1. A preparation method of high-quality sulfur-containing medium-carbon alloy steel is characterized by comprising the following steps:

(1) smelting in a primary smelting furnace, wherein the ingredients of the primary smelting furnace comprise 80-85% of molten iron and 15-20% of scrap steel in percentage by mass; the mass percent of C in the tapping content is more than or equal to 0.10%, and the tapping temperature is 1620-1640 ℃;

(2) in the refining position, performing primary power supply temperature rise on the molten steel in place, stopping power supply when the temperature of the molten steel is 40-50 ℃ higher than the liquidus temperature, measuring and sampling, judging components in the steel, and finely adjusting the components in the steel according to the components of the molten steel to meet the requirement of internal control components; adding 300kg of lime 100, 0-100kg of fluorite, 70-80kg of silicon carbide and 30-50kg of carbon powder; adding 40-50kg of silicon carbide, 20-30kg of carbon powder and 20-30kg of Al particles into the secondary power transmission; the content of sulfur in the refined steel grade is less than or equal to 0.005 percent;

(3) vacuum VD/RH: controlling the vacuum degree to be less than or equal to 67Pa, and keeping the vacuum degree for more than or equal to 20 min; after vacuum breaking, according to Al before vacuum and aluminum loss in the vacuum process, feeding an aluminum wire once according to the target mass percentage of 0.025-0.030%, feeding a calcium silicon wire according to the casting furnace number of 150 m/furnace and the continuous casting furnace number of 120 m/furnace, feeding a sulfur wire after the interval time is more than or equal to 8 minutes to achieve component internal control, and starting to calculate the soft blowing time to be more than or equal to 30 minutes after the components of the sampled steel meet the internal control requirement;

(4) continuous casting: baking the tundish before production, wherein the baking temperature of the tundish in an impact area is more than or equal to 1200 ℃; the temperature of a casting area is more than or equal to 1050 ℃; baking the tundish nozzle to be more than or equal to 950 ℃; argon blowing operation is carried out in the tundish for more than or equal to 5min before casting; and after the operation is finished, blocking a sampling hole in the tundish by using asbestos bonding, pouring and tapping.

2. The preparation method of high-quality sulfur-containing medium-carbon alloy steel according to claim 1, wherein the white slag time is controlled to be more than or equal to 20min, and the soft blowing time is controlled to be more than or equal to 20min after the content of sulfur in the steel grade is determined to be less than or equal to 0.005% in the step (2).

3. The method for preparing the high-quality sulfur-containing medium-carbon alloy steel according to claim 1, wherein the sulfur element is supplemented to the internal control after the vacuum in the step (3); and calculating the soft blowing time which is more than or equal to 30 min.

4. The method for preparing high-quality sulfur-containing medium-carbon alloy steel according to claim 1, wherein in the step (1), the molten iron comprises the components of P with the mass percent of less than or equal to 0.12%, Si with the mass percent of 0.30% -0.65%, and S with the mass percent of less than or equal to 0.045%.

5. The method for preparing the high-quality sulfur-containing medium-carbon alloy steel according to claim 1, wherein the process parameters of the continuous casting in the step (4) are a casting speed: 0.70-0.75m/min, specific water amount: 0.20-0.30L/kg, distribution ratio 36/39/25, initial stirring parameter of 150A/2Hz, and final stirring parameter of 100A/8 Hz.

6. The method for preparing high-quality sulfur-containing medium-carbon alloy steel according to claim 1, wherein in the step (1), during tapping, C powder is added into the steel, and then an aluminum ingot is added into the steel for precipitation deoxidation to perform alloying.

7. The method for preparing high quality medium carbon steel alloy containing sulfur according to claim 6, wherein in the step (1), after the alloying treatment of the steel, the adjustment is performed according to the lower line + -2 required by the steel grade composition.

8. The method for preparing high quality medium carbon sulfur-containing alloy steel according to any one of claims 1 to 7, wherein argon shield is adopted in the whole process of the preparation method.

