A method for producing 8.8-grade non-quenched cold-upsetting steel wire rod

Abstract

The application is a production method of 8.8-grade non-adjusted cold upsetting steel wire rod. The chemical composition of the billet is as follows: C=0.23% to 0.28%, Si=0.20% to 0.28%, Mn=1.45% to 1.6%, P≤0.025%, S≤0.015%, Al=0.02% to 0.05%, and the rest is Fe and inevitable impurity elements. By using the advantages of high-speed wire production line, the wire rod with the main structure of bainite is produced through the controlled rolling and controlled cooling process, the wire rod has uniform structure and good performance, the tensile strength is greater than or equal to 800 MPa, and the extreme difference of the performance of the same circle is less than or equal to 30 MPa.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of cold heading steel wire rod production and relates to a production method of Φ11mm and Φ13mm specification 8.8 grade non-quenched cold heading steel wire rod. BACKGROUND

[0002] At present, cold heading steel for automobile fasteners is mainly quenched and tempered steel, and fastener processing enterprises need to convert part of the production capacity into non-quenched steel production, which can reduce a quenching process and reduce energy consumption, thereby being beneficial to improving production efficiency, reducing production cost and having good economic and social benefits.

[0003] For a steel plant, based on a high-speed wire rod production line, wire rods meeting the fastener steel standard are produced through control of the controlled cooling process, so that higher profits than quenched and tempered steel of the same grade can be obtained. SUMMARY

[0004] The application aims to provide a production method of Φ11mm and Φ13mm specification 8.8 grade non-quenched cold heading steel wire rod, produce Φ11mm and Φ13mm specification 8.8 grade non-quenched cold heading steel wire rod, obtain bainite structure with good drawing performance and cold heading performance, and make the mechanical properties of the wire rod meet the GB / T3098.22 standard and the use requirements of the 8.8 grade bolt with a tensile strength ≥800Mpa.

[0005] The technical scheme of the application is as follows:

[0006] A production method of 8.8 grade non-quenched cold heading steel wire rod for fasteners, the chemical composition of the steel contains, by weight, C=0.23%-0.28%, Si=0.20%-0.28%, Mn=1.45%-1.6%, P≤0.025%, S≤0.015%, Al=0.02%-0.05%, and the rest is Fe and inevitable impurity elements; and the method comprises the following key process steps:

[0007] 1) a continuous casting billet with a cross-sectional size of 150mm*150mm is selected, the preheating section temperature of a heating furnace is ≤950℃, the heating section temperature is 1100-1200℃, the soaking section temperature is 1100-1150℃, and the heating time is 90-200 minutes;

[0008] 2) the furnace discharge temperature is 1000-1060℃;

[0009] 3) the entry sizing temperature is 820-840℃;

[0010] 4) after the sizing, each water tank is uniformly opened, and the wire drawing temperature is 820-850℃;

[0011] 5) Φ11mm specification air cooling line roller speed is 0.40m / s; air cooling roller heat preservation cover opens 14, the cooling fan below the roller opens 5, the air volume is 100%, the temperature of the heat preservation cover is 500~550℃, the rest of the heat preservation cover and the fan are all closed; Φ13mm specification air cooling line roller speed is 0.35m / s, air cooling roller heat preservation cover opens 16, the cooling fan below the roller opens 6, the air volume is 100%, the temperature of the heat preservation cover is 500~550℃, the rest of the heat preservation cover and the fan are all closed; the tensile strength of the 8.8 grade non-adjusted upsetting steel wire rod is ≥800Mpa.

