Precision cutting and forging process for large pitch track links

Abstract

The present invention discloses a precision cutting and forging process suitable for large pitch track segments. First, the steel billet is obtained by smelting and continuous casting according to a specific chemical composition; then, it is hot-rolled into round steel, cut into sections, heated, flattened, pre-forged, final forged, and precision-cut to obtain a track segment blank; finally, it is solution treated under pulse electric field conditions, water quenched, oil cooled, aged, quenched with quenching liquid, tempered, and air-cooled under pulse magnetic field conditions. The present invention screens and obtains a specific chemical composition, and combines it with a corresponding heat treatment process to greatly improve product performance. The process of the present invention is suitable for the processing of track segments with a pitch of more than 200 mm, and the track segments have excellent performance.

Description

Technical Field

[0001] The invention belongs to the technical field of forging processing, and in particular relates to a precision cutting forging process suitable for large-pitch chain track segments. Background Art

[0002] The track link is a key component in the track assembly. It is a core component of engineering machinery and equipment such as excavators, rotary drilling rigs, bulldozers, tanks, self-propelled artillery, and is one of the main essential parts of the travel system of crawler engineering vehicles. The track link needs to be used in complex environments such as mountains and mines. During the working process, it must bear the weight of the machine and the operating load, and provide the operating friction driving force, and at the same time bear the lateral force of the supporting wheels when turning. Since the track link works in harsh conditions and is used in chains, the reliability requirements are very high. Once it breaks during installation and operation, the engineering machinery will stop and cannot continue to work. Therefore, the track link should have high strength, wear resistance and impact toughness. In recent years, with the development of engineering machinery equipment towards large-scale, the chassis track requires a larger pitch. Correspondingly, the thickness of the large-pitch track link increases, and higher performance requirements are placed on the product.

[0003] The conventional processing method of the track link is as follows: round steel blanking → heating → forging → residual heat quenching or conventional quenching → tread milling → tread induction quenching → tempering → machining shaft holes, sleeve holes, bolt holes → pulling nut faces → magnetic particle inspection → assembly. Conventional processing methods have problems such as complex procedures and high production costs, and cannot meet the requirements of modern industrial production. People are constantly improving conventional processing methods. No matter how they are improved, the key to determining the performance of the track link lies in material selection and heat treatment technology.

[0004] The existing track links are mostly made of steel types 50, 50Mn, 40Mn2 and 40MnB, among which the comprehensive performance of special steel 40MnB is the best. However, the track assemblies made of this material often break under certain harsh working conditions, and still cannot meet the requirements of high-power engineering machinery.

[0005] Heat treatment process varies with different materials and is one of the keys to determine the comprehensive mechanical properties of products. For large pitch track links, due to the large pitch, large forging volume and thick thickness, conventional heat treatment will cause problems such as coarse grains, affecting product performance.

[0006] Patent application CN111360488A discloses a method for processing track links for crawlers, including the following steps: round steel blanking, heating, precision forging, overall quenching, tempering, machining shaft holes, sleeve holes, bolt holes, magnetic particle inspection and assembly. This patented technology uses a full hardening heat treatment process to replace the traditional "tempering and tread induction heat treatment" process. When forging the track link, the tread and nut surface use a precision cutting process, which simplifies the process flow, reduces the investment in processing equipment, and reduces production costs. However, this method is not suitable for the processing of large pitch track links, and the performance of the track links is average. Summary of the invention

[0007] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a precision cutting and forging process suitable for large-pitch track segments, which is suitable for processing track segments with a pitch of more than 200 mm and has good performance.

[0008] In order to achieve the above object, the present invention adopts the following technical solution:

[0009] Applicable to the precision cutting and forging process of large pitch track links. The specific steps are as follows:

[0010] (1) firstly smelting and continuously casting a steel billet according to the following chemical composition in weight percentage: C: 0.36-0.40%, Si: 0.08-0.1%, Mn: 1.2-1.5%, Co: 0.8-1%, Nb: 0.3-0.5%, Al: 0.03-0.04%, Ti: 0.02-0.03%, W: 0.02-0.03%, V: 0.01-0.02%, N: 0.009-0.012%, Y: 0.009-0.01%, Sc: 0.009-0.01%, B: 0.001-0.002%, S: ≤0.01%, P: ≤0.01%, and the balance is Fe and other inevitable impurity elements;

