Heat treatment process for improving mechanical properties of alloy steel combination frog products

Abstract

The application relates to a heat treatment process for improving the mechanical properties of an alloy steel combined frog product, wherein the heart rail and wing rail embedded blocks are uniformly arranged and vertically hung before heat treatment, a symmetrical three-layer fan cooling area is arranged, the middle layer adopts a large fan, and the upper and lower layers adopt small fans; through quenching heating, quenching cooling and tempering heating of the heart rail product and the wing rail embedded block product, the alloy steel combined frog product can obtain better comprehensive mechanical properties, special heat treatment equipment is not needed, the equipment is relatively simple, the cost is low, and the production cost is low; in the heating and cooling process, vertical hanging is realized, and in the high-temperature cooling stage, according to the size characteristics of the product, the heart rail adopts the cooling mode of air cooling first and then water cooling, and the wing rail embedded block adopts the cooling mode of air cooling first and then water cooling, so that the heat treatment deformation problem is improved; the alloy steel combined frog product has higher strength, hardness and toughness, the overall quality is better, the service life of the alloy steel combined frog is prolonged, and the alloy steel combined frog is used for heavy-load lines.

Description

Technical Field

[0001] This invention belongs to the field of railway transportation technology, and specifically relates to a heat treatment process for improving the mechanical properties of alloy steel composite frog products. Background Technology

[0002] With the development of the national economy, increasingly busy traffic places higher demands on railways, especially on frog products. At the same time, with the continuous construction and development of heavy-haul lines, higher requirements are placed on the strength, hardness, and toughness of alloy steel frog products. However, to ensure these properties, special and dedicated equipment is required for heat treatment, which is expensive and costly. Summary of the Invention

[0003] To address the aforementioned problems, this invention provides a heat treatment process for improving the mechanical properties of alloy steel composite frog products. This heat treatment process utilizes conventional heat treatment equipment to achieve higher strength, hardness, and toughness in alloy steel composite frog products, while effectively reducing equipment and production costs.

[0004] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0005] A heat treatment process for improving the mechanical properties of alloy steel composite frog products employs traditional heat treatment equipment and strictly controls process parameters such as quenching heating rate, quenching temperature, cooling time of each cooling medium during quenching, final cooling temperature of the workpiece, initial temperature of the tempering furnace, and tempering temperature. This process enables the alloy steel composite frog products to achieve superior comprehensive mechanical properties. The specific steps are as follows:

[0006] Step 1) Before heat treatment, the core rail and wing rail inlay blocks are hung vertically in a uniform arrangement. At the same time, a symmetrical three-layer fan cooling zone is set up according to the product size. The middle layer uses a large fan, which is directly facing the thickest part of the product. The upper and lower layers use small fans, which are corresponding to the two ends of the product.

[0007] Step 2) Quenching and heating: 1) For core rail products, the furnace temperature is ≤500℃, the temperature is raised to 630~670℃, held for 2 hours, and then raised to 900~940℃ and held for 4~5 hours; 2) For wing rail insert products, the furnace temperature is ≤500℃, the temperature is raised to 630~670℃, held for 2 hours, and then raised to 900~940℃ and held for 3~4 hours.

[0008] Step 3) Quenching and Cooling: 1) After the core rail quenching heating and holding is completed and it is taken out of the furnace, it is air-cooled for ≤60s, transferred to the air-cooling zone for 2-4min, transferred to the water tank for 60-100s with an initial water temperature of 25-35℃, then transferred to the air-cooling zone for 12-14min, then air-cooled for 1-3min before being put into the tempering furnace; 2) After the wing rail inlay block quenching heating and holding is completed and it is taken out of the furnace, it is air-cooled for 220-280s, transferred to the water tank for 40-70s with an initial water temperature of 25-35℃, then transferred to the air-cooling zone for 4-8min, then air-cooled for 1-3min before being put into the tempering furnace;

[0009] Step 4) Tempering Heating: 1) First, heat the empty tempering furnace to 250-300℃ to wait for the material. After the core rail is quenched and cooled, put it into the tempering furnace for heating. Heat it to 300-340℃ and hold it for 9-12 hours before taking it out of the furnace and air cooling. 2) First, heat the empty tempering furnace to 250-300℃ to wait for the material. After the wing rail insert is quenched and cooled, put it into the tempering furnace for heating. Heat it to 300-340℃ and hold it for 7-10 hours before taking it out of the furnace and air cooling.

[0010] Due to the adoption of the above technical solution, the present invention has the following advantages:

[0011] The heat treatment process of this invention uses only conventional heat treatment equipment to achieve the process requirements of superior comprehensive mechanical properties for alloy steel composite frog products. It eliminates the need for specialized heat treatment equipment, resulting in relatively simple equipment, low cost, and low production costs. Vertical hanging is achieved during the heating and cooling process, and in the high-temperature cooling stage, based on the product's size characteristics, the frog rail is cooled by first air cooling followed by water cooling, while the wing rail inserts are cooled by first air cooling followed by water cooling, effectively improving the heat treatment deformation problem. Furthermore, compared with other existing methods, the product has higher strength, hardness, and toughness, resulting in better overall quality and extending the lifespan of the alloy steel composite frog products, making it suitable for heavy-load railway construction. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of the symmetrical three-layer fan arrangement in the air-cooled zone of the present invention.

[0013] Figure 2 This is a heat treatment process curve diagram for the core rail product of the present invention.

