CN105779907A - Free-cutting steel containing magnesium and calcium and production process - Google Patents
Free-cutting steel containing magnesium and calcium and production process Download PDFInfo
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/60—Ferrous alloys, e.g. steel alloys containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur
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- B22D11/11—Treating the molten metal
- B22D11/114—Treating the molten metal by using agitating or vibrating means
- B22D11/115—Treating the molten metal by using agitating or vibrating means by using magnetic fields
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- B22—CASTING; POWDER METALLURGY
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- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/16—Controlling or regulating processes or operations
- B22D11/22—Controlling or regulating processes or operations for cooling cast stock or mould
- B22D11/225—Controlling or regulating processes or operations for cooling cast stock or mould for secondary cooling
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- C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
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- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
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- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
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- C22C38/00—Ferrous alloys, e.g. steel alloys
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- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/009—Pearlite
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Abstract
The invention discloses free-cutting steel containing magnesium and calcium and a production process of the free-cutting steel. The free-cutting steel is mainly prepared from, by weight, 0.48%-0.55% of C, 0.20%-0.50% of Si, 0.70%-1.00% of Mn, not larger than 0.04% of P, 0.08%-0.13% of S, 0.001%-0.006% of Mg and 0.0008-0.006% of Ca The process route of converter smelting, LF refining, continuous casting and rolling is adopted for the free-cutting steel, and at the LF refining stage, the improved cutting performance of sulphur-containing free-cutting steel can reach or approximate the standard of lead-containing free-cutting steel through sulfide in magnesium and calcium compound modified steel. The components of the free-cutting steel containing magnesium and calcium are simple and easy to control, and the free-cutting steel containing magnesium and calcium has the excellent mechanical performance and the excellent free-cutting performance, and does not pollute the environment.
Description
Technical field
The invention belongs to field of steel metallurgy, particularly to a kind of automatic steel containing magnesium calcium and production technology thereof.
Background technology
Automatic steel can effectively reduce resistance to cutting, slows down tool wear, improve working performance, meets Digit Control Machine Tool Production requirement efficient, intelligentized well, belongs to energy-saving material, be widely used in the fields such as household electrical appliances, automobile and office equipment.
By Cutting free element classification, automatic steel is broadly divided into resulfurizing series free cutting steel and lead series free cutting steel.Although lead series free cutting steel has excellent cutting ability and mechanical property concurrently, and heat treatment performance, cold and hot working performance and welding performance are also more excellent, but the harm of human body and environment is relatively big and high to producing equipment requirements, so development is restricted.Resulfurizing series free cutting steel is owing to containing MnS in matrix, MnS causes steel matrix easily to produce micro-crack when cutting as stress raiser as favourable field trash and improves cutting ability, and makes MnS softening play lubrication and have reasonable cutting ability when machining owing to temperature raises.But, the cutting ability of resulfurizing series free cutting steel also has a certain distance compared with lead series free cutting steel, this patent is intended to the cutting ability being improved resulfurizing series free cutting steel by the MnS field trash in upgrading steel, it is desirable to the cutting ability of the resulfurizing series free cutting steel after improvement can close to or up lead series free cutting steel.
Simple sulphur free-cutting steel easily extends along rolling direction when rolling due to MnS field trash, reduces the horizontal mechanical performance of steel.Ca element would generally be added in resulfurizing series free cutting steel and MnS is carried out upgrading.Calcium and magnesium are commonly used for deoxidizer or the desulfurizing agent of steel-making, and in solidification of molten steel process, the oxidation product of calcium and magnesium is as sulfide forming core core, it is possible to promote the precipitation of sulfide and being uniformly distributed of sulfide.Calcium and magnesium can also play the effect changing oxide morphology.Calcium and magnesium add (Mn, the Ca) S or (Mn, Mg) S that form compound in steel, thus the deformability reducing sulfide improves the horizontal mechanical performance of steel.Steel inclusion is carried out upgrading by adding Ca, Mg to compound in resulfurizing series free cutting steel by patent of the present invention, produces effect more better than individually interpolation Ca, and then improves the machinability of steel.
