TW201213559A - Ferritic stainless steel - Google Patents

Abstract

A ferritic stainless steel containing, in percent by mass, C: 0.02% or less, N: 0.025% or less, Si: 1.0% or less, Mn: 1.0% or less, P: 0.035% or less, S: 0.01% or less, Cr: 16.0 to 26.0%, Al: 0.12% or less, Ti: 0.05 to 0.35%, Ca: 0.015% or less, and the balance of Fe and unavoidable impurities, wherein the following formula (1) ie satisfied. BI=3Al+Ti+0.5Si+200Ca ≤ 0.8.....(1), where each of Al, Ti, Si, and Ca in formula (1) denotes a content (in percent by mass) of each element in the steel.

Description

201213559 VI. Description of the Invention: Field of the Invention The present invention relates to a ferrite-based iron-based stainless steel in which a black spot of a TIG welded portion is less produced. The present application claims priority on Japanese Patent Application No. 2010-177998, filed on Jan. BACKGROUND OF THE INVENTION In general, ferrite-based iron-based stainless steel is excellent in corrosion resistance, and has a thermal expansion coefficient smaller than that of Worthfield iron-based stainless steel and excellent resistance to stress corrosion cracking. Therefore, the ferrite-based iron-based stainless steel is widely used as a building exterior material, a water storage, a heat storage water-based material, etc., which starts from a tableware, a kitchen machine, or a roofing material. In addition, in recent years, as the price of Ni raw materials has soared, the demand for replacing Worthfield iron-based stainless steel has also increased, and it is expected to be more extensive. In such a stainless steel structure, the welding construction system is indispensable. In the past, the ferrite-based stainless steel has a small solid solution limit of C and N, and is sensitized in the welded portion, and has a problem that the corrosion resistance is lowered. In order to solve this problem, there has been proposed a method of suppressing the sensitization of the metal portion by c, n, or the like by adding a stabilizing element such as Ti or Nb (see, for example, Patent Document〇 In addition, it is widely used in the corrosion resistance of the welded portion of the ferrite-based stainless steel, and the corrosion resistance of the scale is caused by the inertia of the iron-based stainless steel. 201213559 is important. Further, in Patent Document 2, it is disclosed that by adding ή and a 卜 to satisfy the formula? 1 = 5 丨 丨 + 20 (eight 1-0.01) 2 1.5 (in the formula The steel_content of each component) can form a technique of forming an A1 oxide film which can improve the corrosion resistance of the heat affected portion of the welded portion in the surface layer of the steel during welding. Further, in Patent Document 3, it is disclosed that in addition to the composite addition of a丨 and butyl By adding - quantifying the above 8 丨, the technique of the rust resistance of the wire joint. Further, Patent Document 4 discloses that by satisfying 4A1+Ti$〇32 (Ti, Al in the formula) Display the content of each component in the steel), reduce the heat input amount of _ to inhibit the formation of scale in the splicing joint A technique for improving the contact resistance of the welded portion. The conventional technique for improving the resistance of the welded portion or the welded heat affected portion is for the purpose of the touch. Others, the non-refining portion enhances the weather resistance of the material itself and In the method of the gap 2, P is actively added, and an appropriate amount of Cam == is added. For example, Patent Document 5). In Patent Document 5, ^ and 靡 2 are used to control the shape and distribution of non-metallic impurities in the steel. Further, the largest special system of Patent Document 5 adds the p of the mantle, but in Patent Document 5, the effect at the time of welding is not recorded. PRIOR ART DOCUMENT Patent Literature Patent Document 1 Patent Document 2 Japanese Patent Japanese-Japanese Patent Publication No. _2(10) 曰本专利专利开平平 5_7_9号 201213559

