A method for smelting 300 series stainless steel using electric furnace slag steel

Abstract

The present invention discloses a method for smelting 300 series stainless steel using electric furnace slag steel. Before the electric furnace starts arcing, small-grain slag steel is prepared and laid on the furnace bottom. After arcing, it is melted during the smelting process. By utilizing the characteristics of low price and high molten steel yield of small-grain slag steel, not only the slag steel of the electric furnace is recycled, but also the amount of nickel alloy used in smelting 300 series stainless steel in the electric furnace is reduced, the batching cost of the electric furnace is reduced, and the production cost of the enterprise is also reduced. The present invention converts the 300 series slag steel produced by the electric furnace into raw materials for electric furnace smelting after processing, turning waste into treasure, and realizing the recycling of electric furnace slag steel.

Description

Technical Field

[0001] The invention relates to the technical field of stainless steel smelting, and in particular to a method for smelting 300 series stainless steel by using electric furnace slag steel. Background Art

[0002] With the continuous rise in nickel prices, the production cost of 300 series stainless steel has gradually increased, and market competition among enterprises has become increasingly fierce. Reducing the production cost of 300 series stainless steel is the only way for enterprises to survive and develop. In the process of smelting scrap steel in electric furnaces, metallurgical slag will be produced, and its total amount accounts for about 12% of the molten steel output. Since electric furnace slag steel contains carbon (C), silicon (Si), chromium (Cr), nickel (Ni) and other elements, especially the nickel content in slag steel accounts for 5%, if the slag can be recycled, the production cost of 300 series stainless steel can be effectively reduced. Summary of the invention

[0003] The purpose of the present invention is to realize the recycling of electric furnace slag steel and provide a method for smelting 300 series stainless steel using electric furnace slag steel, so as to reduce the production cost of 300 series stainless steel.

[0004] To achieve its purpose, the present invention adopts the following technical solution:

[0005] A method for smelting 300 series stainless steel using electric furnace slag steel comprises the following steps:

[0006] Step 1, preparation of small-grain slag steel: 300 series electric furnace slag steel is washed and magnetically separated to remove waste slag and then air-dried until the moisture content is less than 1%. When the slag steel contains C 2.0%, Si 2.0%, Cr 1.5%, and Ni 5% by weight, it is bagged as small-grain slag steel and sent to the material yard for use in the electric furnace;

[0007] Step 2: Charging of small-grain slag steel: Before the electric furnace starts arcing, the small-grain slag steel and coke prepared in step 1 are laid on the furnace bottom at the same time, and the weight ratio of the small-grain slag steel to the coke is 1:1;

[0008] Step 3: Melting of small-grain slag steel: Use full cold material smelting, supply power reasonably during the melting period, blow oxygen to assist melting, and spray carbon powder to form foam slag;

[0009] a. Reasonable power supply: After the electric furnace starts arcing, low voltage level is used for power supply in the first 2-5 minutes. After the electrode arc is completely buried in the charge, high power and high voltage level is used for power supply;

[0010] b. Oxygen blowing to assist melting: When the charge temperature reaches above 900°C, oxygen is blown to form a molten pool more quickly;

[0011] c. Making foam slag: When the power consumption of the electric furnace is 12000-20000KWh, oxygen blowing and carbon powder injection are carried out to make slag. When the height of the foam slag reaches 500mm, the power supply level is reduced to 18-25 levels;

[0012] d. Reduction steelmaking: When the electric furnace power consumption is 38000-42000KWh, the oxygen consumption is 2000-2500NM 3 When the silicon content of molten steel is 0.3-0.4% and the temperature reaches above 1580℃, it enters the reduction stage. The oxygen gun at the furnace door is switched to nitrogen, and small-grain ferrosilicon is sprayed for reduction and desulfurization operation, and then the steel is tapped.

[0013] As a preferred embodiment of the technical solution of the present invention, the water washing magnetic separation is to grind the 300 series electric furnace slag steel with a water-milled ball mill, and then enter the 18-mesh shaking table for water washing gravity separation, and the small particles of 10-40 mm above the shaking table are sent to the receiving bin, and the waste slag is flushed into the waste slag pool with water.

[0014] Preferably, in step three, the low voltage level is 12-14 levels, and the high power high voltage level is 4-7 levels.

[0015] Preferably, in step 3, during the oxygen blowing and melting operation, the oxygen blowing rate is 2000-3000 NM 3 / h.

[0016] Preferably, in step three, the reduction desulfurization time is 4-6 minutes; after the reduction is completed, the steel slag mixed flushing operation is carried out, and lime powder is manually thrown along with the steel flow for desulfurization again.

[0017] Preferably, the total injection amount of the small-grain ferrosilicon is 200 kg, and the injection time is 2-3 minutes.

[0018] The beneficial effects of the present invention are:

[0019] 1. The 300 series slag steel produced by the electric furnace is processed and turned into raw materials for electric furnace smelting, turning waste into treasure and realizing the recycling of electric furnace slag steel. In the case of continued rise in nickel prices and difficulties in procurement, the recycling of resources can effectively alleviate the shortage of raw materials for electric furnace smelting of 300 series stainless steel.

