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The electric furnace process, namely, electric furnace, refining outside the furnace, continuous casting or die casting, rolling;
N the process of converter, that is, the blast furnace, hot metal pretreatment, converter refining outside the furnace, continuous casting - rolling;
N special smelting method, namely vacuum induction furnace (VIM), electroslag remelting (ESR) - rolling or forging.
The production process of typical chrome steel :
The Swedish SKF: 100 t EF - ASEA - SKF - IC, production Ø 12-90-200 - mm 32 mm rod wire, diameter and 55-110 - mm diameter steel pipe;
N Japan ShanYang: scrap preheating, EF (partial bottom steel) - 90 t LF, RH, CC (vertical flow of 3, 370 mm * 470 mm) or IC - hot rolled (material) and cold rolling. Production Ø 102-600 - mm rod, such as diameter of 50-180 - mm hot rolled steel tubes, 22-95 - mm cold rolled steel pipe diameter;
N Japan datong: scrap preheating -- teaf, LF, RH - 90 CC (370 mm * 370 mm);
N kobe: the blast furnace, hot metal pretreatment, TLD - 80 OTB avoidances the combined-blowing converter - slag - ASEA - SKF ladle refining, continuous casting (2 flow type bending, 300 mm * 430 mm), production Ø 18-105 - mm rod wire;Kawasaki, Japan: the blast furnace, hot metal pretreatment, converter, ladle refining, vacuum - continuous casting (4 flow 400 mm * 560 mm);
N Japan's sumitomo, blast furnace, converter, VAD/RH - continuous casting/molding (410 mm * 560 mm), rod wire;
N Japan's Nippon steel: the blast furnace, converter, LD converter, LF ladle refining, RH, continuous casting, production Ø 19-120 - mm rod wire;
N Japan's aichi steel: EAF - - RH - continuous casting ladle refining, production Ø 16-100 - mm rod wire;
N Germany krupp: 110 t UHP EAF - - ladle metallurgy continuous casting (6 flow 260 mm * 330 mm), production Ø 28-80 - mm wire.
Foreign production process characteristics of bearing steel
N and enlarged the stove; Without the steel slag; Al deoxidized; For a long time under the condition of vacuum or anti-vacuum stirring; High basicity slag refining; Continuous casting.
N related technology embodied in: the ladle refractory alkalization and ladle and the thin in the middle of the high temperature.
N specific refining technology is embodied in: the early low oxidation and the low temperature of liquid steel; At the beginning of the steel smelting furnace steel slag separation; The synthesis of refining slag and liquid phase, and online analysis. Liquid steel refining model (including blowing argon stirring flow, time, and argon blowing position); The ladle pouring steel slag; Temperature and composition and the process of aluminium deoxidizing process control.
Continuous casting technology is embodied in: steel ladle and tundish, Casting steel flow of inert atmosphere and defend; The large volume of intermediate clad steel water; The intermediate clad steel water flow optimization; Mold on the surface of the liquid steel; Continuous casting billet of large scale; Secondary cooling spray evenly; Multi-polarization of electromagnetic stirring; Light technology under pressure.
The basic conditions of bearing steel production.
At the beginning of the large capacity furnace to ensure that the molten steel low phosphorus, component temperature, slag tapping is realized;
N have heating, vacuum, alloy fine-tune the refining device, removing oxygen, hydrogen and other gases. Protect casting secondary oxidation;
N with multipole combined electromagnetic stirring and gently press down technology, ensure the quality of the center of the billet, reduce center segregation;
N are without twisting tension high speed rolling mill rolling mill, rolling size accuracy and surface quality.
N domestic bearing steel refining ratio has reached 100%, the average oxygen content has reached 8 x 10-4%, good 4 x 10-4%, but with the Swedish SKF, Japan ShanYang compared to the advanced manufacturers such as the content of trace impurity elements in steel, surface quality and internal quality stability, there is still a gap. Such as titanium content high, generally over 0.003%.
Rod proportion in our country, accounting for more than 80%, the pipe is almost zero, wire, strip ratio is low.
1 electric arc furnace smelting process of bearing steel
N UHP EAF - LF - VD - CC or IC as an example, the technological process is: the electric furnace steel - LF a contractor (bottom blowing argon), temperature, power supply slagging, deoxidization and desulphurization, adjustment of composition, temperature, VD location - vacuum refining - feed line (al killed or calcium treatment, end of bottom blowing argon) - temperature - casting machine casting casting platform. Central task: deoxidization and nonmetallic inclusion removal and its control.
