Method for effectively controlling decarburized layer of 65Mn hot-rolled narrow strip steel

Abstract

The invention discloses a method for effectively controlling a decarburized layer of 65Mn hot-rolled narrow strip steel, which relates to the technical field of steel production and comprises the step of controlling the temperature of a first heating section and a second heating section in a heating furnace to be higher than a decarburization sensitive temperature interval of 65Mn steel. The depth of the 65Mn steel strip decarburized layer is controlled to be less than or equal to 0.06 mm only by adjusting the temperature setting of each section of the walking beam furnace and strictly controlling the in-furnace time, so that the performance is improved, the delivery and use requirements of users are further met, the method can be directly applied to existing equipment, the existing equipment does not need to be transformed, additional procedures such as blank peeling and coating are not added, and the production cost is reduced. And the cost is effectively reduced.

Description

Technical Field

[0001] The invention relates to the technical field of steel production, in particular to a method for effectively controlling a decarburized layer of 65Mn hot-rolled narrow strip steel. Background Art

[0002] After smelting and continuous casting, 65Mn steel strip needs to be rolled to the specified specifications and shapes before it can be further supplied to users. During the hot rolling process, due to long-term high-temperature treatment, decarburization will occur on the steel surface, so decarburization is inevitable during the hot rolling process. After decarburization occurs, the carbon content on the surface and inside of the steel strip will be inconsistent, which will cause problems such as inconsistent hardenability during the user's subsequent heat treatment process, and finally shorten the service life. Therefore, the smaller the thickness of the decarburization layer on the surface of 65Mn steel, the more conducive it is to extend the service life of the steel strip.

[0003] The decarburization mechanism of 65Mn steel strip is mainly due to the high carbon content of the steel. In the furnace, the decarburizing atmosphere O2, CO2, H2 and other gases react chemically with the carbon atoms on the steel surface, that is, part or all of the carbon atoms on the steel surface are burned off, reducing the carbon content on its surface, so that a full decarburization layer or a semi-decarburization layer is formed on the surface of the steel strip, thereby affecting the surface quality and mechanical properties of the parts. At present, there are many studies and experiments on the decarburization of bars and wires, but there are few studies on the decarburization of narrow strip steel. In addition, narrow strip steel has the deformation characteristics of a relatively single direction. After hot rolling, it is curled, and the curling process will also have a certain temperature recovery, which is different from bars and wires. Therefore, it is extremely important to explore a method to control the decarburization layer of 65Mn hot-rolled narrow strip steel. Summary of the invention

[0004] The technical problem to be solved by the present invention is to overcome the disadvantages of the prior art and provide a method for effectively controlling the decarburization layer of 65Mn hot-rolled narrow strip steel.

[0005] In order to solve the above technical problems, the technical solution of the present invention is as follows: A method for effectively controlling the decarburization layer of 65Mn hot-rolled narrow strip steel comprises: The temperatures of the first and second heating stages in the heating furnace are controlled to be higher than the decarburization sensitive temperature range of 65Mn steel.

[0006] As a preferred embodiment of the method for effectively controlling the decarburization layer of 65Mn hot-rolled narrow strip steel of the present invention, the temperature of the first heating stage and the second heating stage in the heating furnace is controlled to be higher than the decarburization sensitive temperature range of 65Mn steel, which comprises: The temperature of the first heating stage in the heating furnace was controlled to be 1050°C, and the temperature of the second heating stage was controlled to be 1150°C.

[0007] As a preferred embodiment of the method for effectively controlling the decarburization layer of 65Mn hot-rolled narrow strip steel of the present invention, the method further comprises: The feeding method of the heating furnace is to control the spacing between any steel billet in the heating furnace and the previous steel billet to be two steps, and the spacing between any steel billet and the next steel billet to be one step.

[0008] As a preferred solution of the method for effectively controlling the decarburization layer of 65Mn hot-rolled narrow strip steel of the present invention, the length of one step is 400 mm.

[0009] As a preferred embodiment of the method for effectively controlling the decarburization layer of 65Mn hot-rolled narrow strip steel of the present invention, after controlling the spacing between any steel billet in the heating furnace and the previous steel billet to be two steps and the spacing between any steel billet and the next steel billet to be one step, the method further comprises: Control the heating furnace step speed to 2 to 3 minutes per step.

[0010] As a preferred embodiment of the method for effectively controlling the decarburization layer of 65Mn hot-rolled narrow strip steel of the present invention, after controlling the stepping speed of the heating furnace to 2 to 3 minutes per step, the method further comprises: The total furnace time of the steel plate is controlled to be 200 minutes.

[0011] The beneficial effects of the present invention are: The present invention controls the depth of the decarburized layer of the 65Mn steel strip to ≤0.06mm only by adjusting the temperature settings of each section of the walking beam heating furnace and strictly controlling the time in the furnace, so that the performance is improved to further meet the user's delivery requirements, and can be directly applied to existing equipment without the need to modify the existing equipment and adding additional processes such as billet peeling and coating, thereby effectively reducing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative labor.

[0013] Figure 1 Schematic diagram of heating temperature of each section of the heating furnace in the embodiment of the present invention and the common example; Figure 2 This is a schematic diagram of the decarburized layer detection results of a common example; Figure 3 It is a schematic diagram of the decarburized layer detection result according to an embodiment of the present invention. DETAILED DESCRIPTION

[0014] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below according to specific implementation modes and in combination with the accompanying drawings.

