CN101528963B - Ferritic stainless steel having excellent formability of welded zone and corrosion resistance, and method for manufacturing the same - Google Patents
Ferritic stainless steel having excellent formability of welded zone and corrosion resistance, and method for manufacturing the same Download PDFInfo
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/004—Very low carbon steels, i.e. having a carbon content of less than 0,01%
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/28—Ferrous alloys, e.g. steel alloys containing chromium with titanium or zirconium
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Abstract
Disclosed are a ferritic stainless steel and a method for manufacturing the same. The ferritic stainless steel comprises, in terms of % by weight: 0.01% or less C; 0.01% or less N; 1.0% or less Si; 1.0% or less Mn; 10.0-20.0% Cr; 0.15% or less Al; 0.0005-0.002% Ca; 0.0018-0.01% Zr; 0.OO4-0.OO8% O; and the balance of Fe and other unavoidable impurities. The ferritic stainless steel has improved formability of a welding zone and excellent corrosion resistance of the steel by refining solidified grains in the welding zone through combinational addition of Ca and Zr.
Description
Technical field
The present invention relates to the steel of the good and steel excellent corrosion resistance of welding zone formability.More particularly, the present invention relates to a kind of like this ferritic stainless steel, wherein, improve the solidity to corrosion of this ferritic stainless steel by the composition and size of regulating the oxide compound in the steel, and solidified nucleation by making the formability that the crystal grain granular has been improved the welding zone of this ferritic stainless steel of solidifying of welding zone based on oxide compound.
Background technology
In recent years, the common employing of vehicular manufacturer has thermotolerance and corrosion proof ferritic stainless steel replaces traditional foundry goods or aluminising steel plate to be used for the assembly of exhaust system, thereby satisfies the vehicular emission standards of reinforcement and the fuel efficiency of raising by reducing vehicle weight.
The assembly of exhaust system has hull shape and tubular usually, and produces and assemble by welding.Therefore, consider the performance of exhaust gas system, the mass property of guaranteeing the welding zone is very important.For example, when the assembly of production exhaust system, the shape that the pipe of steel plate or welding (by manufacturings such as hight frequency welding, TIG welding, laser welding) is processed to expect, and again welded, thereby produce described assembly.Because exhaust gas system has very complicated shape, so some part of steel plate or pipe stands serious stress inevitably in the course of processing.In the situation of ferrite stainless steel pipe, when experience secondary processing in welding zone for example during crooked or expansion, no matter how good the formability of base material is, on soldered metal or heat affected zone, all can produce welding crack, thereby the formability of deteriorated welding zone, this is so that base material is difficult to show its intrinsic formability.Because when brittle crack occurring during working steel products under the high processing speed or under the low processing temperature in winter, so this phenomenon becomes obvious in the welding zone of pipe.
According to technology known in the art, make the deteriorated reason of formability of welding zone usually can be summarized as four kinds, these four kinds of reasons comprise unrelieved stress during pipe milling (milling), quenching, impurity element for example C and N and the alligatoring of solidifying crystal grain.As the method that discharges unrelieved stress, the most effectively by making homogeneous tube annealing remove welding zone distortion on every side.Announce in the disclosed method in the 1997-125209 Japanese Patent Laid-Open, anneal under 850 ℃～1000 ℃ by the pipe that welding is produced, then with 1 ℃/second or faster rate of cooling cooling.The disclosure has been reported this method can be improved to cold-rolled steel sheet with formability and the toughness of pipe after annealing level.Yet the annealing of pipe has increased manufacturing cost inevitably, and in order to ensure high heat resistance and scale resistance and carried out the highly alloyed pipe fully ensure quality characteristic.
The amount of the quenching of welding zone and alloying element such as Si, Mn, Ti, Nb etc. and impurity element such as C, N etc. is closely related.Alloying element is added in the steel as the infrastructure elements of improving manufacturing process and product performance, and often is difficult to control the content of alloying element.Therefore, active research and developed for example method of the amount of C and N of impurity reduction element.Known technology as this area, with for example vacuum-oxygen decarbonizing of improvement (VOD) refining techniques to process for making, form nitride or carbide by adding stabilizing element such as Ti, Nb, Zr etc., thus the impurity reduction element amount of C and N for example.Yet, pointed out to exist following problem, that is, VOD technique can be reduced to the amount of C+N maximum 100ppm, and causes productivity to descend, and owing to increases the cost increase that technique causes.In addition, in order to reduce the C that dissolves in the steel and the amount of N by adding the formation nitride such as stabilizing element such as Ti, Nb, Zr or carbide, the amount of the stabilizing element that need to add should be 8 times of the amount of C+N, in the situation of welding metal, the amount of stabilizing element can be added to 20 times of amount of C+N.
Yet, in steelmaking process, adding in a large number Ti and be easy to form coarse oxide inclusion or precipitation, this causes the surface crack of continuously cast bloom or the surface imperfection in the operation of rolling, and Zr causes such as problems such as nozzle clogging.In addition, as in the welding zone, when the part experience rapid heating of steel or when cooling off fast, because it is inadequate to produce the time period of precipitation, so only be that the addition that increases Ti, Nb, Zr etc. causes the amount of the sosoloid of Ti, Nb, Zr, C and N in the steel to increase, rather than fully form precipitation.