At the beginning of the ultra high power electric arc furnace smelting.
Main tasks: melting scrap, decarburization, dephosphorization and heating;
N charge of carbon can match to 1.00% 1.3%, with the ore, oxygen decarburization, dephosphorization and slag flow automatically, eccentric tapping, leave a residue of steel. Tapping can control the carbon content in the lower limit of high carbon chromium bearing steel and increasing refining outside the furnace carbon amount is small, convenient operation;
N requirements at the beginning of molten steel smelting furnace at low temperature, low oxygen to prevent the oxidation slag in the ladle.
LF ladle refining furnace
N LF refining purpose: deoxidization, reduce sulfur, alloying, adjust the composition, control proper pouring temperature. The central task of the bearing steel: DNA!
N LF before heating, deoxidization with aluminum on the precipitation of molten steel, and then heating, adjustment liquid steel composition, refining slag composition, blowing argon stirring;Bottom blowing argon control -- is too large, steel slag reaction too hot and molten steel to refractory erosion is serious, oxide and titanium chloride into liquid steel; Too small liquid steel temperature, composition, and steel slag is uneven, inadequate, deoxidizing products is not fully floating;
N the right system of bottom blowing argon: refining argon gas with high pressure stirring early days; Late to smaller argon pressure stir - making titanium content basically stable in the refining process, at the same time can make the sulfur content and oxygen activity falling. General control in 0.2 0.3 MPa.
VD vacuum deairing.Main purpose of the vacuum to hydrogen, vacuum carbon deoxidization continue to DNA, using argon gas mixing to mixed, general denitrification is not obvious;
N before entering the VD, remove the slag, reducing slag basicity, control the intensity of argon blowing, vacuum, Al final deoxidization, slow blowing argon. Early argon blowing is not greater than 0.2 Mpa, later under 0.1 Mpa, can make the liquid steel and slag fully reaction, deoxidizing products fully floating;
N the vacuum time is too short, deoxidizing products cannot fully floating; Too long - liquid steel surface refractory long-term washout and peeling into liquid steel, adverse Yu Gangzhong titanium content of control;After vacuum degassing soft blowing argon stirring, non-metallic inclusion content control. Depending on the liquid steel VD treatment 5 min before the end of the supplementary feeding aluminium wire, aluminum content for weak agitation to cleaning liquid steel;
Continuous casting or ingot casting (IC).
2. converter steelmaking
N good material condition, the purity and quality stability of the molten iron is better than that of scrap steel;
N the hot metal pretreatment, further improve the purity of molten iron;
N bof endpoint carbon control level is high, the reaction tend to be more balanced than the electric furnace steel slag;
N converter steel gas content is low;
N craftsmanship and continuous casting and refining outside the furnace and electric furnace.
production of low phosphorus steel;
N Germany - converter of low carbon technology, guarantee the late converter dephosphorization effect, relying on the carbon steel is increased production of bearing steel.
N hot metal pretreatment: magnesium based desulfurization agent, boiling hot w [S] 0.005% or less, after processing will be grilled slag 100% except;
N: converter smelting high carbon method, endpoint carbon w [C] 0.40% or less, at the same time control w [P] 0.010% or less. Scrap steel temperature distribution into the aluminum manganese titanium mention agent - supplement the finish high carbon control temperature is not enough; The carbon content of steel temperature 1700 ℃, 0.34%, 0.007% phosphorus;
N the process within the package with high Cr alloy steel, Si - Mn alloy alloying and carbonization, carbon powder, yell or slag operation, leading the bottom blowing argon stirring removal of total oxygen in molten steel;
Department of LF refining slag with low alkalinity CaO - Al2O3, desulfurization efficiency of 50% 70%, reduce Al kind inclusions; Consistent with the deoxidizing products components, and the interfacial tension is small, easy to combine low melting point compound, strong ability of absorbing Al2O3 inclusions, eliminate class D inclusions containing CaO. Bottom blowing argon uniform composition and temperature at the same time;
N weak blowing argon stirring: according to the analysis of the components of the reference sample, adding high chromium, manganese, carbon powder, adjusting the chemical composition in meet the requirement of internal control, and the temperature is higher than the sling bag at 20-30 ℃ temperature for weak blowing argon stirring - inclusion further rise;
| Product Model | Inside Diameter | Outside Diameter | Thickness |
| 4T-835/832 NTN | 69.85 | 168.275 | 56.363 |
| 4T-745A/742 NTN | 69.85 | 150.089 | 46.672 |