CN103866194B - Stanniferous low gap ferritic stainless steel of a kind of unusual segregation and preparation method thereof - Google Patents
Stanniferous low gap ferritic stainless steel of a kind of unusual segregation and preparation method thereof Download PDFInfo
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Abstract
Stanniferous low gap ferritic stainless steel of a kind of unusual segregation and preparation method thereof, belonging to metallurgical technology field, is composition by weight percentage containing C? 0.005 ~ 0.03%, Si? 0.2 ~ 0.4%, Mn? 0.2 ~ 0.5%, P≤0.03%, S≤0.02%, Cr? 14 ~ 16%, N≤0.01%, Sn? 0.1 ~ 0.4%, and containing Nb, Ti? and/or V, all the other are iron and inevitable impurity; Tensile strength 445 ~ 451? MPa, pitting potential is 202 ~ 240mV.Preparation method is: (1) smelts by set component and strand of casting; (2) 1150 are heated to? ± 10 DEG C, insulation 1 ~ 3h, then hot-rolled steel sheet is made in hot rolling; (3) 900 ± 10 DEG C of annealing, the time is 2 ~ 3h, is cooled to room temperature, cold rollingly after pickling makes cold-rolled steel sheet; (4) be heated to 800 ± 10 DEG C and carry out normalizing treatment, obtain the stanniferous low gap ferritic stainless steel of unusual segregation.Method of the present invention can significantly reduce stainless production cost, and technical process is simple, and product has higher intensity, hardness and corrosion resistance nature.
Description
Technical field
The invention belongs to metallurgical technology field, stanniferous low gap ferritic stainless steel of particularly a kind of unusual segregation and preparation method thereof.
Background technology
Stainless primary alloy constituent is nickel, chromium etc., and wherein nickel is metal costly, and LME-Ni substantially fluctuates more than tens0000, and a high position reaches more than 40 ten thousand per ton.China is a scarce nickel, few molybdenum, poor chromium and the country of stainless steel scrap resources scarcity, the fast lifting of stainless steel output, and raw material supplying becomes distinct issues; In order to reduce business risk and reduce the impact of prices of raw and semifnished materials fluctuation on stainless steel market, force enterprises of producing stainless steel and downstream user turn to not containing or few nickeliferous chromium system and chrome molybdenum system stainless steel.Along with the further sustainable growth of domestic ferritic stainless steel production capacity and apparent consumption demand, the problem of chromium resource has also emerged and increasingly outstanding.According to incompletely statistics, within 2010, China consumes high carbon ferro-chrome about 3,200,000 tons domestic amounting to, and wherein have about 1,800,000 tons from import, external dependence degree is up to 56%.
(day for announcing is on November 4th, 2009 in the patent application of China Patent Publication No. CN101573466A, name is called the ferritic stainless steel of the discoloration-resistant with excellent corrosion resistance) disclose a kind of high Cr ferritic stainless steel, with Cr, Cu, Ti, Nb etc. replace the high corrosion resistance ferritic stainless steel of the austenitic stainless steel containing expensive Ni, this ferritic stainless steel consist of C :≤0.01%, Si:0.2 ~ 1.0%, Mn :≤0.3%, Cr:20 ~ 22%, Ni:, N :≤0.01%, Al:0.03 ~ 0.1%, Cu:0.3 ~ 0.5%, Zr:0.02 ~ 0.04%, Ti:0.2 ~ 0.4%, Nb:0.06 ~ 0.45%, all the other are Fe and inevitable impurity, in this invention minimizing stainless steel, Ni's adds, save cost, but still need the Ni adding 0.2 ~ 0.4%, and substituted element kind is too much, recovery rate in smelting process is also difficult to ensure.
Publication number is that (day for announcing is on December 14th, 2011 for the Chinese patent application of 102274937A, name is called a kind of preparation method of stanniferous ferritic stainless steel strip of inverse segregation tin) disclose a kind of preparation method of stanniferous ferritic stainless steel strip of inverse segregation tin, carry out as follows: be that the ferritic stainless steel of 0.1 ~ 0.8 is for raw material with stanniferous weight percent, first smelt in the medium-frequency induction furnace under high vacuum environment and obtain molten steel, then the casting of double roll strip casting rolling plant is adopted to obtain the stanniferous ferritic stainless steel band base of the thick inverse segregation tin of 1.0 ~ 3.2mm, wherein, teeming temperature is 1550 ~ 1640 DEG C, roll casting speed is 2 ~ 80m/min, default roll gap is 0.0 ~ 2.2mm, after follow-up rolling and anneal, finally obtain the ferritic stainless steel strip of inverse segregation tin, this invention only provides the rough range of tin in ferritic stainless steel, and other elements in steel are not illustrated, be difficult to ensure that it smelts the material mechanical performance and corrosion resistance nature that steel grade can satisfy the demand.