Through retrieval: China Patent Publication No. is the patent documentation of CN1410583A, disclose a kind of calcium sulfur magnesium series automatic steel, it is characterised in that its composition (wt%) is C:0.42 ~ 0.50, Si:0.20 ~ 0.50, Mn:1.00 ~ 1.20, P:0.01 ~ 0.04, S:0.01 ~ 0.07, Ca:0.002 ~ 0.016, Mg:0.0001 ~ 0.002.This patent is different from part and is in that: this patent automatic steel institute sulfur-bearing, magnesium, calcium component (wt%) respectively S:0.08 ~ 0.13, Mg:0.001 ~ 0.006, Ca:0.0008 ~ 0.006, and this patent automatic steel institute sulfur-bearing, magnesium, calcium component (wt%) respectively S:0.01 ~ 0.07, Mg:0.0001 ~ 0.002, Ca:0.002 ~ 0.016.
China Patent Publication No. is the patent documentation of CN1718828A, disclose a kind of low carbon high sulfur phosphorus easy cutting steel, the composition (wt%) that it is characterized in that it is C:0.03 ~ 0.20, Si:0.01 ~ 0.10, Mn:0.60 ~ 1.80, P:0.04 ~ 0.15, S:0.08 ~ 0.50, N:0.001 ~ 0.02, Ca:0.0001 ~ 0.01, Mg:0.0001 ~ 0.01, Al:0.001 ~ 0.005, O:0.003 ~ 0.015, all the other are Fe；And [Mn]/[C]=10 ~ 50, [Mn]/[Si] >=20, [Si]/[S]≤0.3.This patent is different from part and is in that: this patent automatic steel institute carbon containing, silicon, magnesium, calcium component (wt%) respectively C:0.48 ~ 0.55, Si:0.20 ~ 0.50, Mg:0.001 ~ 0.006, Ca:0.0008 ~ 0.006, and this patent automatic steel institute carbon containing, silicon, magnesium, calcium component (wt%) respectively C:0.03 ~ 0.20, Si:0.01 ~ 0.10, Mg:0.0001 ~ 0.01, Ca:0.0001 ~ 0.01.
nullChina Patent Publication No. is the patent documentation of CN104789908A，Disclose the low plumbous compound automatic steel of a kind of boracic，The composition (wt%) that it is characterized in that it is C:0.09 ~ 0.18、Si:< 0.08、Mn:1.20 ~ 1.50、P :≤0.015、S :≤0.015、N:0.05 ~ 0.07、B:0.03 ~ 0.05、Pb:0.01 ~ 0.029、Ca:0.001 ~ 0.009、Mg:0.002 ~ 0.008、Al:0.01 ~ 0.02、More than Ni:0.01 ~ 0.03 or Cu:0.01 ~ 0.03 or Cr:0.03 ~ 0.05 or two of which with the mixture of arbitrary proportion，Mixture total content is: 0.04 ~ 0.06，All the other are Fe and inevitable impurity.This patent is different from part and is in that: (1) this patent is not leaded and this patent is leaded；(2) without B and N in this patent automatic steel, and B and the N content in the low plumbous compound automatic steel of this boracic is higher, and this automatic steel is to utilize the substantial amounts of BN generated in the steel cutting ability being mingled with to improve steel.
Summary of the invention
The present invention provides a kind of automatic steel containing magnesium calcium and production technology thereof.The technical problem to be solved in the present invention is: by adding Ca, Mg element to the molten steel compound of refine, the sulphide inculsion in upgrading sulphur free-cutting steel, thus improving mechanical performance and the cutting ability of steel.
A kind of automatic steel containing magnesium calcium, it is characterised in that main component (wt%) is: C:0.48 ~ 0.55, Si:0.20 ~ 0.50, Mn:0.70 ~ 1.00, P :≤0.04, S:0.08 ~ 0.13, Mg:0.001 ~ 0.006, Ca:0.0008 ~ 0.006.
Optimal components (wt%) containing the automatic steel of magnesium calcium is: C:0.48 ~ 0.55, Si:0.20 ~ 0.50, Mn:0.70 ~ 1.00, P :≤0.04, S:0.08 ~ 0.13, Mg:0.0015 ~ 0.004, Ca:0.0015 ~ 0.003.