Recently, this area has proposed the solidified structure of steel and the metal area of welding are carried out the technique that granular is improved formability.The technique of regulating solidified structure can be divided into usually: the technology relevant with equipment improvement, and for example, the electromagnetic induction of molten metal stirs (sees Iron﹠amp; Steel (iron and steel), sixth version, 66 volumes,, 38 pages in 1980); With the technology of adding alloying element and promoting that the ferrite nucleation of inclusion is relevant.Employing is known that by obtain the suitable mixing position of molten metal in process of setting based on the technology that electromagnetic induction stirs, can guarantees that steel has about 40%～60% equiaxial crystal ratio.Although this technology can be improved the formability of steel, when steel is melted again, can not guarantee this effect in the situation such as welding.
In order to utilize inclusion to make the solidified structure granular, well known in the prior art is the method (document 3 to 10) of utilizing the method (document 1 and 2) of TiN precipitation and utilizing oxide compound.In the following description, % represents wt% (weight percent).
1.Iron﹠amp; Steel (iron and steel) (66 volumes, 1980,110 pages): 40 ℃ of or less of A process of generatingTiN by regulation of a super heating degree DT of molten metal containing 0.4%Ti and 0.016%N to be (the superheating temperature DT of the molten metal of the N by will comprising 0.4% Ti and 0.016% is adjusted to the technique of 40 ℃ or the lower TiN of generation).
2.JP2000-160299:A technique for ensuring an equiaxed crystal ratio of 60%at an operation of preparing a slab containing 0.01% or more of separate TiNinclusions (preparation comprise 0.01% or the operation of the base of the more TiN inclusion that separates in, guarantee the technology of 60% equiaxial crystal ratio).
3.JP1997-217151, JP1997-271900:A process of refining solidificationstructure of a welded zone through formation of Mg-Al based composite oxides byadding 0.001～0.02% Mg and 0.001～0.2% Al to steel (form the Mg-Al base composite oxidate by in steel, adding 0.001～0.02% Mg and 0.001～0.2% Al, thereby make the technique of the solidified structure granular of welding zone).
4.JP1998-324956:Aprocess of distributing 0.01-5mm Mg-based oxides ata density of 3/mm
2In steel by initiating solidification of molten metal within 180seconds after adding 0.0005-0.01%Mg to the molten metal deoxidized to have0.01%or less oxygen (by to deoxidation be have 0.01% or the molten metal of still less oxygen in add after the Mg of 0.0005%-0.01%, in 180 seconds, start solidifying of molten metal, with 3/mm
2The technique of density Mg base oxide of distribution 0.01-5mm in steel).
5.JP2001-020046:A process of forming composite inclusions of Mg-Albased oxides and Ti-based nitrides in steel with a content ratio between Mg and Alranging from 0.3 to 0.5 (take the scope of the ratio of the content between Mg and the Al as 0.3 to 0.5, in steel, forming the technique of the complex inclusion of Mg-Al base oxide and Ti base nitride).
6.JP2001-181808:A technique for improving formability of steel withoutcold rolling by refining solidification structure using Mg inclusions formed byaddition of 0.0005-0.01%Mg to the steel, while controlling suitable hot rollingconditions (utilizes and to add the Mg inclusion that 0.0005% to 0.01% Mg forms in the steel, by making the solidified structure granular, control simultaneously suitable hot-rolled condition, do not adopt the cold rolling technology of improving the formability of steel).
7.JP2001-288543:A technique for improving formability, surface properties, and corrosion resistance of steel by refining solidified grains through addition ofMg and Ca at an amount of0.006%or less to the steel (by Mg and the Ca of interpolation 0.006% in steel or amount still less, thereby coming by making formability, surface property and the corrosion proof technology that the crystal grain granular is improved steel of solidifying).
8.JP2001-294991:A process of distributing 0.01-5mm composite inclusionsof Mg-based oxides and TiN precipitates at a density of 3/mm
2Or more in steel is (with 3/mm
2Or the technique of higher density 0.01-5mm complex inclusion of distribution Mg base oxide and TiN precipitation in steel).
9.JP2002-285292:A technique of preventing brittle cracks during steel plateand steel pipe manufacturing processes by adding 0.001～0.05% Y, a rare-earthelement, to form inclusions such as Al-Y, Mg-Y, Al-Mg-Y while refining solidifiedgrains is (by adding 0.001～0.05% Y, rare earth element forms for example Al-Y, Mg-Y, the inclusion of Al-Mg-Y, make simultaneously and solidify the crystal grain granular, thereby prevent the technology of the brittle crack during steel plate and the steel tube manufacture technique).
10.JP2002-336990:A process of distributing 0.3mm or more Ti andAl-based nitrides at a density of 1.5 * 10
4/ mm
2Or more in welded metal by adding0.01～0.3%Ti and 0.01～0.2% Al to steel while using Ar, O
2, CO
2, He, and the likeas a protective gas (by add 0.01～0.3% Ti and 0.01～0.2% Al in steel, uses Ar, O simultaneously
2, CO
2, He etc. is as shielding gas, with 1.5 * 10
4/ mm
2Or higher density distribution 0.3mm or larger Ti and technique of Al base nitride in welding metal).