[0011] (2) hot rolling into round steel, cutting into steel segments, heating, flattening, pre-forging, final forging, and fine cutting to obtain the rail segment blank;

[0012] (3) Heat treatment: solution treatment under pulse electric field conditions, water quenching and oil cooling, aging treatment, quenching liquid quenching, tempering, and air cooling under pulse magnetic field conditions;

[0013] The quenching liquid is made of polyacrylamide, polylactic acid-polyethylene glycol copolymer and sodium polyacrylate as raw materials.

[0014] Preferably, the pitch of the chain track segments is ≥200 mm.

[0015] Preferably, the quenching liquid is prepared by the following method: first dissolving polyacrylamide and sodium polyacrylate in deionized water, then adding polylactic acid-polyethylene glycol copolymer while stirring, stirring at 300-500r / min for 20-30 minutes, and ultrasonically oscillating at 500-700W for 10-20 minutes to obtain the quenching liquid; wherein the mass ratio of polyacrylamide, sodium polyacrylate, polylactic acid-polyethylene glycol copolymer, and deionized water is 1:2-3:1-2:30-40, the polyacrylamide is non-ionic, and its molecular weight is 5-6 million, and the molecular weight of sodium polyacrylate is 2-3 million.

[0016] Preferably, in parts by weight, the polylactic acid-polyethylene glycol copolymer is prepared by the following method: under nitrogen protection, 18 to 20 parts of polyethylene glycol 1000, 18 to 20 parts of lactide and 0.09 to 0.1 parts of bismuth laurate are stirred and mixed, stirred and reacted at 180 to 200° C. for 4 to 5 hours, evacuated to -0.095 MPa, and continued to keep warm and stir for 1 to 2 hours to obtain the copolymer.

[0017] Preferably, step (1) adopts LF+VD refining process, argon is blown throughout the LF furnace refining, slag is deoxidized, the white slag is kept for 15 to 20 minutes, the VD furnace is kept at a vacuum degree of 100 Pa for 15 to 20 minutes, and soft blowing is performed for 16 to 18 minutes; continuous casting adopts full-process protective casting, and the superheat of the tundish is 20 to 22°C.

[0018] Preferably, in step (2), the heating temperature is 1120-1140°C, the pre-forging temperature is 1200-1250°C, and the final forging temperature is 750-780°C.

[0019] Preferably, in step (2), the specific method of precision cutting is: first cut off the flash and the skin, and leave a margin to ensure that the misalignment is ≤0.5mm; then cut off the margin, tread, plate joint, two side surfaces, nut surface, pin hole and the skin inside the sleeve hole to ensure that the misalignment is ≤0.2mm.

[0020] Preferably, in step (3), the pulse electric field conditions during the solution treatment are: alternating current, with a root mean square current density in the range of 30000 A / cm 2 , the current amplitude is 28000A / cm 2 , frequency 300-400Hz, duty cycle 0.4; the specific method of solution treatment is: first heat up to 800-820℃ at a heating rate of 3-5℃ / min, keep warm for 50-60 minutes, then heat up to 970-990℃ at a heating rate of 5-7℃ / min, keep warm for 40-50 minutes, then heat up to 1020-1030℃ at a heating rate of 3-4℃ / min, keep warm for 50-60 minutes.

[0021] Preferably, in step (3), the specific method of water quenching and oil cooling is: water quenching for 10 to 15 seconds, transferring to oil and continuing cooling to below 50°C.

[0022] Preferably, in step (3), the specific method of aging treatment is: firstly heating to 700-720°C at a heating rate of 3-5°C / min, keeping warm for 40-50 minutes, then heating to 750-770°C at a heating rate of 5-7°C / min, keeping warm for 5-6 hours.

[0023] Preferably, in step (3), the quenching time of the quenching liquid is 10 to 15 seconds.

[0024] Preferably, in step (3), the tempering process conditions are: tempering treatment at 580-600° C. for 50-60 minutes.