A kind of automatic steel containing magnesium calcium, it is characterised in that its production technology is specific as follows:
1) converter smelting: before converter, molten iron is without pre-desulfurization.The main task bessemerized is decarburization and intensification, it is not necessary to desulfurization and dephosphorization, adopts low basicity slag (R=2 ~ 3), few slag operation；For " protect phosphorus carbon elimination ", reduce the low temperature dephosphorization phase, steel scrap can be added less, it is considered to suitably reduce soft blow (the high rifle position) time, increase and firmly blow (the low rifle position) time；Aim carbon is wanted rationally, can not be too low, slag-stopping tapping.Converter adopts the smelting process of top blowing oxygen BOTTOM ARGON BLOWING.Converter tapping process adopts the first deoxidation of strong deoxidizer (Si-Ca-Ba or silicon aluminum calcium barium alloy), again with ferromanganese control oxygen (tap about half time, deoxidizer will be remained: ferromanganese, sulfur ferrum and ferrophosphorus add together), adopting the quick Determining oxygen probe of zirconia solid electrolyte oxygen concentration cell to measure the oxygen activity in molten steel, after making tapping, the oxygen activity of molten steel controls 60 ~ 200 × 10-6。
2) LF refine: suitably slag making, it is ensured that thickness of slag layer, must control the basicity of slag and reducing atmosphere well, and basicity of slag R, with 0.8 ~ 1.5 for control standard, adds iron sulfide control sulfur content in slag, do not carry out white slag process.The refine later stage adopts Feed aluminum wire to insert Si-Ca core-spun yarn and the control deoxidation of Si-Mg core-spun yarn to molten steel is internal, feeds silk amount fixed according to steel grade and recovery rate.
3) continuous casting: mold liquid level adopts special automatic steel crystallizer protecting residue (concrete composition is in Table 1)；Should controlling the degree of superheat during casting at about 20 ~ 40 DEG C, the strand for 150 × 150mm should control pulling rate at 1.90 ~ 2.10m/min, and the strand for 200 × 200mm should control pulling rate at 1.10 ~ 1.25m/min；Secondary cooling water adopts weak cold, and nozzle mist is cold, specific water 0.60 ~ 0.75L/kg；Adopt M-EMS and solidification end electromagnetic agitation technique, uniform molten steel composition and temperature simultaneously and improve molten steel solidification tissue.
4) rolling: during cogging, heating-up temperature necessarily be greater than 1050 DEG C, controls between 1150 ~ 1200 DEG C, and during stocking, heating and temperature control is at 1100 ~ 1150 DEG C.Strictly control finishing temperature, it is ensured that stocking obtains uniformly tiny ferrite+pearlitic structrure.
Molten steel is controlled deoxidation by present invention calcium-silicon and Si-Mg alloy, has efficiently controlled the form of nonmetallic inclusionsin steel, has refined field trash and crystal grain, makes steel obtain the mechanical property of excellence and good cutting ability.Utilizing the iron core line containing magnesium or the iron core line containing Si-Mg alloy as magnesium source in smelting, be inserted simultaneously in molten steel with silico-calcium core-spun yarn, calcium and magnesium comparatively smoothly can dissolve in molten steel, does not result in big splash, it is possible to guarantees the recovery rate of calcium and magnesium.
The effect of each element of the present invention:
C: strong hardness and the plasticity and toughness of steel are had critically important impact by the height of carbon content.Carbon content is too high, and the ratio of steel medium pearlite increases thus improving the strong hardness of steel, increases machining drag；Ratio of ferrite in the too low then steel matrix of carbon content is higher, and the plasticity and toughness increase of steel causes steel deliquescing, causes when machining chip not easily cataclasm and processing parts size precision is low, also reduce the mechanical property of steel simultaneously.
Si: if silicon can control the deoxidation degree of low-carbon free-cutting steel as deoxidizer, is affect steel medium sulphide content to be mingled with the key element of deformation and cutting ability, is also one of element worsening cutting rolled steel performance simultaneously.Silicon forms silicate in steel, can cause that tool wear, silicon height can promote phosphorus to precipitate out from matrix, is easily formed phosphide thin film at crystal boundary, worsens the hot-working character of steel.
Mn: manganese is a kind of element improving steel hardenability and improving intensity, and the MnS that manganese generates with the sulfur in steel is a kind of important free-cutting phase, it is possible to help improve cutting ability.In order to ensure good cutting ability and mechanical property, the present invention controls the content of manganese 0.7 ~ 1.0.
S: sulfur is one of main Cutting free element, and along with the increase of sulfur content in steel, the machinability rating of steel significantly improves.Sulfur in steel, makes chip easily broken owing to MnS field trash has cut off the seriality of matrix, again owing to the lubrication of MnS reduces the abrasion of cutter, thus improving the machinability of steel with the formal distribution of Manganese monosulfide. (MnS).But MnS easily extends along rolling direction when hot rolling simultaneously, reduce the horizontal mechanical performance of steel.Therefore the present invention controls sulfur content is 0.08 ~ 0.13.