9. High quality sulfur-containing medium carbon alloy steel prepared by the preparation method according to claims 1-8.

Background

Sulfur is a harmful element in steel, causes hot brittleness of steel, reduces ductility and toughness of steel, and simultaneously reduces corrosivity of steel. However, with the development of the machining industry, the cutting speed, precision and automation degree are continuously improved, and higher requirements are made on the cutting performance of steel. Sulfur-containing steels have been widely used because of their good machinability. The sulfur content is generally controlled to be above 0.025%. Domestic sulfur-containing steel is generally concentrated in special steel enterprises, and due to the characteristics of steel types, the production difficulty is high, the process technology is not complete, and only a few enterprises can stably produce the sulfur-containing steel.

The major difficulty in producing sulfur-containing steel is that sulfur reacts with Ca in steel to produce CaS and Al₂O₃The inclusions are the main reasons for nozzle nodulation, so that the castability of the steel is poor and the production difficulty is increased. On the other hand, sulfur reacts with Mn element in steel to produce MnS low-melting-point material, and the casting blank is mainly acted by thermal stress, structural stress and mechanical stress in the solidification process. The thermal stress is stress generated by nonuniform temperature and nonuniform shrinkage of the surface and the interior of the continuous casting billet and is mainly in front of and in the secondary cooling zone. The casting blank generally generates a crack source in the crystallizer, and secondary expansion is formed on the crack through secondary cooling and precipitation of low-melting-point substances. Because the corner of the square billet is two-dimensional, the subcutaneous cracks are mostly generated at the position close to the corner. Under the same process parameters, the proportion of the subsurface crack defects of the sulfur-containing medium carbon steel is more than 20% higher than that of the normal medium carbon steel, and the sulfur-containing steel nodulation is caused.

Disclosure of Invention

The invention provides high-quality sulfur-containing medium-carbon alloy steel and a preparation method thereof, aiming at solving the problem of accretion of sulfur-containing steel in a steel wire produced by metallurgy in the prior art.

The technical scheme of the invention is as follows: a preparation method of high-quality sulfur-containing medium-carbon alloy steel comprises the following steps:

(1) smelting in a primary smelting furnace, wherein the ingredients of the primary smelting furnace comprise 80-85% of molten iron and 15-20% of scrap steel in percentage by mass; the mass percent of C in the tapping content is more than or equal to 0.10%, and the tapping temperature is 1620-1640 ℃;

(2) in the refining position, performing primary power transmission temperature rise on the molten steel in place, stopping power transmission when the temperature of the molten steel is 40-50 ℃ higher than the liquidus temperature, performing measurement sampling, and judging components in the steel; adding 300kg of lime 100, 0-100kg of fluorite, 70-80kg of silicon carbide and 30-50kg of carbon powder; adding 40-50kg of silicon carbide, 20-30kg of carbon powder and 20-30kg of Al particles into the secondary power transmission; the content of sulfur in the refined steel grade is less than or equal to 0.005 percent;

(3) vacuum VD/RH: controlling the vacuum degree to be less than or equal to 67Pa, and keeping the vacuum degree for more than or equal to 20 min; after vacuum breaking, according to Al before vacuum and aluminum loss in the vacuum process, feeding an aluminum wire once according to the target mass percentage of 0.025-0.030%, feeding a calcium silicon wire according to the casting furnace number of 150 m/furnace and the continuous casting furnace number of 120 m/furnace, feeding a sulfur wire after the interval time is more than or equal to 8 minutes to achieve component internal control, and starting to calculate the soft blowing time to be more than or equal to 30 minutes after the components of the sampled steel meet the internal control requirement;

(4) continuous casting: baking the tundish before production, wherein the baking temperature of the tundish in an impact area is more than or equal to 1200 ℃; the temperature of a casting area is more than or equal to 1050 ℃; baking the tundish nozzle to be more than or equal to 950 ℃; argon blowing operation is carried out in the tundish for more than or equal to 5min before casting; and after the operation is finished, blocking a sampling hole in the tundish by using asbestos bonding, pouring and tapping.

And (3) after the content of sulfur in the steel grade is determined to be less than or equal to 0.005 percent in the step (2), controlling the white slag time to be more than or equal to 20min, and controlling the soft blowing time to be more than or equal to 20 min.