Patent Document 3: Japanese Patent Laid-Open Publication No. Hei. No. Hei. No. Hei. No. Hei. No. 2007-270290. Patent Document 5: Japanese Patent Laid-Open No. Hei 7-342 No. 5 SUMMARY OF THE INVENTION Problems to be Solved by the Invention In the conventional fat-grained iron-based stainless steel, even if the shielding conditions in the welded portion are made appropriate, (10) there is still a black spot called a black spot or a melt on the back bead. Black (4) In the TIG (tungsten gas: (4) coffee I (10) t Gas), when the molten metal is solidified, the ai, Τ, Si, Ca, which have a strong affinity with oxygen, form an oxide, and are cured on the welded metal. The conditions of the smelting, especially the masking conditions by the inert gas, will greatly affect the generation of dark spots, and the less the shadows are, the more the black spots will be produced. Since the black spot itself is an oxide, even if there is a small amount of black spots, there is no such thing as a pair of refining parts. However, when the black spots are largely produced or continuously slanted, and the splicing portion of the material is directly used, the appearance is not only impaired, but also the peeling of the black spots occurs in the processing. In the case where the black spot peeling is generated, there is a problem that the workability is lowered, and the gap between the black spot portions after the peeling occurs. X, even if it is not processed after the fusion, when a thick black spot is formed, the structure will be black, and the purity will be lowered when stress is applied to the molten portion. Therefore, in order to improve the resistance record of the TM refining department, it is not only necessary to improve the resistance of the beading part or the rust part itself, and (4) the black spot system generated by the bribery part is important. However, 'for the skin that changes color with the splicing, the method of strengthening the shielding condition of 201213559 can be roughly suppressed. However, for the black spot generated by the tig fusion part, even if the reinforced condition is strengthened, the conventional technique cannot be used. Sufficiently suppressed. The present invention has been developed in such a manner, and the subject is to provide a ferrite-grained steel which is not easy to generate black spots in the TIG section and which is excellent in purity and workability of the material portion. Means for Solving the Problem In order to suppress the amount of generation of black spots, the inventors of the present invention have repeatedly made efforts to study them. As a result, it was found that the formation of black spots in the TIG welded portion can be suppressed by optimizing the amounts of A1, Ti, and Si, and the ferrite-based iron-based steel having less black spot generation in the present invention is conceivable. The gist of the present invention is as follows. The first aspect of the present invention is a ferrite-based iron-based stainless steel containing, by mass%: C: 0.020% or less, N: 0.025% or less, Si: 1.0% or less, Μη: 1.0% or less, and P: 0.035% or less. , S : 0.01% or less, Cr: 16.0 - 25.0%, A1: 0.12% or less, Ti: 〇〇 5 to 0.35%, and Ca: 0.0015% or less, and the remainder is composed of Fe and unavoidable impurities, and satisfies The following formula (1). BI=3Al+Ti+0.5Si+200Ca^°·8···0) (In addition, the content of each component in the Ti, Si, and Ca-based steels in the formula (1) [% by mass] °) In the ferrite-based iron-based stainless steel, the generation of black spots in the welded portion is small. The second aspect of the present invention is the ferrite-based iron-based stainless steel of the first aspect described above, and has a mass of °/. The meter further includes Nb: 〇·6°/° or less. 201213559 The third aspect of the present invention is the ferrite-based stainless steel of the first or second aspect, and further comprises a ferrite-based stainless steel of Mo: 3.0% or less in mass%. The fourth aspect of the present invention is the ferrite-based iron-based stainless steel according to any one of the first to third aspects, further comprising, in mass%, one selected from the group consisting of Cu: 2.0% or less and Ni: 2.0% or less. Two types of ferrite iron stainless steel. The fifth aspect of the present invention is the ferrite-based iron-based stainless steel according to any one of the first to fourth aspects, further comprising, in mass%, one selected from the group consisting of V: 0.2% or less and Zr: 0.2% or less. Or two types of ferrite iron stainless steel. The sixth embodiment of the present invention is the ferrite-based iron-based stainless steel according to any one of the first to fifth aspects, and further comprises, in mass%, a ferrite-based iron-based stainless steel having a B: 0.005% or less. Advantageous Effects of Invention According to the present invention, it is possible to provide a ferrite-based iron-based stainless steel which is less likely to generate black spots in a TIG welded portion and which is excellent in corrosion resistance and workability of a TIG welded portion. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1A is a photograph showing the appearance of black spots generated on the inner side during TIG welding. Fig. 1B is a schematic view showing the appearance of the black spots generated on the back side when the TIG is welded, and corresponds to the pattern of the photograph shown in Fig. 1A. Fig. 2A is a graph showing the results of element depth analysis (concentration distribution of elements in the depth direction) of the welded bead portion in the inner side of the test piece by AES. Fig. 2B is a graph showing the results of the depth analysis (concentration distribution of elements in the depth direction) of the dark spots in the inner side of the test piece by AES. Figure 3 is a graph showing the relationship between the BI value and the black spot generation length ratio. Figure 4 is a graph showing the relationship between BI values and corrosion. The double circle (?) showed excellent results, the round (〇) system showed good results, and the X system showed poor results.

I [The solid package method J is for carrying out the invention. Hereinafter, the present invention will be described in detail. The ferrite-based iron-based stainless steel having a small amount of black spots generated in the welded portion of the present invention satisfies the following formula (1). BI=3Al+Ti+0.5Si+200Ca^ 0.8 ---(1) (In addition, in the formula (1), the content of each component in the Ti, Si, and Ca-based steel [% by mass]. An element with a particularly strong affinity for Si and Ca and oxygen is an element that causes dark spots to form when BG is welded. Further, the more the contents of A1, Ti, Si, and Ca contained in the steel, the more likely the black spots are formed. The coefficient of the contents of A1, Ti, Si, and Ca in the above formula (1) is determined by the size (strength) of the action for promoting the formation of dark spots and the content in the steel. More specifically, as shown in the experimental example described later, A1 is an element which contains the highest concentration in dark spots and which has a particularly large effect of promoting the formation of dark spots. Therefore, in the above formula (1), the coefficient of the A1 content is set to 3. Further, although Ca is contained in a small amount in steel, it is contained in a high concentration in black spots, and is an element which promotes the formation of black spots. Therefore, the coefficient of the Ca content is set to 200. When the aforementioned BI value is greater than 0.8, the generation of dark spots is remarkable. On the other hand, when the ΒΙ value is 0.8 or less, the black spot generation of the TIG welded portion becomes very large. 8 201213559