Summary of the invention
Stanniferous low gap ferritic stainless steel that the object of this invention is to provide a kind of unusual segregation and preparation method thereof, by adjusting stainless composition, through hot rolling, annealing, pickling, cold rollingly make stanniferous ferritic stainless steel with thermal treatment, at the stainless production cost of reduction with while significantly saving the resource such as chromium, nickel, improve stainless erosion resistance and plasticity.
The composition of the stanniferous low gap ferritic stainless steel of unusual segregation of the present invention is by weight percentage containing C 0.005 ~ 0.03%, Si 0.2 ~ 0.4%, Mn 0.2 ~ 0.5%, P≤0.03%, S≤0.02%, Cr 14 ~ 16%, N≤0.01%, Sn 0.1 ~ 0.4%, and containing Nb, Ti and/or V, when containing Nb, the content of Nb is 0.05 ~ 0.15%, when containing Ti, the content of Ti is 0.05 ~ 0.15%, when containing V, the content of V is 0.05 ~ 0.15%, and all the other are iron and inevitable impurity; Tensile strength 445 ~ 451 MPa, pitting potential is 202 ~ 240mV.
The upper yield point of the stanniferous low gap ferritic stainless steel of above-mentioned unusual segregation is 310 ~ 337 MPa, and lower yield point is 306 ~ 325 MPa, and elongation after fracture is 47 ~ 49%.
The preparation method of the stanniferous low gap ferritic stainless steel of unusual segregation of the present invention carries out according to the following steps:
1, to smelt by set component and strand of casting, its composition is by weight percentage containing C 0.005 ~ 0.03%, Si 0.2 ~ 0.4%, Mn 0.2 ~ 0.5%, P≤0.03%, S≤0.02%, Cr 14 ~ 16%, N≤0.01%, Sn 0.1 ~ 0.4%, and containing Nb, Ti and/or V, when containing Nb, the content of Nb is 0.05 ~ 0.15%, when containing Ti, the content of Ti is 0.05 ~ 0.15%, when containing V, the content of V is 0.05 ~ 0.15%, and all the other are iron and inevitable impurity;
2, by after slab cooling to room temperature, be heated to 1150 ± 10 DEG C, insulation 1 ~ 3h, then carry out 5 ~ 6 passage hot rollings, start rolling temperature is 1080 ~ 1100 DEG C, and finishing temperature is 800 ~ 850 DEG C, and rolling reduction is 20 ~ 30%, makes hot-rolled steel sheet;
3, by hot-rolled steel sheet 900 ± 10 DEG C of annealing, the time is 2 ~ 3 h, is cooled to room temperature, then pickling remove surface oxide layer, then carry out cold rolling, cold rolling total reduction is 75 ~ 88%, makes cold-rolled steel sheet;
4, cold-rolled steel sheet is heated to 800 ± 10 DEG C, insulation 10 ~ 30min carries out normalizing treatment, obtains the stanniferous low gap ferritic stainless steel of unusual segregation.
In aforesaid method, when smelting by set component, Sn wherein derives from zinc-plated waste steel plate.
Low gap: C, N element due to atomic volume little, exist with interstitial atom in steel, because C in present method, N content are low, adding, a certain amount of Ti, Nb, V make the C in steel, atom N is fixed to as carbide and nitride, thus substantially reduce the number the number of steel interstitial atoms, improve intergranular corrosion resistance ability, mechanical property and high-temperature behavior.
Unusual segregation: in process of setting, each region of foundry goods exists certain temperature head, therefore, synchronization foundry goods everywhere not solidified amount of liquid phase be also different; In general, cold junction setting rate is very fast, and non-solidification liquid is mutually less, and non-lime set mutually in average solute concentration comparatively hot junction high (K<1); When there is liquid-flow in interdendritic, if liquid flows to cold junction from hot junction, namely from the region that the field flow orientation solutes content that solutes content is lower is higher, the solute average assay in Shi Gai district reduces, then produce unusual segregation; The mechanism of unusual segregation is: along with the carrying out of melt solidifying, soluterich in residual liquid, due to the gaseous tension of separating out in the contraction of solidified shell or residual liquid, make soluterich mutually through limb and the branch gap of the dentrite of formation scull, mobile to ingot casting surface, make ingot casting edge solute higher than ingot casting center.
Because casting billet surface comparatively crystal inner structure loosens, there is larger space, interior can minimizing can be made, promote that in crystal, solute atoms is from being sent to surface of steel ingot migration, so there is tin segregation in surface of steel ingot chill, along with the appearance of segregation line, define the barrier stoping conduct heat away, center, column crystal orientation development in crystallisation process, tin solute atoms is subject to barriers affect while crystal boundary migration, migration amount reduces to some extent, show as segregation degree to decline gradually, the unusual segregation of tin is produced in the operation of rolling, the enrichment region of tin is produced near top layer, formed stanniferous, the fine and close passivation layer of chromium.
For general steel grade, tin is exist with harmful impurity element in steel, has disadvantageous effect, simultaneously because the fusing point of tin is very low, when Theil indices causes compared with Gao Shihui hot-short, the thermoplasticity of steel is declined, worsen the performance of steel to the processing characteristics of steel.