[0025] Preferably, in step (3), the specific method of air cooling under pulsed magnetic field conditions is: first, air is passed into the heating furnace for cooling, and the temperature is cooled to below 500°C at a cooling rate of 100-120°C / min, and then the furnace is taken out for air cooling; the magnetic field pulse frequency is 500-600Hz, and the magnetic field strength is 8-10T.

[0026] Preferably, in step (3), after the heat treatment is completed, the shaft hole, sleeve hole and bolt hole are processed, and finally assembly is performed.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] The present invention first performs smelting and continuous casting according to the chemical composition of a specific composition to obtain a steel billet; then hot-rolls it into round steel, cuts it into steel segments, heats it, flattens it, pre-forges it, final forges it, and fine-cuts it to obtain a track segment blank; finally, solid solution treatment is performed under pulse electric field conditions, water quenching and oil cooling is performed, aging treatment is performed, quenching liquid quenching is performed, tempering is performed, and air cooling is performed under pulse magnetic field conditions. The present invention screens and obtains a specific chemical composition, and combines it with a corresponding heat treatment process to greatly improve product performance. The process of the present invention is suitable for the processing of track segments with a pitch of more than 200 mm, and the track segments have excellent performance.

[0029] The steel billet of the present invention is composed of the following chemical components of specific composition: C, Si, Mn, Co, Nb, Al, Ti, W, V, N, Y, Sc, B, S, P, Fe. Among them, Mn and Co improve hardenability and strength; Nb, Y, Sc, and B play a purifying role and promote grain refinement and improve product toughness; Al and Ti improve product strength and toughness; W and V increase strength and toughness and inhibit grain enlargement. The present invention improves product performance through the synergistic effect of each element.

[0030] The heat treatment of the present invention includes: solution treatment under pulse electric field conditions, water quenching and oil cooling, aging treatment, quenching with quenching liquid, tempering, and air cooling under pulse magnetic field conditions. A pulse electric field is applied during solution treatment, and the solution treatment is heated in steps to promote full dissolution and optimize the organizational structure. After the solution treatment is completed, water quenching and oil cooling are performed, and quenching with quenching liquid is used after aging treatment. Different quenching methods have different effects on the product. The applicant has screened out the corresponding quenching process for each step through research. Among them, the quenching liquid is made of polyacrylamide, polylactic acid-polyethylene glycol copolymer, and sodium polyacrylate as raw materials. The use of the quenching liquid is combined with the aging treatment to optimize product performance. After tempering treatment, the present invention uses air cooling under pulse magnetic field conditions to further optimize the product organizational structure and improve product performance. DETAILED DESCRIPTION

[0031] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of 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.

[0032] Unless otherwise specified, all commodities in this invention are purchased through market channels.

[0033] Example 1

[0034] Applicable to the precision cutting and forging process of large pitch track segments (pitch ≥ 200mm), the specific steps are as follows:

[0035] (1) firstly smelting and continuously casting a steel billet according to the following chemical composition in weight percentage: C: 0.36%, Si: 0.08%, Mn: 1.2%, Co: 0.8%, Nb: 0.3%, Al: 0.03%, Ti: 0.02%, W: 0.02%, V: 0.01%, N: 0.009%, Y: 0.009%, Sc: 0.009%, B: 0.001%, S: ≤0.01%, P: ≤0.01%, the balance being Fe and other inevitable impurity elements;

[0036] (2) hot rolling into round steel, cutting into steel segments, heating, flattening, pre-forging, final forging, and fine cutting to obtain the rail segment blank;

[0037] (3) Heat treatment: solution treatment under pulse electric field conditions, water quenching and oil cooling, aging treatment, quenching liquid quenching, tempering, and air cooling under pulse magnetic field conditions;

[0038] The quenching liquid is made of polyacrylamide, polylactic acid-polyethylene glycol copolymer and sodium polyacrylate as raw materials.

[0039] The quenching liquid is prepared by the following method: first dissolving 1 kg of polyacrylamide and 2 kg of sodium polyacrylate in 30 kg of deionized water, then adding 1 kg of polylactic acid-polyethylene glycol copolymer while stirring, stirring at 300 r / min for 20 minutes, and ultrasonically oscillating at 500 W for 10 minutes to obtain the quenching liquid; wherein the polyacrylamide is non-ionic with a molecular weight of 5 million, and the molecular weight of the sodium polyacrylate is 2 million.

