Engineering machinery driving wheel material and preparation process thereof

Abstract

The invention relates to the technical field of manufacturing of engineering machinery parts, and discloses an engineering machinery driving wheel made of a medium carbon alloy cast steel material. The invention also discloses a preparation process of the engineering machinery driving wheel material, which comprises the following steps: S1, casting treatment: melting the medium carbon alloy steel material, and casting into a driving wheel blank; s2, normalizing heat treatment: carrying out normalizing heat treatment on the driving wheel blank; s3, rough machining treatment; s4, quenching treatment: carrying out induction quenching treatment; and S5, finish machining treatment. The synergistic effect of alloy elements in a medium carbon alloy cast steel material is combined with an optimized air cooling process, so that the cast steel is normalized to obtain a uniform structure which mainly contains superfine pearlite and contains extremely little ferrite, the matrix hardness is stable, and the requirement of a high-performance driving wheel is completely met; after the process route is improved, tempering and shot blasting and flaw detection procedures after tempering are canceled; the technological process is greatly shortened, material turnover is reduced, and the production efficiency is improved.

Description

Technical Field

[0001] This invention relates to the field of engineering machinery parts manufacturing technology, specifically to a material and preparation process for an engineering machinery drive wheel. Background Technology

[0002] Drive wheels are key transmission components of the chassis of construction machinery (such as excavators and bulldozers). They are generally directly connected to the drive motor, directly transmitting power to the tracks to drive the chassis forward. When the drive wheels are working, there is intense friction and impact between the wheel teeth and the track links. Therefore, the drive wheel surface is required to have high hardness and wear resistance, while the core has sufficient strength and toughness, i.e., surface hard and core tough performance.

[0003] Currently, for small-tonnage (≤20 tons) construction machinery, the drive wheels are often made of cast steel such as SCSiMn2H, and their preheating heat treatment usually adopts normalizing process; however, the hardness of the matrix after conventional normalizing (air cooling after furnace exit) is about HB170~HB220, which is difficult to meet the requirements of some users for matrix hardness ≥HB229 (about HRC20); in order to achieve this hardness, the existing technology has to adopt quenching and tempering treatment (quenching + high temperature tempering), but this leads to a long production process, high cost, high energy consumption, and increases the risk of deformation and surface decarburization of the workpiece during the secondary heating process. Summary of the Invention

[0004] The purpose of this invention is to provide a material and manufacturing process for drive wheels of engineering machinery to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: A material for drive wheels of engineering machinery is a medium-carbon alloy cast steel, and its chemical composition by mass percentage is as follows: C: 0.40%~0.47%, Si: 0.30%~0.80%, Mn: 1.00%~1.40%, Cr: 0.14%~0.24%, Mo: 0.05%~0.08%, Ni: 0.07%~0.15%, P≤0.035%, S≤0.035%, Cu≤0.30%, Sn≤0.05%, balance Fe.

[0006] A manufacturing process for a drive wheel material for engineering machinery includes the following steps: S1. Casting process: After melting the medium carbon alloy steel material, it is cast into a drive wheel blank; the pouring temperature is controlled at 1540~1580℃ to ensure that the drive wheel blank has clear tooth shape and dense internal structure. S2. Normalizing heat treatment: Normalizing heat treatment is performed on the drive wheel blank; S3. Rough machining: The drive wheel blank after normalizing heat treatment is shot blasted to remove surface sand and oxide scale; and rough turning is performed, with the machining allowance controlled at 2-5mm. S4. Quenching treatment: The surface of the gear teeth on the drive wheel blank is subjected to induction quenching treatment. S5. Finishing process: After flaw detection and shot blasting, finish processing is carried out, such as precision turning and drilling, to achieve the final dimensions and accuracy required by the drawings, and obtain the finished drive wheel.