But the few high purity ferritic stainless steel with excellent formability of carbon content in the stanniferous low gap ferritic stainless steel of the unusual segregation of the present invention's design then can form the few body centered structure of defect; Originally the stainless steel of chromium is added with compared with carbon steel, even if mix tin also not easily to break, add the high purity ferritic stainless steel with excellent formability subsurface defect reducing carbon and nitrogen content few, body centered structure can make tin be scattered in equably among material, just overcomes tin completely in the dispersed rear crackly problem of material internal; Thus the present invention adds tin replacement nickel in ferritic stainless steel, while its processing characteristics of guarantee, can improve stainless erosion resistance.The interpolation of tin makes ferritic stainless steel that certain lattice distortion occur, the tensile strength of steel is increased by solution strengthening, slightly reduce stainless steel plasticity, improve its plastic strain ratio (r value), and along with the rising of temperature when stretching, stanniferous stainless shaped cavity temperature reduces simultaneously, the interpolation of tin adds stainless moulding on the contrary, it is a large amount of dimple that stanniferous stainless steel breaks rear fracture at 400 ~ 800 DEG C, better moulding at this temperature range steel, during stretching, ductile rupture occurs.
Tin also can also exist certain segregation phenomena in ferrite, can separate out in crystal boundary with simple substance form, tin also has the trend of enrichment around inclusion simultaneously, such as sulfide inclusion, sulfur compound is mingled with and easilier than oxide inclusion brings out spot corrosion, in spot corrosion expansion process, inclusion optimum solvation comes off formation corrosion pit, has promoter action to spot corrosion expansion.When stainless steel is in corrosive medium; point-like inclusion often as spot corrosion core, thus destroys steel, so the enrichment of tin around inclusion and parcel can form the protective layer of tin around inclusion; meet Oxidant and form dense oxide film, thus improve pitting resistance of stainless steel.
In addition, tin in stainless steel to the modifying function of passive film, the characteristic of surface corrosion resistance rete can be caused to change, make passive film finer and close, reduce the blunt current density of dimension, tin plays a part activated cathode in an atmosphere, steel can be impelled to produce anode passivation, thus reduce the erosion rate of steel under certain condition; Stanniferous ferritic stainless steel is when running into corrosive medium, and the tin on steel surface, chromium optimum solvation become the metal oxide of tin and chromium, and under its synergy, generate finer and close passive film, tin can improve the corrosion resistance nature of steel in the enrichment of rusty scale.
In present component design:
Carbon: carbon in steel as interstitial element, in ferritic stainless steel, carbon content is generally less than 0.15%, in super-purity ferrite stainless steel, carbon content is less than 0.02%, if carbon content is too high, carbon can form compound at crystal boundary and chromium, and reduce the erosion resistance of grain boundaries, therefore in steel, the content of carbon is set in less than 0.03%;
Nitrogen: the effect of nitrogen in ferritic stainless steel is similar to carbon, nitrogen is austenite former, also be that a kind of interstitial atom has solution strengthening effect, nitrogen is separated out at crystal boundary and is formed compound with chromium, reduce erosion resistance and the processing characteristics of grain boundaries, nitrogen in steel content is mainly derived from the nitrogen in air, and nitrogen in steel content is set in less than 0.01%;
Silicon: silicon can improve hardness and the intensity of steel in ferritic stainless steel, its effect is only second to phosphorus, and when siliceous steel heats in oxidizing atmosphere, surface forms one deck SiO
2film, thus improve the oxidation-resistance of steel when high temperature.But silicone content is high, ductility and welding property are deteriorated, and the silicon in steel mainly comes from the deoxidation of ferro-silicon and bringing into of steelmaking feed, and in steel, silicone content should be not more than 0.4%;
Manganese: manganese is good reductor and sweetening agent.Generally all contain a certain amount of manganese in steel, it can eliminate or weaken the red brittleness of the steel caused due to sulphur, thus improves the hot workability of steel.The sosoloid that manganese and iron are formed, improves ferritic hardness and intensity in steel.Manganese and sulphur form the higher MnS of fusing point, can prevent the hot-short phenomenon caused because of FeS.But manganese has the tendency and temper brittleness susceptibility that increase crystalline grain of steel alligatoring, and therefore in steel, Fe content should be not more than 0.5%;
Phosphorus: although phosphorus can improve intensity and the hardness of steel, maximum harm is, segregation is serious, increases temper brittleness, causes steel easy embrittlement also so-called " cold short " phenomenon when cold working.Phosphorus also has disadvantageous effect to weldability.Phosphorus is harmful element, and in steel, phosphorus content controls below 0.03%;
