Heating method for reducing surface decarburization of steel for steering gear nut

Abstract

The invention discloses a heating method for reducing surface decarburization of steel for a steering gear nut, which comprises the following steps: 1) carrying out surface grinding treatment for 1mm on a blank rolled after cogging, and grinding off primary scale on the surface of the blank; (2) the secondary heating time in the heating furnace is controlled to be 140-180 min; and (3) the heating temperature is controlled to be 950-1100 DEG C, the soaking temperature is controlled to be 1080-1120 DEG C, and high-temperature oxidation is reduced. By controlling the heating time and the heating temperature in the furnace, the thickness of a decarburized layer on the surface of the steel for the automobile steering gear nut is reduced by 0.08-0.14 mm, the surface quality, the fatigue performance and the yield of the steel for the steering gear nut are improved, and the machining cost is reduced.

Description

Technical Field

[0001] The invention relates to steel smelting, and in particular to a heating method for reducing surface decarburization of steel for steering gear nut. Background Art

[0002] With the rapid development of the global automotive industry, the demand for steel for automotive steering nut is also gradually increasing. During the operation of the car, the steering nut maintains high-speed operation and needs to have good fatigue performance. In order to maintain good mechanical properties, the steel for automotive steering nut needs to be rolled using two-fire billets during production. During the two furnace heating processes, the surface of the billet is easily oxidized to form a thick decarburization layer, which not only significantly reduces the wear resistance and fatigue strength of the material, but also causes surface cracks during the rolling process due to the inability to remove the oxide scale. Therefore, during the processing of steering nut steel, it is usually necessary to peel off the decarburization layer on the surface of the raw material by 0.30-0.50mm. This not only affects the yield rate, but also increases the turning cost.

[0003] Therefore, it is necessary to develop new methods to reduce the thickness of the decarburized layer on the surface of steel used for automobile steering gear nut. 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 heating method for reducing surface decarburization of steel for steering gear nut. By controlling the heating time and heating temperature in the furnace, the thickness of the decarburization layer on the surface of steel for automobile steering gear nut is reduced by 0.08mm-0.14mm, thereby improving the surface quality, fatigue performance and yield rate of steel for steering gear nut, and reducing the processing cost.

[0005] Technical solution: A heating method for reducing surface decarburization of steering gear nut steel of the present invention is characterized by comprising the following steps:

[0006] 1) The surface of the rolled billet after billeting is ground by 1 mm to remove the primary iron oxide scale on the surface of the billet;

[0007] 2) The secondary heating time in the heating furnace is controlled within 140min-180min;

[0008] 3) The heating temperature is controlled at 950℃-1100℃, and the soaking temperature is controlled at 1080℃-1120℃ to reduce high temperature oxidation.

[0009] Wherein, the billet rolled after the billet opening is a 180mm×180mm billet.

[0010] During the rolling, a 320mm×480mm cross-section billet smelted in an electric furnace is heated to 1240°C for billet opening and rolling into a 180mm×180mm×11000mm billet, which is then heated and rolled into steel for steering gear nut to produce Φ30mm-60mm round steel.

[0011] During the 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 installed above the cooling bed.

[0012] The heating time in step 2) includes a preheating section heating time, a heating section heating time and a soaking section heating time.

[0013] Wherein, the heating time of the preheating section is 30min-50min, and the temperature of the preheating section is ≤800°C.

[0014] Wherein, the heating time of the heating section is 50min-70min, and the heating section includes heating section one and heating section two.

[0015] Wherein, the temperature of the first heating stage is ≤950°C, and the temperature of the second heating stage is 1020°C-1100°C.

[0016] The heating time of the soaking section is 60 minutes, and the soaking section includes the first soaking section and the second soaking section.

[0017] Wherein, the temperature of the first stage of the equalization is 1080°C-1140°C, and the temperature of the second stage of the equalization is 1080°C-1120°C.

[0018] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: The present invention controls the heating time and heating temperature, reduces the residence time of the billet in the high temperature section, ensures the uniformity of the billet heating, reduces the oxidation reaction time between the carbon atoms on the billet surface and the furnace gas, and controls the decarburization thickness of the product surface to 0.08mm-0.14mm, which can improve the fatigue life and surface quality of the automotive steering gear wire mother steel, reduce the customer's turning processing costs, and has a high use value. DETAILED DESCRIPTION

[0019] The technical solution of the present invention is further described below in conjunction with specific implementation methods.