11.JP2003-221652:A process of activating ferrite (111) planes as nucleationsites during hot rolling, with CaS or CaO dispersed in steel by controlling thecontents of O and S to be in the range of S/1.25+O/5 〉=0.003 in the steel comprising0.0003～0.003%Ca and 0.01%or less O while optionally adding 0.001～0.3%Zr tothe steel (by control comprise 0.0003～0.003% Ca and 0.01% or the steel of lower O in O and the content of S in the scope of S/1.25+O/5 〉=0.003, CaS or CaO are dispersed in the steel, simultaneously in this steel, add 0.001～0.3% Zr alternatively, the technique that in course of hot rolling, will activate as ferrite (111) face of nucleation site).
The technology of document 1 and document 2 can make the solidified structure granular of steel ingot by making TiN crystallization in the molten metal.Yet these technology are difficult to be applied to the difficult situation of temperature control of molten metal, for example situation of welding.In addition, because a large amount of Ti and TiN reduce the toughness of steel, so TiN can cause forming obvious brittle crack at ferritic stainless steel.
Document 3 to the technology of document 10 is the technique that promotes to solidify nucleation with oxide compound, adds Mg, Y etc. by independent in molten metal or combination and form described oxide compound in molten metal.Yet when adding Mg and Y in molten metal, the high oxidation reactivity of these elements is so that be difficult to expect the rate of recovery (recovery rate), cause between the product made from steel frequently mass deviation, and the explosive characteristic of these elements is so that be difficult to management.Therefore, these technology can not be applied to industrial circle.
The technology of document 11 is to form CaS in molten metal and CaO impels the technique that produces ferrite (111) face that shows high formability in the thermoforming process.In this technology, in molten metal, add after the Ca, add Zr and remove remaining oxygen level, thereby form coarse oxide inclusion or sulfide.This coarse inclusion has reduced the surface quality of steel, and cause with inclusion and base material between the surface area at interface increase relevant solidity to corrosion and descend.In addition, owing to add a large amount of Zr, this technology causes manufacturing cost to increase.
Like this, still, need to guarantee the formability of welding zone and the corrosion proof ferritic stainless steel of steel.
Summary of the invention
Technical problem
The invention is intended to solve the aforementioned problems in the prior, therefore, an aspect of of the present present invention is to provide ferritic stainless steel and the manufacture method thereof of the excellent corrosion resistance that a kind of welding zone has good formability and steel.
Technical scheme
According to an aspect of the present invention, the invention provides a kind of ferritic stainless steel, described ferritic stainless steel comprises by weight percentage: 0.01% or C still less, 0.01% or N still less, 1.0% or Si still less, 1.0% or Mn still less, 10.0%～20.0% Cr, 0.15% or Al still less, 0.0005%～0.002% Ca, 0.0018%～0.01% Zr, 0.004%～0.008% O and Fe and other inevitable impurity of surplus.Here, described ferritic stainless steel can also comprise a kind of among the Ti of 0.01%～0.5% Nb and 0.01%～0.5%.
According to a further aspect in the invention, the invention provides a kind of method of making hot rolling or cold rolling ferritic stainless steel, said method comprising the steps of: the stainless molten metal of preparation in electric furnace; The stainless molten metal of refining preparation; The molten metal of continuous casting refining provides steel ingot; Rolling ingot casting; Rolling steel is annealed, thereby provide ferritic stainless steel, described ferritic stainless steel comprises 0.01% or C still less by weight percentage, 0.01% or N still less, 1.0% or Si still less, 1.0% or Mn still less, 10.0%～20.0% Cr, 0.15% or Al still less, 0.0005%～0.002% Ca, 0.0018%～0.01% Zr, 0.004%～0.008% O, 0.01%～0.5% Ti, and the Fe of surplus and other inevitable impurity, wherein, refinement step comprises according to the order of Zr and Ca order in the molten metal and adds Zr and Ca.Here, described ferritic stainless steel can also comprise a kind of among the Ti of 0.01%～0.5% Nb and 0.01%～0.5%.Described refinement step can also be included in the amount of adding in the molten metal before the Zr oxygen and be controlled at 0.01% or still less.
To describe embodiments of the invention in detail hereinafter.
Solidify the crystal grain granular by making in the welding zone, and reduce remaining C and the amount of N by forming sufficient carbonitride, guarantee that ferritic stainless steel according to the present invention has low temperature formability and the improved solidity to corrosion of improved welding zone.
Now, in connection with the various components of ferritic stainless steel the present invention is described.
C and N:C and N are the elements of the formability of deteriorated base material and welding zone.Therefore, although expectation suppresses the content of C and N as much as possible, consider the increase of manufacturing cost, ferritic stainless steel of the present invention contains 0.01% or C still less and 0.01% or N still less.
Si, Mn, Al, P and S: although always in steel, there are these elements, but the content of these elements too much causes formability and corrosion proof deteriorated as one of stainless main characteristic.Therefore, propose ferritic stainless steel and comprised 1.0% or Si still less, 1.0% or Mn still less, 0.15% or Al still less, 0.040% or P still less and 0.010% or S still less.
