PROCESS FOR SMELTING STEEL FOR ULTRAFINE CARBORUNDUM WIRE

Abstract

A process for smelting steel for ultrafine carborundum sawing wires, comprising: 1) in a vacuum induction furnace, using pure iron and low-phosphorus pig iron as raw materials to be melted into molten steel under the protection of argon; vacuumizing and smelting, and degassing; using silicon iron as a deoxidizer to adjust components of the molten steel; and casting a circular ingot in vacuum; 2) cleaning the surface of the circular ingot to produce an electrode bar; 3) remelting and smelting the electrode bar as raw material to a cylindrical electroslag ingot in an electroslag furnace, wherein the electroslag protecting slag comprises: CaF.sub.2: 45-55%, Al.sub.2O.sub.3: 15-25%, SiO.sub.2: 20-25%, Na.sub.2O: 2-4%, and K.sub.2O: 1-2%; 4) forging the electroslag ingot to a square billet; and 5) rolling the forged billet to a steel wire rod, and the steel wire rod comprising [C]: 0.92-1.1%, [Si]: 0.3-0.4%, [Mn]: 0.5-0.8%, [Al]<0.0008%, [N]<0.005%, [S]<0.01%, and [P]<0.015%.

Claims

1. A process for smelting steel for ultrafine carborundum sawing wires, comprising the following steps of: 1) melting a raw material into liquid molten steel under the protection of argon in a vacuum induction furnace, the raw material uses carbon-free pure iron and low-phosphorus pig iron having a carbon content of 3.5%-4.5% by mass; then vacuumizing to perform vacuum smelting, the vacuum smelting is performed under a condition of less than 300 Pa to degas for 15-20 min, and performing deoxygenation with high-purity silicon iron as a deoxidizer to adjust components of the molten steel; and after the adjustment of the components of the molten steel, casting circular ingots under vacuum condition, wherein each ingot has a mass of 1.5-2.5 tons, a diameter of 0.35-0.4 m and a length of 2-3 m; 2) cleaning the surface of the circular ingots to manufacture electrode bars for electroslag smelting; 3) remelting and smelting the electrode bars as raw materials in an electroslag furnace, wherein an electroslag protecting slag comprises the following in percentage by mass: CaF.sub.2: 45-55%, Al.sub.2O.sub.3: 15-25%, SiO.sub.2: 20-25%, Na.sub.2O: 2-4%, and K.sub.2O: 1-2%; and smelting the electrode bar in the electroslag furnace into a cylindrical electroslag ingot having a diameter of 0.4-0.5 m; 4) forging the electroslag ingot into a forged billet for wire rolling, wherein the forged billet is a square billet having a cross section of square with a side length of 0.140-0.160 m, and the forged billet has a length of greater than 6 m; and 5) rolling the forged billet into a steel wire rod having a diameter of 4.5-5.5 mm by the wire rolling process, wherein the steel wire rod comprises the following chemical elements in percentage by weight: [C]: 0.92-1.1%, [Si]: 0.3-0.4%, [Mn]: 0.5-0.8%, [Al]: less than 0.0008%, [N]: less than 0.005%, [S]: less than 0.01%, [P]: less than 0.015%.

2. The process for smelting steel for ultrafine carborundum sawing wires according to claim 1, wherein the volume of the vacuum induction furnace is 2-5 tons.

3. The process for smelting steel for ultrafine carborundum sawing wires according to claim 1, wherein in step 2), after cleaning the surface of the circular ingot, 5-10 cm of a shrinkage end is cut off.

4. The process for smelting steel for ultrafine carborundum sawing wires according to claim 1, wherein in the step of smelting in the vacuum induction furnace in step 1), after the smelting, the molten steel comprises the following elemental components in percentage by mass: [C]: 0.94-1.1%, [Si]: 0.35-0.45%, [Mn]: 0.6-0.8%, [Al]: less than 0.001%, [N]: less than 0.0045%, [S]: less than 0.01% , [P]: less than 0.015% , and the balance of iron and unavoidable impurities; the temperature of the molten steel is controlled at 1460-1500° C.; and after the smelting, argon is blown in as a protective atmosphere and adjusting the pressure in the vacuum induction furnace to 10000-20000 Pa, then casting under the protective atmosphere.

5. The process for smelting steel for ultrafine carborundum sawing wires according to claim 1, wherein in step 1), a casting mold for casting the ingot is a cast iron mold.