Sulphur: sulphur segregation in steel is serious, worsens the quality of steel, under reduction high temperature, the plasticity of steel, is a kind of harmful element, usually controls below 0.02% to sulphur content;
Chromium: chromium is stainless main alloy element, in order to ensure stainless erosion resistance, in steel of the present invention, chromium content controls 14 ~ 16%, and chromium too high levels can make cost increase;
Copper: copper can be used as the supplementary Addition ofelements of tin, effectively improves the solidity to corrosion effect of tin in steel, improves cold-formed property, but when the hot workability of copper too high levels to steel is unfavorable, the copper therefore in steel controls below 1.5%;
Tin: tin improves top layer passivation film structure and is confirmed to propose heavy alloyed resistance to spot corrosion effect in stainless steel, cast iron, copper alloy, now joined in ferritic stainless steel, add 0.1% and can improve stainless erosion resistance effect, but when its content is greater than after 0.4%, to hot workability, unfavorable and cost increases, and therefore in steel of the present invention, Theil indices controls 0.1 ~ 0.4%;
Molybdenum: molybdenum is ferrite former, and the ability that can improve stainless corrosion-resistant ability and reducing resistance corrosive medium, but molybdenum is precious metal, and therefore molybdenum controls below 2%;
Titanium: titanium and nitrogen, oxygen, carbon have extremely strong avidity; It is the effective element of a kind of good deoxidation getter and fixed nitrogen and carbon.Because the avidity between titanium and carbon is much larger than the avidity between chromium and carbon, in stainless steel, conventional titanium fixes carbon wherein to eliminate the dilution of chromium at grain boundaries, thus elimination or alleviate the intergranular corrosion of steel.In high chromium-stainless steel, usually need add the titanium of about 5 times of carbon contents, not only can improve corrosion stability (mainly anti intercrystalline corrosion) and the toughness of steel; Can also the Grain growth trend of organization steel when high temperature and improve the welding property of steel; In steel, titanium content controls 0.05 ~ 0.15%;
Niobium: niobium part dissolves in sosoloid, plays solution strengthening effect.Trace niobium can improve the intensity of steel when not affecting plasticity or the toughness of steel.When content is greater than 8 times of carbon, almost can fix carbon all in steel, thus eliminate or alleviate the intergranular corrosion of steel; In steel, content of niobium controls 0.05 ~ 0.15%;
Vanadium: similar to niobium, titanium, vanadium and carbon, oxygen, nitrogen have extremely strong avidity, form with it corresponding stable compound.Vanadium mainly exists with the form of carbide in steel.Its Main Function is tissue and the crystal grain of refinement steel, eliminates or alleviate the intergranular corrosion of steel; In steel, content of niobium controls 0.05 ~ 0.15%;
The synergy of tin, copper and chromium: chromium is the main alloy element in ferritic stainless steel, and stainless steel solidity to corrosion also changes with the change of chromium content; Under the prerequisite of not adding nickel, reduction chromium content, by adding trace tin, reach corrosion proof requirement.The tin of 0.1%, the copper of 0.1% and 14% chromium on the one hand can ensure that tensile strength reaches 450MPa, unit elongation >=46%, tin and chromium can form the copper tin chromium composite oxides of one deck densification at stainless steel surface on the other hand, under its synergy, improve erosion resistance further, its pitting potential reaches more than 202mV; By adding zinc-plated steel scrap or tin iron binary alloy ensures Theil indices during smelting.
The present invention, compared with the corrosion-resistant stainless steel of prior art, has following remarkable advantage:
(1) present method can significantly reduce stainless production cost, stanniferous stainless steel decreases noble metal nickel, the adding of molybdenum, under the prerequisite ensureing its good erosion resistance, greatly reduce the production cost of steel, improve the competitive power of enterprise, and saved resource;
(2) product has good erosion resistance and plasticity, when the tin in steel is greater than 0.05%, just has good machinability; Because tin is distributed in crystal boundary and intracrystalline, improve stainless resistance to spot corrosion and intergranular corrosion resistance performance, thus make stainless steel have good corrosion-resistant effect in dilute sulphuric acid and organic chloracid;
(3) tensile strength of product gets a promotion, and the tensile strength of stanniferous ferritic stainless steel is than 430 not stanniferous ferritic stainless steel steel grade increase about 30MPa;
(4) technical process is simple, and the recovery rate of the Sn in smelting process can reach 80%, and is easy to control, and after heat treatment has higher intensity, hardness and corrosion resistance nature.
