Steel for traveling wheel, traveling wheel and heat treatment method and production method of traveling wheel

Abstract

The steel for the traveling wheel comprises the following main chemical components in percentage by weight: 0.41 to 0.45 percent of C, 0.27 to 0.37 percent of Si, 0.65 to 0.80 percent of Mn, 1.10 to 1.30 percent of Cr, 1.30 to 1.45 percent of Ni, 0.15 to 0.25 percent of Mo and 0.025 to 0.035 percent of Nb. According to the invention, the Nb and N elements are added to form a second-phase alloy carbonitride, and a heat treatment process of step increasing water quenching and tempering is matched, so that the heat treatment performance of the traveling wheel is improved. Grains are obviously refined; the performance of the travelling wheel is improved; the tensile strength is 1300-1400 MPa, the yield strength is 1100-1200 MPa, the ductility is larger than or equal to 17%, the rim tread hardness is 360-400 HB, and the hardening depth reaches 30 mm or above.

Description

Technical Field

[0001] The invention belongs to the technical field of steel materials, and in particular relates to a steel for a running wheel, a running wheel and a heat treatment method and a production method thereof. Background Art

[0002] Traveling wheels, also known as crane wheels, are a type of traveling load-bearing wheels for large lifting machinery and equipment, and are widely used in heavy-duty overhead cranes, lifting equipment, dock loading equipment and other mechanical equipment. Traveling wheels are generally made of 42CrMo forged wheels. In recent years, with the increase in the load-bearing capacity of lifting machinery and equipment, 42CrMo traveling wheels have frequently encountered a series of application problems such as rapid wear, frequent fatigue peeling, and short life.

[0003] 42CrMo is the dominant application material for walking wheels. In order to ensure the high efficiency, safety and long life of its products, users have continuously put forward new requirements for material quality technical indicators. Requirement 1: Austenite grain size is greater than or equal to level 6; Requirement 2: The hardness of the walking wheel rim tread is increased from the original 300-350HB to 360-400HB, and the hardening depth is increased from the original 20mm to 30mm.

[0004] However, 42CrMo steel has the problem of coarse grains and low hardness. For example, Chinese patent CN112853066A discloses a method for manufacturing 42CrMo forgings with high comprehensive performance, which includes the following steps: S1, material preparation: based on the chemical composition and mass percentage of the standard material grade 42CrMo, add and adjust the content of microalloying elements to refine and form a blank; S2, forging: forging the blank to form a forging blank; S3, preliminary heat treatment: performing normalizing preliminary heat treatment or quenching preliminary heat treatment on the forging blank; S4, rough machining: performing rough machining on the forging blank to remove the oxide layer on the surface of the forging blank; S5, quenching and tempering: performing quenching and tempering heat treatment on the forging blank. The hardness of the 42CrMo steel disclosed in the patent is relatively low, only 260-310HBW. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a steel for a running wheel. Nb and N elements are added to 42CrMo steel to form a Nb (C, N) composite second phase, which can significantly refine the grains and improve the mechanical properties of the running wheel blank.

[0006] The present invention also provides a running wheel and a heat treatment method and a production method thereof, which adopt a step-by-step water quenching and tempering heat treatment process so that the metallographic structure of the gear blank is tempered troostite and martensite structure, and has good hardness and hardening depth.

[0007] The technical solution adopted by the present invention is as follows:

[0008] A steel for a running wheel comprises the following chemical components in weight percentage: C 0.41-0.45%, Si 0.27-0.37%, Mn 0.65-0.80%, Cr 1.10-1.30%, Ni 1.30-1.45%, Mo 0.15-0.25%, Nb 0.025-0.035%, P≤0.010%, S≤0.008%, T[O]≤0.0010%, [N] 0.0100-0.0120%, Al≤0.015%, Ti≤0.0010%, and the rest is Fe and other inevitable impurities.

[0009] The metallographic structure of the steel for the running wheel is tempered troostite and acicular martensite; the austenite grain size grade is 8-9.

[0010] The present invention also provides a running wheel produced by using the running wheel steel of the present invention, having a tensile strength of 1300-1400 MPa, a yield strength of 1100-1200 MPa, an elongation of ≥17%, a wheel rim tread hardness of 360-400 HB, and a hardening depth of more than 30 mm.

[0011] The present invention also provides a heat treatment method for the running wheel, which comprises the following steps: processing the running wheel steel of the present invention into a running wheel blank, performing tread quenching treatment after heating and heat preservation, and then performing tempering;

[0012] The specific operation of the tread quenching is: a plurality of box-type nozzles are evenly arranged along the circumference of the walking wheel. Within the water spraying time T≤200s, the water flow increases with time. When T=200s, the water pressure and water flow reach the maximum value. When T>200s, the water pressure and water flow remain unchanged at the maximum value.