6. The process for smelting steel for ultrafine carborundum sawing wires according to claim 1, wherein in step 1), after the raw materials are completely melted, 2-5 kg of lime is added per ton of the raw materials for slag making, dephosphorization and desulfurization.

7. The process for smelting steel for ultrafine carborundum sawing wires according to claim 1, wherein the step 3) is carried out under a protective atmosphere, and the step of remelting and smelting in the electroslag furnace is remelting and smelting at a constant melting rate in the electroslag furnace.

8. The process for smelting steel for ultrafine carborundum sawing wires according to claim 4, wherein in step 1), a casting mold for casting the ingot is a cast iron mold.

Description

DETAILED DESCRIPTION

[0026] The present invention provides a process for smelting steel for ultrafine carborundum sawing wires through a new steel-making process path design to produce high-end steel for the ultrafine carborundum sawing wires, which can realize the flexible and stable production of the steel for the carborundum sawing wires, and fundamentally solves the problem of wire breakage in the subsequent carborundum wire drawing process caused by poor control of inclusions.

[0027] The process includes main steps as follows:

[0028] 1) Smelting a molten steel masterbatch of the steel for ultrafine carborundum sawing wires in a vacuum induction furnace by using carbon-free pure iron and low-phosphorus pig iron containing 3.5%-4.5% of carbon and less than 0.06% of phosphorus as raw materials, followed by casting into a circular ingot;

[0029] 2) Manufacturing electrode bars for electroslag smelting from the circular ingot;

[0030] 3) Remelting and smelting the electrode bars as raw materials in an electroslag furnace to manufacture an electroslag ingot, wherein the electroslag protecting slag including the following components in percentage by mass: CaF.sub.2: 45-55%, Al.sub.2O.sub.3: 15-25%, SiO.sub.2: 20-25%, Na.sub.2O: 2-4%, and K.sub.2O: 1-2%;

[0031] 4) Forging; and

[0032] 5) Rolling by wire rolling process for a steel wire rod having a diameter of 4.5-5.5 mm, wherein the steel wire rod includes the following chemical elements in percentage by mass: [C]: 0.92-1.1%, [Si]: 0.3-0.4%, [Mn]: 0.5-0.8%, [Al]: less than 0.0008%, [N]: less than 0.005%, [S]: less than 0.01%, [P]: less than 0.015%, and the balance of iron and unavoidable impurities.

[0033] The steel wire rod can be drawn into a carborundum wire having a diameter of 0.04-0.055 mm while no wire breakage caused by poor control of inclusions will occur in the drawing process.

Example 1

[0034] The process of smelting in a vacuum induction furnace-electroslag-forging-wire rolling provided by the present application is used to produce steel for carborundum sawing wires, and the main process steps thereof are as follows:

[0035] 1) 1.5 tons of carbon-free pure iron rods and 0.5 tons of pig iron containing 4% of carbon (the phosphorus content of the pig iron is less than 0.06%) are used as raw materials to be melted into 2 tons of liquid molten steel under the protection of argon in a vacuum induction furnace with a capacity of 2 tons and having the function of vacuum casting. After the molten steel is completely melted, 10 kg of lime is added, and vacuumizing is performed to start vacuum smelting including degassing for 15 min under a high vacuum condition of 300 Pa or below. In the process of vacuum smelting, 8 kg of high-purity silicon iron (containing 75% of silicon) and 18 kg of pure manganese alloy are added to adjust components of the molten steel, wherein after the smelting in this step, the molten steel comprises the following chemical elements in percentage by mass: [C]: 1.05%, [Si]: 0.41% of [Si], [Mn]: 0.7%, [Al]: 0.00079% of, [N]: 0.0040%, [S]: 0.008%, [P]: 0.014%, and the balance of iron and unavoidable impurities. Then, argon is blown into the vacuum induction furnace while adjusting the pressure in the furnace to 10000 Pa or slightly higher and the temperature of the molten steel to 1465° C. and finally a circular ingot is cast under vacuum. The ingot solely has a mass of 2 tons, a diameter of 0.35 m and a length of 2.8 m.

[0036] 2) The surface of the circular ingot is cleaned by grinding, and 5 cm of the ingot head with a shrinkage end is cut off to produce an electrode bar for electroslag smelting.

[0037] 3) The electrode bar is used as raw material for remelting and smelting at a constant melting rate in an electroslag furnace under a protective atmosphere of argon. The electroslag protecting slag comprises the following in percentage by mass: CaF.sub.2: 45%, Al.sub.2O.sub.3: 25%, SiO.sub.2: 25%, Na.sub.2O: 3%, and K.sub.2O: 2% of. The electrode bar is smelted in the electroslag furnace into a cylindrical electroslag ingot with a diameter of 0.45 m and a length of 1.6 m.

