CN104162678B - A kind of method utilizing intercrystalline corrosion to prepare high-compressibility water atomization stainless steel powder - Google Patents
A kind of method utilizing intercrystalline corrosion to prepare high-compressibility water atomization stainless steel powder Download PDFInfo
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- CN104162678B CN104162678B CN201410444933.XA CN201410444933A CN104162678B CN 104162678 B CN104162678 B CN 104162678B CN 201410444933 A CN201410444933 A CN 201410444933A CN 104162678 B CN104162678 B CN 104162678B
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Abstract
The invention discloses a kind of method utilizing intercrystalline corrosion to prepare high-compressibility water atomization stainless steel powder, before smelting molten steel terminates to carry out water atomization pulverization, carbon is added in smelting molten steel, control and regulate C content to be 0.10% ~ 1.00%, carry out the sensitization of intercrystalline corrosion chemical composition, then water atomization pulverization; Again under argon gas atmosphere protection, at 450 DEG C ~ 750 DEG C temperature, carry out intercrystalline corrosion heat treatment sensitization to stainless steel powder, heat treatment sensitization time is 1h ~ 10h; Last in adjustable atmosphere furnace, pass into steam, at oxygen content 1% ~ 30%, hydrogen chloride gas body burden 0% ~ 5%, corrosion temperature 450 DEG C ~ 850 DEG C, carry out intercrystalline corrosion to stainless steel powder, the time is 0.1h ~ 5h.The present invention can reduce the adverse effect of sponge iron loose structure to pressed density greatly, and the water atomization stainless steel powder hardness obtained is low, thus improves compressibility.
Description
Technical field
The present invention relates to the preparation of stainless steel powder, specifically refer to a kind of method 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 when the condition such as pressing pressure, mold tooling is constant, powder compressibility directly decides 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 obtained powder forming is poor, powder green compact intensity is low, is difficult to practical application.The beginning of the seventies in last century, Germany was by high temperature reduction technique, obtained compressibility and formability all shows 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 increase in geometric progression with the increase of density.Central South University Li Songlin, 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 take 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≤the 90HV of particle, the straight iron powder compressibility after process reaches 7.20g/cm
3(uniaxially suppressing under 600MPa).But density is at 7.20g/cm at present
3above auto industry high-quality sintered alloy steel construction part still dependence on import or traditional machining.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.The raw material that Canadian Quebec metal dust company adopts is the byproduct-high-carbon pure iron water of smelting titanic iron ore, and the quality of raw material molten iron is high, impurity content is low, limits its production technology be not suitable for carrying out large-scale production in China to the rigors of raw material.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.
The alloying element uniformity such as Cr, Ni, Cu are added poor when preparing steel construction part.When preparing steel construction part with straight iron powder, the alloyed powder containing elements such as Cr, Ni, Cu need be added.Alloyed powder is mixing with straight iron powder, is carrying and produce segregation unavoidably in suppression process.In sintering circuit, uniform alloyization also needs long-time high temperature diffusion annealing, easily causes grain coarsening.In actual production technique, in order to avoid grain coarsening, be often in the pseudo-alloy state of mechanical mixture in sintered article between alloyed powder and straight iron powder, limit the raising of product properties.
Alloying in smelting molten steel, uniform composition, 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, its hardness requirement cannot be met.Although can form the sponge iron of loose structure after powder surface redox, can reduce hardness, but the loose structure of sponge iron cannot be eliminated completely in compacting and sintering, thus reduces the density of goods.
Summary of the invention
For prior art above shortcomings, the object of this invention is to provide a kind of method 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 obtained is low, thus 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: the component requirements processing the powder metallurgical stainless steel constitutional detail obtained as required, determines the composition of its raw water atomization stainless steel powder;
2) smelting molten steel: by the 1st) composition of water atomization stainless steel powder determined of step gets the raw materials ready and carries out smelting molten steel;
3) intercrystalline corrosion chemical composition sensitization: before smelting molten steel terminates to carry out water atomization pulverization, add carbon in smelting molten steel, controls and regulates C content to be 0.10% ~ 1.00%;
4) water atomization pulverization;
5) intercrystalline corrosion heat treatment sensitization: under argon gas atmosphere protection, carry out intercrystalline corrosion heat treatment sensitization to stainless steel powder at 450 DEG C ~ 750 DEG C temperature, heat treatment sensitization time is 1h ~ 10h;
6) intercrystalline corrosion: in adjustable atmosphere furnace, pass into steam, at oxygen content 1% ~ 30%, hydrogen chloride gas body burden 0% ~ 5%, corrosion temperature 450 DEG C ~ 850 DEG C, carry out intercrystalline corrosion to stainless steel powder, the time is 0.1h ~ 5h;
7) high temperature reduction, then carry out follow-up pulverizing, grinding and screening process and namely obtain high-compressibility water atomization stainless steel powder.