[0013] Furthermore, within the water spraying time T≤200s, the nozzle water pressure is controlled according to P=0.1+0.001T, and the nozzle water flow is controlled according to V=15+0.3T, wherein P is in MPa, V is in L, and T is in s.

[0014] The heating and heat preservation conditions are: heating and heat preservation at 850-890° C. for 2.5-3.5 hours.

[0015] The tempering conditions are: keeping at 380-420°C for 4-6h and air cooling after being taken out of the furnace.

[0016] The number of the box-type nozzles is 6.

[0017] The present invention also provides a production method for a running wheel, which comprises the following steps: electric furnace smelting → LF furnace refining → RH furnace vacuum degassing → continuous casting to obtain a casting billet with the chemical composition of the present invention → ingot cutting → upsetting → preforming → forming → slow cooling → heat treatment → processing → inspection; the heat treatment is carried out using the heat treatment method described in the present invention.

[0018] In the components of the wheel steel provided by the present invention, the addition of Nb can form microalloyed steel, in which there are both microalloying elements and carbon and nitrogen elements, so that the second phase is a composite phase of alloy carbonitride, which can significantly refine the grains and improve the performance of the gear blank; therefore, Nb is controlled to be 0.025-0.035%, [N] 0.0100-0.0120%. Aluminum and titanium have stronger binding force with nitrogen than niobium and vanadium. In order to protect the formation of niobium vanadium carbonitride, the content of Al and Ti elements is strictly controlled. The present invention controls Al≤0.015% and Ti≤0.0010%.

[0019] The present invention utilizes the addition of Nb and N elements to form second-phase alloy carbonitrides, and cooperates with the heat treatment process of step-by-step water quenching and tempering to significantly refine the grains and improve the performance of the wheel. Compared with the traditional full-immersion water quenching cooling method, the step-by-step water quenching of the tread can quantitatively control the organizational state and performance level of the wheel rim, meeting the high-performance requirements of the rim part.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The present invention adds Nb and N elements to the components of the wheel steel to form a Nb (C, N) composite second phase, which can significantly refine the grains and significantly improve the hardenability, organizational state and mechanical properties of the wheel in combination with a reasonable heat treatment process. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is the austenite grain diagram of the wheel steel in Example 1;

[0023] Figure 2 is the austenite grain diagram of the wheel steel in Comparative Example 1;

[0024] Figure 3 The metallographic structure state diagram of the wheel steel in Example 1;

[0025] Figure 4 This is the metallographic structure diagram of the wheel steel in comparative example 1. DETAILED DESCRIPTION

[0026] The present invention is described in detail below with reference to the embodiments.

[0027] Example 1

[0028] The outer diameter specification of the running wheel in this embodiment is 780mm, and its production process is: electric furnace steelmaking → LF furnace refining → RH furnace vacuum treatment → continuous casting → ingot cutting → heating → roughing → preforming → forming → slow cooling to room temperature → heat treatment → processing → inspection. The specific heat treatment process is shown in Table 2.

[0029] The chemical composition of the gear blank described in this embodiment 1 is shown in Table 1. The remainder not shown in Table 1 is Fe and unavoidable impurities.

[0030] Comparative Example 1

[0031] The outer diameter specification of the walking wheel in this comparative example is 780mm, and its production process is: electric furnace steelmaking → LF furnace refining → RH furnace vacuum treatment → continuous casting → ingot cutting → heating → roughing → preforming → forming → slow cooling to room temperature → heat treatment → processing → inspection. The specific heat treatment process is shown in Table 2.

[0032] The chemical composition of the gear blank described in Comparative Example 1 is shown in Table 1. The remainder not shown in Table 1 is Fe and unavoidable impurities. The specifications are the same as those in Example 1.

[0033] Example 2

[0034] The outer diameter specification of the running wheel in this embodiment is 630mm, and its production process is: electric furnace steelmaking → LF furnace refining → RH furnace vacuum treatment → continuous casting → ingot cutting → heating → roughing → preforming → forming → slow cooling to room temperature → heat treatment → processing → inspection. The specific heat treatment process is shown in Table 2.

[0035] The chemical composition of the gear blank described in this embodiment 1 is shown in Table 1. The remainder not shown in Table 1 is Fe and unavoidable impurities.

[0036] Comparative Example 2

[0037] The outer diameter specification of the walking wheel in this comparative example is 6300mm, and its production process is: electric furnace steelmaking → LF furnace refining → RH furnace vacuum treatment → continuous casting → ingot cutting → heating → roughing → preforming → forming → slow cooling to room temperature → heat treatment → processing → inspection. The specific heat treatment process is shown in Table 2.

[0038] The chemical composition of the gear blank described in Comparative Example 1 is shown in Table 1. The remainder not shown in Table 1 is Fe and unavoidable impurities. The specifications are the same as those in Example 1.

