CN104162678A - Method for preparing high-compressibility water atomization stainless steel powder through intergranular corrosion - Google Patents
Method for preparing high-compressibility water atomization stainless steel powder through intergranular corrosion Download PDFInfo
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- CN104162678A CN104162678A CN201410444933.XA CN201410444933A CN104162678A CN 104162678 A CN104162678 A CN 104162678A CN 201410444933 A CN201410444933 A CN 201410444933A CN 104162678 A CN104162678 A CN 104162678A
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- stainless steel
- water atomization
- intercrystalline corrosion
- steel powder
- compressibility
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Abstract
The invention discloses a method for processing high-compressibility water atomization stainless steel powder through intergranular corrosion. Carbon elements are added into molten steel after molten steel melting is finished and before water atomization power preparing, the content of C is controlled and adjusted to range from 0.10 percent to 1.00 percent, intergranular corrosion chemical component sensitization is carried out, and water atomization power preparing is carried out. Intergranular corrosion heat processing sensitization is carried out on the stainless steel power for one hour to ten hours under the protection of argon at the temperature ranging from 450 DEG C to 750 DEG C. Steam is fed into an adjustable atmosphere furnace, the content of oxygen ranges from 1 percent to 30 percent, the content of hydrogen chloride ranges from 0 percent to 5 percent, and intergranular corrosion is carried out on the stainless steel powder for 0.1 hour to 5 hours at the temperature ranging from 450 DEG C to 850 DEG C. According to the method, the adverse effect of a sponge iron multi-hole structure on the pressed density can be greatly reduced, the hardness of the obtained water atomization stainless steel powder is low, and accordingly the compressibility is improved.
Description
Technical field
The present invention relates to the preparation of stainless steel powder, specifically refer to a kind of method of utilizing intercrystalline corrosion to prepare high-compressibility water atomization stainless steel powder, belong to powder metallurgical technology.
Background technology
Compressibility is one of most important processing performance of steel powder product, and in the situation that the condition such as pressing pressure, mold tooling is constant, powder compressibility is directly determining density and the mechanical property thereof of part.Nineteen sixty-five, the U.S. takes the lead in adopting hydraulic atomized technology to produce mild steel powder, and the powder forming that makes is poor, powder green compact intensity is low, is difficult to practical application.The beginning of the seventies in last century, Germany passed through high temperature reduction technique, had obtained compressibility and formability and had all showed excellent water-atomized iron powder.P/m Iron Base extrudate density reaches 7.2g/cm
3after, its hardness, tensile strength, fatigue strength, toughness etc. all can be geometric progression with the increase of density and increase.The Li Songlin of Central South University, Cui Jianmin etc. disclose the patent (application number: 201110275149.7) of " a kind of high-compressibility water-atomized iron powder and preparation method ".This patent is taking steel scrap as raw material, by controls such as raw alloy constituent content, smelting molten steel composition, high temperature reductions, iron powder purity is reached: C≤0.01%, O≤0.15%, S≤0.01%, Mn+ P+ Si≤0.20%, Cr+Ni+Cu≤0.1%, microhardness≤90 HV of particle, straight iron powder compressibility after treatment reaches 7.20g/cm
3(600MPa places an order and axially suppresses).But density is at 7.20g/cm at present
3still dependence on import or traditional machining of high-quality sintered alloy steel construction part for above auto industry.Reason is:
China lacks the raw material that quality is high, impurity content is low.The raw material that Sweden He Genasi adopts is the distinctive carbonyl iron refined ore of Sweden.Byproduct-high-carbon pure iron water that the raw material that Canadian Quebec metal dust company adopts is smelting titanic iron ore, the quality of raw material molten iron is high, impurity content is low, the harshness of raw material is required to limited its production technology and be not suitable for carrying out large-scale production in China.The domestic steel scrap that nearly all adopts does raw material, and steel scrap is various in style, and the raw scrap material of alloying element content extremely low (Cr+Ni+Cu≤0.1%) is few, and selected difficulty is higher.
