A pressurized electroslag remelting slag material for improving nitrogen uniformity of corrosion-resistant plastic mold steel

Abstract

The invention discloses a pressurized electroslag remelting slag material for improving the nitrogen uniformity of corrosion-resistant plastic mold steel. In order to reduce the nitrogen element deviation at the filling end and the bottom pad end and improve the uniformity, the slag material is optimized and designed and prepared according to the following percentages: CaF2:Al2O3:CaO:SiO2:FeNCr:Si3N4=(30%-45%):(22%-35%):(20%-35%):(1%-5%):(0.5%-3%):(0.5%-3%), and the rest are inevitable impurities. Compared with the prior art, the present invention has the following advantages: it has good fluidity and air permeability while having high slag resistance, so that the slag pool temperature is high, which is conducive to the melting of the solid nitriding alloy material in the slag pool and improves the solubility of nitrogen; the slag contains a small amount of SiO2 to improve the surface quality of the steel ingot and is conducive to the hot processing of the steel ingot; the added FeNCr and Si3N4 are used to compensate for the burning loss of chromium elements and stabilize the dissolution amount of nitrogen elements in the arc starting and slag forming stage, thereby improving the uniformity of nitrogen.

Description

Technical Field

[0001] The invention belongs to the technical field of iron and steel metallurgy, and in particular relates to a pressurized electroslag remelting slag material for improving nitrogen uniformity of corrosion-resistant plastic mould steel. Background Art

[0002] High nitrogen corrosion-resistant plastic mold steel is a type of martensitic steel. Nitrogen is added to the steel to replace part of the carbon, which plays a role in improving strength and corrosion resistance. After being replaced, the reduction of carbon in the steel can further improve the uniformity of the microstructure and improve toughness. It is the best composition ratio for plastic mold steel that requires high mirror surface, high corrosion resistance, precision and complexity. When the nitrogen content in the corrosion-resistant plastic mold steel is required to be greater than 0.2%, it cannot be obtained by smelting using conventional methods. Fushun Special Steel Co., Ltd. introduced a 15-ton pressurized electroslag furnace and used a solid nitrogen-enhancing agent to increase the high nitrogen content in corrosion-resistant plastic mold steel. When a solid nitrogen-enhancing agent is used, there is a deviation in the nitrogen content at the filling end and the bottom pad end of the remelting electroslag ingot. The main reason is that the nitrogen-enhancing agent dropped from the silo above the electroslag furnace during the arc starting and slag making stage and the slow pressure increase make the nitrogen dissolved in the molten steel insufficient, and the nitrogen element cannot meet the target requirements, resulting in uneven nitrogen content at both ends. Due to the linkage of the pressurized electric slag furnace system, the parameters of the addition rate of the nitrogen-increasing agent and the temperature in the slag-making stage cannot be changed. Therefore, it is necessary to optimize the slag design to improve uniformity. Summary of the invention

[0003] The invention discloses a pressurized electroslag remelting slag material for improving the nitrogen uniformity of corrosion-resistant plastic mold steel. In order to reduce the nitrogen element deviation at the filling end and the bottom pad end and improve the uniformity, the slag material used for pressurized electroslag remelting is optimized and designed, and is prepared according to the following percentages: CaF2: Al2O3: CaO: SiO2: FeNCr: Si3N4 = (30% to 45%): (22% to 35%): (20% to 35%): (1% to 5%): (0.5% to 3%): (0.5% to 3%), and the rest are inevitable impurities.

[0004] Compared with the prior art, the present invention has the following advantages:

[0005] The corrosion-resistant plastic mold steel pressurized electroslag remelting slag system disclosed in the present invention has good fluidity and air permeability and high slag resistance, so that the slag pool temperature is high, which is conducive to the melting of solid nitride alloy material in the slag pool and improves the solubility of nitrogen; the slag contains a small amount of SiO2 to improve the surface quality of the steel ingot and is conducive to the hot processing of the steel ingot; the added FeNCr and Si3N4 are used to compensate for the burning loss of chromium elements and stabilize the dissolution amount of nitrogen elements in the arc starting and slag making stage, thereby improving the uniformity of nitrogen and thus improving the yield rate of steel. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 It is the location distribution map of the chemical composition of the electroslag ingot inspection.