[0012] In the step 5), the Φ11mm specification air cooling line roller speed is 0.40m / s, wherein each roller speed control is S1=0.40m / s, S2=0.42m / s, S3=0.45m / s, S4=0.50m / s, S5=0.50m / s, S6=0.50m / s, S7=0.45m / s, S8=40m / s, S9=0.30 / s, S10=0.30m / s, S11=0.30m / s, S12=0.30m / s, S13=0.30m / s, S14=0.35m / s, S15=0.35m / s. The Φ13mm specification air cooling line roller speed is 0.35m / s, wherein each roller speed control is S1=0.35m / s, S2=0.37m / s, S3=0.40m / s, S4=0.45m / s, S5=0.50m / s, S6=0.45m / s, S7=0.40m / s, S8=30m / s, S9=0.30 / s, S10=0.30m / s, S11=0.30m / s, S12=0.30m / s, S13=0.30m / s, S14=0.35m / s, S15=0.35m / s. The air cooling line roller is 118 meters long, has 24 cooling modules, each module is 4.5 meters long, corresponds to 1 fan and 2 heat preservation covers.

[0013] The beneficial effects of the application are: the wire rod produced has hot rolling structure of bainite, through a small amount of drawing hardening, the performance meets the requirements of 8.8 grade fasteners, and the purpose of producing 8.8 grade bolt without adjusting quality heat treatment is achieved. The hot rolling wire rod has uniform structure, small performance fluctuation in the same circle, eliminates banded structure, and the longitudinal and transverse performance is more stable. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 It is the metallographic structure diagram of the wire rod of example 1.

[0015] Figure 2 It is the metallographic structure diagram of the wire rod of example 2. PREFERRED EMBODIMENT Example 1

[0016] The production of non-tempering upsetting steel wire rod for 8.8-grade fasteners, a high-speed wire mill rolls Φ11mm specification XGFT8, the chemical composition of the billet is 0.25% of C, 0.25% of Si, 1.50% of Mn, 0.010% of P, 0.008% of S, 0.03% of Al, and the rest is Fe and inevitable impurity elements, including the following key steps:

[0017] The billet is selected as 150mm*150mm continuous casting billet, the preheating section temperature of the heating furnace is 820~850℃, the heating section temperature is 1100~1160℃, the soaking section temperature is 1110~1150℃, and the heating time is 100 minutes.

[0018] The discharge temperature is 1020~1040℃.

[0019] The reducing diameter temperature is 825~836℃.

[0020] After reducing diameter, each water tank is evenly opened, and the wire drawing temperature is 830~840℃.

[0021] The air cooling line roller speed is 0.40m / s; 14 air cooling roller bed heat preservation covers are opened, 5 air cooling fans under the roller bed are opened, the air volume is 100%, the temperature into the heat preservation cover is 520~540℃. The rest of the heat preservation covers and fans are all closed.

[0022] In the step 5), the air cooling line roller speed of Φ11mm specification is 0.40m / s, wherein the roller speed control is S1=0.40m / s, S2=0.42m / s, S3=0.45m / s, S4=0.50m / s, S5=0.50m / s, S6=0.50m / s, S7=0.45m / s, S8=40m / s, S9=0.30 / s, S10=0.30m / s, S11=0.30m / s, S12=0.30m / s, S13=0.30m / s, S14=0.35m / s, S15=0.35m / s. The air cooling line roller is 118 meters long, there are 24 cooling modules, each module is 4.5 meters long, corresponding to 1 fan and 2 heat preservation covers. The hot rolling performance of the wire rod is shown in Table 1.

[0023] Example 2

[0024] The production of non-tempering upsetting steel wire rod for 8.8-grade fasteners, a high-speed wire mill rolls Φ13mm specification XGFT8, the chemical composition of the billet is 0.26% of C, 0.25% of Si, 1.51% of Mn, 0.009% of P, 0.06% of S, 0.032% of Al, and the rest is Fe and inevitable impurity elements, including the following key steps:

[0025] The billet is selected as 150mm*150mm continuous casting billet, the preheating section temperature of the heating furnace is 830-860℃, the heating section temperature is 1120-1160℃, the soaking section temperature is 1110-1145℃, and the heating time is 103 minutes.

[0026] The delivery temperature is 1045-1057℃.

[0027] The reducing diameter temperature is 822-840℃.

[0028] After the reducing diameter, each water tank is opened uniformly, and the wire spitting temperature is 827-846℃.

