CN101724790B - Low-nickel austenitic stainless steel and manufacturing method thereof - Google Patents
Low-nickel austenitic stainless steel and manufacturing method thereof Download PDFInfo
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Abstract
The invention relates to a low-nickel austenitic stainless steel, which comprises the following chemical components by weight percent: no less than 0.05% and no more than 0.15% of C, less than 1.00% of Si, more than 9.00% and less than 10.00% of Mn, no less than 14.00% and no more than 16.00% of Cr, no less than 0.50% and less than 1.00%, more than 0.15% and no more than 0.25% of N, more than 1.50% and no more than 2.00% of Cu, no less than 10*10<-4>% and no more than 30*10<-4>% of B, no less than 1*10<-4> and no more than 50*10<-4>% of Ca, less than 0.030% of P, no less than 0.020% of S and the balance of Fe and inevitable impurities. For the stainless steel, heat processing performance of materials is improved through B alloying treatment on premise of further reducing the content of precious metal of nickel, and the purity of the liquid steel is enhanced through Ca treatment. The formability of stainless steel is enhanced through the reasonable alloy system design and a micro-alloy treatment method, the defects of sand buckle, sand holes, and the like are avoided in the forming process, the delayed rupture phenomenon is lightened, and the application scope of the festival nickel austenitic stainless steel is further broadened.
Description
Technical field
The present invention relates to austenitic stainless steel, specifically, relate to a kind of hot workability and the low-nickel austenitic stainless steel that has excellent moldability.
Background technology
Present domestic and international widely used austenitic stainless steel; With 300 be and 200 be to be main; Austenitic stainless steel such as AISI304 and AISI201 for example; Yet more nickel is contained in these austenite stainless steel capital, and the interpolation of a large amount of nickel has caused the raising of these austenitic stainless steel material cost, has therefore limited the range of application and the Sustainable development of these steel.
Traditional nickel-saving type austenitic stainless steel; Comprise AISI201 and AISI301 etc., as described in Table 2, generally be to have adopted nitrogen, manganese alloyage process for nickel; Obviously reduced material cost; But because the reduction of austenite stabilizer element nickel content, other austenite stabilizer element such as manganese, nitrogen equal size are not high enough in addition, strain-induced martensite can occur when directly causing these stainless steels at room temperature to be out of shape.Though the martensitic appearance of strain-induced can improve the intensity and the hardness of material in the deformation process; Thereby improve the ability of stainless steel opposing external force deformation; But because martensitic appearance can be sacrificed stainless plasticity; Especially afterwards delayed crack can occur through the punching press distortion, thereby these stainless steels are not suitable for using stainless steel as pressed part.
In field of Austenitic stainless steel, under different service conditions,, adopted different mentalities of designing in order to reduce cost and to improve the room temperature plasticity of austenitic stainless steel and good hot workability based on austenitic stainless steel.Especially in recent years since the high position operation of nickel valency with big ups and downs and be directed against the delayed crack phenomenon that strain-induced martensite causes; People have adopted and in stainless steel, have further reduced nickel content and further interpolation austenite stabilizer element manganese and nitrogen in the steel, and add the alloying thinking of little copper in order to improve stainless ductility and austenitic stability.Shown in table 1 and table 2 pertinent literature and the corresponding chemical ingredients and the characteristic of the nickel-saving type austenitic stainless steel of prior art.
In table 1 and the table 2; Publication number is the patented claim of CN1978694 and the chemical constitution that patent ZL200510013238.9 has described a kind of nickel-saving type austenitic stainless steel; But manganese content lower (≤8.5%) in these chemical constitutions; And nickel content higher relatively (Ni>=3.0%) is unfavorable for that the minimization of cost principle obtains plasticity and the good nickel-saving type austenitic stainless steel of hot workability.
In table 1 and the table 2; Publication number is the chemical constitution that a kind of nickel-saving type austenitic stainless steel has been described in the patented claim of CN1584098; Though in these chemical constitutions, adopted further reduction nickel content (Ni≤1.2%); Improve the alloyage process of manganese content (8.5%≤Mn≤10.0%), but owing to do not consider because the hot-work difficulty that reduction brought of nickel content, just hot worked manufacturability is relatively poor and be unfavorable for the manufacturing of low-nickel austenitic stainless steel.
In table 1 and the table 2; Patent ZL02152273.1 and ZL200410047238.6 have described a kind of chemical constitution of nickel-saving type austenitic stainless steel; Though in these chemical constitutions, also adopted further reduction nickel content (1.0%≤Ni≤5.0%); Improve the alloyage process of manganese content (7.5%≤Mn≤10.5%), and patent ZL02152273.1 considers that also adding micro-B improves hot-work.But nickel content is still higher, and does not consider that Ca handle to improve that molten steel purity and inclusion modification can avoid occurring in the forming process peeling, trachoma and the effect that improves the stainless steel plasticity.