Further, the 3rd), in the sensitization of step intercrystalline corrosion chemical composition, it is 0.50% ~ 0.8% that C content controls.
Further, the 5th) optimum condition of step intercrystalline corrosion heat treatment sensitization is that temperature 500 DEG C ~ 720 DEG C, the time is 2h ~ 6h.
Further, the 6th) optimum condition of step intercrystalline corrosion is that oxygen content 4% ~ 10%, hydrogen chloride gas body burden 1% ~ 3%, temperature 550 DEG C ~ 700 DEG C, the time is 1h ~ 2h.
Compared to existing technology, the present invention has the following advantages:
1, after intercrystalline corrosion, the sponge iron that comminuted steel shot surface grain boundary structure is formed after being reduced by the crystal boundary be not corroded and corrosion oxidation product forms, and the loose structure of sponge iron weakens 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 uniform close and be 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, and intensity low (under pressing pressure, its crystal boundary can destroy completely, forms monocrystal), the inhibition of crystal boundary to plastic deformation is little, is easy to plastic deformation.
4, compared with surface oxidation embrane method, intercrystalline corrosion scope is little, accelerates intercrystalline corrosion, suppresses general corrosion, and the loose structure formed after at utmost can reducing corrosion product reduction is to the adverse effect of 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, forms the loose structure of sponge iron to the adverse effect of pressed density after can reducing corrosion product reduction to greatest extent.
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, C content is increased in smelting molten steel, spray quenching forms supersaturated solid solution, in intercrystalline corrosion sensitive temperature (i.e. 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 the subsequent high temperature reduction reduction of operation and decarburization, eliminate its impact on product properties.Concrete technology is as follows:
1) composition is determined: the component requirements processing the powder metallurgical stainless steel constitutional detail obtained as required, determines the composition of its raw water atomization stainless steel powder;
2) smelting molten steel: by the 1st) composition of water atomization stainless steel powder determined of step gets the raw materials ready and carries out smelting molten steel;
3) intercrystalline corrosion chemical composition sensitization: before smelting molten steel terminates to carry out water atomization pulverization, supplements and adds carbon in smelting molten steel, controls and regulates C content to be 0.10% ~ 1.00% of whole molten steel content;
4) water atomization pulverization; Comprise water atomization, dehydration, drying, magnetic separation, screening etc.;
5) intercrystalline corrosion heat treatment sensitization: under argon gas atmosphere protection, carry out intercrystalline corrosion heat treatment sensitization to stainless steel powder at 450 DEG C ~ 750 DEG C temperature, heat treatment sensitization time is 1h ~ 10h;
6) intercrystalline corrosion: in adjustable atmosphere furnace, pass into steam, at oxygen content 1% ~ 30%, hydrogen chloride gas body burden 0% ~ 5%, corrosion temperature 450 DEG C ~ 850 DEG C, carry out intercrystalline corrosion to stainless steel powder, the time is 0.1h ~ 5h;
7) high temperature reduction, then carry out follow-up pulverizing, grinding and screening process and namely obtain high-compressibility water atomization stainless steel powder.
The present invention, in existing water atomization stainless steel powder preparation technology, adds 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 comparatively large to Influence on test result, belong to committed step of the present invention.
3rd), in the sensitization of step intercrystalline corrosion chemical composition, C content preferably controls to be 0.50% ~ 0.8%.
5th) optimum condition of step intercrystalline corrosion heat treatment sensitization is, temperature 500 DEG C ~ 720 DEG C, the time is 2h ~ 6h.
