A method for producing 45# steel

Abstract

The application discloses a production method of 45# steel, which comprises the following steps: blast furnace molten iron, molten iron pretreatment, top and bottom combined blowing smelting of a converter, LF refining, small billet continuous casting, slow cooling, long material mill rolling; billet heating, high-pressure water descaling, rough rolling, medium rolling, finish rolling, controlled cooling water tank, wire drawing, Stelmor cooling, coil collecting, trimming, sampling inspection, collecting and bundling, weighing, and finished wire rod. The application aims to provide a production method of 45# steel, so that the 45# steel can meet the performance requirements of customers, the tensile strength of the 45# steel can be stabilized at more than 700 MPa, the elongation after fracture is greater than or equal to 20%, the area reduction is greater than or equal to 45%, and the product size and appearance are free of defects.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of metallurgy and rolling technology, and particularly relates to a production method of 45# steel. BACKGROUND

[0002] After drawing, the 45# steel is widely used in the machining of rod, shaft, bolt and other parts in the automobile and machinery industries, and the machining process is complex and various, generally including turning, hot forging, cold heading, heat treatment and the like, and the surface quality and mechanical properties of the round steel are required to be higher. According to the national standard, when the mechanical properties of the 45# steel are detected, the sample needs to be subjected to normalizing treatment at 850 DEG C first, and then the tensile test is carried out. The downstream processing enterprises generally carry out a series of deformation processing first, and then heat treatment is carried out on the workpiece to meet the use requirements. Therefore, the stability of the mechanical properties of the 45# steel in the hot-rolled state is the main influencing factor for ensuring the smooth production of the subsequent processing. SUMMARY

[0003] The purpose of the application is to provide a production method of 45# steel, so that the 45# steel meets the performance requirements of customers, the tensile strength is stabilized at more than 700 MPa, the elongation after fracture is greater than or equal to 20%, the area reduction is greater than or equal to 45%, and the product size and appearance are free of defects.

[0004] To solve the above technical problems, the application adopts the following technical scheme:

[0005] The production method of the 45# steel comprises the following steps: blast furnace molten iron-molten iron pretreatment-top and bottom combined blowing of converter-smelting in LF-refining in small billet continuous casting-slow cooling-rolling in long material plant; heating of the billet-high pressure water descaling-rough rolling-medium rolling-fine rolling-control cooling water tank-wire drawing-Stelmor cooling-coiling-trimming-sampling inspection-collection and bundling-weighing-finished wire rod; and the main production process comprises the following steps:

[0006] 1) the gas content of the casting billet is required to be O≤30ppm and N≤60ppm; single slag or double slag operation is adopted according to the molten iron condition, and the terminal point basicity is 2.7-3.5;

[0007] 2) high pulling and supplementary blowing operation is adopted in the converter, and the composition C≥0.10% and T≥1610 DEG C at the end of tapping;

[0008] 3) the connection with the tank is strengthened at the time of tapping, and the argon blowing operation is carried out according to the regulation. The argon control requirement is that large argon stirring is carried out before tapping, and the argon flow is reduced for slag blocking operation when the tapping amount is greater than 2 / 3, so that the alloy is not clumped and the top slag material is well melted;

[0009] 4) the starting pulling speed is 0.25m / min, and the target constant pulling speed is 2.0m / min;

[0010] 5) Rolling temperature control: 1000±20℃ for starting rolling temperature, 920±20℃ for finishing rolling temperature, and 880±20℃ for wire drawing temperature;

[0011] 6) Fan opening degree: 100% for 1#-5# fans, and 50% for 6#-8# fans;

[0012] 7) The speed of the Stelmor roller is set as shown in the following table:

[0013]

[0014] The 45# steel has the following chemical components (mass percentage): C: 0.42%; Si: 0.17-0.37%; Mn: 0.50-0.80%; P≤0.035%; S:≤0.035%; the balance is Fe and a small amount of impurity elements.

[0015] Further, the Si content of the molten iron entering the furnace is ≤0.5, and single-slag operation is adopted when the Si content is >0.5.

[0016] Further, the gas content of the cast slab is required to be ≤28ppm.

[0017] Further, the gas content of the cast slab is required to be ≤50ppm.

[0018] Further, the speed fluctuation range of the drawing speed is ±0.1m / min.

[0019] Compared with the prior art, the present application has the following beneficial technical effects:

[0020] Through the preparation process of the present application, the 45# steel can meet the performance requirements of customers, and the tensile strength can be stabilized at more than 700MPa, the elongation after fracture is greater than or equal to 20%, the area reduction is greater than or equal to 45%, and the product size and appearance have no defects. DETAILED DESCRIPTION

[0021] The 45# steel involved in the present application has the following chemical components (mass percentage): C: 0.42%; Si: 0.17-0.37%; Mn: 0.50-0.80%; P≤0.035%; S:≤0.035%; the balance is Fe and a small amount of impurity elements.