[0007] As a further aspect of the present invention: in step S2, the specific steps of the normalizing heat treatment are as follows: S21. Heating: The cast drive wheel blank is placed into the heating furnace and heated in the air medium. That is, the drive wheel blank is placed into the furnace when the furnace temperature is low (such as room temperature), and then the equipment is started to make the drive wheel blank and the furnace slowly heat up together at a set speed until the target temperature is reached. The heating rate is controlled at 100-200℃ / h, and the temperature is heated to 880-900℃ to reduce stress and deformation. S22. Insulation: Insulate at 880-900℃ for 2.5-3.5 hours; S23. Cooling: After the heat preservation is completed, the workpiece is taken out of the furnace and cooled by forced air cooling with a wind speed of not less than 5m / s until the drive wheel blank is cooled to room temperature.

[0008] As a further aspect of the present invention: in step S21, the heating temperature is preferably 890°C.

[0009] As a further aspect of the present invention: in step S22, the heat preservation time is preferably 3 hours.

[0010] As a further aspect of the present invention: in step S4, an induction hardening process is performed using a medium-frequency induction hardening device with a frequency range of 2.5 to 4 kHz to ensure a hardened layer depth of 5 to 20 mm.

[0011] As a further aspect of the present invention: in step S4, the specific steps of the quenching treatment are as follows: S41. Rapidly heat the toothed portion of the drive wheel blank to an austenitizing temperature of 880-920°C; S42. Immediately cool the gear teeth by spraying water or polymer quenching liquid to obtain a high-hardness martensitic structure on the surface of the gear teeth. S43. After quenching, cool to 180-220℃ and hold for 2-3 hours for low-temperature tempering to eliminate internal stress and stabilize the structure.

[0012] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention combines the synergistic effect of alloying elements in medium-carbon alloy cast steel with an optimized air-cooling process, resulting in a uniform microstructure of cast steel after normalizing, dominated by extremely fine pearlite and containing very little ferrite. The matrix hardness is stable, fully meeting the requirements of high-performance drive wheels. The improved process route eliminates the tempering and shot blasting and flaw detection processes after tempering, greatly shortening the process flow, reducing material turnover, and improving production efficiency. Attached Figure Description

[0013] Figure 1 Microscopic images of the metallographic structure in the embodiments of the present invention; Figure 2 Microscopic image of the metallographic structure of the drive wheel of the engineering machinery in Comparative Example 1; Figure 3 Microscopic image of the metallographic structure of the drive wheel of the engineering machinery in Comparative Example 2; Figure 4 The image shows the metallographic structure of the drive wheel of the engineering machinery in Comparative Example 3. Detailed Implementation

[0014] The present invention will be further described in detail below with reference to embodiments.

[0015] The process steps of Comparative Examples 1-3 and the Examples are as follows: S1. Casting process: After melting the medium carbon alloy steel material, it is cast into a drive wheel blank; the pouring temperature is controlled at 1540~1580℃ to ensure that the drive wheel blank has clear tooth shape and dense internal structure. S2. Normalizing heat treatment: Normalizing heat treatment is performed on the drive wheel blank; S3. Rough machining: The drive wheel blank after normalizing heat treatment is shot blasted to remove surface sand and oxide scale; and rough turning is performed, with the machining allowance controlled at 2-5mm. S4. Quenching treatment: The tooth portion of the drive wheel blank is rapidly heated to an austenitizing temperature of 900℃ using a medium-frequency induction quenching equipment with a frequency of 2.5~4kHz; immediately cooled by water spraying or polymer quenching liquid spraying to obtain a high-hardness martensitic structure on the tooth surface; after quenching, the temperature is lowered to 200℃, held for 2.5h, and then subjected to low-temperature tempering treatment to obtain a hardened layer depth of 5~20mm. S5. Finishing process: After flaw detection and shot blasting, the drive wheel is finished to obtain the finished product.

[0016] In Comparative Examples 1-3 and the Examples, the process steps are identical except for the normalizing heat treatment step. Hardness, flaw detection, and metallographic analysis were performed on the drive wheels processed in Comparative Examples 1-3 and the Examples; the specific results are as follows: Comparative Example 1: The standard SCSiMn2 cast steel material was used, and its specific composition was analyzed to be: C 0.46%, Si 0.60%, Mn 1.18%, P 0.027%, S 0.021%, Cr 0.1485%, Mo 0.0025%, Ni 0.032%, Cu 0.009%, Sn 0.0001%, with the balance being Fe. Normalizing treatment was carried out: the furnace was heated to 890℃, the heating rate was controlled at 100~200℃ / h, and after holding at that temperature for 3 hours, the material was removed from the furnace and air-cooled.