In table 1 and the table 2; Patent ZL200610103367.1 has described a kind of chemical constitution of nickel-saving type austenitic stainless steel; Though in these chemical constitutions, also adopted further reduction nickel content (0.6%≤Ni≤1.3%); Improve the alloyage process of manganese content (8.5%≤Mn≤12.0%), and consider that also adding the trace rare-earth element cerium improves hot workability.But nitrogen in steel content lower (N≤0.15%); And nitrogen is the element of strong formation and stable austenite in stainless steel; The reduction of nitrogen content is difficult to avoid the appearance of strain induced martensite; And do not consider that Ca handle to improve that molten steel purity and inclusion modification can avoid occurring in the forming process peeling, trachoma and the effect that improves the stainless steel plasticity, simultaneously REE in industrialized production, be difficult to add and also yield unstable and be unfavorable for the tissue of industrialized production.
In table 1 and the table 2; Patent ZL99110134.0 has described a kind of chemical constitution of nickel-saving type austenitic stainless steel; Though in these chemical constitutions, also adopted further reduction nickel content (1.0%≤Ni≤4.0%); Improve the alloyage process of manganese content (5.0%≤Mn≤11.0%); And also consider and add micro-B and Ca processing, but this patent nickel content is still higher and this patent is not mentioned the nitrogen element, make the product of this patent have good solidity to corrosion and but do not possess good plasticity.
In table 1 and the table 2; Patent ZL98117555.4 has described a kind of chemical constitution of nickel-saving type austenitic stainless steel; In these chemical constitutions, nickel content has been reduced to utmost point low levels (0.1%≤Ni≤2.0%); But manganese content (5.0%≤Mn≤9.0%) be not very high and also scope wide, can reduce austenitic stability, thereby be difficult to avoid in the deformation at room temperature process excessive strain-induced martensite to occur and reduce stainless plasticity.
Summary of the invention
The nickel-saving type austenitic stainless steel and the method for manufacture thereof that the object of the present invention is to provide a kind of hot workability and room temperature to have excellent moldability.
Austenitic stainless steel of the present invention, its chemical component weight per-cent consists of: 0.05%≤C≤0.15%, Si<1.00%, 9.00%<mn<10.00%, 14.00%≤Cr≤16.00%, 0.50%≤Ni<1.00%, 0.15%<n≤0.25%, 1.50%<cu≤2.00%, 10 * 10
-4%≤B≤30 * 10
-4%, 1 * 10
-4%≤Ca≤50 * 10
-4%, P<0.030%, S<0.020%, surplus is Fe and inevitable impurity.
Preferably, when 1250 ℃ of high temperature, its δ of austenitic stainless steel of the present invention-ferritic volume(tric)fraction is less than 10%.
Preferably, its stabilization of austenite temperature of austenitic stainless steel of the present invention Md
30/50(℃) scope is less than 25 ℃, described stabilization of austenite temperature is confirmed by following formula:
Md
30/50(℃)=551-462 * (C%+N%)-9.2 * Si%-8.1 * Mn%-29 * (Ni%+Cu%)-13.8 * Cr%-18.5 * Mo%-68 * Nb%-1.42 * (ASTM grain fineness number No.-8.0).
The method of manufacture of austenitic stainless steel of the present invention comprises the steps:
Smelt or the non-vacuum induction furnace melting through electric arc furnace list refining method, electric furnace+AOD two-step approach, electric furnace+AOD+VOD three-step approach;
Molten steel is carried out Ca processing and B processing;
Continuous casting or be molded into steel billet;
Forging or rolling;
Process annealing;
Pickling.
Preferably, Ca handles and adopts mode Ca content in steel of feeding the Ca-Si-Ba silk to satisfy 1 * 10
-4%≤Ca≤50 * 10
-4During %, stop to feed the Ca-Si-Ba silk, ladle bottom blew the soft stirring of Ar more than 10 minutes, and molten steel left standstill more than 10 minutes after soft stirring was accomplished.
More preferably, feeding Ca-Si-Ba silk temperature is 1520～1600 ℃.
Preferably, after above-mentioned molten steel leaves standstill completion, carry out the B Alloying Treatment, join in the molten steel with the mode of Fe-B silk, B content satisfies 10 * 10 in steel
-4%≤B≤30 * 10
-4During %, stop to feed the Fe-B silk.
More preferably, feeding Fe-B silk temperature is 1480～1550 ℃.
Preferably, after Ca processing and B processing, the fine setting temperature satisfies continuous casting or the casting of molten steel is carried out in the die casting requirement, and the continuous casting pouring temperature is 1465～1490 ℃, and the die casting pouring temperature is 1520～1600 ℃.
Through solution treatment, preferably solid solution temperature is 1040～1100 ℃ to molten steel when test solid solution attitude mechanical property.
Molten steel in the cold rolling attitude of test or when rolling hard attitude mechanical property without solution treatment.
Preferably, in the method for manufacture of austenitic stainless steel of the present invention, the starting temperature scope of hot rolling or heat forged is 1170～1250 ℃.
Preferably, in the method for manufacture of austenitic stainless steel of the present invention, the process annealing temperature is 1000～1100 ℃.