Cr: cause that the solidity to corrosion as one of stainless fundamental characteristics lacks because the content of Cr is less than 10%, so the content of Cr is set to 10% or more.On the other hand, because the content of Cr too much often causes the toughness of welding zone deteriorated, so the content of Cr has 20% or the lower upper limit.
Ca: one of major objective of the present invention is to improve weldability, and Ca improves the necessary element of weldability.In order to improve weldability, expectation adds 0.0005% or more Ca in the steel.When interpolation 0.002% in steel or more Ca, the size of oxide inclusion increases, and adversely affects solidity to corrosion.Therefore, the content of Ca has 0.002% the upper limit.
Zr: similar with Ca, one of major objective of the present invention is to improve weldability, and Zr improves the necessary element of weldability.In addition, Zr is by improving the minimized in size of oxide particle the solidity to corrosion of steel.In addition, Zr forms nitride or carbide usually, and nitride or carbide form complex inclusion with oxide compound subsequently.In order to improve weldability and solidity to corrosion, expectation comprises 0.002% or more Zr.Yet, when interpolation 0.01% in steel or more Zr, exist because addition increases the problem of the cost increase that causes and the problem of the nozzle blockage in process for making.Therefore, the content of Zr has 0.01% the upper limit.
O:O is the element that forms Zr and Ca base oxide.The content of O is less than or equals 0.004% and causes being difficult to form oxide compound, and the content of O is equal to or greater than 0.008% weak effect that causes quality-improving.Must have in the welding zone in the situation of fabulous formability, exist ferritic stainless steel preferably to comprise O 0.005% or still less.
Ti:Ti adds as the element that improves formability.When Ti with 0.01% or more amount when adding, can show the effect of Ti.Yet, when the content of Ti surpasses 0.5%, exist because the amount increase of the Ti that dissolves in the steel causes the deteriorated problem of formability.
Can also in the steel with above-mentioned composition, add other alloying element according to the characteristic of the expectation of steel.For example, when attempting to improve solidity to corrosion, can also add at least a among Mo, Ni and the Cu with 0.1%～2.0% amount.When at least a content among Mo, Ni and the Cu more than or equal to 0.1% the time, can improve solidity to corrosion.Yet above-mentioned content surpasses 2.0% and causes the deteriorated and cost increase of formability.In addition, Nb can be increased to 0.5%.When the content of Nb surpasses 0.5%, exist the amount owing to the Nb that dissolves in the steel to increase the deteriorated problem of formability that causes.Thereby in order to form the improvement formabilities such as NbN, NbC by adding Nb, the content of Nb is preferably in 0.01%～0.5% scope.
When satisfying according to composition of the present invention, ladle contains Ca-Zr or Ca-Zr-Ti base oxide.These oxide compounds are of a size of 1 μ m～3 μ m, and with 5 particle/mm
2To 10 particle/mm
2Density distribution.In this case, steel can have Ti or Nb base precipitation, and described precipitation has 1 μ m or less size and with 39000 precipitation/mm
2Or larger density distribution.
Then, with the method for describing according to manufacturing ferritic stainless steel of the present invention.
Ferritic stainless steel of the present invention is made by following technique.At first, the stainless molten metal of preparation in electric furnace.Then, molten metal provides steel ingot through refining and continuous casting, and then, steel ingot is rolled the product made from steel that provides rolling.At last, rolling product made from steel is annealed.
According to exemplary embodiment of the present invention, the order according to Zr and Ca in refining operation is sequentially added Zr and Ca in molten metal, thereby obtains Ca-Zr or Ca-Zr-Ti base oxide.In this case, can control to by the content with oxygen 0.01% or still less come more effectively to regulate the amount of oxide compound.Traditionally, remaining oxygen can remove according to the mode of sequentially adding Ca and Zr in molten metal.Yet, in this case, form coarse CaO or CaS, thus the surface quality of deteriorated steel and solidity to corrosion, and add in a large number Zr increase manufacturing cost.
React separately in the situation that forms CaO at Ca and oxygen, because the excessive size of oxide compound can cause occuring above problem.In addition, ZrO can not be as freezing nuclei because its size is little.Therefore, target of the present invention is to regulate the size of oxide compound by the composite oxides that form Ca and Zr, thereby oxide compound is suitable for as freezing nuclei.
Here, because the oxygen reactivity of Ca is reactive higher than the oxygen of Zr, so Zr should add in the molten metal, in molten metal, adds a large amount of Zr when perhaps adding at the same time Ca and Zr after adding Ca, thereby obtain the effect of expectation of the present invention.Yet, add in a large number Zr result and cause brittle crack by producing a large amount of ZrO and ZrN, and increase manufacturing cost.
According to the present invention, before Ca, Zr is added in the molten metal.When adding a small amount of Zr in the molten metal in advance, because formation ZrO has reduced oxygen concentration.After this, add Ca, and Ca forms composite oxides with Zr, thereby improve formability and solidity to corrosion by the size of optimizing oxide compound.