Ca: calcium adds in steel as inclusion modification agent, with the combined oxidation such as silicon, aluminum, formation anorthite (CaO Al2O3·2SiO2).When cutting temperature raises, these composite oxides can soften on Tool in Cutting sword face and pile up, and form built-up edge, slow down tool wear.Calcium is commonly used for the deoxidizer of steel-making.In solidification of molten steel process, the oxidation product of calcium is as sulfide forming core core, it is possible to promote the precipitation of sulfide and being uniformly distributed of sulfide.Calcium can also play the effect changing oxide morphology.Calcium adds (Mn, the Ca) S forming compound in steel, thus the deformability reducing sulfide improves the horizontal mechanical performance of steel.
The upgrading route of field trash in molten steel is shown in that Fig. 1, Ca both can react generation CaO, CaS or Ca-O-S directly as deoxidizer and desulfurizing agent with O, the S in molten steel by Ca；If being previously added Al in molten steel as deoxidizer, then the Ca added can also with the Al of generation in molten steel2O3In conjunction with generating CaO Al2O3, and as the forming core core of MnS, forming the inside is CaO Al2O3It is surrounded by the complex inclusion of MnS or Ca-Mn-S.
Mg: magnesium is the metallic element more more active than calcium, is commonly used for deoxidizer in steel production and desulfurizing agent.In solidification of molten steel process, its oxidation product is as the forming core core of sulfide, it is possible to promotes the precipitation of sulfide and is uniformly distributed.Magnesium can also play the effect changing oxide morphology.Calcium adds (Mn, the Mg) S forming compound in steel, thus the deformability reducing sulfide improves the horizontal mechanical performance of steel.
The upgrading route of field trash in molten steel is shown in that Fig. 2, Mg both can react generation MgO, MgS or Mg-O-S directly as deoxidizer and desulfurizing agent with O, the S in molten steel by Mg；Can also reacting with the O in molten steel and generate the MgO forming core core directly as MnS, forming the inside is the MgO complex inclusion being surrounded by MnS or Mg-Mn-S；If being previously added Al in molten steel as deoxidizer, then the Mg added can with the Al of generation in molten steel2O3In conjunction with generating MgO Al2O3, and as the forming core core of MnS, forming the inside is MgO Al2O3It is surrounded by the complex inclusion of MnS or Mg-Mn-S.
Ca, Mg in molten steel participates in shown in the thermodynamic data following (chemical formula one, two) of desulphurization reaction:
(chemical formula one) [Ca]+[S]=CaS(s)△G1 θ=-541158.26+193.33T
(chemical formula two) [Mg]+[S]=MgS(s)△G2 θ=-537258.5+205.77T
The thermodynamical equilibrium relation of Ca in 1873K molten steel, Mg and S can be obtained according to activity theory:
1873Ka[Ca]·a[S]=10-5a[Mg]·a[S]=5.75×10-5
By the thermodynamical equilibrium relation of Ca, Mg and S, when can obtain 1873K balance, in steel, the concentration relationship of [Ca], [Mg] and [S] is as shown in Figures 3 and 4.
As seen from Figure 3, calcium is a kind of very strong desulfurizing agent, along with the increase of [Ca] content in steel, when reaching to balance, it is possible to the dissolved oxygen content in steel is reduced to extremely low level.
As seen from Figure 4, magnesium is also a kind of very strong desulfurizing agent, it is possible to quickly drop to relatively low level dissolving sulfur content, but Mg desulphurizing ability is markedly less than Ca desulphurizing ability.
Accompanying drawing explanation
Fig. 1 is that Ca is to the upgrading route of field trash in molten steel.
Fig. 2 is that Mg is to the upgrading route of field trash in molten steel.
Fig. 3 is calcium sulfur balance figure.
Fig. 4 is magnesium sulfur balance figure.
Detailed description of the invention
The following example light plate is the chemical composition designed by the present invention, smelts prepared by continuous casting process, rolling mill practice.
Embodiment 1: a kind of automatic steel containing magnesium calcium in the present embodiment, being made up of following components in percentage by weight: C:0.50%, Si:0.30%, Mn:1.00%, P:0.04%, S:0.10%, Mg:0.003%, Ca:0.002%, its surplus is Fe and inevitable impurity.Casting blank specification is 150 × 150mm.