[0020] The heating method for reducing decarburization on the surface of steel for steering gear nut of the present invention comprises the following steps:

[0021] 1) The 180mm×180mm billet rolled after billet opening is subjected to surface grinding for 1mm, and the oxidized iron scale on the surface of the billet is removed once, and the oxidized iron scale on the surface is ground clean.

[0022] 2) The secondary heating time in the heating furnace is controlled within 140min-180min; when the billet is put into the furnace, the method of loading one empty step is adopted to control the heating time of the preheating section in the heating furnace to be controlled within 30min-50min, and the heating time of the heating section is controlled within 50min-70min; the heating time of the soaking section is controlled at about 60min, which reduces the high-temperature residence time of the billet in the heating furnace, reduces the reaction time of the carbon atoms on the surface of the billet with the furnace gas, and reduces the thickness of the oxidation decarburization layer on the surface of the finished product.

[0023] 3) The heating temperature is controlled at 950℃-1100℃, and the soaking temperature is controlled at 1080℃-1120℃ to reduce high-temperature oxidation. The preheating temperature is ≤800℃; the heating temperature is ≤950℃, and the heating temperature is 1020℃-1100℃; the soaking temperature is 1080℃-1140℃, and the soaking temperature is 1080℃-1120℃. Since the blank is ground after slab rolling, the process of rapid heating in a short time is adopted to reduce the oxidation rate of the blank in a high temperature environment, thereby reducing the thickness of the decarburized layer.

[0024]

[0025] During rolling, the 320mm×480mm section billet smelted in an electric furnace is heated to 1240°C for billet opening and rolling into a 180mm×180mm×11000mm billet, and then heated and rolled into a steel for a steering screw mother, producing a Φ30mm-60mm round steel. 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.

[0026] The chemical composition of the steel for the steering gear nut of the present invention is as follows: 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.

[0027] The present invention controls the heating time and the heating temperature, reduces the residence time of the blank in the high temperature section, ensures the uniformity of the blank heating, reduces the oxidation reaction time of the carbon atoms on the surface of the blank with the furnace gas, and controls the decarburization thickness of the product surface to be 0.08mm-0.14mm. The fatigue life and surface quality of the mother steel for automobile steering gears can be improved, the turning processing cost of customers can be reduced, and the invention has a high use value.

Claims

1. A heating method for reducing surface decarburization of steel for steering gear nut, characterized in that: The steps include: 1) The surface of the rolled billet after billeting is ground by 1 mm to remove the primary iron oxide scale on the surface of the billet; 2) The secondary heating time in the heating furnace is controlled within 140min-180min; 3) The heating temperature is controlled at 950℃-1100℃, and the soaking temperature is controlled at 1080℃-1120℃ to reduce high temperature oxidation.

2. The heating method for reducing surface decarburization of steering gear nut steel according to claim 1, characterized in that: The billet rolled after the billet opening is a 180mm×180mm billet.

3. The heating method for reducing surface decarburization of steering gear nut steel according to claim 1, characterized in that: During the rolling, a 320mm×480mm cross-section billet smelted in an electric furnace is heated to 1240°C for billet opening and rolling into a 180mm×180mm×11000mm billet, which is then heated and rolled into steel for steering gear nut to produce Φ30mm-60mm round steel.

4. The heating method for reducing surface decarburization of steering gear nut steel according to claim 3, characterized in that: During the 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 installed above the cooling bed.

5. The heating method for reducing surface decarburization of steering gear nut steel according to claim 1, characterized in that: The heating time in step 2) includes a preheating section heating time, a heating section heating time and a soaking section heating time.

6. The heating method for reducing surface decarburization of steering gear nut steel according to claim 5, characterized in that: The heating time of the preheating section is 30min-50min, and the temperature of the preheating section is ≤800°C.

7. The heating method for reducing surface decarburization of steering gear nut steel according to claim 6, characterized in that: The heating time of the heating section is 50min-70min, and the heating section includes heating section one and heating section two.

8. The heating method for reducing surface decarburization of steering gear nut steel according to claim 7, characterized in that: The temperature of the first heating stage is ≤950°C, and the temperature of the second heating stage is 1020°C-1100°C.

9. The heating method for reducing surface decarburization of steering gear nut steel according to claim 8, characterized in that: The heating time of the soaking section is 60 minutes, and the soaking section includes the first soaking section and the second soaking section.

10. The heating method for reducing surface decarburization of steering gear nut steel according to claim 9, characterized in that: The temperature of the first stage of the soaking is 1080°C-1140°C, and the temperature of the second stage of the soaking is 1080°C-1120°C.

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