[0038] 4) The electroslag ingot is forged into a forged billet for wire rolling, wherein the forged billet is a square billet having a cross section of square with a side length of 0.140 m, and the forged billet has a length of 12.5 m.

[0039] 5) The forged billet is rolled into a steel wire rod having a diameter of 4.5 mm by a wire rolling process. The steel wire rod includes the following chemical elements in percentage by mass: [C]: 1.02%, [Si]: 0.35%, [Mn]: 0.6%, [Al]: 0.0005%, [N]: 0.0048%, [S]: 0.008%, [P]: 0.014%, and the balance of iron and unavoidable impurities. Inclusions in the steel wire rod are detected as a CaF.sub.2-CaO-SiO.sub.2-Al.sub.2O.sub.3-Na.sub.2O-K.sub.2O composite inclusion, and a SiO.sub.2-Al.sub.2O.sub.3-MnO-CaO-MgO-Na.sub.2O-K.sub.2O composite inclusion (the SiO.sub.2 contents in both composite inclusions are greater than 50%). These two series of inclusions have good plasticity, and the widths of the inclusions are all less than 6 μm, which are harmless inclusions and will not cause wire breakage in the steel wire rod drawing process.

[0040] The steel wire rod produced in this example can finally be drawn into a carborundum master wire with a diameter of 0.05 mm while no wire breakage will occur in the drawing process and the carborundum wire can be used for high efficiency cutting of silicon chips, gemstones and the like.

Example 2

[0041] The process of smelting in a vacuum induction furnace-electroslag-forging-wire rolling provided by the present application is used to produce steel for carborundum sawing wires, and the main process steps thereof are as follows:

[0042] 1) 3.75 tons of carbon-free pure iron rods and 1.25 tons of pig iron containing 3.9% of carbon (the phosphorus content of the pig iron is less than 0.06%) are used as raw materials to be melted into 5 tons of liquid molten steel under the protection of argon in a vacuum induction furnace with a capacity of 5 tons and having the function of vacuum casting. After the molten steel is completely melted, 20 kg of lime is added, and vacuumizing is performed to start vacuum smelting including degassing for 20 min under a high vacuum condition of 300 Pa or below. In the process of vacuum smelting, 20 kg of high-purity silicon iron (containing 75% of silicon) and 45 kg of pure manganese alloy are added, wherein after the smelting, the molten steel in this step, the molten steel comprises the following chemical elements in percentage by mass: [C]: 0.96%, [Si]: 0.45%, [Mn]: 0.75%, [Al]: 0.0009%, [N]: 0.0038%, [S]: 0.0095%, [P]: 0.013%, and the balance of iron and unavoidable impurities. Then, argon is blown into the vacuum induction furnace while adjusting the pressure in the furnace to 12000 Pa or slightly higher and the temperature of the molten steel to 1485° C., and finally two circular ingots are cast under vacuum, each ingot having a mass of 2.5 tons, a diameter of 0.4 m and a length of 2.6 m.

[0043] 2) The surface of the circular ingot is cleaned by grinding, and 6 cm of the ingot head with a shrinkage end is cut off to produce an electrode bar for electroslag smelting.

[0044] 3) The electrode bar is used as raw material for remelting and smelting at a constant melting rate in an electroslag furnace under a protective atmosphere of argon The electroslag protecting slag including in percentage by mass: CaF.sub.2: 51%, A1.sub.2O.sub.3: 22%, SiO.sub.2: 23%, Na.sub.2O: 3%, and K.sub.2O: 1%. The electrode bar is smelted in the electroslag furnace into a cylindrical electroslag ingot with a diameter of 0.5 m and a length of 1.5 m.

[0045] 4) The electroslag ingot is forged into a forged billet for wire rolling, wherein the forged billet is a square billet having a cross section of square with a side length of 0.16 m, and the forged billet has a length of 12 m.