The smelting of the present embodiment, continuous casting and rolling mill practice are as follows:
1) converter smelting: before converter, molten iron is without pre-desulfurization.The main task bessemerized is decarburization and intensification, it is not necessary to desulfurization and dephosphorization, adopts low basicity slag (R=2 ~ 3), few slag operation；For " protect phosphorus carbon elimination ", reduce the low temperature dephosphorization phase, steel scrap can be added less, it is considered to suitably reduce soft blow (the high rifle position) time, increase and firmly blow (the low rifle position) time；Aim carbon is wanted rationally, can not be too low, slag-stopping tapping.Converter adopts the smelting process of top blowing oxygen BOTTOM ARGON BLOWING.Converter tapping process adopts the first deoxidation of strong deoxidizer (Si-Ca-Ba or silicon aluminum calcium barium alloy), again with ferromanganese control oxygen (tap about half time, deoxidizer will be remained: ferromanganese, sulfur ferrum and ferrophosphorus add together), adopting the quick Determining oxygen probe of zirconia solid electrolyte oxygen concentration cell to measure the oxygen activity in molten steel, after making tapping, the oxygen activity of molten steel controls 60 ~ 200 × 10-6。
2) LF refine: suitably slag making, it is ensured that thickness of slag layer, must control the basicity of slag and reducing atmosphere well, and basicity of slag R, with 0.8 ~ 1.5 for control standard, adds iron sulfide control sulfur content in slag, do not carry out white slag process.The refine later stage adopts Feed aluminum wire to insert Si-Ca core-spun yarn and the control deoxidation of Si-Mg core-spun yarn to molten steel is internal, feeds silk amount fixed according to steel grade and recovery rate.
3) continuous casting: mold liquid level adopts special automatic steel crystallizer protecting residue；Controlling the degree of superheat during casting at about 20 ~ 40 DEG C, strand controls pulling rate 2.00m/min；Secondary cooling water adopts weak cold, and nozzle mist is cold, and specific water is 0.6L/kg；Adopt M-EMS and solidification end electromagnetic agitation technique, uniform molten steel composition and temperature simultaneously and improve molten steel solidification tissue.
4) rolling: during cogging, heating-up temperature necessarily be greater than 1050 DEG C, controls between 1150 ~ 1200 DEG C, and during stocking, heating and temperature control is at 1100 ~ 1150 DEG C.Strictly control finishing temperature, it is ensured that stocking obtains uniformly tiny ferrite+pearlitic structrure.
Embodiment 2: a kind of automatic steel containing magnesium calcium in the present embodiment, being made up of following components in percentage by weight: C:0.55%, Si:0.40%, Mn:1.00%, P:0.04%, S:0.10%, Mg:0.004%, Ca:0.003%, its surplus is Fe and inevitable impurity.Casting blank specification is 200 × 200mm.
The smelting of the present embodiment, continuous casting and rolling mill practice are as follows:
1) converter smelting: before converter, molten iron is without pre-desulfurization.The main task bessemerized is decarburization and intensification, it is not necessary to desulfurization and dephosphorization, adopts low basicity slag (R=2 ~ 3), few slag operation；For " protect phosphorus carbon elimination ", reduce the low temperature dephosphorization phase, steel scrap can be added less, it is considered to suitably reduce soft blow (the high rifle position) time, increase and firmly blow (the low rifle position) time；Aim carbon is wanted rationally, can not be too low, slag-stopping tapping.Converter adopts the smelting process of top blowing oxygen BOTTOM ARGON BLOWING.Converter tapping process adopts the first deoxidation of strong deoxidizer (Si-Ca-Ba or silicon aluminum calcium barium alloy), again with ferromanganese control oxygen (tap about half time, deoxidizer will be remained: ferromanganese, sulfur ferrum and ferrophosphorus add together), adopting the quick Determining oxygen probe of zirconia solid electrolyte oxygen concentration cell to measure the oxygen activity in molten steel, after making tapping, the oxygen activity of molten steel controls 60 ~ 200 × 10-6。
2) LF refine: suitably slag making, it is ensured that thickness of slag layer, must control the basicity of slag and reducing atmosphere well, and basicity of slag R, with 0.8 ~ 1.5 for control standard, adds iron sulfide control sulfur content in slag, do not carry out white slag process.The refine later stage adopts Feed aluminum wire to insert Si-Ca core-spun yarn and the control deoxidation of Si-Mg core-spun yarn to molten steel is internal, feeds silk amount fixed according to steel grade and recovery rate.