Accompanying drawing explanation
Fig. 1 is the microtexture metallograph of stanniferous low gap ferritic stainless steel under Carl Zeiss metaloscope of the unusual segregation in the embodiment of the present invention 1;
Fig. 2 is the scanning electron microscope (SEM) photograph of stanniferous low gap ferritic stainless steel under Japanese Shimadzu Corporation SSX-550 scanning electron microscope of the unusual segregation in the embodiment of the present invention 1, is illustrated as the segregation phenomena of tin around sulfide;
Fig. 3 is the scanning electron microscope (SEM) photograph of stanniferous low gap ferritic stainless steel under Japanese Shimadzu Corporation SSX-550 scanning electron microscope of the unusual segregation in the embodiment of the present invention 1, is illustrated as the Surface scan result of tin element in the visual field;
Fig. 4 gets analytical results to the stanniferous low gap ferritic stainless steel of the unusual segregation in the embodiment of the present invention 1 ready to its inclusion ambient components under Japanese Shimadzu Corporation SSX-550 scanning electron microscope and X-ray energy spectrometer; In figure, the weight content of Cr is 14.28%, and atomic percent is 15.21%; The weight content of Fe is 85.21%, and atomic percent is 84.55%; The weight content of Sn is 0.51%, and atomic percent is 0.24%;
Fig. 5 is the sample position distribution plan of stanniferous low gap ferritic stainless steel under Japanese Shimadzu Corporation SSX-550 scanning electron microscope to the unusual segregation in the embodiment of the present invention 1; In figure, A is top layer sampling, and B is 1 group of sample position, and 2,3,4 are respectively 2,3,4 groups of sample position;
Fig. 6 is the top layer sampling of the stanniferous low gap ferritic stainless steel of unusual segregation in the embodiment of the present invention 1 and the quantitative analysis graphic representation of 1,2,3,4 group of sampling tin element, carbon under Japanese Shimadzu Corporation SSX-550 scanning electron microscope and X-ray energy spectrometer analysis; In figure, ■ is carbon, and ▼ is tin element;
Fig. 7 is stanniferous low gap ferritic stainless steel middle inclusion defects scintigram under Japanese Shimadzu Corporation SSX-550 scanning electron microscope of the unusual segregation in the embodiment of the present invention 1.
Embodiment
Smelting by set component and strand of casting in the embodiment of the present invention, smelting adopts electric furnace or converter smelting, VOD refining, the refining of LF stove, and casting adopts sheet billet continuous casting; Or directly by vacuum induction furnace smelting, casting is die casting or sheet billet continuous casting.
The pickle solution that in the embodiment of the present invention, pickling adopts is by 100 mL HF, 50 mL HNO
3with 1 L H
2o prepares.
In the embodiment of the present invention, tested for tensile strength is accepted standard is GB/T228-2002, rolled sample nc wire-cutting Linear cut after thermal treatment is become gauge length 50mm, wide is the room temperature tensile sample of 12.5mm, and INSTRON-4206 almighty test machine carries out tensile tests at room.
Testing pitting potential in the embodiment of the present invention is be 10.1mm × 10.1mm steel sample by the stainless-steel sheet Linear cut of preparation, falls surface scale, reserve the working area 1cm of sample with No. 100 sand paperings
2a surface, remaining surface with epoxy resin be coated with envelope; Sample with No. 200, No. 400, No. 600, No. 800 sand paper grindings, will be noted during grinding avoiding sample to generate heat (wet-milling is to No. 800 sand paper) successively; In order to prevent crevice corrosion, carry out after grinding Passivation Treatment (50 DEG C, soak 1h in the nitric acid of 20 ~ 30%), select electrochemical method, according to GB/T17899-19999 stainless steel pitting potential measuring method, measured the negative anodic polarization curve of sample to be tested by potentiodynamic technique, obtain stainless pitting potential.
To test upper and lower yield-point in the embodiment of the present invention be accepted standard is GB/T228-2002, the stainless steel nc wire-cutting Linear cut of preparation is become gauge length 50mm, wide is the room temperature tensile sample of 12.5mm, and INSTRON-4206 almighty test machine carries out tensile tests at room.
To test elongation after fracture in the embodiment of the present invention be accepted standard is GB/T228-2002, the stainless steel nc wire-cutting Linear cut of preparation is become gauge length 50mm, wide is the room temperature tensile sample of 12.5mm, and INSTRON-4206 almighty test machine carries out tensile tests at room.
To test plastix strain in the embodiment of the present invention be accepted standard is GB/T228-2002, the stainless steel nc wire-cutting Linear cut of preparation is become gauge length 50mm, wide is the room temperature tensile sample of 12.5mm, and INSTRON-4206 almighty test machine carries out tensile tests at room.
