[0030] The following describes the specific embodiments of the present invention in further detail through the description of the best embodiments.
[0031] The manufacturing process of the alloy steel for rail frogs includes the following processes: smelting-casting-forging-heat treatment; specifically;
[0032] (1) Smelting
[0033] In the smelting process, it is necessary to control the proportion of harmful components such as P and S. At the same time, it is necessary to control harmful gases such as N, H, O, etc., to prevent the tensile strength of steel due to the impure removal of inclusions and excessive residual harmful gases. Unqualified performance such as low temperature impact and low temperature impact occurs; smelting is divided into three processes: roughing, refining and vacuum degassing, specifically:
[0034] Rough smelting: use electric arc furnace, add pig iron, scrap steel, recarburizer, silicon carbide into the electric arc furnace; use spectrum analyzer to control the composition of molten steel, C>0.50% when the molten steel is melted in the electric arc furnace, if the C content does not meet the requirements Composition requirements: add C into the electric arc furnace until C>0.50%, control the molten steel temperature above 1560℃, blow oxygen to dephosphorize and decarburize when the slag fluidity is good, the C content is 0.1-0.13% when the oxidation is complete, P≤0.012 %, when this composition requirement is met, the molten steel will be slagging off;
[0035] After removing all the oxidized slag, quickly add a pre-deoxidizer for deoxidation. The pre-deoxidizer is silicon carbide; add a thin slag material weighing 1-1.5% of molten steel, the thin slag material is fluorite (lump ore), the chemical composition is: CaF2 SiO2, S, P; carry out the reduction reaction, adjust the alloy composition in the molten steel, and control the alloy composition to the lower limit of its range, namely Si is 1.60%, Mn is 1.60%, Cr is 1.40%, Ni is 0.50%, Mo is 0.33% , The temperature of molten steel is 1680-1700℃ for tapping; the pre-deoxidizer and thin slag material can be purchased directly in the market;
[0036] Refining: Use electric arc furnace to add refining slag into molten steel. The chemical composition of refining slag is: CaF2, Al2O3, SiO2, CaO, Fe2O3, MgO, H2O. Refining slag can be purchased directly on the market; keep the slag in good condition , Use a spectrum analyzer to control the composition of molten steel, and control the composition of each alloy to the middle limit of its range, that is, Si is 1.90%, Mn is 1.90%, Cr is 1.65%, Ni is 0.55%, Mo is 0.38%, and the temperature of molten steel is at Stop refining at 1700-1710°C; after tapping, add pig iron, ferrochrome, ferromolybdenum, medium carbon ferromanganese, high carbon ferromanganese, ferrosilicon and electrolytic nickel to the molten steel again, and then the molten steel enters the vacuum furnace for vacuum degassing;
[0037] Vacuum degassing: use vacuum furnace, vacuum degassing treatment for 18-20 minutes, timing start time is controlled at 5-6 minutes, argon blowing during treatment, argon pressure should not be too large, just keep the molten steel surface boiling properly, vacuum degassing Add aluminum to the molten steel after the gas, and add the rare earth alloy Ce; according to the results of the spectrum analysis, when the carbon content is insufficient, feed carbon, but the carbon supplementation amount should be less than 0.01%, and control the composition of molten steel in the range of C: 0.23~0.28%, Si :1.60~2.20%, Mn: 1.60~2.00%, Cr: 1.40~1.90%, Ni: 0.50~0.60%, Mo: 0.33~0.43%, Al: 0.15~0.20%, Ce: 0.01~0.02%, P≤ 0.02%, S≤0.02%, the rest is Fe, control the content of inclusions: N content is ≤80.0PPm; H content is ≤1.2ppm; O content is ≤20.0ppm; the tapping temperature is 1575-1585℃,
[0038] (2) Casting
[0039] After the molten steel comes out of the vacuum furnace, the molten steel temperature is 1560-1565℃, and the molten steel starts to be poured. If the molten steel temperature is not reached, put the molten steel into the refining furnace to heat up; during casting, mold flux is added to the mold. The chemical composition of the flux is: C, Al2O3, SiO2, CaO, Fe2O3, MgO; add heating agent when molten steel rises to the cap, the chemical composition of the heating agent: Al and H2O; add heat preservation agent, the chemical composition of the heat preservation agent: C, Al2O3, SiO2, CaO , H2O, enter the slow cooling pit 2.5 hours after pouring; protective slag, heating agent and heat preservation agent are directly purchased on the market;
[0040] (3) Forging
[0041] The forging uses mechanical presses, flat forging machines, air hammers and other equipment, and the used forging pressure is 3 to 4 tons; the volume of the blank after forging is 95-97% of the volume of the blank before forging;
[0042] (4) Heat treatment
[0043] The heat treatment is divided into three steps, including annealing-quenching-tempering. The heat treatment process adopts electric furnace, and adopts PLC automatic temperature control gas heating and heat preservation;
[0044] Annealing; firstly, heat up the processed blank of (3) to 680~700℃ and keep it for 2~2.5 hours; then heat it up to 880~900℃ and keep it for 4.5~5 hours; reduce the temperature to 280~300℃ and keep it for 5.5~6 hours ;
[0045] Quenching; heat the annealed billet to 900~920℃, then take out the billet and hang it for natural cooling;
[0046] Tempering: The quenched billet is heated to 330-350°C, after holding for 5.5-6 hours, the billet is taken out and cooled naturally.
