Rolling process for improving widmanstatten structure of medium-carbon cold heading steel

Abstract

The invention relates to a rolling process for improving a medium carbon cold heading steel widmanstatten structure, and belongs to the technical field of steel rolling in the metallurgical industry. According to the technical scheme, the steel billet heating temperature ranges from 1130 DEG C to 1190 DEG C, the steel billet soaking temperature ranges from 1130 DEG C to 1190 DEG C, the steel billet heating time ranges from 65 min to 125 min, the finish rolling temperature ranges from 870 DEG C to 940 DEG C, the spinning temperature ranges from 880 DEG C to 920 DEG C, and the roller way speed parameter ranges from 0.19 m / s to 0.30 m / s. The method has the beneficial effects that on the premise of not increasing any additional equipment and investment, the existing production equipment and technological process are fully utilized, the defects of the continuous casting procedure are made up by optimizing rolling technological parameters aiming at the element segregation problem generally existing in the continuous casting procedure, the microstructure of the SWRCH35K wire is improved, and the yield of the SWRCH35K wire is improved. And the distribution of widmanstatten tissues is effectively improved, so that the overall performance of the material is improved.

Description

Technical Field

[0001] The invention relates to a rolling process for improving the widmanstatten structure of medium carbon cold heading steel, belonging to the technical field of steel rolling in the metallurgical industry. Background Art

[0002] SWRCH35K is a typical medium carbon cold heading steel, which has been widely used in the industrial field due to its excellent mechanical properties and processing performance. However, SWRCH35K is prone to produce Widmanstatten structure during rolling, which reduces the toughness and plasticity of the material and increases the risk of brittle fracture.

[0003] In the production process of medium carbon cold heading steel, element segregation is a common problem in the continuous casting process. In addition, improper control of rolling process parameters is the main cause of widmanstatten structure, resulting in material properties unable to meet the application requirements of high strength and high toughness. Summary of the invention

[0004] The purpose of the present invention is to provide a rolling process for improving the widmanstatten structure of medium carbon cold heading steel, which can effectively improve the widmanstatten structure, improve the toughness and plasticity of SWRCH35K, meet the needs of high strength and high toughness applications, and solve the problems existing in the background technology.

[0005] The technical solution of the present invention is: A rolling process for improving the widmanstatten structure of medium carbon cold heading steel, wherein the billet heating temperature is 1130-1190°C, the finishing rolling temperature is 870-940°C, and the wire drawing temperature is 880-920°C.

[0006] In the above rolling process for improving the widmanstatten structure of medium carbon cold heading steel, the billet soaking temperature is 1130~1190℃.

[0007] In the above rolling process for improving the widmanstatten structure of medium carbon cold heading steel, the billet heating time is 65-125 minutes.

[0008] The above rolling process for improving the widmanstatten structure of medium carbon cold heading steel has a roller speed parameter of 0.19m / s-0.30m / s.

[0009] In the above rolling process for improving the widmanstatten structure of medium carbon cold heading steel, the heating furnace adopts a three-stage continuous heating furnace, including a preheating section, a heating section and a soaking section.

[0010] The present invention adopts a three-stage continuous heating furnace, improves the segregation of the steel billet through a higher heating temperature and a longer heating time, and optimizes the rolling process by combining the calculation of the phase change temperature with the CCT curve of the SWRCH35K cold heading steel, thereby achieving the purpose of improving the SWRCH35K Widmanstatten structure.

[0011] The beneficial effects of the present invention are as follows: without adding any additional equipment and investment, the present invention makes full use of existing production equipment and process flow, targets the element segregation problem commonly existing in the continuous casting process, optimizes the rolling process parameters, makes up for the shortcomings of the continuous casting process, improves the microstructure of the SWRCH35K wire, effectively improves the distribution of the widmanstatten structure, and thus improves the overall performance of the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is a comparison diagram of the present invention and the background technology in Example 1; Figure 2 This is a comparison diagram of the present invention and the background technology in Example 2; Figure 3 This is a comparison diagram of Example 3 of the present invention and the background technology; Figure 4 This is a comparison diagram of the present invention and the background technology in Example 4; DETAILED DESCRIPTION

[0013] The present invention will be further described below by way of examples with reference to the accompanying drawings.

