006] In a preferred example, the present application can be further configured as follows: in the normalizing step, the 20CrMnTi seamless steel pipe is heated to Ac3 or Accm or above and kept at 30 to 50°C, and then cooled in air to obtain a pearlite-like structure.

[0007] In a preferred example, the present application can be further configured as follows: in the carburizing step, exhaust is performed after the furnace is loaded, the kerosene dripping rate is 35-65 drops / minute, and the heating temperature is 900-920°C.

[0008] In a preferred example, the present application can be further configured as follows: in the quenching step, after the carburized layer reaches the requirements, the temperature is lowered to 840±10°C for pre-cooling for 30 minutes.

[0009] The present application has the following advantages: 1. The seamless 20CrMnTi seamless steel pipe is used, the material utilization rate is increased by 45%, and two roughing processes are reduced; 2.20CrMnTi seamless steel pipe adopts preparatory normalizing heat treatment, which can better refine the grains and eliminate the structural defects to obtain pearlite + a small amount of ferrite structure, preparing for subsequent carburizing; 3. The coreless lathe is combined with a high-speed saw. The combination of these two machining processes can quickly and efficiently complete the initial cutting and roughing. 4. Rough and fine processing, with fixtures, reliable positioning and clamping, easy installation, and rapid mass production; 5. The use of normalizing preparatory heat treatment in the early stage plus the final gas carburizing residual temperature single medium oil quenching combined with low temperature tempering can make the mechanical properties of 20CrMnTi material reach the best state.

[0010] The present application improves the processing efficiency of the pin sleeve, reduces the production cost, and is used in conjunction with a tooling fixture to improve the overall processing accuracy of the pin sleeve. The preliminary heat treatment and the final heat treatment are used to bring the mechanical properties of 20CrMnTi to an optimal state. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is a process diagram of this application.

[0012] Figure 2 This is a schematic diagram of residual temperature quenching in this application.

[0013] Figure 3 It is a schematic diagram of the cross-sectional structure of the mandrel and cap tooling of the present application.

[0014] Figure numerals: 1. column; 2. limiting ring; 3. connecting column; 4. connecting cap; 5. nut. DETAILED DESCRIPTION

[0015] The present application is further described in detail below in conjunction with the accompanying drawings.

[0016] Reference Figure 1-Figure 3, which is a pin sleeve processing method for a chain rail disclosed in the present application, comprising the following steps: a normalizing step, placing a whole bundle of customized length of 20CrMnTi seamless steel pipes in a trolley furnace and heating them to 920~950℃, keeping them warm, air cooling, and performing overall normalizing treatment; a turning step, turning the entire 20CrMnTi seamless steel pipe after normalizing on a centerless lathe with a single side reserved for 0.8mm on the outer circle; a sawing step, sawing the pin sleeve length on a disc high-speed saw with a single side reserved for 1mm; a rough turning step, rough turning the end face, outer circle, and inner hole chamfering of the pin sleeve; a carburizing step, performing carburizing treatment in a carburizing furnace; a quenching step, after carburizing treatment, the temperature drops to a certain temperature and then quenching is performed with residual temperature; a tempering step, completing tempering within 2 hours after quenching; a fine turning step, fine turning the outer circle to ensure that the concentricity tolerance of the outer circle on both sides is less than 0.05mm; and a grinding step, grinding the two end faces to obtain the required pin sleeve finished product.

[0017] In the normalizing step, the whole bundle of 20CrMnTi seamless steel pipes is normalized, the steel is heated to Ac3 or Accm above 30-50℃, and cooled in air to obtain pearlite-like structure. The grains are refined and the structural defects are eliminated to obtain pearlite + a small amount of ferrite structure.

[0018] In the turning step, the entire 20CrMnTi seamless steel pipe after normalizing is turned on the centerless lathe with 0.8mm reserved on one side of the outer circle; this allows the excess of the 20CrMnTi seamless steel pipe to be removed quickly and efficiently, while removing the appearance defects of the hot-drawn seam steel pipe blank.

[0019] In the rough turning step, the flexible clamping jaws are clamped to clamp the blank, the outer circle runout is corrected by 0.2mm, and the end face, outer circle and inner hole of the pin sleeve are roughly turned; turn around, clamp the flexible clamping jaws to roughly turn the outer circle, correct the outer circle runout by 0.2mm, and roughly turn the end face, outer circle and inner hole of the pin sleeve to ensure that the rough machining allowance of the pin sleeve is not less than 0.8mm.