The present invention passes through to reduce nickel (nickel content is less than 1.0%) content, thereby has significantly practiced thrift raw materials cost.But, and can improve stainless ductility and plasticity owing to nickel is formation in the stainless steel, stablizes and enlarge the element of austenite structure.Be reduced to when nickel content under the situation of 0.5～1.0wt.%, can dwindle the high temperature austenite phase region on the one hand and bring difficulty, occur the limit easily and split, show to split equilateral quality and surface quality defect to thermoplasticity processing (hot rolling, forge hot); In addition, because the reduction of nickel can reduce stainless ductility and plasticity, especially in punching course, occur defectives such as peeling, trachoma, particularly low-nickel austenitic stainless steel easily and occur strain-induced martensite easily and delayed crack takes place at punching course.Defective and stainless metallurgical qualities such as the peeling in the forming process, trachoma; Factor strong correlations such as The amount of inclusions, kind, size, distribution just; And the delayed crack that occurs in the room temperature forming process be with room temperature condition under austenitic stable strong correlation, just with temperature Md
30/50The temperature strong correlation.
To the above fact, the mode that the present invention adopts Theoretical Calculation and verification experimental verification to combine is confirmed alloy system.At first adopt theoretical method to design alloy system; Each element in the rational Match stainless steel just; Especially austenite forms and elements such as stabilizing element such as carbon, nitrogen, manganese, copper, and whether the stainless steel that designs through verification experimental verifications such as Magnetic Measurement, metallographic structure checks is austenitic stainless steel.Through the microalloying processing, just handle purity and the inclusion modification that improves molten steel thereupon, and verify the effect that Ca handles through the inclusion morphology observation through Ca.B handles and improves the stainless thermoplasticity processing characteristics of the present invention, and through its thermoplasticity processing characteristics of the rolling stainless steel checking of hot continuous rolling mode.It is rolling according to different draught stainless steel of the present invention to be carried out room temperature, checks the mensuration of the martensite content that different draught bring out to define the room temperature stability of austenite structure and check whether occur phenomenons such as peeling, trachoma in the operation of rolling.Show its austenite equilibrium temperature Md especially
30/50Be lower than 25 ℃, thereby alleviate and even avoid the delayed crack phenomenon in the low-nickel austenitic stainless steel forming process.And when 1250 ℃ of high temperature, its δ-ferritic volume(tric)fraction is less than 10%, is suitable for the hot continuous rolling mode and makes with goods and use stainless steel.
Therefore, hot workability of the present invention and the low-nickel austenitic stainless steel that has excellent moldability, its chemical component weight per-cent consists of: 0.05%≤C≤0.15%, Si<1.00%, 9.00%<mn<10.00%, 14.00%≤Cr≤16.00%, 0.50%≤Ni<1.00%, 0.15%<n≤0.25%, 1.50%<cu≤2.00%, 10 * 10
-4%≤B≤30 * 10
-4%, 1 * 10
-4%≤Ca≤50 * 10
-4%, P<0.030%, S<0.020%, surplus is Fe and inevitable impurity.
Nickel-saving type austenitic stainless steel of the present invention at room temperature carries out the following time of cold rolling of 30% true strain, in the said nickel-saving type austenitic stainless steel martensite content less than 50%, the stainless Md of the present invention just
30/50Temperature is lower than 25 ℃.
Particularly, in the nickel-saving type austenitic stainless steel of the present invention:
C:0.05%≤C≤0.15%, carbon are strong formation, the element of stablizing and enlarge the austenitic area, and in nickel-saving type austenitic stainless steel of the present invention, because nickel content is extremely low, carbon plays an important role to forming austenite structure under the room temperature.Can reduce stainless plasticity but carbon is too high, and unfavorable to stainless solidity to corrosion, and the too low meeting of carbon causes stainless austenite structure stability not enough, so carbon will have suitable percentage composition.
Ni:0.50%≤Ni 1.00%, the element of formation and stable austenite and expansion austenitic area.
< < 10.00%, manganese is more weak austenite former to Mn to Mn:9.00%, but is intensive austenite structure stable element in stainless steel, and can improve the solubleness of nitrogen in steel.In nickel-saving type austenitic stainless steel, element generation compound actions such as carbon, nitrogen in manganese and the steel replace nickel with part, and guarantee that stainless steel at room temperature is austenite structure, also can significantly reduce stainless Md simultaneously
30/50Temperature value.In order to reach above purpose, manganese content must be greater than 9.0%.In addition, because manganese content is greater than 10.0% o'clock, the austenitizing formation ability of manganese element weakens, and promotes the formation of ferritic structure even, so stainless steel manganese content of the present invention must be less than 10.0%.
< Cu≤2.00%, interpolation copper can improve ductility and improve stainless plasticity with reducing stainless work hardening Cu:1.50% in stainless steel.For nickel-saving type austenitic stainless steel; Because nickel content is extremely low; And copper is to form austenitic element, is austenite structure down in order to ensure the stainless steel room temperature state, thus in the stainless steel of the present invention copper content greater than 1.5%; But the interpolation of excess copper can reduce stainless hot workability, thus copper on be limited to 2.0% and guarantee that stainless steel has good hot workability.
