Production control method for improving bending degree of steel for steering gear nut

Abstract

The invention discloses a production control method for improving the bending degree of steel for a steering gear nut, which comprises the following steps of: 1) optimizing the heating temperature, enabling a walking beam of a heating furnace to advance at 110 seconds per step in the production process, ensuring that a steel billet for the steering gear nut is uniformly heated in the heating furnace, and enabling the temperature fluctuation of a single thermocouple to be less than or equal to 15 DEG C; (2) the initial rolling temperature is controlled to be 980-1020 DEG C, and the speed of four rolling mills for initial rolling is reduced to 0.48 m / s; 3) during rolling, using 3 # and 4 # water tanks and closing water tank booster pumps, keeping the pressure of the 3 # and 4 # water tanks at 6.5 Bar, and all 5 #, 6 # and 7 # water tanks off line; and (4) a heat preservation cover is abandoned for the cooling bed, the multiple length of the upper cooling bed is set to be 82-90 m, the cooling bed acts one tooth and one motion, and the cooling bed moves one time every 22 s. By controlling the rolling temperature, the cooling temperature and the sawing temperature after rolling, the straightness of the steel for the nut is effectively improved, the straightening procedure is omitted, the production cost is reduced, and the delivery speed is increased.

Description

Technical Field

[0001] The invention relates to a field, and in particular to a production control method for improving the curvature of a steel used for a steering gear nut. Background Art

[0002] As an important component in automobile gearboxes, steering nut has a large market demand. The steel has high requirements for surface quality, fatigue performance and straightness. The content of Cr, Mo, Mn and other alloys in nut steel is high, and high-temperature rolling is required. After rolling, the cooling bed cooling and sawing process usually cause shoulder pole bending due to uneven cooling rate. Repeated straightening is required to ensure straightness, and then the flaw detection and packaging process is carried out, which not only increases the processing cost, but also increases the delivery time by about 15 days.

[0003] Therefore, it is necessary to develop new production control methods in a targeted manner to improve flatness, reduce production costs and increase delivery speed. Summary of the invention

[0004] Purpose of the invention: In view of the shortcomings and defects of the prior art, the present invention provides a production control method for improving the curvature of steering gear nut steel. By controlling the rolling temperature and cooling temperature, as well as the post-rolling sawing temperature, the straightness of the nut steel is effectively improved, the straightening process is omitted, the production cost is reduced, and the delivery speed is improved.

[0005] Technical solution: A production control method for improving the curvature of a steering nut steel of the present invention is characterized in that it comprises the following steps:

[0006] 1) Optimize the heating temperature. During the production process, the walking beam of the heating furnace moves forward at 110s / step to ensure that the steel billet for the steering screw nut is evenly heated in the heating furnace, and the temperature fluctuation of a single thermocouple is ≤15°C;

[0007] 2) The rolling temperature is controlled at 980℃-1020℃, and the speed of the four initial rolling mills is reduced to 0.48m / s;

[0008] 3) During rolling, use 3# and 4# water tanks and turn off the water tank booster pump. The pressure of 3# and 4# water tanks is maintained at 6.5 Bar, and 5# / 6# / 7# water tanks are all offline;

[0009] 4) The cooling bed abandons the heat preservation cover, and the length of the upper cooling bed is set at 82m-90m. The cooling bed moves one tooth at a time, and the movement rhythm of the cooling bed is controlled according to 22s to ensure that the rolled material is cooled slowly on the cooling bed;

[0010] 5) The steel is supported flat on the cooling bed for less than 1 minute, and sawing is carried out when the sawing temperature is less than 150℃. After the steel is off the line, it is put into the slow cooling pit for slow cooling, and the slow cooling time is greater than 24 hours.

[0011] Among them, the steel for steering gear nut includes the following components in mass percentage: C: 0.48%-0.67%, Mn: 0.66%-0.82%, Si: 0.28%-0.46%, Mo: 0.14%-0.22%, Cr: 0.95%-1.12%, Ni≤0.15%, Cu≤0.20%, P+S<0.10%, Fe balance.

[0012] Wherein, in the step 2), the rolling temperature is controlled at 1000°C.

[0013] Wherein, the steel used for the steering gear nut is round steel with a diameter of Φ30mm-60mm.

[0014] The steering gear nut steel is made of 320mm×480mm cross-section billet smelted in an electric furnace, heated to 1240°C, rolled into 180mm×180mm×11000mm billet, and then hot-rolled into Φ30mm-60mm diameter steering gear nut steel.