[0014] Figure 3 This is a heat treatment process curve diagram for the wing rail insert block product of the present invention.

[0015] In the diagram: 1 - Large fan; 2 - Small fan. Detailed Implementation

[0016] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0017] Example 1: Taking a composite frog product made of a certain alloy steel with material U26Mn2Si2CrNiMo as an example, its heat treatment process steps are as follows:

[0018] Step 1) Before heat treatment, the core rail and wing rail inlay blocks are hung vertically in a uniform arrangement. At the same time, a symmetrical three-layer fan cooling zone is set up according to the product size. The middle layer uses a large fan, which is directly facing the thickest part of the product. The upper and lower layers use small fans, which are corresponding to the two ends of the product.

[0019] Step 2), Quenching and Heating: 1) Place the core rail product into a heat treatment furnace with an initial furnace temperature ≤500℃, first heat it to 650±10℃, hold it for 2 hours, then continue to heat it to 930±10℃, and hold it for 5 hours; 2) Place the wing rail insert product into a heat treatment furnace with an initial furnace temperature ≤500℃, first heat it to 650±10℃, hold it for 2 hours, then continue to heat it to 930±10℃, and hold it for 3 hours.

[0020] Step 3), Quenching and Cooling: 1) After the core rail is quenched, heated and kept at the same temperature, it is transferred to the air-cooling zone for 3 minutes as quickly as possible. The air-cooling time during the transfer should be ≤60 seconds. After the air-cooling is completed, it is transferred to the water tank for 70 seconds with an initial water temperature of 29°C. Then it is transferred to the air-cooling zone for 13 minutes, followed by air-cooling for 3 minutes before being placed in the tempering furnace. 2) After the wing rail inlay block is quenched, heated and kept at the same temperature, it is air-cooled for 265 seconds, transferred to the water tank for 58 seconds with an initial water temperature of 31°C, transferred to the air-cooling zone for 5 minutes, followed by air-cooling for 2 minutes before being placed in the tempering furnace.

[0021] Step 4) Tempering Heating: 1) First, heat the empty tempering furnace to 270℃ to wait for the material. After the core rail is quenched and cooled, put it into the tempering furnace for heating. Heat it to 315±10℃ and hold it for 10 hours before taking it out of the furnace and air cooling. 2) First, heat the empty tempering furnace to 270℃ to wait for the material. After the wing rail insert is quenched and cooled, put it into the tempering furnace for heating. Heat it to 330±10℃ and hold it for 8 hours before taking it out of the furnace and air cooling.

[0022] Compare with Example 1:

[0023] The heat treatment process is produced using traditional air-cooling methods.

[0024] The products of the examples and control examples were tested, and the results are shown in Table 1 below.

[0025] Table 1 Mechanical property test data of the products in the examples and control examples

[0026]

[0027] Based on the specific dimensions of the product, this invention employs a combination of three different cooling methods—air cooling, wind cooling, and water cooling—along with a uniformly arranged vertical hanging method for heating and cooling. This not only effectively improves the product's heat treatment deformation problem but also achieves superior comprehensive mechanical properties, fully demonstrating the significant advantages of this invention.

Claims

1. A heat treatment process for improving the mechanical properties of alloy steel combined frog products, using traditional heat treatment equipment, strictly controlling the quenching heating rate, quenching temperature, cooling time of each cooling medium in the quenching cooling process, and the process parameters of the final cooling temperature of the workpiece, the initial temperature of the tempering furnace and the tempering temperature, so that the alloy steel combined frog products obtain better comprehensive mechanical properties, the specific steps are as follows: Step 1), before heat treatment, the heart rail and wing rail embedded block is hung vertically in a uniform row, and the air cooling area is set with symmetrical 3 layers of fans according to the size of the product, the middle layer uses a large fan, and the upper and lower layers use small fans corresponding to the two ends of the product; Step 2), quenching heating: 1) for heart rail products, the furnace temperature is ≤500℃, the temperature is raised to 630-670℃, and the temperature is kept for 2h, then the temperature is raised to 900-940℃, and the temperature is kept for 4-5h; 2) for wing rail embedded block products, the furnace temperature is ≤500℃, the temperature is raised to 630-670℃, and the temperature is kept for 2h, then the temperature is raised to 900-940℃, and the temperature is kept for 3-4h; Step 3), quenching cooling: 1) after the heart rail quenching heating and keeping is finished, air cooling for ≤60S, then air cooling in the air cooling area for 2-4min, then water cooling in the water tank for 60-100S with initial water temperature of 25-35℃, then air cooling in the air cooling area for 12-14min, then air cooling for 1-3min before entering the tempering furnace; 2) after the wing rail embedded block quenching heating and keeping is finished, air cooling for 220-280S, then water cooling in the water tank for 40-70S with initial water temperature of 25-35℃, then air cooling in the air cooling area for 4-8min, then air cooling for 1-3min before entering the tempering furnace; Step 4), tempering heating: 1) first, the empty tempering furnace is heated to 250-300℃, then the heart rail is put into the tempering furnace after quenching cooling, the temperature is raised to 300-340℃, and the temperature is kept for 9-12h before the furnace is discharged and air cooled; 2) first, the empty tempering furnace is heated to 250-300℃, then the wing rail embedded block is put into the tempering furnace after quenching cooling, the temperature is raised to 300-340℃, and the temperature is kept for 7-10h before the furnace is discharged and air cooled.

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