Ti and N reaction form TiN, have reduced the concentration of nitrogen, thereby have improved formability.Although before refining operation, namely, before adding Zr and Ca to molten metal, in molten metal, add Ti, but because the fusing point of TiN is lower than the fusing point of Ca-Zr or Ca-Zr-Ti base oxide, so after Ca-Zr or Ca-Zr-Ti base oxide, form TiN, and TiN forms complex inclusion according to the mode that TiN centers on a part of Ca-Zr or Ca-Zr-Ti base oxide with Ca-Zr or Ca-Zr-Ti base oxide.Similar with the situation of Ti, Nb also forms nitride, and nitride forms another kind of complex inclusion with Ca-Zr or Ca-Zr-Ti base oxide subsequently.Nb can be optionally or associativity ground add in the molten metal with Ti.
Because oxide compound and complex inclusion have high-melting-point, even so in the situation that the steel that is formed with oxide compound and complex inclusion in the molten metal operation is welded, oxide compound and complex inclusion keep and as the freezing nuclei of the new solidified structure of steel, so oxide compound and complex inclusion are being effective aspect the formability of the welding zone that improves steel and the solidity to corrosion.
The Ti or the reaction of the carbon in Nb and the molten metal that consist of Ti or Nb base precipitation form the precipitation of TiC or NbC form, thereby improve formability.Although consist of the chief component of precipitation by carbide, nitride also can partly consist of precipitation.
According to an example of refinery practice of the present invention shown in the table 1.
Table 1
| The interpolation order | Nitride | Oxide compound | Precipitation | Complex inclusion |
| Ti→Ca→Zr | TiN | CaO、ZrO | TiC | - |
| Ti→Zr→Ca | TiN | Ca-Zr or Ca-Zr-Ti base composite oxidate | TiC | The complex inclusion of Ca-Zr or Ca-Zr-Ti base oxide and nitride |
In table 1, when before in molten metal, adding Zr, adding Ca, because that the oxygen reactivity of Ca is higher than the oxygen of Zr is reactive, so form the single oxide compound of CaO for example or ZrO.On the other hand, when before in molten metal, adding Ca, adding Zr, form for example composite oxides of Ca-Zr base oxide.In this case, improved the rate of recovery of Zr.
According to the present invention, as long as weld through fusing and solidifying process, for example GTA welding of any weldprocedure, laser welding and plasma body welding have all improved weldability.Welding conditions can be selected corresponding to the thickness of the composition of various conditions such as steel, steel plate, target etc.
Beneficial effect
As mentioned above, ferritic stainless steel of the present invention adds Ca and Zr by combination to be made and solidifies the crystal grain granular in the welding zone, has improved the formability of welding zone and the good solidity to corrosion of steel.
Embodiment
Below, in connection with example the present invention is described, provide these examples by the mode that illustrates, these examples do not limit the scope of the invention.
Test examples 1
With the different 10 kinds of ferrite stainless product made from steel fusings that form that have shown in the table 2, then carry out hot rolling, annealing, pickling, cold rolling, white picking etc., prepare the steel plate that thickness is 1.5mm.Then, each steel plate experience GTA welding.In table 2, the base alloy that example 1 has STS409L forms, and example 2 and example 3 comprise the Ca that adds to separately wherein.Example 4 to example 9 is included in combination in the situation of the content that changes C+N and adds wherein Ca and Zr to.Example 10 is the comparative examples of not regulating oxygen level.For Nb, example 4 comprises 0.14%, and example 9 comprises 0.012%, and other example comprises 0.031%.
Table 2
The composition of the molten metal of ferritic stainless steel (wt%)
| Sequence number | C | N | O | Si | Mn | P | S | Cr | Ti | Zr | Ca |
| 1 | 0.006 | 0.006 | 0.0053 | 0.45 | 0.30 | 0.01 | 0.002 | 11.3 | 0.23 | - | - |
| 2 | 0.006 | 0.006 | 0.0056 | 0.45 | 0.31 | 0.01 | 0.002 | 11.3 | 0.23 | - | 0.0009 |
| 3 | 0.006 | 0.006 | 0.005 | 0.45 | 0.30 | 0.01 | 0.002 | 11.3 | 0.23 | - | 0.0014 |
| 4 | ＜0.005 | 0.0067 | 0.005 | 0.518 | 0.326 | 0.01 | ＜0.002 | 11.25 | 0.21 | 0.0018 | 0.0009 |
| 5 | ＜0.005 | 0.0067 | 0.005 | 0.485 | 0.281 | 0.01 | ＜0.002 | 11.41 | 0.26 | 0.0022 | 0.0007 |
| 6 | ＜0.005 | 0.0060 | 0.005 | 0.443 | 0.291 | 0.01 | ＜0.002 | 11.39 | 0.256 | 0.0050 | 0.0010 |
| 7 | 0.008 | 0.010 | 0.005 | 0.459 | 0.303 | 0.01 | ＜0.002 | 11.31 | 0.238 | 0.0025 | 0.0012 |
| 8 | 0.007 | 0.0088 | 0.005 | 0.472 | 0.295 | 0.01 | ＜0.002 | 11.32 | 0.233 | 0.0046 | 0.0014 |
| 9 | 0.006 | 0.0099 | 0.005 | 0.440 | 0.295 | 0.01 | ＜0.002 | 11.34 | 0.233 | 0.009 | 0.0015 |
| 10 | ＜0.005 | 0.0060 | 0.011 | 0.480 | 0.290 | 0.01 | ＜0.002 | 11.31 | 0.253 | 0.0025 | 0.0012 |
Method of the present invention comprises: preparation has the stainless molten metal of the composition shown in the table 1 in electric furnace, the stainless molten metal of refining preparation, the molten metal of continuous casting refining provides steel ingot, rolling ingot casting, rolling steel is annealed, wherein, refining operation comprises that the amount with oxygen controls to 0.004%～0.008%, and just before continuous casting operation the order according to Zr and Ca in molten metal, sequentially add Zr and Ca.