The alloying element purifying costs such as Cr, Ni, Cu are high.The element purifying such as C, O, S, P can carry out in smelting molten steel and high temperature reduction operation, and the alloying element purifying costs such as Cr, Ni, Cu will be multiplied.
While preparing steel construction part, add the alloying element uniformities such as Cr, Ni, Cu poor.While preparing steel construction part with straight iron powder, need to add the alloyed powder that contains the elements such as Cr, Ni, Cu.Alloyed powder and straight iron powder are unavoidable mixing, in conveying and suppression process produces segregation.In sintering circuit, uniform alloyization also needs long-time high temperature diffusion annealing, easily causes grain coarsening.In actual production technique, for fear of grain coarsening, in sintered article, the pseudo-alloy state in mechanical mixture often between alloyed powder and straight iron powder, has limited the raising of product properties.
Alloying in smelting molten steel, composition is even, and this is the significant advantage of water atomization comminuted steel shot.But water atomization comminuted steel shot hardness is high, and compressibility is low, be difficult to practical application.Adopt traditional high annealing, decarburization and feed purification, cannot meet its hardness requirement.Though after powder surface redox, can form the sponge iron of loose structure, reduce hardness, but the loose structure of sponge iron compacting and sintering in cannot eliminate completely, thereby reduction goods density.
Summary of the invention
For prior art above shortcomings, the object of this invention is to provide a kind of method of utilizing intercrystalline corrosion to prepare high-compressibility water atomization stainless steel powder, this method can reduce the adverse effect of sponge iron loose structure to pressed density greatly, the water atomization stainless steel powder hardness obtaining is low, thereby improves compressibility.
Technical scheme of the present invention is achieved in that
Utilize intercrystalline corrosion to prepare a method for high-compressibility water atomization stainless steel powder, step is as follows,
1) composition is determined: process as required the composition requirement of the powder metallurgical stainless steel constitutional detail obtaining, determine the composition of its raw water atomization stainless steel powder;
2) smelting molten steel: by the 1st) composition of the definite water atomization stainless steel powder of step gets the raw materials ready and carries out smelting molten steel;
3) intercrystalline corrosion chemical composition sensitization: finish to carry out, before water atomization pulverization, to add carbon in smelting molten steel at smelting molten steel, controlling and regulating C content is 0.10%～1.00%;
4) water atomization pulverization;
5) intercrystalline corrosion heat treatment sensitization: under argon gas atmosphere protection, at 450 DEG C～750 DEG C temperature, stainless steel powder is carried out to intercrystalline corrosion heat treatment sensitization, heat treatment sensitization time is 1h～10h;
6) intercrystalline corrosion: in adjustable atmosphere furnace, pass into steam, at 450 DEG C～850 DEG C of oxygen contents 1%～30%, hydrogen chloride gas body burden 0%～5%, corrosion temperature, stainless steel powder is carried out to intercrystalline corrosion, the time is 0.1h～5h;
7) high temperature reduction, then carry out follow-up pulverizing, grinding and screening and process and obtain high-compressibility water atomization stainless steel powder.
Further, the 3rd) in the sensitization of step intercrystalline corrosion chemical composition, the control of C content is 0.50%～0.8%.
Further, the 5th) optimum condition of step intercrystalline corrosion heat treatment sensitization is, 500 DEG C～720 DEG C of temperature, and the time is 2h～6h.
Further, the 6th) optimum condition of step intercrystalline corrosion is, oxygen content 4%～10%, and hydrogen chloride gas body burden 1%～3%, 550 DEG C～700 DEG C of temperature, the time is 1h～2h.
Compared to existing technology, the present invention has the following advantages:
1, after intercrystalline corrosion, comminuted steel shot top layer grain boundary structure is made up of the crystal boundary not being corroded and the rear sponge iron forming of corrosion oxidation product reduction, and the loose structure of sponge iron has weakened the adhesion between surface layer grain.Under pressing pressure, surface layer grain intercrystalline fracture, the fine particle of generation can be filled in space, improves compressibility.
