A kind of low-magnetic austenitic stainless steel of good-mirror polishability and manufacture method thereof
The present invention relates to a kind of austenitic stainless steel and manufacture method thereof, relate in particular to a kind of good-mirror polishability in fields such as electron device, phone housing and the austenitic stainless steel and manufacture method thereof of low magnetic property of being mainly used in.
Field such as electron device and mobile phone has good mechanical performance, corrosion resistance nature and processability with austenitic stainless steel except requiring it, also requires to have good polishing performance and no magnetic or low magnetic property.Be applied at present this field many be 304 class austenitic stainless steels, in the majority with cold-reduced sheet especially because cold-reduced sheet has more excellent surface quality and polishing performance.And for portions of electronics industry steel, Cold Rolled Plate Thickness can't satisfy its actual demand, and cost is higher, therefore generally all adopt hot-rolled sheet to replace cold-reduced sheet, and hot-rolled sheet surface is the pickling rear surface, and its roughness is generally 2～5 μ m, can use after need being polished to minute surface.
For the austenite stainless steel hot-rolled sheet of conventional ingredient and explained hereafter, as 304, there are defectives such as pit, pin hole, easy rust staining in its surface of polished, and polishing time is long and material wastage rate is higher.For austenitic stainless steel 304, the hardness that two important indicators that influence its polishing performance are material itself and inner quality (separating out mutually) as inclusion grade, second.304 austenitic stainless steels for common process production, because solidity to corrosion in order to guarantee that it is excellent, generally need hot rolling or cold rolling after carry out solution heat treatment, this has just caused its low hardness and wear resistance, and if do not carry out anneal, will separate out and influence its solidity to corrosion and mirror polishability owing to carbide, therefore improving hardness and improving the material internal performance be the direction that solves such technical barrier.
The solution that improves hot rolling austenitic stainless steel hardness at present mainly is directly to use by the smooth back of the room temperature of solid solution attitude austenitic stainless steel being carried out heavy reduction, but cold deformation easily causes material inside organization inhomogeneous, hardness along the cross-wise direction skewness, the steel plate planeness is relatively poor and magnetic permeability is higher; It is longer to prepare such materials processing flow process in addition, and cost is higher, and steel plate thickness specification is limited.
Open patent 2001-247938 discloses the preparation method of a kind of used for electronic device high strength, high flat degree austenitic stainless steel, its disclosed composition is: 0.01%＜carbon＜0.08%, 0.1%＜silicon＜2.0%, Mn＜3.0%, 10.0%＜chromium＜20.0%, 3.0%＜nickel＜12.0%, 0.08%＜nitrogen＜0.25%, 0.01%＜niobium＜0.50%, and Md=500-458 (C+N)-9 (Si+Mn)-13Cr-19Ni-65Nb is greater than 0 less than 80, surplus are iron and unlike evitable impurity.Direct cold rolling after the hot rolling, draft are 20%, apply less than the tension force of material yield intensity below 0.2% at 650 ℃～1000 ℃ then, and keep below the 300s.This material has high strength, high rigidity and low unrelieved stress; but because such material has only solved the high rigidity problem; and do not solve the polishability problem of material, because this alloy is by the reinforcement that separates out of Nb-N compound, these particles of separating out can influence the mirror polishability of material.
Patent CN 1166805C discloses a kind of straight shape degree good high strength and high hardness austenic stainless steel belt and manufacture method thereof, its disclosed chemical ingredients is: carbon＜0.20%, silicon＜4.0%, Mn＜5.0%, 12.0%＜chromium＜20.0%, 3.0%＜nickel＜12.0%, nitrogen＜0.15%, molybdenum＜5.0%, surplus are that iron reaches unlike evitable impurity.And Md (N) value is in the scope of 0-125.Its manufacture method is to carry out solution treatment after the hot rolling, and cold rolling back is 500-700 ℃ of insulation.Such stainless steel improves intensity and hardness by the deformation induced martensite phase transformation, replys by partial martensite and makes the steel band straight shapeization.But, can not satisfy desired excellent polishing of such material and low magnetic owing to still exist more martensite to separate out mutually in the material with second.
Patent JP09003605A discloses a kind of austenitic stainless steel that has excellent polishing by extrusion molding, its disclosed composition is: carbon 0.01-0.10%, silicon≤1.0%, manganese≤3.0%, nickel 6.0-10.0%, chromium 15.0-19.0%, copper 1.0-4.0%, aluminium 0.2-2.5%, nitrogen≤0.05%, all the other are iron and unavoidable impurities.Improve its hardness by nickel equivalent being controlled to be 21.0-22.5 and grain fineness number greater than 8 grades, thereby improve its polishability.But because such material is that the specification that can produce, production cost and scale all have considerable restraint by extrusion molding.