[0015] Among them, when the steering gear nut steel is rolled, a heating furnace and high-pressure water descaling are configured online, 23 horizontal and vertical alternating short stress line rolling mills, 4 three-roller KOCKS rolling mills, 5 flying shears and 7 water tanks for online controlled cooling, and an insulation cover device is installed above the cooling bed.

[0016] Wherein, when optimizing the heating temperature in step 1), the heating temperature of the preheating section is controlled to be ≤800°C.

[0017] Wherein, when optimizing the heating temperature in step 1), the heating temperature of the first heating stage is controlled to be ≤950°C, and the heating temperature of the second heating stage is controlled to be 1020°C-1100°C.

[0018] Wherein, when optimizing the heating temperature in step 1), the heating temperature of the first stage of the equalization is controlled to be 1080°C-1140°C, and the heating temperature of the second stage of the equalization is controlled to be 1080°C-1120°C.

[0019] Wherein, during the rolling in step 3), the sizing temperature is ensured to be between 910°C and 950°C to avoid the precipitation of proeutectoid ferrite and to perform rolling in the single-phase region.

[0020] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: the present invention improves the straightness of round steel through low-temperature rolling + controlled rolling and controlled cooling, and solves the bending problem of Φ30mm-60mm steering nut steel; by controlling the rolling temperature and cooling temperature, as well as the post-rolling sawing temperature, the straightness of the nut steel is effectively improved, the straightening process is omitted, the production cost is reduced, and the delivery speed is improved.

[0021] After testing, the proportion of the steel used for the steering screw nut with a straightness within 0.25% is above 99.00%. The straightening cost can be saved by 225 yuan / ton through the scheme of the present invention. DETAILED DESCRIPTION

[0022] The technical solution of the present invention is further described below in conjunction with specific implementation methods.

[0023] The steel for steering gear nut of the present invention comprises the following components in mass percentage: C: 0.48%-0.67%, Mn: 0.66%-0.82%, Si: 0.28%-0.46%, Mo: 0.14%-0.22%, Cr: 0.95%-1.12%, Ni≤0.15%, Cu≤0.20%, P+S<0.10%, and Fe balance.

[0024] The steel for the steering nut of the present invention adopts a 320mm×480mm cross-section billet smelted in an electric furnace, which is heated to 1240°C for blanking and rolling into a 180mm×180mm×11000mm billet, and then heated and rolled into a steel for the steering nut with a diameter of Φ30mm-60mm. During rolling, a heating furnace, high-pressure water descaling, 23 horizontal and vertical alternating short stress line rolling mills, 4 three-roller KOCKS rolling mills, 5 flying shears and 7 water tanks for online controlled cooling are configured online, and a heat preservation cover device is provided above the cooling bed.

[0025] The production control method for improving the curvature of the steering gear nut steel of the present invention comprises the following steps:

[0026] 1) Optimize the heating temperature. During the production process, the walking beam of the heating furnace moves forward at 110s / step to ensure that the steel billet for the steering screw is evenly heated in the heating furnace, and the temperature fluctuation of a single thermocouple is ≤15℃. When optimizing the heating temperature, control the heating temperature of the preheating section to ≤800℃; control the heating temperature of the first heating section to ≤950℃, and control the heating temperature of the second heating section to 1020℃-1100℃; control the heating temperature of the first soaking section to 1080℃-1140℃, and control the heating temperature of the second soaking section to 1080℃-1120℃.

[0027]

[0028] 2) The rolling temperature is controlled at 980°C-1020°C, and the speed of the four initial rolling mills is reduced to 0.48m / s; the intermediate billet is deformed to form a hard shell.

[0029] 3) During rolling, use 3# and 4# water tanks and turn off the water tank booster pump. The pressure of 3# and 4# water tanks is maintained at 6.5 Bar. Weak water penetration is performed before controlled rolling to ensure that the sizing temperature is between 910℃ and 950℃ to avoid the precipitation of proeutectoid ferrite and to carry out rolling in the single-phase region. All 5# / 6# / 7# water tanks are offline.

[0030] 4) The cooling bed abandons the insulation cover, and the upper cooling bed length is set at 82m-90m. The cooling bed moves one tooth at a time, and the movement rhythm of the cooling bed is controlled according to 1 movement per 22s to ensure that the rolled material is cooled slowly on the cooling bed.