2, between this method comminuted steel shot surface layer grain, still there is stronger adhesion, be equivalent to additional fine particle and be evenly closely wrapped in coarse granule surface, less on the impact of apparent density of powder, mobility and particle segregation.
3, the fine particle that the present invention suppresses generation has been intercrystalline corrosion, and crystal boundary is few, intensity low (under pressing pressure, its crystal boundary can destroy completely, forms monocrystal), and crystal boundary is little to the inhibition of moulding distortion, is easy to moulding distortion.
4, compared with surface oxidation embrane method, intercrystalline corrosion scope is little, accelerates intercrystalline corrosion, suppresses general corrosion, can at utmost reduce the adverse effect of the loose structure forming after corrosion product reduction to pressed density.
Detailed description of the invention
The present invention utilizes intercrystalline corrosion to prepare water atomization stainless steel powder, and intercrystalline corrosion scope is little, accelerates intercrystalline corrosion, suppresses general corrosion, can reduce to greatest extent the adverse effect of the loose structure that forms sponge iron after corrosion product reduction to pressed density.
The technology of the present invention route is substantially identical with existing water atomized steel powder technology path.Difference is: the present invention utilizes crystal boundary poor Cr theory, in smelting molten steel, increase C content, spray quenching forms supersaturated solid solution, in intercrystalline corrosion sensitive temperature (being step 5 heat treatment sensitizing temperature) tempering, C separates out at crystal boundary, forms compound with Cr, consumes the Cr of grain boundaries, cause the poor chromium of crystal boundary, accelerate intercrystalline corrosion.Chromium in stainless steel powder can form fine and close passivating film on its surface and suppress general corrosion.By reduction and the decarburization of follow-up high temperature reduction operation, eliminate its impact on product properties.Concrete technology is as follows:
1) composition is determined: process as required the composition requirement of the powder metallurgical stainless steel constitutional detail obtaining, determine the composition of its raw water atomization stainless steel powder;
2) smelting molten steel: by the 1st) composition of the definite water atomization stainless steel powder of step gets the raw materials ready and carries out smelting molten steel;
3) intercrystalline corrosion chemical composition sensitization: finish to carry out before water atomization pulverization at smelting molten steel, to supplementing and add carbon in smelting molten steel, controlling and regulating C content is 0.10%～1.00% of whole molten steel content;
4) water atomization pulverization; Comprise water atomization, dehydration, dry, magnetic separation, screening etc.;
5) intercrystalline corrosion heat treatment sensitization: under argon gas atmosphere protection, at 450 DEG C～750 DEG C temperature, stainless steel powder is carried out to intercrystalline corrosion heat treatment sensitization, heat treatment sensitization time is 1h～10h;
6) intercrystalline corrosion: in adjustable atmosphere furnace, pass into steam, at 450 DEG C～850 DEG C of oxygen contents 1%～30%, hydrogen chloride gas body burden 0%～5%, corrosion temperature, stainless steel powder is carried out to intercrystalline corrosion, the time is 0.1h～5h;
7) high temperature reduction, then carry out follow-up pulverizing, grinding and screening and process and obtain high-compressibility water atomization stainless steel powder.
The present invention, in existing water atomization stainless steel powder preparation technology, has increased step 3), 5) and 6), by the Cr of carbon consumption grain boundaries, cause the poor chromium of crystal boundary, accelerate intercrystalline corrosion.Therefore step 3), 5) and 6) control larger on result impact, belong to committed step of the present invention.
The 3rd), in the sensitization of step intercrystalline corrosion chemical composition, it is 0.50%～0.8% that C content is preferably controlled.
The 5th) optimum condition of step intercrystalline corrosion heat treatment sensitization is, 500 DEG C～720 DEG C of temperature, and the time is 2h～6h.
The 6th) optimum condition of step intercrystalline corrosion is, oxygen content 4%～10%, and hydrogen chloride gas body burden 1%～3%, 550 DEG C～700 DEG C of temperature, the time is 1h～2h.