Supplementing the sulfur element to the internal control after the vacuum in the step (3); and calculating the soft blowing time which is more than or equal to 30 min.

In the step (1), the molten iron comprises P with a mass percent of less than or equal to 0.12%, Si with a mass percent of 0.30% -0.65%, and S with a mass percent of less than or equal to 0.045%.

The technological parameters of continuous casting in the step (4) are casting speed: 0.70-0.75m/min, specific water amount: 0.20-0.30L/kg, distribution ratio 36/39/25, initial stirring parameter of 150A/2Hz, and final stirring parameter of 100A/8 Hz.

During the tapping process, C powder is firstly added into steel, and then aluminum ingots are added into the steel for precipitation deoxidation and alloying.

After alloying treatment is carried out on the tapping, the adjustment is carried out according to the off-line +/-2 of the component requirement of the steel grade.

Argon is adopted for protection in the whole process of the preparation method.

On the other hand, the invention provides high-quality sulfur-containing medium-carbon alloy steel which is prepared by the preparation method.

The invention has the beneficial effects that:

according to the invention, through improvement of the preparation method of the alloy steel, the molten steel is subjected to primary power transmission temperature rise, and when the temperature of the molten steel is higher than the liquidus temperature by 40 ℃, power transmission is stopped for measurement and sampling, so that the components in the steel are judged. Adding lime, fluorite, diffusion deoxidizer silicon carbide and carbon powder; the secondary power transmission diffusion deoxidizer uses silicon carbide, carbon powder and Al particles; controlling the white slag time to be more than or equal to 20 min. The soft blowing time is more than or equal to 20min, and the micro motion of the slag surface is ensured. The S content in the molten steel is removed, and the S is supplemented subsequently, so that the reaction of the steel S and other chemical elements of the steel S to produce inclusions is reduced, and the problem of sulfur-containing steel nodulation in a steel wire produced by metallurgy is solved; and has the advantage of simple operation.

Drawings

FIG. 1 is a schematic diagram showing the results of lateral macroscopic examination in example 1 of the present invention;

FIG. 2 is a schematic diagram showing the results of longitudinal macroscopic examination in example 1 of the present invention;

FIG. 3 shows the results of segregation test in example 1 of the present invention.

Detailed Description

The technical solutions of the present invention are further described below with reference to the following examples, but the present invention is not limited thereto, and any modifications or equivalent substitutions may be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention. The process equipment or apparatus not specifically mentioned in the following examples are conventional in the art, and if not specifically mentioned, the raw materials and the like used in the examples of the present invention are commercially available; unless otherwise specified, the technical means used in the examples of the present invention are conventional means well known to those skilled in the art.

The invention provides a preparation method of high-quality sulfur-containing medium-carbon alloy steel, which comprises the following steps:

(1) 80-85% of molten iron and 20-25% of scrap steel are used for smelting in the primary smelting furnace, and the molten iron comprises the following components, by mass, not more than 0.12% of P, 0.30-0.65% of Si and not more than 0.045% of S; the temperature of molten iron is more than or equal to 1200 ℃. The tapping temperature C is more than or equal to 0.10 percent, the tapping temperature P is less than or equal to 0.012 percent and the tapping temperature 1610 and 1640 ℃ are adopted.

(2) The refining site firstly removes the S element in the steel to ensure that the S content is less than or equal to 0.005 percent. And all internal control of components is ensured before secondary power transmission.

(3) After vacuum, the sulfur element is supplemented to the internal control, and the soft blowing time is calculated.

(4) When all the components are adjusted to be controlled internally, the soft blowing time is calculated, and the soft blowing time is more than or equal to 20 min. The secondary casting head furnace can properly increase the temperature of molten steel and improve the casting performance of continuous casting. Ensuring the micro motion of the slag surface and preventing the secondary oxidation caused by the contact control of molten steel.

(5) And (3) blowing the tundish with argon before continuous casting and casting, wherein the blowing time is more than or equal to 5min, and reducing harmful gas in the tundish.

(6) Argon seal protection is used in the whole process, and secondary oxidation of molten steel is prevented.

(7) The tundish in the continuous casting process ensures constant temperature and constant speed blank drawing, and the secondary cooling uses a weak cooling mode.