[0020] In the carburizing step, exhaust gas is discharged after the furnace is loaded, the kerosene dripping rate is 35-65 drops / minute, the heating temperature is heated to 900-920℃, and the holding time is measured at 0.15-0.2mm / h. The heating temperature does not exceed 920℃ to avoid grain growth; the internal structure from the surface to the core is: pearlite + secondary cementite → pearlite → pearlite + ferrite → core structure.

[0021] In the quenching step, after carburizing treatment, when the carburized layer meets the requirements, the temperature is cooled to 840±10℃ for pre-cooling for 30 minutes to prepare for quenching: When the surface W(C)>0.8% of the 20CrMnTi pin sleeve is carburized, high carbon martensite + carbide + residual austenite is obtained, which has high hardness, up to 60~66HRC, and martensite + residual austenite is obtained in the core, with a hardness of 35~45HRC. After tempering treatment, it can meet the performance requirements of the parts.

[0022] In the tempering step, tempering is completed within 2 hours after quenching; during tempering, martensite can be decomposed, carbide can be precipitated and transformed into tempered martensite, quenching internal stress can be partially eliminated, and micro cracks obtained during quenching can also be mostly healed, so low-temperature tempering can significantly improve the toughness of steel with little reduction in hardness, and improve the strength and wear resistance of the pin sleeve, so that the 20CrMnTi pin sleeve has excellent mechanical properties. It can also stabilize the organization, so that the 20CrMnTi pin sleeve does not undergo organizational transformation during the application process, reduce or eliminate quenching internal stress, reduce deformation of the workpiece and prevent cracking, thereby ensuring that the size and shape of the workpiece remain unchanged.

[0023] In the finishing step, a mandrel and cap tooling is used, with one clamp and one push, to finish turning the outer circle R angle; the concentricity of the outer circles on both sides is ensured to be better than 0.02mm; flexible clamping claws are used to clamp and flatten the two end surfaces to ensure the total length; the inner hole is finish turned to ensure the concentricity of the inner circle and outer hole is better than 0.05.

[0024] In the grinding step, a surface grinder is used to grind both end surfaces to ensure a roughness of 0.8.

[0025] The core shaft cap 4 tooling includes a column 1, on which is provided a limiting ring 2 for limiting the pin sleeve, and on which is also provided a connecting column 3. The diameter of the connecting column 3 is smaller than the diameter of the column 1 and is located at one end of the column 1. In use, the pin sleeve is sleeved on the column 1 and one end is against the limiting ring 2. The cap 4 is sleeved on the connecting column 3 and is against the pin sleeve. The connecting column 3 is also threadedly connected with a nut 5, and the nut 5 is located on the side of the cap 4 away from the pin sleeve.

[0026] The implementation principle of this embodiment is: through the above-mentioned production process, the production efficiency of the pin sleeve can be increased and the energy consumption can be reduced.

[0027] The embodiments of this specific implementation method are all preferred embodiments of the present application, and are not intended to limit the protection scope of the present application. Therefore, all equivalent changes made based on the structure, shape, and principle of the present application should be included in the protection scope of the present application.

Claims

1. A method for processing a pin sleeve for a chain rail, characterized in that: The method comprises the following steps: a normalizing step, placing a 20CrMnTi seamless steel pipe in a trolley furnace and heating it to 920-950°C, keeping the temperature, air cooling, and performing overall normalizing treatment; a turning step, turning the outer circle of the whole normalized 20CrMnTi seamless steel pipe on a centerless turning device with a single side reserved for 0.8mm; a sawing step, sawing the pin sleeve length on a disc high-speed saw device with a single side reserved for 1mm; a rough turning step, rough turning the end face, outer circle, and inner hole chamfer of the pin sleeve; a carburizing step, performing carburizing treatment in a carburizing furnace; a quenching step, after carburizing treatment, performing residual temperature quenching after the temperature drops to a certain temperature; a tempering step, completing tempering within 2 hours after quenching; a fine turning step, fine turning the outer circle, ensuring that the concentricity tolerance of the outer circles on both sides is less than 0.05mm; and a grinding step, grinding the two end faces to obtain the required pin sleeve finished product.

2. A method for processing a pin sleeve for a chain rail according to claim 1, characterized in that: In the normalizing step, the 20CrMnTi seamless steel pipe is heated to Ac3 or Accm or above and kept at 30-50°C, and then cooled in air to obtain a pearlite structure.

3. A method for processing a pin sleeve for a chain rail according to claim 1, characterized in that: In the carburizing step, the furnace is exhausted after loading, the kerosene dripping rate is 35~65 drops / minute, and the heating temperature is heated to 900~920℃.

4. A method for processing a pin sleeve for a chain rail according to claim 1, characterized in that: In the quenching step, after the carburized layer reaches the requirements, the temperature is lowered to 840±10℃ for pre-cooling for 30 minutes.

Images