[0020] 2. Small-grained slag steel has the characteristics of low price and high molten steel yield. Using small-grained slag steel to smelt 300 series stainless steel can effectively reduce the use of nickel alloy, reduce the ingredient cost of the electric furnace, and thus reduce the production cost of 300 series stainless steel.

[0021] 3. After calculation, excluding the processing cost of slag, the cost of ingredients can be reduced by about 2,000 yuan when using 1 ton of small-grained slag steel in an electric furnace. DETAILED DESCRIPTION

[0022] The present invention is described in detail below through specific embodiments.

[0023] The composition of the small-grained slag steel described in the following embodiments of the present invention, measured by weight percentage, includes C 2.0%, Si 2.0%, Cr 1.5%, and Ni 5%.

[0024] Example 1

[0025] Electric furnace production of S30408 ​​steel:

[0026] Step 1: Charging of small-grain slag steel: Before the electric furnace starts arcing, small-grain slag steel and coke are laid on the bottom of the furnace in a weight ratio of 1:1;

[0027] Step 2: Smelting of small slag steel:

[0028] a. Adopting full cold material smelting, the furnace composition contains C: 2.89%, Si: 1.41%, Ni%: 7.64%, Cr: 11.17%, P: 0.03%, S: 0.15%;

[0029] b. Melting and oxidation: After the electric furnace starts arcing, use 12-level voltage to supply power for 2 minutes; enter the main melting period, adjust the voltage intensity to 5 levels, and when the initial molten pool is formed in the furnace, blow oxygen, and continuously add 5 tons of nickel-iron 35 alloy and 5 tons of lime for slag making. When the scrap steel charge is completely melted and enters the flat pool operation, the voltage level is adjusted to 21 levels. When the charge temperature reaches 1500℃, dephosphorization operation is carried out, and the molten clear sample is taken for rapid analysis and compared with the phosphorus entering the furnace. When the phosphorus is removed by more than 70%, spray carbon powder into the furnace to make slag (450Kg carbon powder), the height of the foam slag is 300mm, and the power supply level is reduced to 22 levels. When the power consumption is 38000KWh, the oxygen consumption is 2200NM 3 , the silicon content of molten steel is 0.32%, the temperature is 1580℃, and it enters the reduction stage.

[0030] c. Reduction stage: After the oxygen blowing is completed, the reduction stage begins. Small ferrosilicon particles are sprayed through the oxygen lance at the furnace door, and the oxygen in the oxygen lance is switched to nitrogen for stirring reduction desulfurization operation. The reduction time is 5 minutes.

[0031] d. Steel-making operation: After the reduction is completed, the steel slag mixed flushing steel-making operation is carried out, and hand-thrown lime powder is added again with the steel flow for desulfurization.

[0032] Example 2

[0033] Electric furnace production of SUS304 steel:

[0034] Step 1: Charging of small-grain slag steel: Before the electric furnace starts arcing, small-grain slag steel and coke are laid on the bottom of the furnace in a weight ratio of 1:1;

[0035] Step 2: Smelting of small slag steel:

[0036] a. Adopting full cold material smelting, the composition of the furnace contains C: 2.89%, Si: 1.48%, Ni%: 7.51%, Cr: 12.41%, P: 0.03%, S: 0.14%;

[0037] b. Melting and oxidation: After the electric furnace starts arcing, use 12-level voltage to supply power for 3 minutes; enter the main melting period, adjust the voltage intensity to 5 levels, and when the initial molten pool is formed in the furnace, blow oxygen, and continuously add 5 tons of nickel-iron 35 alloy and 5 tons of lime for slag making. When the scrap steel charge is completely melted and enters the flat pool operation, the voltage level is adjusted to 21 levels. When the charge temperature reaches 1500℃, dephosphorization operation is carried out, and the molten clear sample is taken for rapid analysis and compared with the phosphorus entering the furnace. When the phosphorus is removed by more than 70%, spray carbon powder into the furnace to make slag (250Kg carbon powder), the height of the foam slag is 300mm, and the power supply level is reduced to 23 levels. When the power consumption is 39000KWh and the oxygen consumption is 2300NM 3 , the silicon content of molten steel is 0.25%, the temperature is 1584℃, and it enters the reduction stage.

[0038] c. Reduction stage: After the oxygen blowing is completed, the reduction stage begins. Small ferrosilicon particles are sprayed through the oxygen lance at the furnace door, and the oxygen in the oxygen lance is switched to nitrogen for stirring reduction desulfurization operation. The reduction time is 4 minutes.

[0039] d. Steel-making operation: After the reduction is completed, the steel slag mixed flushing steel-making operation is carried out, and hand-thrown lime powder is added again with the steel flow for desulfurization.