(8) The continuous casting process parameters are as follows: the pulling speed is 0.70m/min, the secondary cooling specific water amount is 0.2L/kg, the distribution ratio is 38/38/24, the crystallizer water amount is 2450L/min, the initial stirring parameter is 150A/2Hz, the final stirring parameter is 100A/8Hz, and the soft reduction parameter is 0/2/4/4. The center porosity of the produced casting blank is less than or equal to grade 1, the shrinkage cavity is less than or equal to grade 0, and no crack defect exists.

Using a five-machine five-flow 250 x 280 bloom continuous casting machine for production, wherein the drawing speed is as follows: 0.70m/min, specific water amount: 0.20kg/t (static mode); the distribution ratio of the secondary cooling section is 38/38/24, the initial stirring parameter is 150A/2Hz, and the final stirring parameter is 100A/8 Hz. The soft reduction parameter 0/2/4/4 is that the casting blank has low-power rating center porosity less than or equal to 1 grade, shrinkage cavity less than or equal to 0.5 grade, and segregation test less than or equal to 1.05. The center segregation index is less than or equal to 1.08.

Before continuous casting production, argon blowing operation is carried out on the tundish, so that the oxygen content in the tundish is reduced, and secondary oxidation of molten steel is reduced.

Wherein: (1) primary smelting furnace control

1) The primary smelting furnace is used for preparing 85% of molten iron and 15% of scrap steel, so that the maximum heat energy is released, the tapping C is more than or equal to 0.10%, and the tapping temperature is 1620-1640.

2) The alloy is roasted in advance, so that the heat loss of the molten steel is reduced when the alloy is contacted with the molten steel, and the yield of the alloy is ensured to the maximum extent by deep deoxidation.

3) During the tapping process, C powder is firstly added into the steel to react with oxygen in the molten steel to generate CO₂When the steel is added with aluminum ingots for precipitation and deoxidation and the tapping is carried out at 1/2, the alloying is carried out, thereby improving the yield of the alloy to the maximum extent and reducing the cost.

(2) Refining station (LF)

1) And (3) carrying out primary power transmission temperature rise on the in-place molten steel, and stopping power transmission for measurement sampling when the temperature of the molten steel is 40 ℃ higher than the liquidus temperature, so as to judge the components in the steel.

2) Adding 300Kg of lime 100-100 Kg, fluorite 0-100Kg, silicon carbide as diffusion deoxidizer 70-80Kg and carbon powder 30-50 Kg. 40-50Kg of silicon carbide, 20-30Kg of carbon powder and 20-30Kg of Al particles are used as the secondary power transmission diffusion deoxidizer.

3) The components of the molten steel are finely adjusted, the components are ensured to enter an internal control range, and meanwhile, the control of the S element is ensured to be less than or equal to 0.003 percent. The harmful elements in the steel are minimized.

4) When the components completely enter the internal control, the components leave the station.

(3) Vacuum operation

1) After vacuum, the sulfur element is added to the internal control. The soft blowing time is calculated to be more than or equal to 20 min.

2) The refining position is carried out by a method of firstly desulfurizing and then supplementing sulfur.

(4) Continuous casting

1) Constant temperature and constant speed: the drawing speed and the drawing temperature are important factors for controlling the quality of the casting blank, the component segregation of the casting blank is reduced through the control of the superheat degree and the drawing speed, the solidification position of the tail end is stabilized, and the quality of the casting blank reaches the expected effect by matching with soft reduction.

2) A cooling system: as the result of natural separation and crystallization in the solidification process, segregation of components can be caused in the solidification process of the casting blank, so that reasonable control and cooling are an important means for solving the segregation of the casting blank. If the secondary cooling strength is not enough, the temperature of the casting blank is high, and the volume of the columnar crystal expands continuously in the growth process, so that the casting blank is easy to bulge and dent, and the corner crack defect is generated. If the secondary cooling strength is too high, columnar crystals develop in the solidification process of the casting blank, which affects the uniformity of the internal structure and components of the casting blank and even the crystal penetration. Therefore, the cooling intensity is ensured to be sufficient, and the cooling water is reasonably distributed.