Embodiment 1
Smelt by set component and strand of casting, its composition is by weight percentage containing C 0.005%, Si 0.4%, Mn 0.2%, P 0.016%, S 0.018%, Cr 14%, N 0.005%, Sn 0.24%, Nb 0.05%, and all the other are iron and inevitable impurity; The Sn adopted during smelting derives from zinc-plated waste steel plate;
After slab cooling to room temperature, be heated to 1150 ± 10 DEG C, insulation 1h, then carry out 5 passage hot rollings, start rolling temperature is 1080 DEG C, and finishing temperature is 800 DEG C, and rolling reduction is 30%, make hot-rolled steel sheet;
By hot-rolled steel sheet 900 ± 10 DEG C of annealing, the time is 2 h, is cooled to room temperature, then surface oxide layer is removed in pickling, and then carry out cold rolling, cold rolling total reduction is 75%, makes cold-rolled steel sheet;
Cold-rolled steel sheet is heated to 800 ± 10 DEG C, insulation 10min carries out normalizing treatment, obtains the stanniferous low gap ferritic stainless steel of unusual segregation; Its tensile strength 451 MPa, pitting potential is 202mV, and upper yield point is 310MPa, and lower yield point is 306MPa, and elongation after fracture is 47%; Carry out moulding strain testing, r value is 1.46, n value be 0.24, △ r value is 0.77, and Erichsen number is 9.84; The forming property of compound material, can meet the requirement of deep drawability energy aspect;
Microtexture metallograph under Carl Zeiss metaloscope as shown in Figure 1, the scanning electron microscope (SEM) photograph of the segregation phenomena of tin around sulfide as shown in Figure 2, the Surface scan result of tin element as shown in Figure 3, inclusion ambient components get analytical results (Japanese Shimadzu Corporation SSX-550 scanning electron microscope and X-ray energy spectrometer) as shown in Figure 4 ready, the distribution of stainless steel sample position after thermal treatment is as shown in Figure 5; According to shown in Fig. 5 from stainless steel top layer to the quantitative analysis curve of the tin element of the sample location of central core, carbon as shown in Figure 6; Inclusion defects scanning result as shown in Figure 7;
Carry out simultaneous test, smelt and the composition of the ingot casting of casting by weight percentage containing C 0.020%, Si 0.229%, Mn 0.381%, Cr 15.0%, P 0.021%, S 0.017%, surplus is iron and inevitable impurity; Make ferritic stainless steel by above-mentioned same manner, its tensile strength 432MPa, pitting potential is 105mV, and upper yield point is 310MPa, lower yield point is 302MPa, and elongation after fracture is 49%, carries out moulding strain testing, and r value is 1.49, n value is 0.23, △ r value is 0.85, and Erichsen number is 9.28.
Embodiment 2
Smelt by set component and strand of casting, its composition is by weight percentage containing C 0.01%, Si 0.35%, Mn 0.25%, P 0.017%, S 0.014%, Cr 14.5%, N 0.007%, Sn 0.31%, Ti 0.05%, and all the other are iron and inevitable impurity; The Sn adopted during smelting derives from zinc-plated waste steel plate;
After slab cooling to room temperature, be heated to 1150 ± 10 DEG C, insulation 2h, then carry out 6 passage hot rollings, start rolling temperature is 1100 DEG C, and finishing temperature is 850 DEG C, and rolling reduction is 20%, make hot-rolled steel sheet;
By hot-rolled steel sheet 900 ± 10 DEG C of annealing, the time is 2.5h, is cooled to room temperature, then surface oxide layer is removed in pickling, and then carry out cold rolling, cold rolling total reduction is 88%, makes cold-rolled steel sheet;
Cold-rolled steel sheet is heated to 800 ± 10 DEG C, insulation 20min carries out normalizing treatment, obtains the stanniferous low gap ferritic stainless steel of unusual segregation; Tensile strength 451 MPa, pitting potential is 220mV, and upper yield point is 311MPa, and lower yield point is 308 MPa, and elongation after fracture is 48%; Carry out moulding strain testing, r value is 1.44, n value be 0.22, △ r value is 1.15, and Erichsen number is 9.63; The forming property of compound material, can meet the requirement of deep drawability energy aspect.
Embodiment 3
Smelt by set component and strand of casting, its composition is by weight percentage containing C 0.015%, Si 0.33%, Mn 0.28%, P 0.019%, S 0.015%, Cr 14.8%, N 0.009%, Sn 0.19%, V 0.05%, and all the other are iron and inevitable impurity; The Sn adopted during smelting derives from zinc-plated waste steel plate;
After slab cooling to room temperature, be heated to 1150 ± 10 DEG C, insulation 3h, then carry out 5 passage hot rollings, start rolling temperature is 1090 DEG C, and finishing temperature is 830 DEG C, and rolling reduction is 25%, make hot-rolled steel sheet;
By hot-rolled steel sheet 900 ± 10 DEG C of annealing, the time is 3 h, is cooled to room temperature, then surface oxide layer is removed in pickling, and then carry out cold rolling, cold rolling total reduction is 85%, makes cold-rolled steel sheet;
Cold-rolled steel sheet is heated to 800 ± 10 DEG C, insulation 30min carries out normalizing treatment, obtains the stanniferous low gap ferritic stainless steel of unusual segregation; Tensile strength 445MPa, pitting potential is 240mV, and upper yield point is 337 MPa, and lower yield point is 325 MPa, and elongation after fracture is 49%; Carry out moulding strain testing, r value is 1.53, n value be 0.23, △ r value is 1.21, and Erichsen number is 9.78; The forming property of compound material, can meet the requirement of deep drawability energy aspect.