Cr:14.00%≤Cr≤16.00%; Chromium is most important alloying element in the stainless steel, can guarantee that steel obtains rustless property and certain solidity to corrosion, the content range of chromium among the present invention; Can guarantee that steel has good stainless corrosion-resistant property, can guarantee that again steel is single-phase austenite structure under the room temperature.
N:0.15% N≤0.25%, nitrogen in stainless steel be very intensive form, stable and enlarge the element of austenitic area.Nitrogen except substituting precious resource, outside nickel, and can obviously improve the intensity of material under not obvious reduction material plasticity and flexible prerequisite in stainless steel.Can also improve stainless rustless property and solidity to corrosion and delay carbide and separate out etc.But because the solubleness of nitrogen in stainless steel is limited; Subsurface bubble appears in process of setting for fear of steel; Nitrogen content confirm must with other alloying element coordinative role; Guaranteeing that nitrogen exists with solid solution condition, and guarantee that with other alloying element compound action stainless steel at room temperature is single-phase austenite structure.In addition, in order to reduce stainless steel Md
30/50Temperature value and avoid in the deformation process occurring excessive strain-induced martensite; Nitrogen content, also can be guaranteed when 1250 ℃ of high temperature smaller or equal to 0.25% greater than 0.15% simultaneously in this invention; δ in the stainless steel-ferritic volume(tric)fraction is suitable for the hot continuous rolling mode and makes less than 10%.
Si: < 1.00%, silicon is to form ferritic alloying element in stainless steel, is single-phase austenite structure at room temperature in order to ensure stainless steel of the present invention therefore, and silicone content must in addition certain restriction in the steel.
P: < 0.030%, phosphorus is regarded as harmful element in stainless steel, should control low more well more as far as possible.
< 0.020%, sulphur also is regarded as harmful element to S:S in stainless steel.Especially in the present invention, manganese content is high in the steel, needs the content of strict control sulphur, and is low more good more.
B: an amount of boron joins in the stainless steel; Can improve stainless hot workability through grain-boundary strengthening; Especially as far as nickel-saving type austenitic stainless steel; The effect of B seems even more important, worsens hot workability on the contrary but excessive boron can generate low-melting eutectic phase, so boron content is controlled at 10～30ppm among the present invention.
Ca: because Ca and O and S have very strong avidity, therefore, the metallargist is devoted for years in adopting Ca to handle furnace outer refining technology and takes off O and take off S, can reduce the activity of oxygen in the steel rapidly, accelerates deoxidation speed and the total oxygen demand that reduces steel.In addition,, be easy in the steel generate the MnS inclusion, and MnS is a kind of lower melting point inclusion, in course of hot rolling, can becomes strip and reduce stainless mechanical property because the manganese content of nickel-saving type austenitic stainless steel is higher.The CaO that after steel carries out Ca processing deoxidation, generates is beneficial to and takes off S; Take off that S product or come-up are removed and in cleaning molten steel or the residual steel, the inclusion in the residual steel is when steel cools off, the S solubleness in the inclusion reduces and separates out with CaS; And CaS is a HMP Spherical Inhomogeneity thing; Indeformable in course of hot rolling, the size of the inclusion of separating out is little and be the distribution of disperse shape, plays the purpose of cleaning molten steel and inclusion modification therefrom.But, so the Ca content that adds in the molten steel can not be too high, otherwise can reduce stainless hot workability, so Ca content is controlled at 1～50ppm among the present invention because the solubleness of Ca in steel is low and vapour pressure is high.
The chemical ingredients proportioning of nickel-saving type austenitic stainless steel of the present invention is calculated through thermodynamics of alloys; Like ThermoCalc calculation of thermodynamics software; At first calculate under the normal pressure solubleness of nitrogen in the molten steel and the solid solubility of nitrogen in steel when solid-state; And combine the nickel equivalent of steel and chromium equivalent to calculate, designing under the room temperature is austenite structure, and austenitic Md
30/50Temperature value less than 25 ℃, its Md
30/50(℃) calculating formula be:
Md
30/50(℃)=551-462 * (C%+N%)-9.2 * Si%-8.1 * Mn%-29 * (Ni%+Cu%)-13.8 * Cr%-18.5 * Mo%-68 * Nb%-1.42 * (ASTM grain fineness number No.-8.0)
According to above calculation formula, 0.05%≤C in steel≤0.15%, Si<1.00%, 9.00%<mn<10.00%, 14.00%≤Cr≤16.00%, 0.50%≤Ni<1.00%, 0.15%<n≤0.25%, 1.50%<cu≤2.00%, 10 * 10
-4%≤B≤30 * 10
-4%, 1 * 10
-4%≤Ca≤50 * 10
-4%, P<0.030%, S<0.020%, when surplus was Fe and inevitable impurity, the calculation result of low-nickel austenitic stainless steel strain-induced Martensite temperature of the present invention was as shown in Figure 1.
As can be seen from Figure 1: stainless steel of the present invention 50% martensitic temperature Md occurs producing true strain 30%
30/50Less than 25 ℃; That is to say at normal temperatures; External force effects such as that stainless steel of the present invention receives is rolling, bump and when deforming; The martensite content that stainless steel of the present invention generates is less, does not have even, thereby and even helps improving stainless plasticity and alleviate the generation of avoiding delayed crack.