[0046] 5) The forged billet is rolled into a steel wire rod having a diameter of 5 mm by a wire rolling process. The steel wire rod includes the following chemical elements in percentage by mass: [C]: 0.93%, [Si]: 0.4%, [Mn]: 0.5%, [Al]: 0.0006%, [N]: 0.0040%, [S]: 0.0095%, [P]: 0.013%, and the balance of iron and unavoidable impurities. Inclusions in the steel wire rod are detected as a CaF.sub.2-CaO-SiO.sub.2-Al.sub.2O.sub.3-Na.sub.2O-K.sub.2O composite inclusion, and a SiO.sub.2-Al.sub.2O.sub.3-MnO-CaO-MgO-Na.sub.2O-K.sub.2O composite inclusion (the SiO.sub.2 contents in both composite inclusions are greater than 60%). These two series of inclusions have good plasticity, and the widths of the inclusions are all less than 7 μm, which are harmless inclusions and will not cause wire breakage in the steel wire rod drawing process.

[0047] The steel wire rod produced in this example can finally be drawn into a carborundum master wire with a diameter of 0.055 mm while no wire breakage will occur in the drawing process, and the carborundum wire can be used for high efficiency cutting of silicon chips, gemstones and the like.

Example 3

[0048] The process of smelting in a vacuum induction furnace-electroslag-forging-wire rolling provided by the present application is used to produce steel for carborundum sawing wires, and the main process steps thereof are as follows:

[0049] 1) 3 tons of carbon-free pure iron rods and 1 ton of pig iron containing 4.2% of carbon (the phosphorus content of the pig iron is less than 0.06%) are used as raw materials to be melted into 4 tons of liquid molten steel under the protection of argon in a vacuum induction furnace with a capacity of 4 tons and having the function of vacuum casting. After the molten steel is completely melted, 15 kg of lime is added, and vacuumizing is performed to start vacuum smelting including degassing for 18 min under a high vacuum condition of 250 Pa or below. In the process of vacuum smelting, 15 kg of high-purity silicon iron (containing 75% of silicon) and 33 kg of pure manganese alloy are added as a deoxidizer for deoxygenation, wherein after the smelting in this step, the molten steel comprises the following chemical elements in percentage by weight: [C]: 1.1%, [Si]: 0.35%, [Mn]: 0.6%, [Al]: 0.0007%, [N]: 0.0034%, [S]: 0.0099%, [P]: 0.012%, and the balance of iron and unavoidable impurities. Then, argon is blown into the vacuum induction furnace while adjusting the pressure in the furnace to 15000 Pa or slightly higher and the temperature of the molten steel to 1495° C., and finally two circular ingots are cast under vacuum, each ingot having a mass of 2 tons, a diameter of 0.38 m and a length of 2.4 m.

[0050] 2) The surface of the circular ingot is cleaned by grinding, and 8 cm of the ingot head with a shrinkage end is cut off to produce an electrode bar for electroslag smelting.

[0051] 3) The electrode bar is used as raw material for remelting and smelting at a constant melting rate in an electroslag furnace under a protective atmosphere of argon The electroslag protecting slag including in percentage by mass: CaF.sub.2: 55%, Al.sub.2O.sub.3: 15%, SiO.sub.2: 24%, Na.sub.2O: 4%, and K.sub.2O: 2%. The electrode bar is smelted in the electroslag furnace into a cylindrical electroslag ingot with a diameter of 0.45 m and a length of 1.5 m.

[0052] 4) The electroslag ingot is forged into a forged billet for wire rolling, wherein the forged billet is a square billet having a cross section of square with a side length of 0.15 m, and the forged billet has a length of 10.3 m.

[0053] 5) The forged billet is rolled into a steel wire rod having a diameter of 5.5 mm by a wire rolling process. The steel wire rod includes the following chemical elements in percentage by mass: [C]: 1.05%, [Si]: 0.3%, [Mn]: 0.5%, [Al]: 0.0005%, [N]: 0.0038%, [S]: 0.0099%, [P]: 0.012%, and the balance of iron and unavoidable impurities. Inclusions in the steel wire rod are detected as a CaF.sub.2-CaO-SiO.sub.2-Al.sub.2O.sub.3-Na.sub.2O-K.sub.2O composite inclusion, and a SiO.sub.2-Al.sub.2O.sub.3-MnO-CaO-MgO-Na.sub.2O-K.sub.2O composite inclusion (the SiO.sub.2 contents in both composite inclusions are greater than 50%) These two series of inclusions have good plasticity, and the widths of the inclusions are all less than 5 μm, which are harmless inclusions and will not cause wire breakage in the steel wire rod drawing process.

[0054] The steel wire rod produced in this example can finally be drawn into a carborundum master wire with a diameter of 0.04 mm while no wire breakage will occur in the drawing process, and the carborundum wire can be used for high efficiency cutting of silicon chips, gemstones and the like.