[0014] See attached Figure 1-4 , a rolling process for improving the widmanstatten structure of medium carbon cold heading steel, the billet heating temperature is 1130~1190℃, the finishing rolling temperature is 870-940℃, and the wire drawing temperature is 880-920℃.

[0015] The billet uniform heating temperature is 1130~1190℃.

[0016] The billet heating time is 65-125min.

[0017] The roller speed parameter is 0.19m / s-0.30m / s.

[0018] The heating furnace adopts a three-stage continuous heating furnace, including a preheating section, a heating section and a soaking section. Example 1

[0019] The steel grade is SWRCH35K, the rolling specification is Ф18mm, and the hot-rolled wire rod rolling process is: billet heating → rolling cooling. The heating temperature is 1140℃, the soaking temperature is 1140℃, the heating time is controlled at 75min, the finishing rolling temperature is controlled at 880℃, and the wire laying temperature is controlled at 890℃. The roller speed parameter is 0.19m / s-0.30m / s.

[0020] There is no obvious needle-shaped Widmanstatten structure on the edge of the finished wire rod and the Widmanstatten level is ≤1.0, there is no mixed crystal and no abnormally coarse Widmanstatten structure on the edge. Example 2

[0021] The steel grade is SWRCH35K, the rolling specification is Ф6.5mm, and the hot-rolled wire rod rolling process is: billet heating → rolling cooling. The heating temperature is 1180℃, the soaking temperature is 1180℃, the heating time is controlled at 70min, the finishing rolling temperature is controlled at 900℃, and the wire laying temperature is controlled at 900℃. The roller speed parameter is 0.20m / s-0.29m / s.

[0022] The level of the Widmanstatten structure in the center of the wire rod is ≤1.0, and there is no obvious mixed crystal and abnormally coarse Widmanstatten structure at the edge. Example 3

[0023] The steel grade is SWRCH35K, the rolling specification is Ф18mm, and the hot-rolled wire rod rolling process is: billet heating → rolling cooling. The heating temperature is 1160℃, the soaking temperature is 1160℃, the heating time is controlled at 75min, the finishing rolling temperature is controlled at 870℃, and the wire laying temperature is controlled at 910℃. The roller speed parameter is 0.19m / s-0.30m / s.

[0024] There is no obvious needle-shaped Widmanstatten structure in the core of the finished wire rod and the Widmanstatten level is ≤1.0. There is no mixed crystal or abnormally coarse Widmanstatten structure at the edge, and the structure is uniform and normal. Example 4

[0025] The steel grade is SWRCH35K, the rolling specification is Ф6.5mm, and the hot-rolled wire rod rolling process is: billet heating → rolling cooling. The heating temperature is 1190℃, the soaking temperature is 1190℃, the heating time is controlled at 70min, the finishing rolling temperature is controlled at 890℃, and the wire laying temperature is controlled at 920℃. The roller speed parameter is 0.20m / s-0.29m / s.

[0026] There is no obvious needle-shaped Widmanstatten structure in the core of the finished wire rod and the Widmanstatten level is ≤1.0. There is no mixed crystal or abnormally coarse Widmanstatten structure at the edge, and the structure is uniform and normal.

Claims

1. A rolling process for improving the widmanstatten structure of medium carbon cold heading steel, characterized in that: The billet heating temperature is 1130-1190℃, the finishing rolling temperature is 870-940℃, and the wire drawing temperature is 880-920℃.

2. The rolling process for improving the widmanstatten structure of medium carbon cold heading steel according to claim 1, characterized in that: The billet uniform heating temperature is 1130~1190℃.

3. The rolling process for improving the widmanstatten structure of medium carbon cold heading steel according to claim 2, characterized in that: The billet heating time is 65-125min.

4. The rolling process for improving the widmanstatten structure of medium carbon cold heading steel according to claim 1, characterized in that: The roller speed parameter is 0.19m / s-0.30m / s.

5. The rolling process for improving the widmanstatten structure of medium carbon cold heading steel according to claim 1, characterized in that: The heating furnace adopts a three-stage continuous heating furnace, including a preheating section, a heating section and a soaking section.

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