3) continuous casting: mold liquid level adopts special automatic steel crystallizer protecting residue；Controlling the degree of superheat during casting at about 20 ~ 40 DEG C, strand controls pulling rate 1.20m/min；Secondary cooling water adopts weak cold, and nozzle mist is cold, and specific water is 0.75L/kg；Adopt M-EMS and solidification end electromagnetic agitation technique, uniform molten steel composition and temperature simultaneously and improve molten steel solidification tissue.
4) rolling: during cogging, heating-up temperature necessarily be greater than 1050 DEG C, controls between 1150 ~ 1200 DEG C, and during stocking, heating and temperature control is at 1100 ~ 1150 DEG C.Strictly control finishing temperature, it is ensured that stocking obtains uniformly tiny ferrite+pearlitic structrure.
Claims (3)
1. the automatic steel containing magnesium calcium, it is characterized in that chemical composition (wt%) is: C:0.48 ~ 0.55, Si:0.20 ~ 0.50, Mn:0.70 ~ 1.00, P :≤0.04, S:0.08 ~ 0.13, Mg:0.001 ~ 0.006, Ca:0.0008 ~ 0.006, its surplus is Fe and inevitable impurity.
2. the automatic steel containing magnesium calcium as claimed in claim 1, it is characterised in that the composition (wt%) of automatic steel is: C:0.48 ~ 0.55, Si:0.20 ~ 0.50, Mn:0.70 ~ 1.00, P :≤0.04, S:0.08 ~ 0.13, Mg:0.0015 ~ 0.004, Ca:0.0015 ~ 0.003.
3. the production technology of the automatic steel containing magnesium calcium as claimed in claim 1, it is characterised in that this processing step is as follows:
1) converter smelting: before converter, molten iron is without pre-desulfurization；The main task bessemerized is decarburization and intensification, it is not necessary to desulfurization and dephosphorization, adopts low basicity slag, and basicity of slag R is with 2 ~ 3 for the few slag operation of control standard；For " protect phosphorus carbon elimination ", reduce the low temperature dephosphorization phase, steel scrap can be added less, it is considered to suitably reduce the soft blow time, increase and firmly blow the time；Aim carbon is wanted rationally, can not be too low, slag-stopping tapping；Converter adopts the smelting process of top blowing oxygen BOTTOM ARGON BLOWING；Adopting the deoxidation of strong deoxidizer elder generation in converter tapping process, then with ferromanganese control oxygen, adopt the quick Determining oxygen probe of zirconia solid electrolyte oxygen concentration cell to measure the oxygen activity in molten steel, after making tapping, the oxygen activity of molten steel controls 60 ~ 200 × 10-6；
2) LF refine: suitably slag making, it is ensured that thickness of slag layer, must control the basicity of slag and reducing atmosphere well, and basicity of slag R, with 0.8 ~ 1.5 for control standard, adds iron sulfide control sulfur content in slag, carries out white slag process；The refine later stage adopts Feed aluminum wire to insert Si-Ca core-spun yarn and the control deoxidation of Si-Mg core-spun yarn to molten steel is internal, feeds silk amount fixed according to steel grade and recovery rate；
3) continuous casting: mold liquid level adopts special automatic steel crystallizer protecting residue；Should controlling the degree of superheat during casting at 20 ~ 40 DEG C, the strand for 150 × 150mm should control pulling rate at 1.90 ~ 2.10m/min, and the strand for 200 × 200mm should control pulling rate at 1.10 ~ 1.25m/min；Secondary cooling water adopts weak cold, and nozzle mist is cold, specific water 0.60 ~ 0.75L/kg；Adopt M-EMS and solidification end electromagnetic agitation technique, uniform molten steel composition and temperature simultaneously and improve molten steel solidification tissue；
4) rolling: during cogging, heating-up temperature necessarily be greater than 1050 DEG C, controls between 1050 ~ 1200 DEG C, and during stocking, heating and temperature control is at 1100 ~ 1150 DEG C；Strictly control finishing temperature, it is ensured that stocking obtains uniformly tiny ferrite+pearlitic structrure.
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| CN111286678A (en) * | 2020-04-08 | 2020-06-16 | 中天钢铁集团有限公司 | High-sulfur non-quenched and tempered steel for automobile camshaft and production process thereof |
| CN113604745A (en) * | 2021-08-12 | 2021-11-05 | 山东钢铁股份有限公司 | High-sulfur free-cutting tool steel bar and preparation method thereof |
| CN113913676A (en) * | 2021-10-27 | 2022-01-11 | 广东韶钢松山股份有限公司 | Metallurgy method for improving morphology of as-cast sulfide of medium-carbon high-sulfur free-cutting steel |
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