3) An electromagnetic stirring technology: electromagnetic stirring is taken as an important technology for improving the segregation index of the casting blank at present, on one hand, the thermodynamic and kinetic conditions of columnar crystal development inhibition, component uniformity promotion and floating and refining of inclusions are promoted, and then the solidification structure of the casting blank is controlled to improve the quality of the casting blank. On the other hand, the flow of molten steel is increased, the heat transfer between solidification phases is improved, the superheat degree is favorably reduced, the temperature gradient of the solidification front is reduced, and the directional increase of columnar crystals is inhibited.

4) The surface temperature of the casting blank is controlled to be in a certain temperature return range, so that overlarge thermal stress caused by repeated temperature return of the molten steel is prevented.

The invention solves the problem of accretion of sulfur-containing steel in the steel wire produced by metallurgy; and has the advantage of simple operation.

Example 1

(1) Smelting in a primary smelting furnace, wherein the ingredients of the primary smelting furnace comprise 85% of molten iron and 15% of scrap steel; the tapping content is 0.10 percent, and the tapping temperature is 1620 ℃; the molten iron comprises 0.12% of P, 0.5% of Si and 0.045% of S;

(2) in the refining position, performing primary power transmission temperature rise on the molten steel in place, stopping power transmission when the temperature of the molten steel is 40 ℃ higher than the liquidus temperature, performing measurement sampling, and judging components in the steel; adding 100kg of lime, 70kg of silicon carbide and 30kg of carbon powder; adding 40kg of silicon carbide, 20kg of carbon powder and 20kg of Al particles into the secondary power transmission; the content of sulfur in the refined steel grade is 0.005 percent; controlling the white slag time to be 20 min; the soft blowing time is 20 min;

(3) vacuum VD/RH: controlling the vacuum degree to be 67Pa and the holding time to be 20 min; feeding an aluminum wire once according to the target 0.025 percent, feeding a silico-calcium wire according to the casting furnace number of 150 m/furnace and the continuous casting furnace number of 120 m/furnace after vacuum breaking according to Al before vacuum and the aluminum loss in the vacuum process, feeding a sulfur wire after the interval time is 8 minutes to achieve internal control of components, and starting to calculate the soft blowing time to be 30 minutes after the components of the sampled steel reach the internal control requirement;

(4) continuous casting: baking the tundish before production, wherein the baking temperature of the tundish in an impact area is 1200 ℃; the temperature of a casting area is 1050 ℃; baking the tundish nozzle to 950 ℃; argon blowing operation is carried out in the tundish for 5min before casting; and after the operation is finished, the sampling port in the tundish is blocked by using asbestos adhesion, and protective pouring is performed. The technological parameters of continuous casting are: 0.70m/min, specific water amount: 0.20L/kg, distribution ratio 36/39/25, head stirring parameter of 150A/2Hz, and end stirring parameter of 100A/8 Hz. In the step (1), during tapping, C powder is added into steel, and then aluminum ingots are added into the steel for precipitation deoxidation and alloying. The whole process of the preparation method adopts argon protection.

A high-quality sulfur-containing medium-carbon alloy steel is prepared by a preparation method.

Referring to the attached drawings 1-3, the center porosity is less than or equal to 1 level, the shrinkage cavity is less than or equal to 0.5 level, and the center segregation index is less than or equal to 1.08. No subcutaneous crack defect.

Example 2

A preparation method of high-quality sulfur-containing medium-carbon alloy steel comprises the following steps:

(1) smelting in a primary smelting furnace, wherein the ingredients of the primary smelting furnace comprise 80% of molten iron and 20% of scrap steel; the tapping content is 0.20 percent, and the tapping temperature is 1640 ℃; the molten iron comprises 0.02% of P, 0.3% of Si and 0.035% of S.

