Method for controlling decarburization of a spring steel for railway

Abstract

The application discloses a control method for reducing decarburization of a railway spring steel, and the method comprises the following steps: 1) by controlling the quantity of the blank in the heating furnace, the total heating time of the railway spring steel blank in the heating furnace is controlled to be 140min-180min; and 2) the temperature of the second heating section is controlled to be 950 DEG C-1050 DEG C, and the soaking temperature is controlled to be 1020 DEG C-1070 DEG C. By controlling the high-temperature section time and the heating temperature of the blank in the furnace, the surface decarburization layer of the 60Si2MnA is reduced, the production cost is saved, the environmental pollution is avoided, and the delivery speed is ensured.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of steel smelting, in particular to a control method for reducing decarburization of railway spring steel. BACKGROUND

[0002] Decarburization is the most common problem in the process of steel material processing, and the fatigue strength and hardness of the steel surface after decarburization decrease obviously. The spring steel 60Si2MnA is the raw material of railway spring steel, and due to the high Si content, silicon oxide is easily formed during heating, causing the surface decarburization of the blank, and the customer requires that there is no full decarburization layer on the surface of the material; the heating furnace of the medium bar plant of Nanjing Steel is divided into three sections of preheating, heating and soaking, with a total length of 42.6 meters, the 60Si2MnA blank is 250mmx300mmx11000mm, and the small size spring steel production is slower, generally heated in the furnace for more than 5-6 hours, and the surface decarburization layer of the rolled material is thicker, which cannot meet the delivery requirements; usually, the surface of the blank is painted or the surface of the blank is stripped to reduce the surface decarburization of the rolled material, which not only increases the production cost, but also causes environmental pollution.

[0003] Therefore, it is necessary to develop a new control method to reduce the surface decarburization layer of 60Si2MnA. SUMMARY

[0004] The present application provides a control method for reducing decarburization of railway spring steel, which controls the high-temperature section time and heating temperature of the blank in the furnace to reduce the surface decarburization layer of 60Si2MnA, not only saves the production cost, but also avoids environmental pollution, and ensures the delivery speed.

[0005] Technical scheme: The control method for reducing decarburization of railway spring steel provided by the present application has the following characteristics:

[0006] 1) The total heating time of the railway spring steel blank in the heating furnace is controlled to be 140min-180min by controlling the number of blanks in the heating furnace;

[0007] 2) The temperature of the second heating section is controlled to be 950℃-1050℃, and the soaking temperature is controlled to be 1020℃-1070℃.

[0008] The railway spring steel includes the following components in mass percentage: C: 0.61%-0.72%, Si: 0.20%-0.30%, Mn: 0.80%-0.95%, Cr: 0.80%-0.90%, Ni+Cu≤0.25%, P+S≤0.025%, and the balance is Fe.

[0009] The step 1) controls the blank quantity in the heating furnace, and the blank quantity in the furnace is controlled according to the blank quantity in the furnace, and the blank quantity in the furnace is controlled according to the blank quantity in the furnace.

[0010] The step 1) controls the blank quantity in the heating furnace, and the blank quantity in the furnace is controlled according to the blank quantity in the furnace, and the blank quantity in the furnace is controlled according to the blank quantity in the furnace.

[0011] The total heating time in the heating furnace includes the preheating time, the heating time and the soaking time.

[0012] The preheating time is controlled to be 40 min, the heating time is controlled to be 50 min-80 min, and the soaking time is controlled to be 50 min-60 min.

[0013] The preheating temperature of the preheating section is 550℃-650℃.

[0014] The heating section includes a first heating section and a second heating section, and the soaking section includes a first soaking section and a second soaking section.

[0015] The heating temperature of the first heating section is ≤900℃, and the heating temperature of the second heating section is 950℃-1050℃.

[0016] The heating temperature of the first soaking section is 1020℃-1070℃, and the heating temperature of the second soaking section is 1020℃-1070℃.

[0017] Compared with the prior art, the present application has the following advantages: the present application reduces the surface decarburization problem of the bar Φ16mm-21mm grade 60Si2MnA. The total decarburization layer of the 60Si2MnA spring steel is controlled to be 0.04mm-0.10mm, and the surface decarburization layer of the spring steel is 0. The decarburization requirement of the customer is met, the fatigue strength of the spring steel is improved, the production cost is saved, the environmental pollution is avoided, and the delivery speed is ensured. The present application has high use value. DETAILED DESCRIPTION

[0018] The technical solutions of the present application will be further described below in combination with specific embodiments.

[0019] The present application is a control method for reducing the decarburization of a railway spring steel, which comprises the following steps:

[0020] 1) The total heating time of the railway spring steel blank in the heating furnace is controlled to be 140min-180min by controlling the blank quantity in the heating furnace.

