Preparation method of special drilling tool hot-rolled round steel for coal mining

Abstract

The invention discloses a preparation method of hot-rolled round steel of a special drilling tool for coal mining, which specifically comprises the following steps: (1) blowing molten steel by using an electric furnace, alloying tapping after the furnace, and controlling the content of C in the tapping to be less than or equal to 0.06% and the content of P in the tapping to be less than or equal to 0.004%; (2) LF refining is conducted, the refining time is 50-100 min, and components are controlled; (3) after the components are qualified, carrying out VD vacuum degassing under the conditions that the vacuum degree is 0.55-0-6 mbar, the vacuum holding time is 20-30 minutes, carrying out soft blowing Ar stirring for 15-30 minutes, and enabling the slag surface to slightly move without light during static stirring; (4) carrying out four-flow casting on the molten steel through a bloom continuous casting machine, and adding crystallizer electromagnetic stirring and tail end electromagnetic stirring in the casting and solidification processes; (5) the cast blank is placed in a heating furnace and heated in a reducing atmosphere, and the heating temperature is controlled to be 1100-1280 DEG C; and (6) discharging from the furnace, descaling by high-pressure water, rolling in a rolling procedure, cooling by passing through a water tank after rolling, conveying to a cooling bed by a conveying roller, air-cooling after discharging from the cooling bed, and cooling and collecting the round steel pile.

Description

Technical Field

[0001] The invention relates to a method for preparing hot-rolled round steel for a special drilling tool for coal mining. Background Art

[0002] The amount of steel consumed in the process of coal mining is relatively large. Different mines consume about 7-13 tons of steel to produce 10,000 tons of coal. According to the construction of coal mines and coal production in my country, it is estimated that the national coal industry will consume about 4.8 million tons of steel in 2024. For a long time in the future, coal will still dominate the primary energy consumption structure in my country. The development of the coal industry will continue to drive the growth of steel demand. The implementation of coal industry policies and technological progress in the coal industry will drive the growth of steel demand.

[0003] With the continuous increase in the rate of mechanical mining, higher requirements are placed on the impact resistance and high toughness of steel. However, the current control level of banded structure of coal mining drill steel on the market is generally above level 2.5, which cannot meet the needs of users for high-end products. At the same time, research has found that the control of banded structure of round steel is at a relatively low level. Therefore, developing hot-rolled round steel for coal mining drill tools to solve the problem of banded structure not only has very good social and economic benefits, but also has good market prospects. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method for preparing hot-rolled round steel for special drilling tools for coal mining in view of the shortcomings of the above prior art.

[0005] The technical solution of the present invention to solve the above technical problems is: a method for preparing hot-rolled round steel for special drilling tools for coal mining, the method specifically comprising the following steps: (1) Use electric furnace to blow molten steel, and alloy the steel after the furnace, with the C content of the steel being ≥ 0.06% and the P content of the steel being ≤ 0.006%; (2) LF refining, refining time 50-100 min, and control the composition, specifically: C 0.30%-0.40%, Si 0.15%-0.35%, Mn 0.80%-1.20%, Cr 0.80%-1.20%, Mo 0.20%-0.40%, Ti 0.010-0.035%, P≤0.008%, S≤0.002%, Al / N≥2; (3) After the ingredients are qualified, VD vacuum degassing is carried out, the vacuum degree is 0.55-0-6mbar, the vacuum is maintained for 20-30min, soft blowing Ar is stirred for 15-30min, and the slag surface moves slightly during static stirring without light; (4) The molten steel is cast by four streams of a large square billet continuous casting machine, and electromagnetic stirring of the crystallizer and the end of the crystallizer are added during the casting and solidification process; (5) The cast billet is placed in a heating furnace and heated in a reducing atmosphere. The heating temperature is controlled at 1100-1280°C and the temperature difference of the billet section is less than 25°C. (6) After being taken out of the furnace, the steel is descaled by high-pressure water and then sent to the rolling process for rolling. After rolling, it passes through a water tank for cooling, is transported to a cooling bed by conveyor rollers, and is air-cooled after leaving the cooling bed. The round steel is piled up for cooling and collected to obtain hot-rolled round steel for special drilling tools for coal mining.