[0047] In the smelting (1) process, during roughing and refining, the C content in pig iron is 4.20 to 4.50%; the chromium content in ferrochrome is 59 to 60%, the C content is 0.20 to 0.25%; the molybdenum content in molybdenum is 58 ~60%, the manganese content in the medium carbon manganese steel is 79-80%, the C content is 1.40-1.50%, the P content is 0.16-0.18%; the manganese content in the high-carbon ferromanganese is 75-76%, and the C content is 6.60 ~ 6.80%, P content is 0.12 ~ 0.14%; silicon content in ferrosilicon is 75 ~ 76%; nickel content in electrolytic nickel is 100%.
[0048] The manufacturing process of the alloy steel for the track frog, the steel ingot mold, the alloy materials, the refractory material for casting, the drainage agent, and the protective slag should be baked at a temperature above 100°C for more than 2 hours, and other materials such as heat preservation agent and heat generating agent should not be baked. Bake, but it must be kept dry. The placed pouring system should use high-pressure air to blow off the dust and other debris in the system, and use a suction pipe to suck out the remaining dust in the net ingot mold; pouring the ingot body for 5-7 minutes, and the cap Shrink 4-6 minutes and control the pouring speed to ensure that the molten steel rises steadily in the ingot mold.
[0049] The content of harmful component N in the alloy steel manufactured by the manufacturing process of the alloy steel for rail frog is ≤80.0PPm, the content of H is ≤1.2ppm, and the content of O is ≤80.0PPm.
[0050] According to the manufacturing process of alloy steel for rail frog, the chemical composition of alloy steel for rail frog includes, in weight percentage: C: 0.23~0.28%, Si: 1.60~2.20%, Mn: 1.60~2.00% , Cr: 1.40~1.90%, Ni: 0.50~0.60%, Mo: 0.33~0.43%, Al: 0.15~0.20%, Ce: 0.01~0.02%, P≤0.02%, S≤0.02%, the rest is Fe;
[0051] among them:
[0052] Carbon: increase the yield point and tensile strength of steel, but reduce plasticity and impact;
[0053] Silicon: Silicon is a reducing agent and a deoxidizer. Silicon can improve the elastic polarity of steel. The combination of silicon and molybdenum, tungsten, chromium, etc., can improve corrosion resistance and oxidation resistance;
[0054] Manganese: Manganese is a good deoxidizer and desulfurizer. Compared with general steel, it has sufficient toughness, and has higher strength and hardness, improves the hardenability of steel, and improves the hot workability of steel;
[0055] Chromium: Chromium can significantly improve the rigidity, hardness and wear resistance, and improve the oxidation resistance and corrosion resistance of steel;
[0056] Nickel: can improve the plasticity and toughness of steel, and has the ability to prevent rust and heat at high temperatures;
[0057] Molybdenum: refines the grain of steel, improves hardenability and thermal strength, and maintains sufficient strength and creep ability of steel at high temperatures;
[0058] Aluminum: A deoxidizer in steel that can refine grains and improve impact toughness. The combination of aluminum, chromium and silicon can significantly improve the high-temperature non-skinning performance and high-temperature corrosion resistance of steel;
[0059] Cerium: improves ductility, reduces and eliminates the performance hazards of oxygen and sulfur to steel.
[0060] The manufacturing process of the alloy steel for rail frogs is achieved by controlling the proportions of harmful components such as P and S in the smelting and pouring processes; using alloy raw materials with specific proportions, using specific adding steps, and using a direct reading spectrum analyzer The control of molten steel composition and the preparation of alloy elements are implemented; the use of LF refining and vacuum degassing process can greatly reduce the content of inclusions and harmful gases such as N, H, and O in molten steel, and avoid the resulting tensile strength and The occurrence of unqualified performance such as low temperature impact; heat treatment adopts specific stability to improve product performance, and adopts PLC automatic temperature control gas heating method, and the temperature control is accurate and rapid; thus greatly increasing the product weight and service life; made by this manufacturing process The product properties of alloy steel for rail frogs are: tensile strength σb≥1250MPa; yield strength σ0.2≥1100MPa; elongation δ5(‰) ≥10; reduction of area ψ(‰)≥25; room temperature impact toughness αku( 42℃)≥75J/cm2; low-temperature impact toughness σku(-40℃)≥35J/cm2; hardness HRC37-42; the tensile strength and low-temperature impact properties of rail frogs made of alloy steel are much better than those of high manganese The service life of steel and track frogs can be greatly improved without frequent replacement, which can greatly reduce track operating costs.