Patent JP03023001A discloses a kind of manufacture method of improvement 304 polishabilities, its disclosed manufacture method is: hot-rolled coil carries out cold rolling behind annealing and pickling, 304 surface hardnesses are brought up to 300Hv, heart portion brings up to 250Hv, by the abrasive band surfaceness is milled to 0.2 μ m, thereby makes material have good polishing performance.This method also is to produce martensite by material cold working to improve hardness, improves its polishing performance by reducing surfaceness.But can there be martensite in material internal and causes its big magnetic permeability.
Relevant patent composition contrast, as shown in table 1:
The relevant patent composition contrast of table 1
Summary of the invention
The purpose of this invention is to provide a kind of by improving hardness, minimizing inclusion and reducing carbide and separate out good low-magnetic austenitic stainless steel and the manufacture method thereof of polishability that obtains, to improve the performance of traditional austenitic stainless steel.
Design of the present invention: on the basis based on 304 composition of steel, reduce inclusion by Ca, Al and the control oxygen level of adding trace, adjust the nickel chromium triangle equivalent and be 0～2 and control austenitic stability, avoid second to separate out mutually by improving finishing temperature with the curling temperature of reduction in the operation of rolling, it is cold rolling directly to carry out 1～3 passage after the hot rolling, reduction in pass is not less than 10%, and the accumulative total percentage pass reduction is not more than 35%; Pickling obtains the austenitic stainless steel hot-rolled coil after 800～950 ℃ of annealing, makes such stainless steel have good polishing performance, and has low magnetic property.
The object of the present invention is achieved like this:
A kind of low-magnetic austenitic stainless steel of good-mirror polishability, its chemical component weight per-cent is:
Surplus is Fe and unavoidable impurities;
Preferably, this stainless Ni-bal scope is 0～2.0;
Wherein, described Ni-bal adopts following formula to calculate:
Nitrogen and carbon are strong austenite formers, increase the carbon nitrogen content and not only can reduce ferrite content in the austenitic stainless steel, increase the stability of austenitic stainless steel, can also the solid solution austenite improve intensity and hardness in mutually.But the increase of excessive carbon and nitrogen element can make carbonitride separate out again, thereby influences the polishability of material, therefore the nitrogen element is controlled to be less than 0.20%, and carbon content is controlled to be less than 0.05%, and C+N is greater than 0.10%.
Good polishability just requires the austenitic stainless steel endogenous inclusion tiny, and proper C a, Al add can pure steel, improve inclusion morphology, thereby reduced the inclusion grade, help the raising of polishing performance; But this content can not be too high, and too high can causing again forms new inclusion and precipitated phase, thereby influences the polishing performance of material.With Control for Oxygen Content is less than 0.005%, also is in order further to reduce the inclusion grade, because if too high oxygen level forms inclusion easily in the material, too high oxygen level also shows and formed too much oxide inclusion in the material simultaneously.
Rationally determine the content of nickel equivalent forming element Ni, Mn, N, C and chromium equivalent forming element Cr, Si, to guarantee that Ni-bal is 0～2, according to the calculation formula of Ni-bal as can be seen, the Ni-bal value is high more, show that this austenitic stainless steel nickel equivalent is high more, promptly austenite structure is stable more in the process of deformation.When Ni-bal less than 0 the time, such austenitic stainless steel will produce a large amount of martensite deformation in the process of cold deformation, material still has certain magnetic after the low-temperature annealing.And will cause austenite structure too stable greater than 2 the time as Ni-bal, and in cold worked process, can not produce work hardening, the hardness of material improves not obvious after low-temperature annealing.
Particularly, the present invention is 0～2 to guarantee the stability of its austenite structure by adjusting Ni-bal, control by the carbon nitrogen content is to guarantee the hardness and the austenitic stability of material, by adding micro-Ca, Al element and control oxygen level, improve its polishing performance less than 0.005% to reduce austenitic stainless steel endogenous inclusion grade.
A kind of manufacture method of low-magnetic austenitic stainless steel of above-mentioned good-mirror polishability, it comprises the steps:
1) continuously cast bloom that obtains according to casting after the described proportioning melting;
2) hot rolling behind heat tracing, finishing temperature scope are 1000～1050 ℃; Be chilled to 500～700 ℃ soon, and under this temperature, curl;
3) it is cold rolling to carry out 1～3 passage, reduction in pass 〉=10%, accumulative total percentage pass reduction≤35%;
4) carry out low-temperature annealing thermal treatment at 800～950 ℃;
Preferably, it is cold rolling to carry out 1 passage in the step 3).
The present invention is owing to adopted above technical scheme, make it compared with prior art, have the following advantages and positively effect: the austenitic stainless steel hot-rolled coil that the present invention obtained has good hardness, be that hardness is greater than 240Hv, lower inclusion grade, i.e. A+B+C+D≤2.5 grade, single-phase austenite structure and low magnetic or nonmagnetic energy, this permeability is less than 1.2Gs/Oe, therefore have good polishing performance, can be applied to fields such as electronic devices and components and phone housing.