[0029] The roller way speed of the Φ13mm specification air cooling line is 0.35m / s; 16 air cooling roller way heat preservation covers are opened, 6 air cooling fans under the roller way are opened, the air volume is 100%, the temperature into the heat preservation cover is 520-550℃. The remaining heat preservation covers and fans are all closed.

[0030] In the step 5), the roller way speed of the Φ13mm specification air cooling line is 0.35m / s, wherein the roller way speed control is S1=0.35m / s, S2=0.37m / s, S3=0.40m / s, S4=0.45m / s, S5=0.50m / s, S6=0.45m / s, S7=0.40m / s, S8=30m / s, S9=0.30 / s, S10=0.30m / s, S11=0.30m / s, S12=0.30m / s, S13=0.30m / s, S14=0.35m / s, S15=0.35m / s. The air cooling line roller way is 118 meters long, has 24 cooling modules, each module is 4.5 meters long, corresponds to 1 fan and 2 heat preservation covers.

[0031] The hot rolling performance detection results of the wire rod produced in the example are shown in Table 1.

[0032] Table 1: Hot rolling performance and bolt performance of the example wire rod

[0033] .

Claims

1. A method for producing non-cold heading steel wire rod for 8.8 grade fasteners, characterized in that: The steel's chemical composition by weight percentage is C = 0.23%–0.28%, Si = 0.20%–0.28%, Mn = 1.45%–1.6%, P ≤ 0.025%, S ≤ 0.015%, Al = 0.02%–0.05%, with the remainder being Fe and unavoidable impurity elements; it includes the following key process steps: 1) Select a continuous casting billet with a cross-sectional size of 150mm×150mm. The temperature of the preheating section of the heating furnace is ≤950℃, the temperature of the heating section is 1100~1200℃, the temperature of the soaking section is 1100~1150℃, and the heating time is 90~200 minutes. 2) Furnace temperature: 1000–1060℃; 3) Infeed sizing temperature: 820–840℃; 4) After the diameter reduction, each water tank is opened evenly, and the silk spinning temperature is 820-850℃; 5) The speed of the Φ11mm air-cooled roller conveyor is 0.40m / s; 14 insulation covers of the air-cooled roller conveyor are open, 5 cooling fans below the roller conveyor are open, with an air volume of 100%, and the temperature entering the insulation cover is 500~550℃. All other insulation covers and fans are closed. The speed of the Φ13mm air-cooled roller conveyor is 0.35m / s; 16 insulation covers of the air-cooled roller conveyor are open, 6 cooling fans below the roller conveyor are open, with an air volume of 100%, and the temperature entering the insulation cover is 500~550℃. All other insulation covers and fans are closed. This yields grade 8.8 non-cooled heading steel wire rod with a tensile strength ≥800Mpa.

2. The method for producing non-cold heading steel wire rod for 8.8 grade fasteners according to claim 1, characterized in that: In step 5), the speed of the roller conveyor for the Φ11mm air-cooled line is 0.40 m / s, with the speeds of each roller controlled as follows: S1=0.40 m / s, S2=0.42 m / s, S3=0.45 m / s, S4=0.50 m / s, S5=0.50 m / s, S6=0.50 m / s, S7=0.45 m / s, S8=40 m / s, S9=0.30 m / s, S10=0.30 m / s, S11=0.30 m / s, S12=0.30 m / s, S13=0.30 m / s, S14=0.35 m / s, S15=0.35 m / s; the speed of the roller conveyor for the Φ13mm air-cooled line is 0.3 m / s. The speed is 5 m / s, with the speed of each roller controlled as follows: S1=0.35 m / s, S2=0.37 m / s, S3=0.40 m / s, S4=0.45 m / s, S5=0.50 m / s, S6=0.45 m / s, S7=0.40 m / s, S8=30 m / s, S9=0.30 m / s, S10=0.30 m / s, S11=0.30 m / s, S12=0.30 m / s, S13=0.30 m / s, S14=0.35 m / s, S15=0.35 m / s. The air-cooled roller conveyor is 118 meters long and has 24 cooling modules, each module is 4.5 meters long, corresponding to 1 fan and 2 insulation covers.

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