Embodiment 4
Smelt by set component and strand of casting, its composition is by weight percentage containing C 0.02%, Si 0.31%, Mn 0.3%, P 0.022%, S 0.014%, Cr 15.1%, N 0.003%, Sn 0.36%, Nb 0.15%, Ti 0.15%, and all the other are iron and inevitable impurity; The Sn adopted during smelting derives from zinc-plated waste steel plate;
After slab cooling to room temperature, be heated to 1150 ± 10 DEG C, insulation 1h, then carry out 6 passage hot rollings, start rolling temperature is 1080 DEG C, and finishing temperature is 800 DEG C, and rolling reduction is 25%, make hot-rolled steel sheet;
By hot-rolled steel sheet 900 ± 10 DEG C of annealing, the time is 2h, is cooled to room temperature, then surface oxide layer is removed in pickling, and then carry out cold rolling, cold rolling total reduction is 82%, makes cold-rolled steel sheet;
Cold-rolled steel sheet is heated to 800 ± 10 DEG C, insulation 15min carries out normalizing treatment, obtains the stanniferous low gap ferritic stainless steel of unusual segregation; Tensile strength 451 MPa, pitting potential is 240mV, and upper yield point is 331MPa, and lower yield point is 321 MPa, and elongation after fracture is 49%; Carry out moulding strain testing, r value is 1.44, n value be 0.23, △ r value is 1.12, and Erichsen number is 10.25; The forming property of compound material, can meet the requirement of deep drawability energy aspect.
Embodiment 5
Smelt by set component and strand of casting, its composition is by weight percentage containing C 0.025%, Si 0.27%, Mn 0.33%, P 0.021%, S 0.017%, Cr 15.5%, N 0.002%, Sn 0.22%, Ti 0.15%, V 0.15%, and all the other are iron and inevitable impurity; The Sn adopted during smelting derives from zinc-plated waste steel plate;
After slab cooling to room temperature, be heated to 1150 ± 10 DEG C, insulation 2h, then carry out 5 passage hot rollings, start rolling temperature is 1100 DEG C, and finishing temperature is 850 DEG C, and rolling reduction is 30%, make hot-rolled steel sheet;
By hot-rolled steel sheet 900 ± 10 DEG C of annealing, the time is 2.5h, is cooled to room temperature, then surface oxide layer is removed in pickling, and then carry out cold rolling, cold rolling total reduction is 78%, makes cold-rolled steel sheet;
Cold-rolled steel sheet is heated to 800 ± 10 DEG C, insulation 25min carries out normalizing treatment, obtains the stanniferous low gap ferritic stainless steel of unusual segregation; Tensile strength 448MPa, pitting potential is 216mV, and upper yield point is 329MPa, and lower yield point is 314MPa, and elongation after fracture is 48%; Carry out moulding strain testing, r value is 1.50, n value be 0.24, △ r value is 1.10, and Erichsen number is 9.93; The forming property of compound material, can meet the requirement of deep drawability energy aspect.
Embodiment 6
Smelt by set component and strand of casting, its composition is by weight percentage containing C 0.03%, Si 0.24%, Mn 0.38%, P 0.021%, S 0.016%, Cr 16%, N 0.004%, Sn 0.4%, Nb 0.15%, V 0.15%, and all the other are iron and inevitable impurity; The Sn adopted during smelting derives from zinc-plated waste steel plate;
After slab cooling to room temperature, be heated to 1150 ± 10 DEG C, insulation 3h, then carry out 6 passage hot rollings, start rolling temperature is 1090 DEG C, and finishing temperature is 830 DEG C, and rolling reduction is 20%, make hot-rolled steel sheet;
By hot-rolled steel sheet 900 ± 10 DEG C of annealing, the time is 3 h, is cooled to room temperature, then surface oxide layer is removed in pickling, and then carry out cold rolling, cold rolling total reduction is 84%, makes cold-rolled steel sheet;
Cold-rolled steel sheet is heated to 800 ± 10 DEG C, insulation 10min carries out normalizing treatment, obtains the stanniferous low gap ferritic stainless steel of unusual segregation; Tensile strength 450 MPa, pitting potential is 228mV, and upper yield point is 332MPa, and lower yield point is 320 MPa, and elongation after fracture is 47%; Carry out moulding strain testing, r value is 1.48, n value be 0.23, △ r value is 1.01, and Erichsen number is 9., 92; The forming property of compound material, can meet the requirement of deep drawability energy aspect.
Embodiment 7
Smelt by set component and strand of casting, its composition is by weight percentage containing C 0.008%, Si 0.22%, Mn 0.41%, P 0.026%, S 0.015%, Cr 15.7%, N 0.06%, Sn 0.3%, Nb 0.08%, Ti 0.11%, V 0.09%, all the other are iron and inevitable impurity; The Sn adopted during smelting derives from zinc-plated waste steel plate;
After slab cooling to room temperature, be heated to 1150 ± 10 DEG C, insulation 1h, then carry out 5 passage hot rollings, start rolling temperature is 1080 DEG C, and finishing temperature is 800 DEG C, and rolling reduction is 20, make hot-rolled steel sheet;
By hot-rolled steel sheet 900 ± 10 DEG C of annealing, the time is 2.5h, is cooled to room temperature, then surface oxide layer is removed in pickling, and then carry out cold rolling, cold rolling total reduction is 80%, makes cold-rolled steel sheet;
Cold-rolled steel sheet is heated to 800 ± 10 DEG C, insulation 20min carries out normalizing treatment, obtains the stanniferous low gap ferritic stainless steel of unusual segregation; Tensile strength 446 MPa, pitting potential is 233mV, and upper yield point is 319MPa, and lower yield point is 315 MPa, and elongation after fracture is 47%; Carry out moulding strain testing, r value is 1.49, n value be 0.22, △ r value is 1.14, and Erichsen number is 9.96; The forming property of compound material, can meet the requirement of deep drawability energy aspect.