[0031] 5) The steel is supported flat on the cooling bed for less than 1 minute, and sawing is carried out when the sawing temperature is less than 150℃. After the steel is off the line, it is put into the slow cooling pit for slow cooling, and the slow cooling time is greater than 24 hours.

[0032] The invention improves the straightness of round steel by low-temperature rolling + controlled rolling and controlled cooling, thereby solving the bending problem of Φ30mm-60mm steering nut steel; by controlling the rolling temperature and the cooling temperature, as well as the post-rolling sawing temperature, the straightness of the nut steel is effectively improved, the straightening process is omitted, the production cost is reduced, and the delivery speed is improved.

[0033] After testing, the proportion of the steel used for the steering screw nut with a straightness within 0.25% is above 99.00%. The straightening cost can be saved by 225 yuan / ton through the scheme of the present invention.

Claims

1. A production control method for improving the curvature of steering nut steel, characterized in that: The steps include: 1) Optimize the heating temperature. During the production process, the walking beam of the heating furnace moves forward at 110s / step to ensure that the steel billet for the steering screw nut is evenly heated in the heating furnace, and the temperature fluctuation of a single thermocouple is ≤15°C; 2) The rolling temperature is controlled at 980℃-1020℃, and the speed of the four initial rolling mills is reduced to 0.48m / s; 3) During rolling, use 3# and 4# water tanks and turn off the water tank booster pump. The pressure of 3# and 4# water tanks is maintained at 6.5 Bar, and 5# / 6# / 7# water tanks are all offline; 4) The cooling bed abandons the insulation cover, the upper cooling bed length is set at 82m-90m, the cooling bed moves one tooth at a time, and the cooling bed moves once every 22s to control the movement rhythm, ensuring that the rolled material cools slowly on the cooling bed; 5) The steel is supported flat on the cooling bed for less than 1 minute, and sawing is carried out when the sawing temperature is less than 150℃. After the steel is off the line, it is put into the slow cooling pit for slow cooling, and the slow cooling time is greater than 24 hours.

2. The production control method for improving the curvature of the steering nut steel according to claim 1, characterized in that: The steel for steering gear nut comprises the following components in mass percentage: C: 0.48%-0.67%, Mn: 0.66%-0.82%, Si: 0.28%-0.46%, Mo: 0.14%-0.22%, Cr: 0.95%-1.12%, Ni≤0.15%, Cu≤0.20%, P+S<0.10%, Fe balance.

3. The production control method for improving the curvature of the steering gear nut steel according to claim 1, characterized in that: In the step 2), the rolling temperature is controlled at 1000°C.

4. The production control method for improving the curvature of the steering nut steel according to claim 1, characterized in that: The steel used for the steering gear nut is round steel with a diameter of Φ30mm-60mm.

5. The production control method for improving the curvature of the steering gear nut steel according to claim 4, characterized in that: The steering gear nut steel is made of 320mm×480mm cross-section billets smelted in an electric furnace, heated to 1240°C, rolled into 180mm×180mm×11000mm billets, and then hot-rolled into steering gear nut steel with a diameter of Φ30mm-60mm.

6. The production control method for improving the curvature of the steering gear nut steel according to claim 5, characterized in that: When the steel for the steering gear nut is rolled, a heating furnace, high-pressure water descaling, 23 horizontal and vertical alternating short stress line rolling mills, 4 three-roller KOCKS rolling mills, 5 flying shears and 7 water tanks for online controlled cooling are configured online, and a heat preservation cover device is installed above the cooling bed.

7. The production control method for improving the curvature of steering gear nut steel according to claim 1, characterized in that: When optimizing the heating temperature in step 1), the heating temperature in the preheating section is controlled to be ≤800°C.

8. The production control method for improving the curvature of the steering gear nut steel according to claim 7, characterized in that: When optimizing the heating temperature in step 1), the heating temperature of the first heating stage is controlled to be ≤950°C, and the heating temperature of the second heating stage is controlled to be 1020°C-1100°C.

9. The production control method for improving the curvature of the steering gear nut steel according to claim 8, characterized in that: When optimizing the heating temperature in step 1), the heating temperature of the first stage of the equalization is controlled to be 1080°C-1140°C, and the heating temperature of the second stage of the equalization is controlled to be 1080°C-1120°C.

10. The production control method for improving the curvature of steering gear nut steel according to claim 1, characterized in that: During the rolling in step 3), the sizing temperature is ensured to be between 910°C and 950°C to avoid the precipitation of proeutectoid ferrite and to perform rolling in the single-phase region.

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