(2) In the refining position, performing primary power transmission temperature rise on the molten steel in place, stopping power transmission when the temperature of the molten steel is higher than the liquidus temperature by 45 ℃, performing measurement sampling, and judging components in the steel; adding 100kg of lime, 100kg of fluorite, 70kg of silicon carbide and 30kg of carbon powder; adding 50kg of silicon carbide, 30kg of carbon powder and 30kg of Al particles into the secondary power transmission; the content of sulfur in the refined steel grade is 0.003 percent; controlling the white slag time to be 30 min;

(3) vacuum VD/RH: controlling the vacuum degree to be 66Pa and the holding time to be 22 min; feeding an aluminum wire at one time according to the target 0.030 percent, feeding a silicon calcium wire at the furnace number of 150 m/furnace for casting and the furnace number of 120 m/furnace for continuous casting after vacuum breaking according to Al before vacuum and aluminum loss in the vacuum process, feeding a sulfur wire after the interval time is 9 minutes to achieve internal control of components, and starting to calculate the soft blowing time to be 40 minutes after the components of the sampled steel reach the internal control requirement;

(4) continuous casting: baking the tundish before production, wherein the baking temperature of the tundish in an impact area is 1250 ℃; the temperature of a casting area is 1080 ℃; baking the tundish nozzle to 1050 ℃; argon blowing operation is carried out in the tundish for 6min before casting; and after the operation is finished, the sampling port in the tundish is blocked by using asbestos adhesion, and protective pouring is performed. The technological parameters of continuous casting are: 0.70-0.75m/min, specific water amount: 0.20-0.30L/kg, distribution ratio 36/39/25, initial stirring parameter of 150A/2Hz, and final stirring parameter of 100A/8 Hz. In the step (1), during the tapping process, C powder is added into steel, and then aluminum ingots are added into the steel for precipitation deoxidation and alloying. Argon is adopted for protection in the whole process of the preparation method.

High-quality sulfur-containing medium-carbon alloy steel is prepared by the preparation method.

Example 3

(1) Smelting in a primary smelting furnace, wherein the ingredients of the primary smelting furnace comprise 83% of molten iron and 17% of scrap steel; the tapping content C is 0.10 percent, and the tapping temperature is 1630 ℃; the molten iron had a composition of P0.12%, Si 0.65%, and S0.045%.

(2) In the refining position, performing primary power transmission temperature rise on the molten steel in place, stopping power transmission when the temperature of the molten steel is higher than the liquidus temperature by 50 ℃, performing measurement sampling, and judging components in the steel; adding 200kg of lime, 50kg of fluorite, 75kg of silicon carbide and 40kg of carbon powder; adding 44kg of silicon carbide, 25kg of carbon powder and 25kg of Al particles into the secondary power transmission; the content of sulfur in the refined steel grade is 0.005 percent; controlling the white slag time to be 20 min. The soft blowing time is 20 min;

(3) vacuum VD/RH: controlling the vacuum degree to be 67Pa and the holding time to be 20 min; after vacuum breaking, feeding an aluminum wire at one time according to Al before vacuum and aluminum loss in the vacuum process, feeding a calcium-silicon wire at the furnace number of casting of 150 m/furnace and the furnace number of continuous casting of 120 m/furnace according to the target of 0.025-0.030%, feeding a sulfur wire after the interval time is 8 minutes to achieve component internal control, and starting to calculate the soft blowing time to be 30 minutes after the components of the sampled steel reach the internal control requirement;

(4) continuous casting: baking the tundish before production, wherein the baking temperature of the tundish in an impact area is 1200 ℃; the temperature of a casting area is 1050 ℃; baking the tundish nozzle to 950 ℃; argon blowing operation is carried out in the tundish for 5min before casting; and after the operation is finished, the sampling port in the tundish is blocked by using asbestos adhesion, and protective pouring is performed. The technological parameters of continuous casting are: 0.72m/min, specific water amount: 0.23L/kg, distribution ratio 36/39/25, head stirring parameter of 150A/2Hz, and end stirring parameter of 100A/8 Hz.

Argon is adopted for protection in the whole process of the preparation method.

A high-quality sulfur-containing medium-carbon alloy steel is prepared by a preparation method.

According to the invention, through improvement of the preparation method of the alloy steel, the S content in the molten steel is removed, and the S is supplemented subsequently, so that the reaction of the steel S and other chemical elements of the steel S to produce inclusions is reduced, and the problem of sulfur-containing steel nodulation in a steel wire produced by metallurgy is solved; and has the advantage of simple operation.