[0040] The polylactic acid-polyethylene glycol copolymer is prepared by the following method: under nitrogen protection, 1.8 kg of polyethylene glycol 1000, 1.8 kg of lactide and 9 g of bismuth laurate are stirred and mixed, stirred and reacted at 180° C. for 4 hours, evacuated to -0.095 MPa, and continued to keep warm and stir for 1 hour to obtain the copolymer.

[0041] Step (1) adopts LF+VD refining process, argon is blown throughout the LF furnace refining, slag is deoxidized, the white slag is kept for 15 minutes, the VD furnace is kept at a vacuum degree of 100Pa for 15 minutes, and soft blowing is performed for 16 minutes; continuous casting adopts full-process protective casting, and the superheat of the tundish is 20°C.

[0042] In step (2), the heating temperature is 1120°C, the pre-forging temperature is 1200°C, and the final forging temperature is 750°C.

[0043] In step (2), the specific method of precision cutting is: first cut off the flash and the skin, and leave a margin to ensure that the misalignment is ≤0.5mm; then cut off the margin, tread, plate joint, two side surfaces, nut surface, pin hole and the skin inside the sleeve hole to ensure that the misalignment is ≤0.2mm.

[0044] In step (3), the pulse electric field conditions during solution treatment are: alternating current, root mean square current density range is 30000A / cm 2 , the current amplitude is 28000A / cm 2 , frequency 300 Hz, duty cycle 0.4; the specific method of solution treatment is: first heat up to 800 ° C at a heating rate of 3 ° C / min, keep warm for 50 minutes, then heat up to 970 ° C at a heating rate of 5 ° C / min, keep warm for 40 minutes, then heat up to 1020 ° C at a heating rate of 3 ° C / min, keep warm for 50 minutes.

[0045] In step (3), the specific method of water quenching and oil cooling is: water quenching for 10 seconds, transferring to oil and continuing to cool to below 50°C.

[0046] In step (3), the specific method of aging treatment is: firstly heating to 700°C at a heating rate of 3°C / min, keeping the temperature for 40 minutes, then heating to 750°C at a heating rate of 5°C / min, and keeping the temperature for 5 hours.

[0047] In step (3), the quenching time of the quenching liquid is 10s.

[0048] In step (3), the tempering process conditions are: tempering treatment at 580° C. for 50 minutes.

[0049] In step (3), the specific method of air cooling under pulsed magnetic field conditions is: first, air is passed into the heating furnace for cooling, and the temperature is cooled to below 500°C at a cooling rate of 100°C / min, and then the furnace is taken out for air cooling; the magnetic field pulse frequency is 500 Hz, and the magnetic field strength is 8 T.

[0050] In step (3), after the heat treatment is completed, the shaft hole, sleeve hole and bolt hole are processed, and finally assembly is performed.

[0051] Example 2

[0052] Applicable to the precision cutting and forging process of large pitch track segments (pitch ≥ 200mm), the specific steps are as follows:

[0053] (1) firstly smelting and continuously casting a steel billet according to the following chemical composition in weight percentage: C: 0.40%, Si: 0.1%, Mn: 1.5%, Co: 1%, Nb: 0.5%, Al: 0.04%, Ti: 0.03%, W: 0.03%, V: 0.02%, N: 0.012%, Y: 0.01%, Sc: 0.01%, B: 0.002%, S: ≤0.01%, P: ≤0.01%, and the balance is Fe and other inevitable impurity elements;

[0054] (2) hot rolling into round steel, cutting into steel segments, heating, flattening, pre-forging, final forging, and fine cutting to obtain the rail segment blank;

[0055] (3) Heat treatment: solution treatment under pulse electric field conditions, water quenching and oil cooling, aging treatment, quenching liquid quenching, tempering, and air cooling under pulse magnetic field conditions;

[0056] The quenching liquid is made of polyacrylamide, polylactic acid-polyethylene glycol copolymer and sodium polyacrylate as raw materials.