Embodiment 8
Smelt by set component and strand of casting, its composition is by weight percentage containing C 0.019%, Si 0.2%, Mn 0.45%, P 0.019%, S 0.018%, Cr 14.3%, N 0.008%, Sn 0.2%, Nb 0.06%, Ti 0.12%, V 0.12%, all the other are iron and inevitable impurity; The Sn adopted during smelting derives from zinc-plated waste steel plate;
After slab cooling to room temperature, be heated to 1150 ± 10 DEG C, insulation 2h, then carry out 6 passage hot rollings, start rolling temperature is 1100 DEG C, and finishing temperature is 850 DEG C, and rolling reduction is 25%, make hot-rolled steel sheet;
By hot-rolled steel sheet 900 ± 10 DEG C of annealing, the time is 3 h, is cooled to room temperature, then surface oxide layer is removed in pickling, and then carry out cold rolling, cold rolling total reduction is 88%, makes cold-rolled steel sheet;
Cold-rolled steel sheet is heated to 800 ± 10 DEG C, insulation 30min carries out normalizing treatment, obtains the stanniferous low gap ferritic stainless steel of unusual segregation; Tensile strength 446MPa, pitting potential is 219mV, and upper yield point is 322MPa, and lower yield point is 311 MPa, and elongation after fracture is 49%; Carry out moulding strain testing, r value is 1.45, n value be 0.24, △ r value is 0.94, and Erichsen number is 9.57; The forming property of compound material, can meet the requirement of deep drawability energy aspect.
Embodiment 9
Smelt by set component and strand of casting, its composition is by weight percentage containing C 0.024%, Si 0.21%, Mn 0.5%, P 0.029%, S 0.011%, Cr 14.6%, N 0.08%, Sn 0.1%, the content of Nb 0.13%, Ti 0.09%, V is 0.06%, and all the other are iron and inevitable impurity; The Sn adopted during smelting derives from zinc-plated waste steel plate;
After slab cooling to room temperature, be heated to 1150 ± 10 DEG C, insulation 3h, then carry out 5 passage hot rollings, start rolling temperature is 1090 DEG C, and finishing temperature is 830 DEG C, and rolling reduction is 30%, make hot-rolled steel sheet;
By hot-rolled steel sheet 900 ± 10 DEG C of annealing, the time is 2h, is cooled to room temperature, then surface oxide layer is removed in pickling, and then carry out cold rolling, cold rolling total reduction is 75%, makes cold-rolled steel sheet;
Cold-rolled steel sheet is heated to 800 ± 10 DEG C, insulation 15min carries out normalizing treatment, obtains the stanniferous low gap ferritic stainless steel of unusual segregation; Tensile strength 448MPa, pitting potential is 236mV, and upper yield point is 321 MPa, and lower yield point is 310 MPa, and elongation after fracture is 47%; Carry out moulding strain testing, r value is 1.48, n value be 0.22, △ r value is 0.88, and Erichsen number is 9.73; The forming property of compound material, can meet the requirement of deep drawability energy aspect.
Claims (1)
1. a preparation method for the stanniferous low gap ferritic stainless steel of unusual segregation, is characterized in that carrying out according to the following steps:
(1) to smelt by set component and strand of casting, its composition is by weight percentage containing C 0.005 ~ 0.03%, Si 0.2 ~ 0.4%, Mn 0.2 ~ 0.5%, P≤0.03%, S≤0.02%, Cr 14 ~ 16%, N≤0.01%, Sn 0.1 ~ 0.4%, and containing Nb, Ti and/or V, when containing Nb, the content of Nb is 0.05 ~ 0.15%, when containing Ti, the content of Ti is 0.05 ~ 0.15%, when containing V, the content of V is 0.05 ~ 0.15%, and all the other are iron and inevitable impurity;
(2) by after slab cooling to room temperature, be heated to 1150 ± 10 DEG C, insulation 1 ~ 3h, then carry out 5 ~ 6 passage hot rollings, start rolling temperature is 1080 ~ 1100 DEG C, and finishing temperature is 800 ~ 850 DEG C, and rolling reduction is 20 ~ 30%, makes hot-rolled steel sheet;
(3) by hot-rolled steel sheet 900 ± 10 DEG C of annealing, the time is 2 ~ 3 h, is cooled to room temperature, then pickling remove surface oxide layer, then carry out cold rolling, cold rolling total reduction is 75 ~ 88%, makes cold-rolled steel sheet;
(4) cold-rolled steel sheet is heated to 800 ± 10 DEG C, insulation 10 ~ 30min carries out normalizing treatment, and obtain the stanniferous low gap ferritic stainless steel of unusual segregation, its tensile strength 445 ~ 451 MPa, pitting potential is 202 ~ 240mV.
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