[0040] Example 3

[0041] Electric furnace production of S30403 steel:

[0042] Step 1: Charging of small-grain slag steel: Before the electric furnace starts arcing, small-grain slag steel and coke are laid on the bottom of the furnace in a weight ratio of 1:1;

[0043] Step 2: Smelting of small slag steel:

[0044] a. Adopting full cold material smelting, the composition of the furnace contains C: 2.86%, Si: 1.37%, Ni%: 7.74%, Cr: 11.14%, P: 0.03%, S: 0.15%;

[0045] b. Melting and oxidation: After the electric furnace starts arcing, use 12-level voltage to supply power for 2 minutes; enter the main melting period, adjust the voltage intensity to 5 levels, and when the initial molten pool is formed in the furnace, blow oxygen, and continuously add 5 tons of nickel-iron 35 alloy and 5 tons of lime for slag making. When the scrap steel charge is completely melted and enters the flat pool operation, the voltage level is adjusted to 21 levels. When the charge temperature reaches 1500℃, dephosphorization is carried out, and the molten clear sample is taken for rapid analysis and compared with the phosphorus entering the furnace. When the phosphorus is removed by more than 70%, spray carbon powder into the furnace to make slag (350Kg carbon powder), the height of the foam slag is 300mm, and the power supply level is reduced to 22 levels. When the power consumption is in the range of 38500KWh, the oxygen consumption is 2100NM 3 , the silicon content of molten steel is 0.29%, the temperature is 1575℃, and it enters the reduction stage.

[0046] c. Reduction stage: After the oxygen blowing is completed, the reduction stage begins. Small ferrosilicon particles are sprayed through the oxygen lance at the furnace door, and the oxygen in the oxygen lance is switched to nitrogen for stirring reduction desulfurization operation. The reduction time is 6 minutes;

[0047] d. Steel-making operation: After the reduction is completed, the steel slag mixed flushing steel-making operation is carried out, and hand-thrown lime powder is added again with the steel flow for desulfurization.

Claims

1. A method for smelting 300 series stainless steel using electric furnace slag steel, characterized in that: The following steps are involved: Step 1, preparation of small-grain slag steel: 300 series electric furnace slag steel is washed and magnetically separated to remove waste slag and then air-dried until the moisture content is less than 1%. When the slag steel contains C 2.0%, Si 2.0%, Cr 1.5%, and Ni 5% by weight, it is bagged as small-grain slag steel and sent to the material yard for use in the electric furnace; Step 2: Charging of small-grain slag steel: Before the electric furnace starts arcing, the small-grain slag steel and coke prepared in step 1 are laid on the furnace bottom at the same time, and the weight ratio of the small-grain slag steel to the coke is 1:1; Step 3: Melting of small-grain slag steel: Use full cold material smelting, supply power reasonably during the melting period, blow oxygen to assist melting, and spray carbon powder to form foam slag; Reasonable power supply: After the electric furnace starts arcing, low voltage level is used for power supply in the first 2-5 minutes. After the electrode arc is completely buried in the charge, high power and high voltage level is used for power supply; Oxygen blowing to assist melting: When the charge temperature reaches above 900°C, oxygen is blown to form a molten pool more quickly; Making foam slag: When the power consumption of the electric furnace is 12000-20000KWh, oxygen blowing and carbon powder injection are carried out to make slag. When the height of the foam slag reaches 500mm, the power supply level is reduced to 18-25 levels; Reduction steelmaking: When the electric furnace power consumption is 38000-42000KWh, the oxygen consumption is 2000-2500NM 3 When the silicon content of molten steel is 0.3-0.4% and the temperature reaches above 1580℃, it enters the reduction stage. The oxygen gun at the furnace door is switched to nitrogen, and small-grain ferrosilicon is sprayed for reduction and desulfurization operation, and then the steel is tapped.

2. A method for smelting 300 series stainless steel using electric furnace slag steel as claimed in claim 1, characterized in that: The water-washing magnetic separation is to grind the 300 series electric furnace slag steel with a water-milled ball mill, and then put it into an 18-mesh shaking table for water-washing gravity separation. The small particles of 10-40 mm above the shaking table are sent to the receiving bin, and the waste slag is flushed into the waste slag pool with water.

3. A method for smelting 300 series stainless steel using electric furnace slag steel as claimed in claim 1, characterized in that: In step three, the low voltage level is 12-14, and the high power high voltage level is 4-7.

4. A method for smelting 300 series stainless steel using electric furnace slag steel as claimed in claim 1, characterized in that: In step 3, during the oxygen blowing and melting operation, the oxygen blowing rate is 2000-3000NM 3 / h.

5. A method for smelting 300 series stainless steel using electric furnace slag steel as claimed in claim 1, characterized in that: In step three, the reduction desulfurization time is 4-6 minutes; after the reduction is completed, the steel slag mixed flushing operation is carried out, and lime powder is manually thrown along with the steel flow for desulfurization again.

6. A method for smelting 300 series stainless steel using electric furnace slag steel as claimed in claim 5, characterized in that: The total injection amount of the small-grain ferrosilicon is 200 kg, and the injection time is 2-3 minutes.