[0057] The quenching liquid is prepared by the following method: first dissolving 1 kg of polyacrylamide and 3 kg of sodium polyacrylate in 40 kg of deionized water, then adding 2 kg of polylactic acid-polyethylene glycol copolymer while stirring, stirring at 500 r / min for 30 minutes, and ultrasonically oscillating at 700 W for 20 minutes to obtain the quenching liquid; wherein the polyacrylamide is non-ionic with a molecular weight of 6 million, and the molecular weight of the sodium polyacrylate is 3 million.

[0058] The polylactic acid-polyethylene glycol copolymer is prepared by the following method: under nitrogen protection, 2 kg of polyethylene glycol 1000, 2 kg of lactide and 10 g of bismuth laurate are stirred and mixed, stirred and reacted at 200° C. for 5 hours, evacuated to -0.095 MPa, and continued to keep warm and stir for 2 hours to obtain the copolymer.

[0059] Step (1) adopts LF+VD refining process, argon is blown throughout the LF furnace refining, slag is deoxidized, the white slag is kept for 20 minutes, the VD furnace is kept at a vacuum degree of 100Pa for 20 minutes, and soft blowing is carried out for 18 minutes; continuous casting adopts full-process protective casting, and the superheat degree of the tundish is 22°C.

[0060] In step (2), the heating temperature is 1140°C, the pre-forging temperature is 1250°C, and the final forging temperature is 780°C.

[0061] In step (2), the specific method of precision cutting is: first cut off the flash and the skin, and leave a margin to ensure that the misalignment is ≤0.5mm; then cut off the margin, tread, plate joint, two side surfaces, nut surface, pin hole and the skin inside the sleeve hole to ensure that the misalignment is ≤0.2mm.

[0062] In step (3), the pulse electric field conditions during solution treatment are: alternating current, root mean square current density range is 30000A / cm 2 , the current amplitude is 28000A / cm 2 , frequency 400 Hz, duty cycle 0.4; the specific method of solution treatment is: first heat up to 820°C at a heating rate of 5°C / min, keep warm for 60 minutes, then heat up to 990°C at a heating rate of 7°C / min, keep warm for 50 minutes, then heat up to 1030°C at a heating rate of 4°C / min, keep warm for 60 minutes.

[0063] In step (3), the specific method of water quenching and oil cooling is: water quenching for 15 seconds, transferring to oil and continuing to cool to below 50°C.

[0064] In step (3), the specific method of aging treatment is: firstly increase the temperature to 720°C at a heating rate of 5°C / min, keep the temperature for 50 minutes, then increase the temperature to 770°C at a heating rate of 7°C / min, and keep the temperature for 6 hours.

[0065] In step (3), the quenching time of the quenching liquid is 15s.

[0066] In step (3), the tempering process conditions are: tempering treatment at 600° C. for 60 minutes.

[0067] In step (3), the specific method of air cooling under pulsed magnetic field conditions is: first, air is passed into the heating furnace for cooling, and the temperature is cooled to below 500°C at a cooling rate of 120°C / min, and then the furnace is taken out for air cooling; the magnetic field pulse frequency is 600 Hz, and the magnetic field strength is 10T.

[0068] In step (3), after the heat treatment is completed, the shaft hole, sleeve hole and bolt hole are processed, and finally assembly is performed.

[0069] Example 3

[0070] Applicable to the precision cutting and forging process of large pitch track segments (pitch ≥ 200mm), the specific steps are as follows:

[0071] (1) firstly smelting and continuously casting a steel billet according to the following chemical composition in weight percentage: C: 0.38%, Si: 0.09%, Mn: 1.3%, Co: 0.9%, Nb: 0.4%, Al: 0.035%, Ti: 0.025%, W: 0.025%, V: 0.015%, N: 0.01%, Y: 0.01%, Sc: 0.009%, B: 0.001%, S: ≤0.01%, P: ≤0.01%, the balance being Fe and other unavoidable impurity elements;

[0072] (2) hot rolling into round steel, cutting into steel segments, heating, flattening, pre-forging, final forging, and fine cutting to obtain the rail segment blank;

[0073] (3) Heat treatment: solution treatment under pulse electric field conditions, water quenching and oil cooling, aging treatment, quenching liquid quenching, tempering, and air cooling under pulse magnetic field conditions;

[0074] The quenching liquid is made of polyacrylamide, polylactic acid-polyethylene glycol copolymer and sodium polyacrylate as raw materials.