[0039] Table 1 Gear blank alloy composition (mass percentage) of the embodiment and comparative example

[0040] category C Si Mn P S Cr Ni Example 1 0.43 0.35 0.67 0.006 0.001 1.20 1.35 Example 2 0.42 0.33 0.73 0.004 0.002 1.25 1.38 Comparative Example 1 0.43 0.33 0.70 0.008 0.002 1.23 1.35 Comparative Example 2 0.44 0.32 0.68 0.005 0.003 1.22 1.38 Mo Nb V Al Ti N O Example 1 0.28 0.030 0.003 0.009 0.0003 0.0115 0.0009 Example 2 0.22 0.029 0.004 0.013 0.0004 0.0105 0.0007 Comparative Example 1 0.29 0.003 0.002 0.023 0.0005 0.0050 0.0007 Comparative Example 2 0.29 0.002 0.001 0.020 0.0003 0.0117 0.0006

[0041] Table 2 Heat treatment process of gear forgings of embodiment and comparative example

[0042]

[0043]

[0044] The tensile test was carried out in accordance with GB / T 228.1 "Metallic material tensile test Part 1: Room temperature test method", the hardness measurement was carried out in accordance with GB / T231.1 "Metallic Brinell hardness test Part 1: Test method", and the metallographic structure test was carried out in accordance with GB / T 13298 "Metallic microstructure inspection method". The tensile properties, hardness, and structure of the running wheels produced in each embodiment and comparative example are shown in Table 3. Figure 1-4 shown.

[0045] Table 3 Performance of Examples and Comparative Examples

[0046]

[0047]

[0048] From the above data, it can be seen that the wheel performance in Example 1 is significantly better than that in Comparative Example 1, especially in terms of austenite grain size, metallographic structure and hardness. The wheel performance in Example 2 is significantly better than that in Comparative Example 2, especially in terms of austenite grain size, metallographic structure and hardness.

[0049] The above-mentioned detailed description of a steel for a running wheel, a running wheel and a heat treatment method and a production method thereof with reference to the embodiments is illustrative rather than restrictive, and several embodiments can be listed according to the limited scope. Therefore, changes and modifications without departing from the overall concept of the present invention should fall within the scope of protection of the present invention.

Claims

1. A steel for a running wheel, characterized in that: The invention comprises the following chemical compositions in weight percentage: C 0.41-0.45%, Si 0.27-0.37%, Mn 0.65-0.80%, Cr 1.10-1.30%, Ni 1.30-1.45%, Mo 0.15-0.25%, Nb 0.025-0.035%, P≤0.010%, S≤0.008%, T[O]≤0.0010%, [N] 0.0100-0.0120%, Al≤0.015%, Ti≤0.0010%, and the rest are Fe and other inevitable impurities.

2. The steel for running wheels according to claim 1, characterized in that: The metallographic structure of the steel for the running wheel is tempered troostite and acicular martensite.

3. A walking wheel, characterized in that: It is produced by using the steel for the running wheel as described in claim 1 or 2.

4. The running wheel according to claim 3, characterized in that: The tensile strength of the running wheel is 1300-1400MPa, the yield strength is 1100-1200MPa, the elongation is ≥17%, the hardness of the rim tread is 360-400HB, and the hardening depth reaches more than 30mm.

5. The heat treatment method of the running wheel according to claim 3 or 4, characterized in that: The heat treatment method comprises the following steps: processing the wheel steel according to claim 1 into a wheel blank, performing tread quenching treatment after heating and heat preservation, and then performing tempering; The specific operation of the tread quenching is: a plurality of box-type nozzles are evenly arranged along the circumference of the walking wheel. Within the water spraying time T≤200s, the water flow increases with time. When T=200s, the water pressure and water flow reach the maximum value. When T>200s, the water pressure and water flow remain unchanged at the maximum value.

6. The heat treatment method of the running wheel according to claim 5, characterized in that: Within the water spraying time T≤200s, the nozzle water pressure is controlled according to P=0.1+0.001T, and the nozzle water flow is controlled according to V=15+0.3T, where P is in MPa, V is in L, and T is in s.

7. The heat treatment method of the running wheel according to claim 5 or 6, characterized in that: The heating and heat preservation conditions are: heating and heat preservation at 850-890° C. for 2.5-3.5 hours.

8. The heat treatment method of the running wheel according to claim 5 or 6, characterized in that: The tempering conditions are: keeping at 380-420°C for 4-6h and air cooling after being taken out of the furnace.

9. The heat treatment method of the running wheel according to claim 5 or 6, characterized in that: The number of the box-type nozzles is 6.

10. A method for producing a walking wheel, characterized in that: The production method comprises the following steps: electric furnace smelting → LF furnace refining → RH furnace vacuum degassing → continuous casting to obtain a cast billet with the chemical composition described in claim 1 → ingot cutting → upsetting → preforming → forming → slow cooling → heat treatment → processing → inspection; the heat treatment is carried out by the heat treatment method described in any one of claims 5-9.

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