A kind of low-magnetic austenitic stainless steel of good-mirror polishability, its weight percent component is: Cr17.00～21.00%; Ni 8.00～10.00%; N 0.05～0.20%; C≤0.05%; Mn≤2.00%; Si 0.3～1.0%; P≤0.03%; S≤0.005%; Ca 0.0010-0.0050%; O≤0.0050%; Al 0.010～0.060%; Surplus is Fe and unavoidable impurities; And, C+N＞0.10%, the Ni-bal scope is 0～2.0; Described Ni-bal adopts following formula to calculate:
A kind of manufacture method of low-magnetic austenitic stainless steel of above-mentioned good-mirror polishability, it comprises the steps: 1) according to the continuously cast bloom of casting and obtaining after the described proportioning melting; 2) hot rolling behind heat tracing, finishing temperature scope are 1000～1050 ℃; Be chilled to 500～700 ℃ soon, and under this temperature, curl; 3) it is cold rolling to carry out 1～3 passage, (preferred 1 passage is cold rolling) reduction in pass 〉=10%, accumulative total percentage pass reduction≤35%; 4) carry out low-temperature annealing thermal treatment at 800～950 ℃; 5) pickling.
Avoid second to separate out mutually by improving finishing temperature with the curling temperature of reduction in the operation of rolling, wherein finishing temperature is 1000～1050 ℃, and curling temperature is 500～700 ℃.
In the course of hot rolling of austenitic stainless steel, finishing temperature helps the dynamic recrystallization of austenite in course of hot rolling in time more than 1000～1050 ℃, can avoid subsequent anneal thermal treatment, does not also have second and separate out mutually in this temperature; And finishing temperature is crossed the dynamic recrystallization that is unfavorable for when hanging down in the course of hot rolling.The temperature of curling is formulated a low temperature, mainly is to show by calphad, does not have carboritride in this temperature range and separates out, and also can avoid follow-up solution heat treatment, thereby but helps improving the hardness and the polishability of material.
Hot-rolled coil carries out before annealing that 1～3 passage is cold rolling, and reduction in pass is not less than 10%, and the accumulative total percentage pass reduction is not more than 35%, and pickling obtains the austenitic stainless steel hot-rolled coil after 800～950 ℃ of low-temperature annealings.
Hot-rolled coil does not carry out annealing and pickling and directly carries out cold rollingly, mainly is because the hot rolling attitude adopts high finishing temperature and low curling temperature, thereby has avoided second to separate out mutually, and make material guarantee good hardness.Cold rolling 1～3 passage mainly is in order further to improve the hardness of austenitic stainless steel, in the process of cold deformation, if the single pass draught is low excessively, can cause distortion can't be penetrated into material heart portion, therefore is decided to be 10%.If the accumulative total percentage pass reduction is excessive, can cause the too much martensite deformation of material production, therefore be defined as and be not more than 30%.800～950 ℃ of low-temperature annealings mainly is martensitic transformation in order to eliminate to form in the deformation process, thereby helps the improvement of plate of material shape and the acquisition of low magnetic property.
According to austenite stainless composition of steel of the present invention, the one-tenth of embodiment 1～5 and Comparative Examples 1 is respectively in table 2.
Adopt electric furnace to add AOD (argon oxygen stove) melting, pour into continuously cast bloom, hot rolling, cold rolling, obtain the austenite stainless rolled steel plate after the low-temperature annealing pickling, this roll bending has higher hardness, low inclusion grade and does not have second and separate out mutually, therefore obtained good polishing performance, and had low magnetic property, all properties is listed in table 3.Comparative Examples production path is as follows:
Comparative Examples 1: its composition is mainly 304 compositions, do not add Al, Ca, its oxygen level is 0.007%, production technique is identical with the described content of patent, the result shows, its magnetic permeability is higher, and there are defectives such as a large amount of small pits, pinprick in the display material surface after the polishing, has seriously influenced its polishing performance.
Comparative Examples 2: its composition is with embodiment 2 compositions, but it is produced according to traditional processing technology: hot rolling-annealing-pickling-cold deformation, material has than higher hardness behind the cold deformation, though have good polishing performance, but because deformation causes material not have low magnetic property after producing martensite, and plate shape is bad.
Comparative Examples 3: its composition is with embodiment 3 compositions, but its hot rolling technology adopts traditional technology: finishing temperature is 990 ℃, curling temperature is 730 ℃, and other technologies are with the described content of patent, and polish results shows: material is because separating out of carbide causes the surface of polished easy-to-rust.
Comparative Examples 4: its composition and hot rolling technology are with embodiment 4 described contents, and cold rolling back is 1080 ℃ of annealing, and annealing back material hardness obviously descends, and smooth finish is relatively poor after causing polishing, and material wastage rate is bigger.
Table 2, embodiment and Comparative Examples composition
Table 3, embodiment and Comparative Examples processing parameter and performance comparison
Those of ordinary skill in the art will be appreciated that, above embodiment is used for illustrating the present invention, and be not to be used as limitation of the invention, as long as in connotation scope of the present invention, all will drop in claims scope of the present invention variation, the modification of the above embodiment.