[0021] For Φ16mm-18mm steel, with a tapping rhythm >254s, the required charging interval is 1 charging step followed by 3 empty steps, and the re-rolling time is 15 empty steps. For Φ18.5mm-21mm steel, with a tapping rhythm of 196s-254s, the required charging interval is 1 charging step followed by 2 empty steps, and the re-rolling time is 10 empty steps.

[0022]

[0023] By controlling the amount of billet in the heating furnace, the preheating time is controlled at 40 minutes, the heating time at 50-80 minutes, and the homogenization time at around 50-60 minutes. This reduces the heating and homogenization time of the billet in the furnace, lowers the activation energy of carbon atoms on the billet surface, and prevents continuous decarburization of the billet at high temperatures.

[0024] 2) The temperature of the second heating stage is controlled at 950℃-1050℃, and the soaking temperature is controlled at 1020℃-1070℃. The total heating time in the furnace includes the preheating stage heating time, the heating stage heating time, and the soaking stage heating time. The preheating stage heating time is controlled at 40 minutes; the heating stage heating time is controlled at 50-80 minutes; and the soaking stage heating time is controlled at 50-60 minutes. The preheating stage heating temperature is 550℃-650℃. The heating stage includes heating stage one and heating stage two, and the soaking stage includes soaking stage one and soaking stage two. The heating temperature of heating stage one is ≤900℃, and the heating temperature of heating stage two is 950℃-1050℃. The heating temperature of soaking stage one is 1020℃-1070℃, and the heating temperature of soaking stage two is 1020℃-1070℃.

[0025]

[0026] After the billet enters the heating section, it is heated at a low temperature, and no decarburization occurs on the surface of the billet. When the billet enters the soaking section, the activation energy of carbon atoms on the surface of the billet is low, and decarburization is relatively slow. The residence time at high temperature is short, and the surface does not undergo continuous decarburization, thereby reducing the thickness of the decarburized layer on the surface of the finished product.

[0027] The railway spring steel of the present invention comprises the following components in the following mass percentages: C: 0.61%-0.72%, Si: 0.20%-0.30%, Mn: 0.80%-0.95%, Cr: 0.80%-0.90%, Ni+Cu≤0.25%, P+S≤0.025%, and the balance Fe.

[0028] The application shortens the heating and soaking time of the blank in the furnace by controlling the quantity of the blank in the heating furnace, reduces the heating temperature, ensures the temperature uniformity of the blank, reduces the surface carbon atom activation energy of the blank, controls the continuous decarburization reaction on the surface of the blank, controls the total decarburization layer thickness of the rolled material surface at 0.04mm-0.10mm, the full decarburization layer is 0, meets the decarburization requirement of the customer, improves the fatigue strength of the spring steel, saves the production cost, avoids the environmental pollution, ensures the delivery speed, and has high use value.

Claims

1. A method for controlling decarburization of railway spring steel, characterized in that: Includes the following steps: 1) By controlling the amount of billet in the heating furnace, the total heating time of the railway spring steel billet in the heating furnace is controlled to be 140-180 minutes; 2) The temperature of the second heating stage is controlled at 950℃-1050℃, and the soaking temperature is controlled at 1020℃-1070℃; the railway spring steel comprises the following components by mass percentage: C: 0.61%-0.72%, Si: 0.20%-0.30%, Mn: 0.80%-0.95%, Cr: 0.80%-0.90%, Ni+Cu≤0.25%, P+S≤0.025%, balance Fe; In step 1), when controlling the amount of billet in the heating furnace, the steel loading and unloading steps are as follows: for Φ16mm-18mm billets, the steel tapping rhythm is >254s, the steel loading and unloading step requirement is 1 load and 3 unloads, and the re-rolling time is 15 unloads; for Φ18.5mm-21mm billets, the steel tapping rhythm is 196s-254s, the steel loading and unloading step requirement is 1 load and 2 unloads, and the re-rolling time is 10 unloads; the total heating time in the heating furnace includes the preheating section heating time, the heating section heating time, and the soaking section heating time; the heating temperature of the preheating section is 550℃-650℃.

2. The method for controlling decarburization of railway spring steel according to claim 1, characterized in that: The heating time of the preheating section is controlled at 40 minutes; the heating time of the heating section is controlled at 50-80 minutes; and the heating time of the heat spreader section is controlled at 50-60 minutes.

3. The method for controlling decarburization of railway spring steel according to claim 1, characterized in that: The heating section includes a first heating section and a second heating section, and the heat equalization section includes a first heat equalization section and a second heat equalization section.

4. The method for controlling decarburization of railway spring steel according to claim 3, characterized in that: The heating temperature of the first heating stage is ≤900℃, and the heating temperature of the second heating stage is 950℃-1050℃.

5. The method for controlling decarburization of railway spring steel according to claim 3, characterized in that: The heating temperature of the first heat equalization stage is 1020℃-1070℃, and the heating temperature of the second heat equalization stage is 1020℃-1070℃.

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