[0075] The quenching liquid is prepared by the following method: firstly dissolving 1 kg of polyacrylamide and 2-3 kg of sodium polyacrylate in 35 kg of deionized water, then adding 1.5 kg of polylactic acid-polyethylene glycol copolymer while stirring, stirring at 400 r / min for 25 minutes, and ultrasonically oscillating at 600 W for 15 minutes to obtain the quenching liquid; wherein the polyacrylamide is non-ionic with a molecular weight of 6 million, and the molecular weight of the sodium polyacrylate is 2 million.

[0076] The polylactic acid-polyethylene glycol copolymer is prepared by the following method: under nitrogen protection, 1.9 kg of polyethylene glycol 1000, 1.9 kg of lactide and 10 g of bismuth laurate are stirred and mixed, stirred and reacted at 190° C. for 4.5 hours, evacuated to -0.095 MPa, and continued to keep warm and stir for 1.5 hours to obtain the copolymer.

[0077] Step (1) adopts LF+VD refining process, argon is blown throughout the LF furnace refining, slag is deoxidized, the white slag is kept for 18 minutes, the VD furnace is kept at a vacuum degree of 100 Pa for 18 minutes, and soft blowing is carried out for 17 minutes; continuous casting adopts full-process protective casting, and the superheat of the tundish is 21°C.

[0078] In step (2), the heating temperature is 1130°C, the pre-forging temperature is 1230°C, and the final forging temperature is 770°C.

[0079] In step (2), the specific method of precision cutting is: first cut off the flash and the skin, and leave a margin to ensure that the misalignment is ≤0.5mm; then cut off the margin, tread, plate joint, two side surfaces, nut surface, pin hole and the skin inside the sleeve hole to ensure that the misalignment is ≤0.2mm.

[0080] In step (3), the pulse electric field conditions during solution treatment are: alternating current, root mean square current density range is 30000A / cm 2 , the current amplitude is 28000A / cm 2 , frequency 400 Hz, duty cycle 0.4; the specific method of solution treatment is: first heat up to 810°C at a heating rate of 4°C / min, keep warm for 55 minutes, then heat up to 980°C at a heating rate of 6°C / min, keep warm for 45 minutes, then heat up to 1025°C at a heating rate of 3°C / min, keep warm for 55 minutes.

[0081] In step (3), the specific method of water quenching and oil cooling is: water quenching for 12 seconds, transferring to oil and continuing to cool to below 50°C.

[0082] In step (3), the specific method of aging treatment is: firstly increase the temperature to 710°C at a heating rate of 4°C / min, keep the temperature for 45 minutes, then increase the temperature to 760°C at a heating rate of 6°C / min, and keep the temperature for 5 hours.

[0083] In step (3), the quenching time of the quenching liquid is 12s.

[0084] In step (3), the tempering process conditions are: tempering treatment at 590° C. for 55 minutes.

[0085] In step (3), the specific method of air cooling under pulsed magnetic field conditions is: first, air is passed into the heating furnace for cooling, and the temperature is cooled to below 500°C at a cooling rate of 110°C / min, and then the furnace is taken out for air cooling; the magnetic field pulse frequency is 600Hz, and the magnetic field strength is 9T.

[0086] In step (3), after the heat treatment is completed, the shaft hole, sleeve hole and bolt hole are processed, and finally assembly is performed.

[0087] Comparative Example

[0088] A precision cutting and forging process for a track link, the specific steps are as follows:

[0089] (1) firstly smelting and continuously casting a steel billet according to the following chemical composition in weight percentage: C: 0.36%, Si: 0.08%, Mn: 1.2%, Co: 0.8%, Nb: 0.3%, Al: 0.03%, Ti: 0.02%, W: 0.02%, V: 0.01%, N: 0.009%, Y: 0.009%, Sc: 0.009%, B: 0.001%, S: ≤0.01%, P: ≤0.01%, the balance being Fe and other inevitable impurity elements;

[0090] (2) hot rolling into round steel, cutting into steel segments, heating, flattening, pre-forging, final forging, and fine cutting to obtain the rail segment blank;

[0091] (3) Heat treatment: solution treatment under pulse electric field conditions, water quenching and oil cooling, aging treatment, water quenching, tempering, and air cooling under pulse magnetic field conditions.