The nickel-saving type austenitic stainless steel that the present invention designs is cast as steel billet through continuous casting or die casting after electric furnace, AOD, the smelting of VOD three-step approach or electric furnace, AOD two-step smelting or electric furnace or the refining of non-vacuum induction furnace list; Again through forging or operations such as rolling, solution treatment (need pass through solution treatment during test solid solution attitude mechanical property, not need solution treatment when testing cold rolling attitude mechanical property), pickling are processed stainless steel materials, band and bar etc.
No matter the stainless manufacturing processed of the present invention is that operations such as induction furnace, electric furnace, AOD, VOD operation or rolling, solution treatment, pickling are existing routine techniques, repeats no more at this.In order to improve the difficulty of the stainless plasticity of the present invention thermoplasticity brought processing with remedying the reduction of nickel; Stainless steel of the present invention must carry out the Ca processing at continuous casting or before being molded into steel billet and B handles; Handle purity and the inclusion modification that improves molten steel through Ca, improved the hot workability of material through the B Alloying Treatment.Improve stainless plasticity through design of rational alloy system and microalloy treatment process, avoided occurring in the forming process defective such as peeling, trachoma and alleviated the delayed crack phenomenon, further widened the range of application of low-nickel austenitic stainless steel.Ca handles with the B processing and carries out in ladle in continuous casting or die casting.Before molten steel being carried out Ca processing and B processing, molten steel is handled through reduction, and main chemical compositions in the steel must satisfy the stainless claimed range of the present invention like Cr, Mn, Ni, Cu, N, Si, P, S.Carry out Ca then and handle, it is to have adopted the mode of feeding the Ca-Si-Ba silk that Ca handles, and preferably feeding the silk temperature is 1520～1600 ℃.Confirm the add-on of Ca-Si-Ba silk according to the oxygen level in temperature conditions and the steel, as long as Ca content satisfies 1 * 10 in the steel
-4%≤Ca≤50 * 10
-4% promptly stops to feed the Ca-Si-Ba silk.Ladle bottom blow the soft stirring of Ar more than 10 minutes, soft stirring accomplish after molten steel leave standstill more than 10 minutes.The soft stirring of molten steel and to leave standstill all be for the ease of floating foreign and removal.Leaving standstill the B Alloying Treatment of carrying out molten steel after the completion, is that the mode with the Fe-B silk joins in the molten steel, and preferably feeding a silk temperature is 1480～1550 ℃.Confirm the add-on of Fe-B silk according to temperature conditions, as long as B content satisfies 10 * 10 in the steel
-4%≤B≤30 * 10
-4% promptly stops to feed the Fe-B silk.The fine setting temperature satisfies continuous casting or the die casting requirement just can have been carried out the casting of molten steel.
The present invention has following advantage:
1) nickel content is extremely low in the austenitic stainless steel steel of the present invention, and nickel content has significantly reduced the material cost of austenitic stainless steel less than 1.0%.
2) stainless steel of the present invention, has been guaranteed to be single-phase austenite structure under the room temperature state like carbon, manganese, nitrogen, copper through an amount of austenite former that adds on the one hand, has also improved the stability of austenite structure on the other hand, makes stainless Md
30/50Less than 25 ℃, thereby improve stainless plasticity, and even alleviate the generation of avoiding the delayed crack phenomenon.
3) nickel-saving type austenitic of the present invention passes through to add an amount of B, thereby has significantly improved hot workability, is suitable for the hot continuous rolling unit and carries out suitability for industrialized production, and guarantee that stainless steel of the present invention has good limit portion and surface quality.
4) austenitic stainless steel of the present invention is handled through Ca and has been improved molten steel purity and inclusion modification, helps avoid defectives such as occurring peeling and trachoma in the forming process, thereby significantly improves stainless plasticity.
Below further combine embodiment just verification experimental verification stainless steel of the present invention be a kind of stainless steel with good plasticity and hot workability.
Description of drawings
Fig. 1 is alloy system stabilization of austenite temperature Md of the present invention
30/50(℃) Theoretical Calculation result.
Fig. 2 is that embodiment 1 compares with compared steel cold rolling magnetic of following time phase volume fraction.
Fig. 3 is the metallographic structure photo of low-nickel austenitic stainless steel hot-rolled black-skin volume after 1070 ℃ of solution treatment that embodiment 4 makes.
Fig. 4 is the inclusion analysis result of embodiment 5 and compared steel.
Fig. 5 is the stainless steel casting skin volume that embodiment 2 makes.
Embodiment
Below combine accompanying drawing that the present invention is made more detailed description with embodiment.These embodiment only are the descriptions to preferred embodiments of the present invention, scope of the present invention are not had any restriction.
The composition of steel is as shown in table 3 among each embodiment.