[0017] The test results are as follows: Hardness: HB181~212, unacceptable; Flaw detection: ① Visual inspection, dye penetrant testing, or magnetic particle testing to inspect surface and near-surface defects; acceptable. ② Radiographic testing to detect internal defects (acceptance standard ASTM E446 & E186, testing standard ASTM E94); acceptable. Metallographic structure: pearlite + ferrite, such as Figure 2 As shown.

[0018] Comparative Example 2: The same materials and normalizing process as Comparative Example 1 were used, but the cooling method was changed to air cooling after the furnace was removed.

[0019] The test results are as follows: Hardness: HB215~246, some are substandard; Flaw detection: Passed; Metallographic structure: extremely fine pearlite + a very small amount of ferrite (grain size 7-8), such as Figure 3 As shown.

[0020] Comparative Example 3 The same materials and normalizing process as Comparative Example 1 were used, but the cooling method was changed to water mist cooling after exiting the furnace.

[0021] The test results are as follows: Hardness HB232~255, acceptable; Flaw detection: Passed; Metallographic structure: bainite + ferrite + sorbite + a small amount of martensite (grain size 8-9), the metallographic structure is abnormal; and the cooling is uneven, the process is uncontrollable, that is, the atomization is incomplete, water and vapor are present during cooling, and the size of the water mist cannot be controlled. Figure 4 As shown.

[0022] Example: The SCSiMn2H cast steel using the internally controlled composition of this invention has the following specific composition after analysis: C 0.454%, Si 0.487%, Mn 1.2975%, P 0.021%, S 0.0125%, Cr 0.157%, Mo 0.066%, Ni 0.109%, Cu 0.019%, Sn 0.0001%, with the balance being Fe. Normalizing treatment is performed: the steel is heated in the furnace to 890℃, held for 3 hours, and then removed from the furnace for forced air cooling.

[0023] Test results: Hardness: HB232~251, fully qualified and stable; Flaw detection: ① Visual inspection, dye penetrant testing, and magnetic particle testing were used to inspect surface and near-surface defects. All were satisfactory. ② Radiographic testing was used to inspect internal defects (acceptance standards ASTM E446 & E186, testing standards ASTM E94). All were satisfactory. Metallographic structure: extremely fine pearlite + very small amount of ferrite, uniform structure.

[0024] I. The material for the drive wheels of engineering machinery in this invention was obtained through experiments; it is based on the main roles of alloying elements in steel, such as: Si can strengthen ferrite, improving the hardenability, strength, and hardness of steel; Mn can improve the hardenability of steel and has a significant strengthening effect, increasing the strength, hardness, and wear resistance of steel; Cr, within the low-alloy range, can significantly strengthen steel, improving its strength, hardness, and wear resistance, as well as its hardenability and high-temperature mechanical properties; Ni can improve the strength of steel while maintaining good plasticity and toughness, improving its hardenability and low-temperature toughness; Mo can strengthen ferrite, improving the strength and hardness of steel, increasing its hardenability, refining grains, improving its heat resistance and high-temperature strength, increasing its strength without reducing its plasticity, and improving its low-temperature toughness; Cu can increase the strength and toughness of steel, but should not exceed 0.2%.

[0025] The composition of the cast steel SCSiMn2H was adjusted through multiple chemical composition experiments; its composition and hardenability index (DI) verification are shown in Table 1 below: Table 1

[0026] Based on the above experimental results, the chemical composition of the standard range SCSiMn2H was adjusted to obtain the following chemical composition of the medium carbon alloy cast steel material of the present invention: C: 0.40%~0.47%, Si: 0.30%~0.80%, Mn: 1.00%~1.40%, Cr: 0.14%~0.24%, Mo: 0.05%~0.08%, Ni: 0.07%~0.15%, P≤0.035%, S≤0.035%, Cu≤0.30%, Sn≤0.05%, balance Fe.