[0092] Step (1) adopts LF+VD refining process, argon is blown throughout the LF furnace refining, slag is deoxidized, the white slag is kept for 15 minutes, the VD furnace is kept at a vacuum degree of 100Pa for 15 minutes, and soft blowing is performed for 16 minutes; continuous casting adopts full-process protective casting, and the superheat of the tundish is 20°C.

[0093] In step (2), the heating temperature is 1120°C, the pre-forging temperature is 1200°C, and the final forging temperature is 750°C.

[0094] In step (2), the specific method of precision cutting is: first cut off the flash and the skin, and leave a margin to ensure that the misalignment is ≤0.5mm; then cut off the margin, tread, plate joint, two side surfaces, nut surface, pin hole and the skin inside the sleeve hole to ensure that the misalignment is ≤0.2mm.

[0095] In step (3), the pulse electric field conditions during solution treatment are: alternating current, root mean square current density range is 30000A / cm 2 , the current amplitude is 28000A / cm 2 , frequency 300 Hz, duty cycle 0.4; the specific method of solution treatment is: first heat up to 800 ° C at a heating rate of 3 ° C / min, keep warm for 50 minutes, then heat up to 970 ° C at a heating rate of 5 ° C / min, keep warm for 40 minutes, then heat up to 1020 ° C at a heating rate of 3 ° C / min, keep warm for 50 minutes.

[0096] In step (3), the specific method of water quenching and oil cooling is: water quenching for 10 seconds, transferring to oil and continuing to cool to below 50°C.

[0097] In step (3), the specific method of aging treatment is: firstly heating to 700°C at a heating rate of 3°C / min, keeping the temperature for 40 minutes, then heating to 750°C at a heating rate of 5°C / min, and keeping the temperature for 5 hours.

[0098] In step (3), the water quenching time is 10 s.

[0099] In step (3), the tempering process conditions are: tempering treatment at 580° C. for 50 minutes.

[0100] In step (3), the specific method of air cooling under pulsed magnetic field conditions is: first, air is passed into the heating furnace for cooling, and the temperature is cooled to below 500°C at a cooling rate of 100°C / min, and then the furnace is taken out for air cooling; the magnetic field pulse frequency is 500 Hz, and the magnetic field strength is 8 T.

[0101] In step (3), after the heat treatment is completed, the shaft hole, sleeve hole and bolt hole are processed, and finally assembly is performed.

[0102] The chain track segments with a pitch of 228.6 mm were obtained by processing the processes of Examples 1 to 3 and the comparative example, and the performance of the chain track segments was tested, including tensile strength, elongation and impact toughness, with reference to the relevant test standards and methods recorded in JB / T 5932.2-2017 "Sealed crawler tracks of crawler bulldozers Part 2: Chain track segments". The results are shown in Table 1.

[0103] Table 1. Track link performance test results

[0104] Tensile strength(MPa) Elongation(%) <![CDATA[Impact toughness (J / cm 2 )]]> Example 1 1253 15 42 Example 2 1255 15 43 Example 3 1261 16 45 Comparative Example 1146 12 38

[0105] It can be seen from Table 1 that the tensile strength, elongation and impact toughness of the track links obtained in Examples 1 to 3 are much higher than the requirements of JB / T5932.2-2017, and have excellent mechanical properties.

[0106] In the comparative example, the quenching liquid quenching was replaced by water quenching, and the mechanical properties of the track link were significantly deteriorated, indicating that the specific heat treatment of the present invention and the specific composition work synergistically to improve the product performance.