[0022] Main production process:

[0023] Blast furnace molten iron-molten iron pretreatment-top and bottom combined blowing smelting-LF refining-small billet continuous casting-cushion cooling-long material mill rolling

[0024] Billet heating-high pressure water descaling-coarse rolling rolling-medium rolling rolling-fine rolling rolling-control cooling water tank-wire drawing-Stelmor cooling-coiling-trimming-sampling inspection-collection and bundling-weighing-finished wire rod

[0025] Technical improvement scheme

[0026] 1) Casting blank gas content requirement: O≤30ppm, N≤60ppm; According to the hot metal condition, single slag or double slag operation is adopted (it is recommended that single slag operation is adopted when Si≤0.5 of the hot metal, and double slag operation is adopted when Si>0.5), and the final point basicity is 2.7-3.5;

[0027] 2) High pull compensation blowing operation is adopted in the converter, and the composition C≥0.10%, T≥1610℃ at the end of tapping;

[0028] 3) Strengthen the contact with the tank during tapping, and perform argon blowing operation according to the regulations. Argon control requirements: large argon stirring before tapping, and small argon flow for slag blocking operation when the tapping amount is greater than 2 / 3, to ensure that the alloy does not clump and the top slag material melts well;

[0029] 4) Starting speed 0.25m / min, target constant speed 2.0m / min, speed fluctuation range±0.1m / min;

[0030] 5) Rolling temperature control: opening temperature 1000±20℃, finishing temperature 920±20℃, wire drawing temperature 880±20℃;

[0031] 6) Fan opening degree: 1#-5# fan opening degree 100%, 6#-8# fan opening degree 50%;

[0032] 7) The speed of the Stelmor roller is set as follows:

[0033]

[0034] 1, Strictly control the oxygen and nitrogen elements of the casting blank, as shown in the following table:

[0035]

[0036] Through the implementation of technical schemes 1), 2), and 3), the content of two kinds of gases is significantly reduced and stabilized in a fixed range, which plays a great guarantee role for the quality of continuous casting billets.

[0037] 2, The constant speed control results are shown in the following table:

[0038]

[0039] Through the implementation of technical scheme 4), the improved continuous casting billet speed is stably controlled, basically eliminating the phenomenon of continuous casting billet hollow, and preventing the phenomenon of gas hole caused by exceeding the oxygen content during continuous casting.

[0040] The improvement of the stability of the mechanical properties of the product is shown in the following table,

[0041]

[0042] Through the implementation of technical solutions 5), 6) and 7), the mechanical properties of the product fully meet the design requirements.

[0043] The above-described embodiments are merely preferred modes of the present application and are not intended to limit the scope of the present application. Various modifications and improvements to the technical solutions of the present application made by those of ordinary skill in the art without departing from the design spirit of the present application shall fall within the scope of protection of the present application as defined by the claims.

Claims

1. A production method of 45# steel, comprising blast furnace hot metal-hot metal pretreatment-top and bottom combined blowing smelting of converter-LF refining-small billet continuous casting- slow cooling-long material mill rolling; billet heating-high pressure water descaling-coarse rolling rolling-medium rolling rolling-fine rolling rolling-controlling cooling water tank-wire drawing-Stelmor cooling-coiling- trimming-sampling inspection-collecting baling-weighing-finished wire; characterized in that, The main production process includes: 1) Casting blank gas content requirement: O≤30ppm, N≤60ppm; according to the hot metal conditions to take single slag or double slag operation, the end point alkalinity according to 2.7-3.5; 2) Converter adopts high pull compensation blowing operation, tapping end composition C≥0.10%, temperature≥1610℃; 3) Strengthen the contact with the repair tank when tapping, according to the provisions of argon blowing operation; argon control requirements: large argon stirring before tapping, when the tapping amount is greater than 2 / 3, adjust the small argon flow to carry out slag blocking operation, ensure that the alloy does not clump, top slag material melts well; 4) Starting speed 0.25m / min, target constant speed 2.0m / min; 5) Rolling temperature control: opening rolling temperature 1000±20℃, finishing rolling temperature 920±20℃, wire drawing temperature 880±20℃; 6) Fan opening degree: 1#-5# fan opening degree 100%, 6#-8# fan opening degree 50%; 7) The speed of Stelmor roller is set as follows: The chemical composition of the 45# steel is: C: 0.42%; Si: 0.17-0.37%; Mn: 0.50-0.80%; P≤0.035%; S:≤0.035%; the balance is Fe and a small amount of impurity elements.

2. The method of producing 45# steel according to claim 1, characterized by, Hot metal into the furnace Si≤0.5 single slag operation, Si>0.5 double slag operation.

3. The method of producing 45# steel according to claim 1, characterized in that, Casting blank gas content requirement: O≤28ppm.

4. The method of producing 45# steel according to claim 1, characterized in that, Casting blank gas content requirement: N≤50ppm.

5. The method of producing 45# steel according to claim 1, characterized in that, Speed fluctuation range ±0.1m / min.

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