The preferred embodiment of the present invention is: the 3rd), in the sensitization of step intercrystalline corrosion chemical composition, C content is 0.5%～0.6%.The 5th) step intercrystalline corrosion heat treatment sensitization condition is, 600 DEG C～620 DEG C of temperature, and the time is 2h～3h.The 6th) step intercrystalline corrosion condition is, oxygen content 5%～6%, and hydrogen chloride gas body burden 1%～2%, 600 DEG C～650 DEG C of temperature, the time is 1h～2h.
Because water atomization stainless steel powder technology of preparing is through the development of decades, comparative maturity, so the present invention does not all elaborate to existing other step (comprising equipment, technical process and technical parameter etc.).
Intercrystalline corrosion method improves the constrictive principle of water atomization comminuted steel shot:
After intercrystalline corrosion, comminuted steel shot top layer grain boundary structure is made up of the crystal boundary not being corroded and the rear sponge iron forming of corrosion oxidation product reduction, and the loose structure of sponge iron has weakened the adhesion between surface layer grain.Under pressing pressure, surface layer grain intercrystalline fracture, the fine particle of generation can be filled in space, improves compressibility.Compared with additional fine particle, there is following significant advantage.
According to the closeest filling theory of Horsfield, in coarse granule, add step by step fine particle, can effectively reduce porosity, improve powders compression performance.But additional fine particle, can reduce apparent density and the mobility of powder, and frictional resistance while increasing compacting produces particle segregation in powder transhipment, filling and suppression process.And between this method comminuted steel shot surface layer grain, still there is stronger adhesion, and be equivalent to additional fine particle and be evenly closely wrapped in coarse granule surface, less on the impact of apparent density of powder, mobility and particle segregation.
According to Hall-petch formula (s
s=s
0+ kd
-1/2) known, crystal boundary plays inhibition to plastic deformation, and crystal boundary is more, and crystal grain is thinner, and the yield strength of material is higher.Additional tiny water atomized steel powder, crystal grain is tiny, and yield strength is high, is difficult to moulding distortion.And the present invention suppresses the fine particle of generation and has been intercrystalline corrosion, crystal boundary is few, intensity low (under pressing pressure, its crystal boundary can destroy completely, forms monocrystal), and crystal boundary is little to the inhibition of moulding distortion, is easy to moulding distortion.
In addition, compared with surface oxidation embrane method, intercrystalline corrosion scope is little, accelerates intercrystalline corrosion, suppresses general corrosion, can at utmost reduce the adverse effect of the loose structure forming after corrosion product reduction to pressed density.
As seen through the above analysis, intercrystalline corrosion method can significantly improve water atomization comminuted steel shot compressibility.
The above embodiment of the present invention is to be only explanation example of the present invention, and is not the restriction to embodiments of the present invention.For those of ordinary skill in the field, can also make on the basis of the above description other multi-form variation and variations.Here cannot give exhaustive to all embodiments.Everyly belong to apparent variation or the still row in protection scope of the present invention of variation that technical scheme of the present invention amplifies out.
Claims (4)
1. utilize intercrystalline corrosion to prepare a method for high-compressibility water atomization stainless steel powder, it is characterized in that, step is as follows,
1) composition is determined: process as required the composition requirement of the powder metallurgical stainless steel constitutional detail obtaining, determine the composition of its raw water atomization stainless steel powder;
2) smelting molten steel: by the 1st) composition of the definite water atomization stainless steel powder of step gets the raw materials ready and carries out smelting molten steel;
3) intercrystalline corrosion chemical composition sensitization: finish to carry out, before water atomization pulverization, to add carbon in smelting molten steel at smelting molten steel, controlling and regulating C content is 0.10%～1.00%;
4) water atomization pulverization;
5) intercrystalline corrosion heat treatment sensitization: under argon gas atmosphere protection, at 450 DEG C～750 DEG C temperature, stainless steel powder is carried out to intercrystalline corrosion heat treatment sensitization, heat treatment sensitization time is 1h～10h;
6) intercrystalline corrosion: in adjustable atmosphere furnace, pass into steam, at 450 DEG C～850 DEG C of oxygen contents 1%～30%, hydrogen chloride gas body burden 0%～5%, corrosion temperature, stainless steel powder is carried out to intercrystalline corrosion, the time is 0.1h～5h;
7) high temperature reduction, then carry out follow-up pulverizing, grinding and screening and process and obtain high-compressibility water atomization stainless steel powder.