[0006] The present invention further defines the scheme: Preferably, the molten steel in (4) is cast by a four-strand bloom continuous casting machine, the superheat is controlled at 15°C-35°C, and the casting speed is 0.45m / min-0.50m / min.

[0007] Preferably, in step (4), the crystallizer electromagnetic stirring frequency is 1.3 Hz and the current is 540 A; the end electromagnetic stirring frequency is 6 Hz and the current is 500 A.

[0008] Preferably, in step (5), the heating section of the heating furnace is controlled at 1180°C-1250°C, and the soaking section is controlled at 1220-1280°C.

[0009] Preferably, in the intermediate rolling (6), the starting rolling temperature of the intermediate rough rolling is 1050-1150°C, and after 6 passes of rough rolling, the intermediate finishing rolling is performed; the starting rolling temperature of the intermediate rolling is 950-1050°C, and the final rolling temperature is 900-920°C.

[0010] Preferably, the steel in (6) is cooled in a water tank after rolling, and is transported to a cooling bed via a conveyor roller, the temperature of the cooling bed is 650-680°C, and air-cooled, the temperature of the lower cooling bed is lower than 440°C.

[0011] The beneficial effects of the present invention are as follows: the present invention controls the superheat of molten steel, the drawing speed, the electromagnetic stirring parameters, etc. during the continuous casting process, and controls the air cooling during the rolling process, so as to achieve the control of the strip structure of round steel below level 2.5, meet the needs of high-end coal mining drill tools, improve mining efficiency, and reduce steel loss. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is the banded structure diagram of the edge of the round steel of Example 1; Figure 2 This is a quarter banded structure diagram of round steel in Example 1; Figure 3 This is the banded structure diagram of the round steel core of Example 1. DETAILED DESCRIPTION Example

[0013] This embodiment provides a method for preparing hot-rolled round steel for coal mining special drilling tools, and the method specifically comprises the following steps: (1) Use electric furnace to blow molten steel, and alloy the steel after the furnace, with the C content of the steel being ≥ 0.06% and the P content of the steel being ≤ 0.006%; (2) LF refining, refining time 50-100 min, and control the composition, specifically: C 0.30%-0.40%, Si 0.15%-0.35%, Mn 0.80%-1.20%, Cr 0.80%-1.20%, Mo 0.20%-0.40%, Ti 0.010-0.035%, P≤0.008%, S≤0.002%, Al / N≥2; (3) After the ingredients are qualified, VD vacuum degassing is carried out, the vacuum degree is 0.55mbar, the vacuum is maintained for 20min, soft Ar is blown and stirred for 15min, and the slag surface moves slightly and no light is seen during static stirring; (4) The molten steel is cast by a four-stream continuous casting machine with the superheat controlled at 15°C-35°C and the casting speed at 0.45m / min-0.50m / min. During the casting and solidification process, electromagnetic stirring of the mold and electromagnetic stirring of the end are added. The frequency of the electromagnetic stirring of the mold is 1.3Hz and the current is 540A; the frequency of the electromagnetic stirring of the end is 6Hz and the current is 500A. (5) The cast billet is placed in a heating furnace and heated in a reducing atmosphere. The heating section is controlled at 1180°C-1250°C, the soaking section is controlled at 1220°C, and the temperature difference of the billet section is less than 25°C; (6) After being discharged from the furnace, the steel is descaled by high-pressure water and then sent to the rolling process for rolling. The starting temperature of the rough rolling is 1100°C. After 6 passes of rough rolling, the intermediate and finishing rolling is performed. The starting temperature of the intermediate rolling is 990°C, and the final rolling temperature is 920°C. After rolling, the steel passes through a water tank for cooling and is transported to a cooling bed through a conveyor roller. The upper cooling bed temperature is 680°C, air-cooled, and the lower cooling bed temperature is 440°C. The round steel is pile-cooled and collected to obtain hot-rolled round steel for coal mining drilling tools. (7) Heat treatment process: quenching heating temperature 875℃, in the furnace for 180 minutes, cooling with quenching liquid, tempering heating temperature 560℃-580℃, in the furnace for 150 minutes, and water cooling to room temperature after taking out of the furnace.