In AOD or VOD operation, utilize Si or Al reductor to carry out Control for Oxygen Content.On the other hand, when in furnace operation or AOD or VOD operation, adding Ca and Zr in the molten metal, because the volatility of Ca and Zr, so the residue content of Ca and Zr can be lowered.Therefore, just before the continuous casting operation, in molten metal, add Ca and Zr.The plate of Fe-Ca base is as Ca, and the pure metal plate is as Zr.
Utilize DC type welding machine (the maximum weld electric current is 350A) to carry out GTA built-up welding (bead-on-plate welding).The welding conditions that comprises is: welding current is 110A, and welding speed is that 0.32m/min, tungsten electrode diameter are that 2.5mm, electrode drift angle are that 100 degree, arc length are 1.5mm, argon shielding gas (15l/min).
Utilize opticmicroscope to measure the grain size of welding zone.After grinding the cross section of welding zone with sand paper and abrasive, the electrograving of the cross section process nitrification ethanol etchant solution after the grinding of welding zone, and observe.Utilize miniature Vickers hardness tester to measure the Hardness Distribution of welding zone with the interval of 0.2mm under the weight of 200g, the hold-time section is 10 seconds.
In order to measure the distribution of oxide compound and deposit seeds, by utilizing electron probe microanalyzer (EPMA) according to each polishing sample is placed among the EPMA, mapping consists of the element of oxide compound and precipitation, the mode of occupation rate of then calculating oxide compound and deposit seeds is measured size as 1 μ m or larger oxide compound and quantity and the size of deposit seeds, then take 5000 magnitude in 10 visuals field.In addition, oxide compound and precipitation for less than 1 μ m obtain replica with screen cloth, and analyze with 10000～100000 magnitude in 10 visuals field of transmission electron microscope.
By under-60 ℃～100 ℃ probe temperature, 1/4 small size sample (1.5mm thickness * 10mm width * 55mm length) being carried out Charpy impact test test, the DBTT characteristic of testing the welding zone.For spot corrosion test (pitting test), with the sand paper grinding of #600 granularity
5 dish samples were placed 5 hours in air or the longer time, thereby are formed passive film at sample.For this test, use the NaCl solution of 800mL3.5%.
Table 3 shows the corrosion proof test result for the impact characteristics of the welding zone of above-described 10 kinds of specimen and steel.Compare with example 1 to the example 3 of not adding Ca or Zr and adding separately Ca, example 4 to the example 9 that the example of the present invention of Ca and Zr is added in combination has reduced grain-size and the hardness of welding zone, and demonstrates improved DBTT characteristic and striking energy deviation.In addition, can recognize that the example of adding Ca and Zr has increased pitting potential, thereby improve solidity to corrosion simultaneously.Specifically, can recognize when adding Ca and Zr according to array mode, even the level of the C that adds and N also can be guaranteed the solidity to corrosion of low-temperature impact property and the steel of welding zone at 180ppm, perhaps shorten the time of refinery practice.In addition, compare with the example 10 of not regulating oxygen concn, oxygen concn of the present invention be adjusted to 0.01% or lower exemplary refinement weldability and good solidity to corrosion.
Table 3
Test examples 2
With the different 5 kinds of ferrite stainless product made from steel fusings that form that have shown in the table 4, then carry out hot rolling, annealing, cold rolling etc., prepare the steel plate that thickness is 1.5mm.Then, each steel plate experience GTA welding.In table 4, the base alloy that example 11 has STS409L forms, and example 12 comprises the Ca that adds to separately wherein.Example 13 to example 15 is included in combination in the situation of the content that changes C+N and adds wherein Ca and Zr to.For Nb, example 11,12,14 and 15 comprises 0.013%, and example 13 comprises 0.014%.
Table 4
The composition of the molten metal of ferritic stainless steel (wt%)
| Sequence number | C | N | O | Si | Mn | P | S | Cr | Ti | Zr | Ca |
| 11 | 0.0060 | 0.0059 | 0.0089 | 0.45 | 0.30 | 0.01 | 0.002 | 11.30 | 0.230 | - | - |
| 12 | 0.0061 | 0.0060 | 0.010 | 0.45 | 0.30 | 0.01 | 0.002 | 11.30 | 0.230 | - | 0.0010 |
| 13 | ＜0.005 | 0.0067 | 0.008 | 0.518 | 0.326 | 0.01 | ＜0.002 | 11.25 | 0.210 | 0.0018 | 0.0009 |
| 14 | ＜0.005 | 0.0060 | 0.011 | 0.480 | 0.290 | 0.01 | ＜0.002 | 11.31 | 0.253 | 0.0025 | 0.0012 |
| 15 | ＜0.005 | 0.0060 | 0.010 | 0.453 | 0.290 | 0.01 | ＜0.002 | 11.33 | 0.231 | 0.0048 | 0.0010 |
Method of the present invention comprises: preparation has the stainless molten metal of the composition shown in the table 4 in electric furnace, the stainless molten metal of refining preparation, the molten metal of continuous casting refining provides steel ingot, rolling ingot casting, rolling steel is annealed, wherein, refining operation just comprises that the order according to Zr and Ca sequentially adds Zr and Ca in molten metal before the continuous casting operation.