[0107] The present invention illustrates the technical concept of the present invention through the above-mentioned embodiments, but the present invention is not limited to the above-mentioned embodiments, that is, it does not mean that the present invention must rely on the above-mentioned embodiments to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of individual raw materials of the product of the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. Suitable for precision cutting and forging process of large pitch track segments, characterized in that: The specific steps are as follows: (1) firstly smelting and continuously casting a steel billet according to the following chemical composition in weight percentage: C: 0.36-0.40%, Si: 0.08-0.1%, Mn: 1.2-1.5%, Co: 0.8-1%, Nb: 0.3-0.5%, Al: 0.03-0.04%, Ti: 0.02-0.03%, W: 0.02-0.03%, V: 0.01-0.02%, N: 0.009-0.012%, Y: 0.009-0.01%, Sc: 0.009-0.01%, B: 0.001-0.002%, S: ≤0.01%, P: ≤0.01%, and the balance is Fe and other inevitable impurity elements; (2) hot rolling into round steel, cutting into steel sections, heating, flattening, pre-forging, final forging, and fine cutting to obtain the rail segment blank; (3) Heat treatment: solution treatment under pulse electric field conditions, water quenching and oil cooling, aging treatment, quenching liquid quenching, tempering, and air cooling under pulse magnetic field conditions; The quenching liquid is made of polyacrylamide, polylactic acid-polyethylene glycol copolymer and sodium polyacrylate as raw materials; the quenching liquid is prepared by the following method: firstly dissolving polyacrylamide and sodium polyacrylate in deionized water, then adding polylactic acid-polyethylene glycol copolymer while stirring, stirring at 300-500r / min for 20-30 minutes, and ultrasonically oscillating at 500-700W for 10-20 minutes to obtain the quenching liquid; wherein the mass ratio of polyacrylamide, sodium polyacrylate, polylactic acid-polyethylene glycol copolymer and deionized water is 1:2-3:1-2:30-40, the polyacrylamide is non-ionic, and its molecular weight is 5-6 million, and the molecular weight of sodium polyacrylate is 2-3 million; In step (3), the specific method of aging treatment is: firstly heating the temperature to 700-720°C at a heating rate of 3-5°C / min, keeping the temperature for 40-50 minutes, then heating the temperature to 750-770°C at a heating rate of 5-7°C / min, and keeping the temperature for 5-6 hours.

2. The process according to claim 1, characterized in that Step (1) adopts LF+VD refining process, argon is blown throughout the LF furnace refining, slag is deoxidized, the white slag is kept for 15 to 20 minutes, the VD furnace is kept at a vacuum degree of 100 Pa for 15 to 20 minutes, and soft blowing is performed for 16 to 18 minutes; continuous casting adopts full-process protective casting, and the superheat of the tundish is 20 to 22°C.

3. The process according to claim 1, characterized in that In step (2), the heating temperature is 1120-1140°C, the pre-forging temperature is 1200-1250°C, and the final forging temperature is 750-780°C.

4. The process according to claim 1, characterized in that In step (2), the specific method of precision cutting is: first cut off the flash and the skin, and leave a margin to ensure that the misalignment is ≤0.5mm; then cut off the margin, tread, plate joint, two side surfaces, nut surface, pin hole and the skin inside the sleeve hole to ensure that the misalignment is ≤0.2mm.

5. The process according to claim 1, characterized in that In step (3), the pulse electric field conditions during solution treatment are: alternating current, root mean square current density range is 30000A / cm 2 , the current amplitude is 28000A / cm 2 , frequency 300-400Hz, duty cycle 0.4; the specific method of solution treatment is: first heat up to 800-820℃ at a heating rate of 3-5℃ / min, keep warm for 50-60 minutes, then heat up to 970-990℃ at a heating rate of 5-7℃ / min, keep warm for 40-50 minutes, then heat up to 1020-1030℃ at a heating rate of 3-4℃ / min, keep warm for 50-60 minutes.

6. The process according to claim 1, characterized in that In step (3), the specific method of water quenching and oil cooling is: water quenching for 10 to 15 seconds, transferring to oil and continuing to cool to below 50°C.

7. The process according to claim 1, characterized in that In step (3), the quenching time of the quenching liquid is 10 to 15 seconds.

8. The process according to claim 1, characterized in that In step (3), the tempering process conditions are: tempering treatment at 580-600° C. for 50-60 minutes; The specific method of air cooling under pulsed magnetic field conditions is: first, air is passed into the heating furnace for cooling, and the cooling rate is controlled to be 100-120℃ / min to cool to below 500℃, and then air-cooled out of the furnace; the magnetic field pulse frequency is 500-600Hz, and the magnetic field strength is 8-10T.