Embodiment 1:
Take electric arc furnace and AOD two-step approach smelting stainless steel, feed Ca-Si-Ba line and Fe-B line before and realize that Ca handles and the B Alloying Treatment at continuous casting, continuous casting becomes slab, and the thick hot-rolled coil of 3.00mm is processed in hot rolling.Through process annealing, the process annealing temperature is 100～1100 ℃, the strain-induced fraction of martensite volume that occurs when test annealing back is with different cold roling reduction respectively then.Its concrete outcome is as shown in table 4.The chemical ingredients of the nickel-saving type austenitic stainless steel of present embodiment is seen table 3.
Table 4 embodiment 1 and 4%Ni low-nickel austenitic stainless steel be the contrast of strain-induced martensite volume(tric)fraction when different cold roling reduction
Embodiment 2:
Take electric furnace, AOD, VOD three-step approach smelting stainless steel.Before carrying out continuous casting, feed Ca-Si-Ba line and Fe-B line and realize that Ca handles and the B Alloying Treatment, continuous casting becomes slab, and the thick hot-rolled coil of 3.00mm is processed in hot rolling.Through process annealing, pickling, carry out cold rollingly then, test gained nickel-saving type austenitic stainless steel is cold after through 50% cold roling reduction, the changing conditions of the stainless cold-reduced sheet hardness of the present invention, its result is as shown in table 5.The chemical ingredients of the nickel-saving type austenitic stainless steel of present embodiment is seen table 3.
Table 5 embodiment 2 and 4%Ni low-nickel austenitic stainless steel be the hardness contrast when different cold roling reduction
Embodiment 3:
Take electric arc furnace list refining method smelting stainless steel, continuous casting becomes slab.Before carrying out continuous casting, feed Ca-Si-Ba line and Fe-B line and realize that Ca handles and the B Alloying Treatment.Cut the strand of 200mm * 200mm * 100mm then from the continuously cast bloom centre, respectively at 1000 ℃, 1050 ℃; 1100 ℃; 1150 ℃, 1200 ℃, respectively be incubated 30 minutes under 1250 ℃; Adopt the mode of quick water-cooled that high temperature microstructure is fixed and with the ferritic content of ferritic appearance test high temperature, its result is as shown in table 6 thereupon.
Table 6 is through the high temperature ferrite content of embodiment 3 after the heat
| Test conditions | Ferrite content, Vol.% |
| 1000℃+30min | 0.0 |
| 1050℃+30min | 0.0 |
| 1100℃+30min | 0.0 |
| 1150℃+30min | 0.0 |
| 1200℃+30min | 0.0 |
| 1250℃+30min | 3.2 |
Embodiment 4～6
Take the non-vacuum induction furnace smelting stainless steel, be molded into ingot.Before carrying out die casting, feed Ca-Si-Ba line and Fe-B line and realize that Ca handles and the B Alloying Treatment.Then ingot casting is carried out mechanical car's remaining ferrite content in optical measurement ingot casting surface.Forge subsequently and hot rolling, solution treatment and pickling, measure ferrite content once more, its result is as shown in table 7.Stainless steel to after embodiment 4 hot rollings, the solution treatment carries out metallographic structure analysis; Embodiment 5 carries out the inclusion comparative analysis with compared steel; The stainless steel that embodiment 6 is made has carried out the cold rolling of different draught with compared steel; And measured the room temperature tensile mechanical property of rolling hard attitude of hot rolling solution annealing attitude and different draught; The ratio (Rp0.2/Rm) that comprises room temperature ys (Rp0.2), room temperature tensile strength (Rm), room temperature unit elongation (A50mm) and room temperature ys and tensile strength, its result respectively as table 7,8 and table 9 shown in.
The magnetic phase volume fraction measuring result of table 7 embodiment 4～6
| Embodiment | Remaining ferritic volume(tric)fraction behind the ladle barrow light | Remaining ferritic volume(tric)fraction after the hot rolling solution treatment |
| 4 | 0 | 0 |
| 5 | 0 | 0 |
| 6 | 0 | 0 |
The cold rolling processing characteristics of the low-nickel austenitic stainless steel that table 8 embodiment 6 makes
| Thickness (mm) | Draught (%) | Rp0.2(MPa) | Rm(MPa) | A50mm(％) | Rp0.2/Rm |
| 3.15 | 0.00 | 332 | 670 | 58.5 | 49.6 |
| 2.84 | 9.84 | 613 | 842 | 40.0 | 72.8 |
| 2.72 | 13.65 | 692 | 908 | 34.8 | 76.2 |
| 2.55 | 19.05 | 782 | 1025 | 31.5 | 76.3 |
| 2.42 | 23.17 | 840 | 1065 | 25.5 | 78.9 |
| 2.27 | 27.94 | 938 | 1145 | 22.5 | 81.9 |
| 2.10 | 33.33 | 1045 | 1225 | 20.2 | 85.3 |
| 1.85 | 41.27 | 1140 | 1310 | 15.0 | 87.0 |
| 1.76 | 44.13 | 1170 | 1325 | 12.0 | 88.3 |
| 1.62 | 48.57 | 1245 | 1390 | 8.5 | 89.6 |
| 1.44 | 54.29 | 1370 | 1515 | 7.0 | 90.4 |
The cold rolling processing characteristics of the low-nickel austenitic stainless steel that table 9 compared steel makes