When adding Ca and Zr at furnace operation or in AOD or VOD operation in the molten metal, because the volatility of Ca and Zr, so the residue content of Ca and Zr can be lowered.Therefore, just before the continuous casting operation, in molten metal, add Ca and Zr.The plate of Fe-Ca base is as Ca, and the pure metal plate is as Zr.
Utilize DC type welding machine (the maximum weld electric current is 350A) to carry out the GTA built-up welding.The welding conditions that comprises is: welding current is 110A, and welding speed is that 0.32m/min, tungsten electrode diameter are that 2.5mm, electrode drift angle are that 100 degree, arc length are 1.5mm, argon shielding gas (15l/min).
Utilize opticmicroscope to measure the grain size of welding zone.After grinding the cross section of welding zone with sand paper and abrasive, the electrograving of the cross section process nitrification ethanol etchant solution after the grinding of welding zone, and observe.Utilize miniature Vickers hardness tester to measure the Hardness Distribution of welding zone with the interval of 0.2mm under the weight of 200g, the hold-time section is 10 seconds.
In order to measure the distribution of oxide compound and deposit seeds, by utilizing EPMA according to each polishing sample is placed among the EPMA, mapping consists of the element of oxide compound and precipitation, and the mode of occupation rate of then calculating oxide compound and deposit seeds is measured size as 1 μ m or larger oxide compound and quantity and the size of deposit seeds take 5000 magnitude in 10 visuals field.In addition, oxide compound and precipitation for less than 1 μ m obtain replica with screen cloth, and analyze with 10000～100000 magnitude in 10 visuals field of transmission electron microscope.
By under-60 ℃～100 ℃ probe temperature, 1/4 small size sample (1.5mm thickness * 10mm width * 55mm length) being carried out Charpy impact test test, the DBTT characteristic of testing the welding zone.For spot corrosion test (pitting test), with the sand paper grinding of #600 granularity
5 dish samples were placed 5 hours in air or the longer time, thereby are formed passive film at sample.For this test, use the NaCl solution of 800mL 3.5%.
Table 5 shows the test result for the impact characteristics of the welding zone of above-described 5 kinds of specimen.Compare with example 11 to the example 12 of not adding Ca or Zr and adding separately Ca, example 13 to the example 15 that the example of the present invention of Ca and Zr is added in combination has reduced grain-size and the hardness of welding zone, and demonstrates improved DBTT characteristic and striking energy deviation.Specifically, can recognize when adding Ca and Zr according to the mode of combination, even the level of the C that adds and N also can be guaranteed the solidity to corrosion of low-temperature impact property and the steel of welding zone at 180ppm, perhaps shorten the time of refinery practice.
Table 5
Weldability is estimated
| The grain-size of welding zone (μ m) | The hardness of welding zone (Hv) | DBTT(℃) | The deviation of striking energy (J ,-20 ℃) | |
| 11 | 535 | 169 | -10 | 6.06 |
| 12 | 250 | 167 | -25 | 6.0 |
| 13 | 238 | 155 | -35 | 3.26 |
| 14 | 238 | 147 | -35 | 2.6 |
| 15 | 236 | 144 | -40 | 2.1 |
Claims (9)
1. ferritic stainless steel, but described ferritic stainless steel comprises by weight percentage: 0.01% or still less greater than 0% C, 0.01% or still less but greater than 0% N, 1.0% or still less but greater than 0% Si, 1.0% or still less but greater than 0% Mn, 10.0%～20.0% Cr, 0.15% or Al still less, 0.0005%～0.002% Ca, 0.0018%～0.01% Zr, 0.004%～0.008% O, 0.01%～0.5% Ti and the Fe of surplus and other inevitable impurity, wherein, described stainless steel comprises and is of a size of 1～3 μ m and with 5 particle/mm
2To 10 particle/mm
2Ca-Zr or the Ca-Zr-Ti base oxide of density distribution.
2. ferritic stainless steel according to claim 1, wherein, described stainless steel comprises Ti base precipitation.
3. ferritic stainless steel according to claim 1, wherein, when the described stainless steel of welding, stainless welding zone has 300 μ m or less grain-size and 155Hv or less hardness.
4. ferritic stainless steel according to claim 1 also comprises 0.01%～0.5% Nb.