[0015] The present application embodiment provides a method for effectively controlling the decarburization layer of 65Mn hot-rolled narrow strip steel, the method specifically comprising the following steps: Step S101: Control the temperature of the first heating stage and the second heating stage in the heating furnace to be higher than the decarburization sensitive temperature range of 65Mn steel.

[0016] Step S102: Controlling the feeding method of the heating furnace: controlling the spacing between any steel billet in the heating furnace and the previous steel billet to be two steps, and the spacing between any steel billet and the next steel billet to be one step.

[0017] It should be noted that the length of one step is 400 mm.

[0018] Step S103: Control the heating furnace step speed to 2-3 min / step, and control the total time of the steel plate in the furnace to 200 min.

[0019] In this embodiment, the chemical composition and mass percentage of the 65Mn hot-rolled narrow strip steel used are: C: 0.63-0.67%, Si: 0.18-0.35%, Mn: 0.92-1.07%, P: ≤0.028%, S: ≤0.025%, Cr: ≤0.20%, Ni: ≤0.20%, Cu: ≤0.20%, and the balance is Fe and unavoidable impurities.

[0020] Comparing the embodiments of the present application with the common examples, the blank sizes are both 250*300mm.

[0021] The heating temperatures of the heating furnaces of the embodiments of the present invention and the conventional examples are as follows: Figure 1 As shown. In order to avoid the decarburization sensitive temperature range of 65Mn steel, the embodiment of the present invention increases the temperature of the first heating stage and the second heating stage, and the temperature of the third heating stage and the soaking stage does not change much. That is, the temperature of the first heating stage in the heating furnace is controlled to be 1050℃, and the temperature of the second heating stage is controlled to be 1150℃. In the ordinary example, the temperature of the first heating stage is 950℃, and the temperature of the second heating stage is 1080℃.

[0022] The feeding method adopted in the common example is one-in-one-empty, that is, the distance between any billet in the heating furnace and the previous billet is controlled to be one step, and the distance between any billet and the next billet is controlled to be one step. The feeding method adopted in the embodiment of the present invention is two-in-one-empty, that is, the distance between any billet in the heating furnace and the previous billet is controlled to be two step distances, and the distance between any billet and the next billet is controlled to be one step distance.

[0023] The stepping speed of the common example is 3-4 min / step, and the total time in the furnace is more than 250 minutes. The stepping speed in the embodiment of the present invention is 2-3 min / step, and the total time in the furnace is about 200 minutes. The rolling process does not change much, and the temperature of each rolling process is strictly controlled mainly by controlled rolling and controlled cooling. After rolling, the thickness of the product is 1.5-12.0 mm and the width is 160-450 mm.

[0024] The results of the decarburization layer test in the common case are as follows: Figure 2 As shown in FIG. 1 , the depth of the decarburized layer is between 0.07 and 0.08 mm, which cannot meet the requirements of the 65Mn steel strip for the decarburized layer. The high-quality 65Mn steel strip requires a decarburized layer ≤ 0.06 mm. Figure 3 As shown, the depth of the decarburization layer is between 0.03 and 0.04 mm, which can meet the requirements of high-quality 65Mn strip steel for the decarburization layer.

[0025] Therefore, the technical solution of the present application controls the depth of the decarburization layer of the 65Mn steel strip to ≤0.06mm by only adjusting the temperature settings of each section of the walking-beam heating furnace and strictly controlling the time in the furnace, so that the performance is improved to further meet the user's delivery requirements, and can be directly applied to existing equipment without the need to modify existing equipment, and without adding additional processes such as billet peeling and coating, thereby effectively reducing costs.

[0026] In addition to the above embodiments, the present invention may also have other implementation modes; any technical solutions formed by equivalent replacement or equivalent transformation shall fall within the protection scope required by the present invention.

Claims

1. A method for effectively controlling the decarburization layer of 65Mn hot-rolled narrow strip steel, characterized in that: include: The temperatures of the first and second heating stages in the heating furnace are controlled to be higher than the decarburization sensitive temperature range of 65Mn steel.

2. The method for effectively controlling the decarburization layer of 65Mn hot-rolled narrow strip steel according to claim 1, characterized in that: The temperature of the first and second heating stages in the heating furnace is controlled to be higher than the decarburization sensitive temperature range of 65Mn steel, including: The temperature of the first heating stage in the heating furnace was controlled to be 1050°C, and the temperature of the second heating stage was controlled to be 1150°C.

3. The method for effectively controlling the decarburization layer of 65Mn hot-rolled narrow strip steel according to claim 1, characterized in that: Also includes: The feeding method of the heating furnace is to control the spacing between any steel billet in the heating furnace and the previous steel billet to be two steps, and the spacing between any steel billet and the next steel billet to be one step.

4. The method for effectively controlling the decarburization layer of 65Mn hot-rolled narrow strip steel according to claim 3, characterized in that: The length of one of the steps is 400 mm.

5. The method for effectively controlling the decarburization layer of 65Mn hot-rolled narrow strip steel according to claim 3, characterized in that: After controlling the spacing between any steel billet in the heating furnace and the previous steel billet to be two steps and the spacing between any steel billet and the next steel billet to be one step, the method further comprises: Control the heating furnace step speed to 2 to 3 minutes per step.

6. The method for effectively controlling the decarburization layer of 65Mn hot-rolled narrow strip steel according to claim 5, characterized in that: After controlling the heating furnace step speed to 2 to 3 minutes per step, the method further comprises: The total furnace time of the steel plate is controlled to be 200 minutes.

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