6th) optimum condition of step intercrystalline corrosion is, oxygen content 4% ~ 10%, hydrogen chloride gas body burden 1% ~ 3%, and temperature 550 DEG C ~ 700 DEG C, 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%.5th) step intercrystalline corrosion heat treatment sensitization condition is, temperature 600 DEG C ~ 620 DEG C, the time is 2h ~ 3h.6th) step intercrystalline corrosion condition is, oxygen content 5% ~ 6%, hydrogen chloride gas body burden 1% ~ 2%, and temperature 600 DEG C ~ 650 DEG C, 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 other step existing (comprising equipment, technical process and technical parameter etc.).
Intercrystalline corrosion method improves the principle of water atomization comminuted steel shot compressibility:
After intercrystalline corrosion, the sponge iron that comminuted steel shot surface grain boundary structure is formed after being reduced by the crystal boundary be not corroded and corrosion oxidation product forms, and the loose structure of sponge iron weakens 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 fine particle step by step, can effective reduce orifice porosity, improve powders compression performance.But additional fine particle, can reduce apparent density and the mobility of powder, increase frictional resistance when suppressing, in powder transhipment, filling and suppression process, produce particle segregation.And still there is between this method comminuted steel shot surface layer grain stronger adhesion, and be equivalent to additional fine particle uniform close and be 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 namely 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 plastic deformation.And the fine particle that the present invention suppresses generation has been intercrystalline corrosion, crystal boundary is few, and intensity low (under pressing pressure, its crystal boundary can destroy completely, forms monocrystal), the inhibition of crystal boundary to plastic deformation is little, is easy to plastic deformation.
In addition, compared with surface oxidation embrane method, intercrystalline corrosion scope is little, accelerates intercrystalline corrosion, suppresses general corrosion, and the loose structure formed after at utmost can reducing corrosion product reduction is to the adverse effect of 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 only for example of the present invention is described, and is not the restriction to embodiments of the present invention.For those of ordinary skill in the field, other multi-form change and variations can also be made on the basis of the above description.Here cannot give exhaustive to all embodiments.Every belong to technical scheme of the present invention the apparent change of amplifying out or variation be still in the row of protection scope of the present invention.
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: the component requirements processing the powder metallurgical stainless steel constitutional detail obtained as required, determines the composition of its raw water atomization stainless steel powder;
2) smelting molten steel: by the 1st) composition of water atomization stainless steel powder determined of step gets the raw materials ready and carries out smelting molten steel;
3) intercrystalline corrosion chemical composition sensitization: before smelting molten steel terminates to carry out water atomization pulverization, add carbon in smelting molten steel, controls and regulates C content to be 0.10% ~ 1.00%;
4) water atomization pulverization;
5) intercrystalline corrosion heat treatment sensitization: under argon gas atmosphere protection, carry out intercrystalline corrosion heat treatment sensitization to stainless steel powder at 450 DEG C ~ 750 DEG C temperature, heat treatment sensitization time is 1h ~ 10h;
6) intercrystalline corrosion: in adjustable atmosphere furnace, pass into steam, at oxygen content 1% ~ 30%, hydrogen chloride gas body burden 0% ~ 5%, corrosion temperature 450 DEG C ~ 850 DEG C, carry out intercrystalline corrosion to stainless steel powder, the time is 0.1h ~ 5h;
7) high temperature reduction, then carry out follow-up pulverizing, grinding and screening process and namely obtain high-compressibility water atomization stainless steel powder.
2. the method 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, and it is 0.50% ~ 0.8% that C content controls.
3. the method utilizing intercrystalline corrosion to prepare high-compressibility water atomization stainless steel powder according to claim 1, is characterized in that: the 5th) condition of step intercrystalline corrosion heat treatment sensitization is, temperature 500 DEG C ~ 720 DEG C, the time is 2h ~ 6h.
4. the method utilizing intercrystalline corrosion to prepare high-compressibility water atomization stainless steel powder according to claim 1, it is characterized in that: the 6th) condition of step intercrystalline corrosion is, oxygen content 4% ~ 10%, hydrogen chloride gas body burden 1% ~ 3%, temperature 550 DEG C ~ 700 DEG C, the time is 1h ~ 2h.
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| 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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| JP2006038840A (en) * | 2004-06-24 | 2006-02-09 | Chugoku Electric Power Co Inc:The | Method for grain boundary etching of metal surface |
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