5. method of making ferritic stainless steel, described ferritic stainless steel comprise by weight 0.01% or still less but greater than 0% C, 0.01% or still less but greater than 0% N, 1.0% or still less but greater than 0% Si, 1.0% or still less but greater than 0% Mn, 10.0%～20.0% Cr, 0.15% or still less Al, 0.0005%～0.002% Ca, 0.0018%～0.01% Zr, 0.004%～0.008% O, 0.01%～0.5% Ti and Fe and other inevitable impurity of surplus, said method comprising the steps of:
The stainless molten metal of preparation in electric furnace;
The stainless molten metal of refining preparation;
The molten metal of continuous casting refining provides steel ingot;
Rolling ingot casting;
Rolling steel is annealed;
Wherein, refinement step comprises according to the order of Zr and Ca order in the molten metal and adds Zr and Ca.
6. method according to claim 5, wherein, when the described stainless steel of welding, stainless welding zone has 300 μ m or less grain-size and 155Hv or less hardness.
7. method according to claim 5, wherein, described stainless steel also comprises 0.01%～0.5% Nb.
8. method according to claim 5 wherein, before refinement step is included in and adds to Zr in the molten metal is controlled to be the amount of oxygen 0.01% or still less.
9. method according to claim 8, wherein, when the described stainless steel of welding, described stainless welding zone comprises and is of a size of 1 μ m～3 μ m and with 5～10 particle/mm
2Ca-Zr or the Ca-Zr-Ti base oxide of density distribution, and be of a size of 1 μ m or less and with 39000 precipitation/mm
2Or the Ti of larger density distribution base precipitation.
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| Application Number | Priority Date | Filing Date | Title |
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| KR10-2006-0102134 | 2006-10-20 | ||
| KR1020060102134A KR100825630B1 (en) | 2006-10-20 | 2006-10-20 | Ferritic stainless steel having excellent formability of welded zone, and method for manufacturing the same |
| KR1020060102135 | 2006-10-20 | ||
| KR1020060102134 | 2006-10-20 | ||
| KR10-2006-0102135 | 2006-10-20 | ||
| KR1020060102135A KR100825632B1 (en) | 2006-10-20 | 2006-10-20 | Ferritic stainless steel having excellent formability of welded zone and corrosion resistance, and method for manufacturing the same |
| PCT/KR2007/005048 WO2008048030A1 (en) | 2006-10-20 | 2007-10-16 | Ferritic stainless steel having excellent formability of welded zone and corrosion resistance, and method for manufacturing the same |
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| KR102443422B1 (en) | 2020-12-09 | 2022-09-16 | 주식회사 포스코 | High strength ferritic stainless steel with improved intergranular corrosion resistance |
| CN114836673B (en) * | 2022-04-14 | 2023-04-11 | 江苏省沙钢钢铁研究院有限公司 | Welding wire steel and preparation process thereof |
Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1104686A (en) * | 1993-05-19 | 1995-07-05 | 川崎制铁株式会社 | Ferrite stainless steel with good atmospheric corrosion and cracking corrosion resisting |
| JP2002080943A (en) * | 2000-07-04 | 2002-03-22 | Kawasaki Steel Corp | Ferritic stainless steel having excellent secondary processing brittleness resistance and high temperature fatigue characteristic in weld zone |
| JP2003213366A (en) * | 2002-01-24 | 2003-07-30 | Nippon Steel Corp | Steel having excellent toughness in base metal and large -small heat input weld heat-affected zone |
| JP2003221652A (en) * | 2001-11-20 | 2003-08-08 | Nisshin Steel Co Ltd | Ferritic stainless steel plate with good deep drawability and workability |
| JP2004018914A (en) * | 2002-06-14 | 2004-01-22 | Jfe Steel Kk | Ferritic stainless steel with excellent high-temperature strength, high-temperature oxidation resistance and high-temperature salt damage resistance |
| CN1836056A (en) * | 2003-08-19 | 2006-09-20 | 杰富意钢铁株式会社 | High strength stainless steel pipe excellent in corrosion resistance for use in oil well and method for production thereof |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| US6426039B2 (en) * | 2000-07-04 | 2002-07-30 | Kawasaki Steel Corporation | Ferritic stainless steel |
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Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1104686A (en) * | 1993-05-19 | 1995-07-05 | 川崎制铁株式会社 | Ferrite stainless steel with good atmospheric corrosion and cracking corrosion resisting |
| JP2002080943A (en) * | 2000-07-04 | 2002-03-22 | Kawasaki Steel Corp | Ferritic stainless steel having excellent secondary processing brittleness resistance and high temperature fatigue characteristic in weld zone |
| JP2003221652A (en) * | 2001-11-20 | 2003-08-08 | Nisshin Steel Co Ltd | Ferritic stainless steel plate with good deep drawability and workability |
| JP2003213366A (en) * | 2002-01-24 | 2003-07-30 | Nippon Steel Corp | Steel having excellent toughness in base metal and large -small heat input weld heat-affected zone |
| JP2004018914A (en) * | 2002-06-14 | 2004-01-22 | Jfe Steel Kk | Ferritic stainless steel with excellent high-temperature strength, high-temperature oxidation resistance and high-temperature salt damage resistance |
| CN1836056A (en) * | 2003-08-19 | 2006-09-20 | 杰富意钢铁株式会社 | High strength stainless steel pipe excellent in corrosion resistance for use in oil well and method for production thereof |
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| CN101528963A (en) | 2009-09-09 |
| KR20080035733A (en) | 2008-04-24 |
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