[0027] This invention satisfies the overall performance requirements of the drive wheel by controlling the content of alloying elements and using a normalizing process, thereby reducing production costs. At the same time, it saves on equipment, personnel, and tooling consumption during quenching and tempering, and reduces the further distortion and surface decarburization of the workpiece during quenching and tempering.

[0028] Assuming the drive wheels are 313X drive wheels, the weight after rough machining is 39.3 kg (i.e., the weight after tempering); the tempering cost is calculated at 1.6 yuan / kg; The cost savings would be: 39.3 × 1.6 = 62.88 yuan / piece; calculated based on 500 sets per year: 62.88 × 500 × 2 = 62,880 yuan.

[0029] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A material for drive wheels of engineering machinery, which is a medium-carbon alloy cast steel material, characterized in that, Its chemical composition by mass percentage is as follows: C: 0.40%~0.47%, Si: 0.30%~0.80%, Mn: 1.00%~1.40%, Cr: 0.14%~0.24%, Mo: 0.05%~0.08%, Ni: 0.07%~0.15%, P≤0.035%, S≤0.035%, Cu≤0.30%, Sn≤0.05%, balance Fe.

2. A preparation process for the material used in the drive wheel of engineering machinery as described in claim 1, characterized in that, Includes the following steps: S1. Casting process: The medium carbon alloy steel material with the chemical composition as described in claim 1 is melted and cast into a drive wheel blank; wherein, the pouring temperature is controlled at 1540 to 1580°C to ensure that the drive wheel blank has clear tooth shape and dense internal structure. S2. Normalizing heat treatment: Normalizing heat treatment is performed on the drive wheel blank; S3. Rough machining: The drive wheel blank after normalizing heat treatment is shot blasted to remove surface sand and oxide scale; and rough turning is performed, with the machining allowance controlled at 2-5mm. S4. Quenching treatment: The surface of the gear teeth on the drive wheel blank is subjected to induction quenching treatment. S5. Finishing process: After flaw detection and shot blasting, finish processing is carried out, such as precision turning and drilling, to achieve the final dimensions and accuracy required by the drawings, and obtain the finished drive wheel.

3. The preparation process of a drive wheel material for engineering machinery according to claim 2, characterized in that, In step S2, the specific steps of the normalizing heat treatment are as follows: S21. Heating: The cast drive wheel blank is placed into the heating furnace and heated in the air medium. That is, the drive wheel blank is placed into the furnace when the furnace temperature is low (such as room temperature), and then the equipment is started to slowly heat the drive wheel blank and the furnace together at a set rate until the target temperature is reached. The heating rate is controlled at 100-200℃ / h, and the temperature is heated to 880-900℃ to reduce stress and deformation. S22. Insulation: Maintain the temperature at 880-900℃ for 2.5-3.5 hours; S23. Cooling: After the heat preservation is completed, the workpiece is taken out of the furnace and cooled by forced air cooling with a wind speed of not less than 5m / s until the drive wheel blank is cooled to room temperature.

4. The preparation process of a drive wheel material for engineering machinery according to claim 3, characterized in that, In step S21, the heating temperature is preferably 890°C.

5. The preparation process of a drive wheel material for engineering machinery according to claim 3, characterized in that, In step S22, the heat preservation time is preferably 3 hours.

6. The preparation process of a drive wheel material for engineering machinery according to claim 2, characterized in that, In step S4, an induction hardening process is performed using a medium-frequency induction hardening device with a frequency range of 2.5 to 4 kHz to ensure a hardened layer depth of 5 to 20 mm.

7. The preparation process of a drive wheel material for engineering machinery according to claim 2, characterized in that, In step S4, the specific steps of the quenching process are as follows: S41. Rapidly heat the toothed portion of the drive wheel blank to an austenitizing temperature of 880-920°C; S42. Immediately cool the gear teeth by spraying water or polymer quenching liquid to obtain a high-hardness martensitic structure on the surface of the gear teeth. S43. After quenching, cool to 180-220℃ and hold for 2-3 hours for low-temperature tempering to eliminate internal stress and stabilize the structure.

Images