| Thickness (mm) | Draught (%) | Rp0.2(MPa) | Rm(MPa) | A50mm(％) | Rp0.2/Rm |
| 3.11 | 0.00 | 228 | 565 | 61.3 | 40.4 |
| 2.84 | 8.68 | 445 | 662 | 47.2 | 67.2 |
| 2.66 | 14.47 | 527 | 723 | 41.5 | 72.9 |
| 2.54 | 18.33 | 612 | 788 | 34.5 | 77.7 |
| 2.35 | 24.44 | 698 | 853 | 28.5 | 81.8 |
| 2.25 | 27.65 | 800 | 925 | 24.0 | 86.5 |
| 2.10 | 32.48 | 885 | 985 | 22.3 | 89.8 |
| 1.95 | 37.30 | 955 | 1035 | 12.2 | 92.3 |
| 1.74 | 44.05 | 1055 | 1155 | 9.5 | 91.3 |
| 1.60 | 48.55 | 1090 | 1170 | 7.5 | 93.2 |
| 1.45 | 53.38 | 1165 | 1250 | 5.8 | 93.2 |
Can find out from table 4: the stainless steel that embodiment 1 makes is after hot-roll annealing is handled, and the stainless steel that makes through ferritic appearance measurement embodiment 1 is no magnetic.Table 7 can be found out: the stainless steel that embodiment 4～6 makes is all to be magnetism-free stainless steel after ingot casting or the hot rolling solution treatment.Especially the low-nickel austenitic stainless steel hot-rolled black-skin volume that makes of the embodiment 4 that provides of Fig. 3 can draw through the metallographic structure photo after 1070 ℃ of solution treatment: the stainless steel steel that the present invention makes is after passing through solution treatment; Its room temperature state for no magnetic, that is to say that the stainless steel that the present invention makes is an austenitic stainless steel down.
Can find out that from the result of table 3, table 4 and Fig. 2 nickel-saving type austenitic stainless steel embodiment 1 of the present invention is after different draught are cold rolling, it is more less slightly than the low-nickel austenitic stainless steel of 4%Ni the strain-induced fraction of martensite volume to occur.Stabilization of austenite slightly is better than the low-nickel austenitic stainless steel of 4%Ni under the room temperature state of illustrative embodiment 1.Explain that the austenite that adopts the present invention to make is obviously reducing on the basis of nickel content, its stabilization of austenite still can reach the low-nickel austenitic stainless steel level of 4%Ni.In addition, under room temperature state, carry out true strain 30% depress (draft 25.92%) time, the martensite volume(tric)fraction has only～about 5%, even cold rolling draft is 52.83% o'clock, the martensite volume(tric)fraction also has only 15.57%, the Md of illustrative embodiment 1
30/50(℃) temperature is far below room temperature, helps improving stainless plasticity, especially can slow down the incidence of delayed crack.
Can find out from the result of table 3 and table 5; Nickel-saving type austenitic stainless steel embodiment 2 of the present invention is after different draught are cold rolling; Occur after strain-induced martensitic hardening and the work hardening; The hardness of embodiment 2 is higher than the low-nickel austenitic stainless steel of 4%Ni, explains when being out of shape, and the present invention needs bigger external force.
Can find out that from the result of table 3 and table 6 embodiment 3 is through after the soak, after 1250 ℃ of insulations 30 minutes, its high temperature ferritic volume(tric)fraction has only 3.2%, and illustrative embodiment 3 has good hot workability.
Table 8 and table 9 are respectively the cold rolling processing characteristics of embodiment 6 and 4.0%Ni low-nickel austenitic stainless steel compared steel, the room temperature ys (Rp0.2) when detected result comprises the hot-roll annealing attitude with different draught, tensile strength (Rm), unit elongation (A
50mm) and the ratio (Rp0.2/Rm) of ys and tensile strength.Can find out from detected result: embodiments of the invention 6 need be through 48.57% following time of cold rolling, and the ratio of its ys and tensile strength (Rp0.2/Rm) just can reach 89.6%.And 4.0%Ni low-nickel austenitic stainless steel compared steel only need be through 32.48% following time of cold rolling, and the ratio of its ys and tensile strength (Rp0.2/Rm) just reaches 89.8%.Explain that the stainless steel room temperature processing characteristics that the present invention makes is better than 4.0%Ni low-nickel austenitic stainless steel compared steel.In addition, from embodiment 6 and the Strength Changes situation of compared steel cold-rolled process: the intensity of embodiment 6 will be higher than compared steel, explains that stainless steel of the present invention needs bigger external force in cold-rolled process.
In addition; Also can find out from the result of table 8 and table 9: the embodiment of the invention 6 prepared stainless steels; Compare under the situation of remarkable reduction nickel content with compared steel; Its hot-roll annealing attitude room temperature unit elongation is basic suitable with compared steel, proves once more that also the low-nickel austenitic stainless steel that adopts alloyage process of the present invention to make has good extension and forming property.
