In the past, the general requirements of spring steel is mainly in electric furnace,
converter, open hearth furnace smelting, casting, open-train mill rolling.High quality requirements (mainly to reduce the content of inclusions in the steel) mainly adopts electric furnace + esr or vacuum remelting process production.
At the beginning of the typical production process is: steel water provided by the electric furnace or converter, according to the requirement of different steel grade, quality level and producers of * * * * condition choose secondary refining method, used in the continuous casting process to reduce the number of non-metallic inclusion technology (to prevent the secondary oxidation, non-metallic inclusion floatation and separation) and prevent segregation technology (low superheat casting and electro-magnetic stirring, etc.), can produce high quality steel billet in the quality of casting ingot part.Billet heating generally adopts step furnace, accompanied by controlled atmosphere system, control decarburization, oxygenation loss of billet.In between reheating furnace and roughing mill, equipped with high-pressure water descaling machine, remove the billet surface oxidation iron.Use without high torsional stiffness to engine rolling tandem mill (controlled rolling cold), for high dimensional accuracy, surface quality and satisfaction of internal organization.In order to guarantee product quality, adopt magnetic powder or eddy current and ultrasonic flaw detector online check steel surface and internal defects.To identify the defective product to clean up or out.At the same time, the quality requirements of high suspension spring steel wire rod and valve spring wire to for billet grinding, softening and finished products, surface treatment, after peeling, cold drawing, annealing, pickling and oil quenching/tempering, inspection, corrosion and a series of working procedure, to ensure the surface quality of steel.The specific process is as follows.
1, spring steel production process: electric furnace and converter - refining furnace (RH or LF + RH or ULO ASEA - SKF or ULO + ULTiN or VAD) - continuous casting - rolling - finishing.
2, suspension spring alloy steel wire rod production process: electric furnace and converter - refining furnace - cc - roughing - grinding - wire rod rolling - inspection - softening - surface treatment - packing.
3, valve oil quenching steel wire production process: wire rod inspection - skin - cold drawing, annealing, pickling/cycle - oil quenching tempering - eddy current flaw detection - embalmed - packing.
RH vacuum degassing method, LF, RH, ASEA SKF and VAD vacuum degassing heating method is everybody is familiar with the process, only to introduce ULO, ULO + ULTiN refining method:
1, ULO (extra-low oxygen steel treatment process, is Japan datong steel on the basis of RH, for more effectively reduce the number of inclusions in steel by means of.Specific steps are: in one high power alkaline eaf melting molten steel, and then after oxygen to join in molten steel deoxidization process, Fe - Si or At. With high basicity slag.Then the molten steel in ladle and RH circulation degassing equipment "two legs" insert in the molten steel, derive the molten steel into the vacuum chamber of degassing equipment.Held by large capacity injection pump, vacuum degree < 13.3 Pa, and the small flow of argon gas into liquid steel, steel foam into the vacuum chamber, the molten steel in the carbon deoxidization reaction quickly, thus steel deoxidized.When the carbon and oxygen reaction equilibrium, join like Al right deoxidizer.In order to promote the rise of deoxidizing products to separate and purify, and maintain the stability of solid state, continue deoxidizing operations, adjust and Al.RH degassing after oxygen levels fall below 15 x 10-6.The process is to realize the suspension spring steel 2000 mpa stress value of a means.
2, ULTiN (low titanium nitride) steel process: first select raw materials, in order to get Ti content (30 ~ 50) x 10-6 of the molten steel, and then for degassing operation, to reduce nitrogen content (40 ~ 60) x 10 to 6.If ULO ULTiN processing again after processing (i.e. ULO + ULTiN), oxide and TiN inclusions in steel can be dropped substantially, the fatigue limit of steel with vacuum arc remelting steel is the same, it can produce up to high strength spring steel valve spring.
With the continuous development of machinery industry, especially the development of automobile industry, the development trend of spring is a lightweight, large-scale.In order to adapt to the spring of all kinds of working conditions and meet the requirements of high strength, high life, spring steel in addition to with good comprehensive performance.