[0014] In this embodiment, the mechanical properties are tested by sampling according to the standard requirements and compared with the performance of conventional drill tool steel. The strength and toughness of the product of Example 1 are better than those of conventional products.

[0015] The banded structure detection implementation standard of this embodiment is based on the requirements of GB / T 34474. The banded structures at the edge, quarter and core of the round steel are detected and graded respectively. The banded structure meets the requirements of ≤2.5 level. For details, see the attached manual. Figure 1-3 .

[0016] In addition to the above embodiments, the present invention may also have other implementation modes. Any technical solution formed by equivalent replacement or equivalent transformation falls within the protection scope required by the present invention.

Claims

1. A method for preparing hot-rolled round steel for special drilling tools for coal mining, characterized in that: The method specifically comprises the following steps: (1) Use electric furnace to blow molten steel, and alloy the steel after the furnace, with the steel C content ≥ 0.06% and the steel P content ≤ 0.006%; (2) LF refining, refining time 50-100 min, and control the composition, specifically: C 0.30%-0.40%, Si 0.15%-0.35%, Mn 0.80%-1.20%, Cr 0.80%-1.20%, Mo 0.20%-0.40%, Ti 0.010-0.035%, P≤0.008%, S≤0.002%, Al / N≥2; (3) After the ingredients are qualified, VD vacuum degassing is carried out, the vacuum degree is 0.55-0-6mbar, the vacuum is maintained for 20-30min, soft blowing Ar is stirred for 15-30min, and the slag surface moves slightly during static stirring without light; (4) The molten steel is cast by four streams of a large square billet continuous casting machine, and electromagnetic stirring of the crystallizer and the end of the crystallizer are added during the casting and solidification process; (5) The cast billet is placed in a heating furnace and heated in a reducing atmosphere. The heating temperature is controlled at 1100-1280°C and the temperature difference of the billet section is less than 25°C. (6) After being taken out of the furnace, the steel is descaled by high-pressure water and then sent to the rolling process for rolling. After rolling, it passes through a water tank for cooling, is transported to a cooling bed by conveyor rollers, and is air-cooled after leaving the cooling bed. The round steel is piled up for cooling and collected to obtain hot-rolled round steel for special drilling tools for coal mining.

2. The method for preparing hot-rolled round steel for coal mining special drilling tools according to claim 1, characterized in that: The molten steel in (4) is cast by four streams of a large square billet continuous casting machine, the superheat is controlled at 15°C-35°C, and the casting speed is 0.45m / min-0.50m / min.

3. The method for preparing hot-rolled round steel for coal mining special drilling tools according to claim 1, characterized in that: In the step (4), the crystallizer electromagnetic stirring frequency is 1.3 Hz and the current is 540 A; the end electromagnetic stirring frequency is 6 Hz and the current is 500 A.

4. The method for preparing hot-rolled round steel for coal mining special drilling tools according to claim 1, characterized in that: In the step (5), the heating section of the heating furnace is controlled at 1180°C-1250°C, and the soaking section is controlled at 1220°C-1280°C.

5. The method for preparing hot-rolled round steel for coal mining special drilling tools according to claim 1, characterized in that: In the intermediate rolling (6), the starting rolling temperature of the intermediate rough rolling is 1050-1150°C, and after 6 passes of rough rolling, the intermediate finishing rolling is performed; the starting rolling temperature of the intermediate rolling is 950-1050°C, and the final rolling temperature is 900-920°C.

6. The method for preparing hot-rolled round steel for coal mining special drilling tools according to claim 1, characterized in that: After rolling, the steel is cooled in a water tank and transported to a cooling bed via a conveyor roller. The upper cooling bed temperature is 650-680°C. The steel is air-cooled and the lower cooling bed temperature is lower than 440°C.

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