2. the method for utilizing intercrystalline corrosion to prepare high-compressibility water atomization stainless steel powder according to claim 1, is characterized in that: the 3rd), in the sensitization of step intercrystalline corrosion chemical composition, the control of C content is 0.50%～0.8%.
3. the method for utilizing intercrystalline corrosion to prepare high-compressibility water atomization stainless steel powder according to claim 1, is characterized in that: the 5th) optimum condition of step intercrystalline corrosion heat treatment sensitization is, 500 DEG C～720 DEG C of temperature, and the time is 2h～6h.
4. the method for utilizing intercrystalline corrosion to prepare high-compressibility water atomization stainless steel powder according to claim 1, it is characterized in that: the 6th) optimum condition of step intercrystalline corrosion is oxygen content 4%～10%, hydrogen chloride gas body burden 1%～3%, 550 DEG C～700 DEG C of temperature, the time is 1h～2h.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106694871A (en) * | 2017-02-28 | 2017-05-24 | 四川理工学院 | Method for improving compactibility of manganese-containing steel powder |
| CN107127349A (en) * | 2017-06-05 | 2017-09-05 | 华北理工大学 | A kind of method of high temperature liquid iron aerosolization decarburization steel-making |
| CN110195152A (en) * | 2019-06-11 | 2019-09-03 | 河南神州精工制造股份有限公司 | A method of improving austenitic stainless steel anti intercrystalline corrosion ability |
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| JPS5726108A (en) * | 1980-07-24 | 1982-02-12 | Takasago Tekko Kk | Production of stainless steel powder |
| JP2006038840A (en) * | 2004-06-24 | 2006-02-09 | Chugoku Electric Power Co Inc:The | Method for grain boundary etching of metal surface |
| CN102350497A (en) * | 2011-09-16 | 2012-02-15 | 中南大学 | High-compressibility water atomization iron powder and preparation method thereof |
| CN102689008A (en) * | 2011-03-23 | 2012-09-26 | 杰富意钢铁株式会社 | Method of finish heat treatment of iron powder and apparatus for finish heat treatment |
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2014
- 2014-09-03 CN CN201410444933.XA patent/CN104162678B/en not_active Expired - Fee Related
Patent Citations (5)
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|---|---|---|---|---|
| JPS5263802A (en) * | 1975-11-25 | 1977-05-26 | Hitachi Ltd | Process of basic material for sintering of stainless steel |
| JPS5726108A (en) * | 1980-07-24 | 1982-02-12 | Takasago Tekko Kk | Production of stainless steel powder |
| JP2006038840A (en) * | 2004-06-24 | 2006-02-09 | Chugoku Electric Power Co Inc:The | Method for grain boundary etching of metal surface |
| CN102689008A (en) * | 2011-03-23 | 2012-09-26 | 杰富意钢铁株式会社 | Method of finish heat treatment of iron powder and apparatus for finish heat treatment |
| CN102350497A (en) * | 2011-09-16 | 2012-02-15 | 中南大学 | High-compressibility water atomization iron powder and preparation method thereof |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106694871A (en) * | 2017-02-28 | 2017-05-24 | 四川理工学院 | Method for improving compactibility of manganese-containing steel powder |
| CN107127349A (en) * | 2017-06-05 | 2017-09-05 | 华北理工大学 | A kind of method of high temperature liquid iron aerosolization decarburization steel-making |
| CN107127349B (en) * | 2017-06-05 | 2019-11-19 | 华北理工大学 | A kind of method of high temperature liquid iron aerosolization decarburization steel-making |
| CN110195152A (en) * | 2019-06-11 | 2019-09-03 | 河南神州精工制造股份有限公司 | A method of improving austenitic stainless steel anti intercrystalline corrosion ability |
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