Fig. 4 is the low-nickel austenitic stainless steel that makes of the embodiment of the invention 5 and the inclusion analysis result of compared steel.As can beappreciated from fig. 4: because the present invention has adopted the Ca treatment process; The stainless inclusion that makes serves as main with disperse shape ball property inclusion and quantity is lacked than compared steel; And compared steel is in the majority and size is bigger with long-chain shape inclusion; Therefore the present invention has improved the purity of molten steel through the Ca treatment technology and has obtained the effect of inclusion modification, helps the improvement of the stainless cold-forming property of the present invention and can avoid occurring in the forming process defective such as peeling, trachoma and improve plasticity.
Fig. 5 is the casting skin volume quality information of low-nickel austenitic stainless steel through obtaining after the hot rolling of hot continuous rolling unit that the embodiment of the invention 2 makes; Quality of edges from the casting skin volume: the casting skin flanging part does not have tangible limit and splits defective; And casting skin volume surface do not have oxide debris defective such as nip yet, and explain that the stainless steel that the present invention makes has good hot continuous rolling processing characteristics afterwards through the B Alloying Treatment.
In sum; The present invention has improved the purity of molten steel through the Ca treatment technology and has obtained the effect of fiery foreign material modification, helps the improvement of the stainless cold-forming property of the present invention and can avoid occurring the defective of peeling, trachoma in the forming process and improve plasticity.The stainless steel that the present invention makes is through after the hot continuous rolling, and the casting skin volume that makes has good limit portion and surface quality, has good hot continuous rolling processing characteristics.Nickel-saving type austenitic stainless steel of the present invention obviously reducing under the prerequisite of nickel, just is reduced to nickel content in the scope of 0.5～1.0wt.% its Md
30/50(℃) temperature spot is a little less than the low-nickel austenitic stainless steel of 4.0%Ni, helps to improve stainless plasticity of the present invention and the incidence that reduces delayed crack.In addition, the stainless room temperature unit elongation that the present invention makes is suitable with the 4.0%Ni low-nickel austenitic stainless steel, has guaranteed that also stainless steel of the present invention has favorable extensibility and plasticity.But add man-hour under the stainless room temperature state of the present invention, its hardness is bigger, needs bigger external force when distortion is described.
Though more than through embodiment characteristics of the present invention have been carried out more detailed explanation, be not limited only to these embodiment, do not breaking away under the condition of the present invention design, more other equivalent embodiment can also be arranged.
Claims (3)
1. low-nickel austenitic stainless steel, its chemical component weight per-cent consists of: 0.05%≤C≤0.15%, Si＜1.00%, 9.00%＜Mn＜10.00%, 14.00%≤Cr≤16.00%, 0.50%≤Ni＜1.00%, 0.15%＜N≤0.25%, 1.50%＜Cu≤2.00%, 10 * 10
-4%≤B≤30 * 10
-4%, 1 * 10
-4%≤Ca≤50 * 10
-4%, P＜0.030%, S＜0.020%, surplus are Fe and inevitable impurity;
When 1250 ℃ of high temperature, its δ-ferritic volume(tric)fraction is less than 10%;
Stabilization of austenite temperature Md
30/50(℃) less than 25 ℃;
Wherein, Md
30/50(℃)=551-462 * (C%+N%)-9.2 * Si%-8.1 * Mn%-29 * (Ni%+Cu%)-13.8 * Cr%-18.5 * Mo%-68 * Nb%-1.42 * (ASTM grain fineness number No.-8.0).
2. the method for manufacture of low-nickel austenitic stainless steel as claimed in claim 1 comprises the steps:
Smelt or the non-vacuum induction furnace melting through electric arc furnace list refining method, electric furnace+AOD two-step approach, electric furnace+AOD+VOD three-step approach;
Molten steel is carried out Ca processing and B processing; Ca handles and adopts the mode of feeding the Ca-Si-Ba silk, and Ca content satisfies 1 * 10 in steel
-4%≤Ca≤50 * 10
-4Stop during % feeding the Ca-Si-Ba silk, ladle bottom blew the soft stirring of Ar more than 10 minutes, and molten steel left standstill more than 10 minutes after soft stirring was accomplished; Carry out the B Alloying Treatment said after leaving standstill completion, join in the molten steel with the mode of Fe-B silk, B content satisfies 10 * 10 in steel
-4%≤B≤30 * 10
-4During %, stop to feed the Fe-B silk; Feeding Ca-Si-Ba silk temperature is 1520～1600 ℃; Feeding Fe-B silk temperature is 1480～1550 ℃;
Continuous casting or be molded into steel billet; The continuous casting pouring temperature is 1465～1490 ℃, and the die casting pouring temperature is 1520～1600 ℃;
Rolling; Hot rolled starting temperature scope is 1170～1250 ℃;
Process annealing; The process annealing temperature is 1000～1100 ℃;
Pickling.
3. the method for manufacture of low-nickel austenitic stainless steel as claimed in claim 2 is characterized in that, process solution treatment during test solid solution attitude mechanical property; Without solution treatment, solid solution temperature is 1040～1100 ℃ when testing cold rolling attitude or rolling hard attitude mechanical property.
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