[0007] Attached figure icons: 1- filling end center, 2- 1 / 2 radius of filling end, 3- filling end edge, 4- bottom pad end center, 5- 1 / 2 radius of bottom pad end, 6- bottom pad end edge. DETAILED DESCRIPTION

[0008] The present invention is further described in detail below with reference to the embodiments.

[0009] The composition and percentage of slag for remelting high nitrogen corrosion-resistant plastic mold steel in a pressurized electric slag furnace are CaF2:Al2O3:CaO:SiO2:FeNCr:Si3N4=(30%~45%):(22%~35%):(20%~35%):(1%~5%):(0.5%~3%):(0.5%~3%), and the rest are unavoidable impurities.

[0010] The preferred composition and percentage of slag for remelting high nitrogen corrosion-resistant plastic mold steel in a pressurized electric slag furnace are CaF2:Al2O3:CaO:SiO2:FeNCr:Si3N4=(30%~40%):(25%~30%):(25%~30%):(1%~3%):(0.5%~1.5%):(0.5%~1.5%), and the rest are unavoidable impurities.

[0011] Example 1

[0012] The steel grade is 30Cr 15Mo1 N0.4. The electrode rod is prepared by conventional electric furnace + LF + VD smelting method, and the nitrogen content of the electrode rod is 0.19%. The electroslag ingot is remelted in a 15-ton pressurized electroslag furnace, and the target nitrogen content is 0.40%.

[0013] The composition and percentage of the slag used for electroslag remelting are CaF2:Al2O3:CaO:SiO2:FeNCr:Si3N4=39.41%:28.82%:27.90%:1.46%:1.03%:1.38%, and the rest are inevitable impurities. After hot working, nitrogen elements are sampled and analyzed at the positions corresponding to the bottom pad end and the filling end of the finished steel. The results are shown in Table 1, and the nitrogen elements are uniform.

[0014] Table 1

[0015]

[0016] Example 2

[0017] The steel grade is 25Cr 13MoN i N0.25. The electrode rod is prepared by conventional electric furnace + LF + VD smelting method, and the nitrogen content of the electrode rod is 0.15%. The electroslag ingot is remelted in a 15-ton pressurized electroslag furnace, and the target nitrogen content is 0.25%.

[0018] The composition and percentage of the slag used for electroslag remelting in this embodiment are CaF2:Al2O3:CaO:SiO2:FeNCr:Si3N4=38.83%:29.15%:28.93%:1.16%:0.97%:0.96%, and the rest are inevitable impurities. After hot working, nitrogen elements are sampled and analyzed at the positions corresponding to the bottom pad end and the filling end of the finished steel. The results are shown in Table 2, and the nitrogen elements are uniform.

[0019] Table 2

[0020]

[0021] Example 3

[0022] The steel grade is 40Cr 15Mo2VN0.3. The electrode rod is prepared by conventional electric furnace + LF + VD smelting method, and the nitrogen content of the electrode rod is 0.175%. The electroslag ingot is remelted in a 15-ton pressurized electroslag furnace, and the target nitrogen content is 0.30%.

[0023] The composition and percentage of the slag used for electroslag remelting in this embodiment are CaF2:Al2O3:CaO:SiO2:FeNCr:Si3N4=39.88%:26.15%:29.93%:2.03%:0.97%:1.04%, and the rest are inevitable impurities. After hot working, nitrogen elements are sampled and analyzed at the positions corresponding to the bottom pad end and the filling end of the finished steel. The results are shown in Table 3, and the nitrogen elements are uniform.

[0024] Table 3

[0025]

Claims

1. A pressurized electroslag remelting slag material for improving the nitrogen uniformity of corrosion-resistant plastic mold steel, characterized in that: The slag is optimized and formulated according to the following percentages: CaF2:Al2O3:CaO:SiO2:FeNCr:Si3N4=(30%~45%):(22%~35%):(20%~35%):(1%~5%):(0.5%~3%):(0.5%~3%), and the rest are inevitable impurities.

2. The pressurized electroslag remelting slag material for improving nitrogen uniformity of corrosion-resistant plastic mold steel according to claim 1, characterized in that: The slag is optimized and formulated according to the following percentages: CaF2:Al2O3:CaO:SiO2:FeNCr:Si3N4=(30%~40%):(25%~30%):(25%~30%):(1%~3%):(0.5%~1.5%):(0.5%~1.5%), and the rest are inevitable impurities.

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