In the severe processing, peeling occurs, and under the condition that the generation rate of the black spot is small, the black spots are not easily peeled off. It is therefore considered the starting point of corrosion. On the other hand, since the thickness thereof is also thinned, it is estimated that even if it is confirmed that the generation of black spots is suppressed, the resistance of the fusion portion can be improved. Receiver' detailed composition of the fermented iron-based stainless steel of the present invention. First, the above-mentioned (the element of the U type. Inscription (A1): 0.012% by mass or less of the A1-based important deoxidizing element') and the composition of the non-metallic inclusions are controlled, and the structure is refined. A1 is the most beneficial factor for the formation of dark spots. In addition, the excessive addition of A1 will lead to the coarsening of non-metallic inclusions, and it may become a starting point for the production of defects. Therefore, the upper limit of A1 content It is set to 0.12%. For deoxidation, it is preferable to contain A1 of 〇〇1% or more. A1 is preferably 0.03% to 0.10%. Titanium (!1): 质量 〇 〇 5% 〇. 350/0

The Ti system is used to fix C and N, and it is possible to suppress the grain boundary corrosion of the welded portion and to improve the handling properties. However, excessive addition of Ti not only causes generation of black spots, but also causes surface defects during manufacture. Therefore, the range of the Ti content is set to 0.05% to 0_35%. Preferably, it is 0.07% to 0.20 〇/〇.矽(Si): 1.0% or less by mass% 201213559

The important deoxidizing element of the Si system can also effectively improve the contact resistance and the oxidation resistance. However, excessive addition of Si not only promotes the formation of dark spots, but also deteriorates workability and manufacturability. Therefore, the upper limit of the Si content is set to 丨〇0/〇. It is preferred to contain 0,01% or more of Si for deoxidation. The Si content is preferably 0.05% to 0.55%. Calcium (匚3): 5% by mass or less Ca 15% or less Ca is a very important deoxidizing element and is contained in steel as a non-metallic inclusion. However, since Ca is very easily oxidized, it is the biggest cause of black spots when welding. Further, there is a case where the water solubility is lost and the corrosion resistance is lowered. Therefore, the Ca content is extremely low, and the upper limit of the Ca content is made 0.0015%. Preferably, the 〇3 content is 〇 〇〇 12% or less. Next, other elements constituting the ferrite-based non-mineral steel of the present invention will be described. Carbon (C): 0.020% or less by mass% Since C will reduce the rotability and workability of the grain boundary, it is necessary to reduce the content. Therefore, the upper limit of the C content is set to (four) 20% or less. However, when the content of c is excessively lowered, the refining cost is deteriorated, so that the c content is preferably 0.002% to 0.015%. Gas (N). 5% by mass or less N% N is similar to C, and it is required to reduce the grain resistance and workability. Therefore, the upper limit of the N content is set to 〇〇25%. However, when the content of N is excessively lowered, since the refining cost is deteriorated, it is preferably 0.002% to 0.015%. Manganese (Μη): 〇% or less by mass% Μη is an important deoxygenated sulphate. However, when it is added excessively, it will easily form 10 201213559 which becomes the MnS of the starting point of rot and destabilizes the ferrite iron structure. Therefore, the Μη content is set to ι·〇% or less. For deoxidation, it is preferred to contain Μ1% or more of Μη. Preferably, it is 〇.05%~〇.5%. The better is 〇 〇 5% ~ 〇 3 〇 / 〇. Phosphorus (Ρ): 5% by mass or less 质量 〇 35% or less Ρ not only reduces weldability and workability, but also tends to cause grain boundary corrosion. Therefore, the niobium content is set to 〇 35% or less. The better is 0.001% to 0.02%. Sulfur (S): 质量1% or less by mass% S is required to form water-soluble inclusions such as CaS or MnS which are the starting point of the rice. Therefore, the S content is set to 〇.01% or less. However, excessive reduction will result in poor costs. Therefore, it is preferable that the S content is from 0 0001% to 0 005%. Chromium (Cr): 16.0 to 25.0% by mass%

Cr is the most important element for ensuring the corrosion resistance of stainless steel, and it is required to contain 16.0% or more in order to stabilize the ferrite structure. However, since Cr deteriorates workability and manufacturability, the upper limit is made 25.0%. The Cr content is preferably from 16.5% to 23% by weight, more preferably from 18.0% to 22.5%.铌(Nb): 0.6% or less by mass%

Nb can be added alone or in combination with Ti in its characteristics. When Nb is contained together with ruthenium, it is preferable to satisfy (Ti + Nb) / (C + N) g6 (the content [mass) of each component in the Ti, Nb, C, and N-type steels in the formula. Similarly to T i , N b is an element which fixes C and N, suppresses grain boundary corrosion of a welded part, and improves workability. However, excessive addition of Nb lowers workability, so it is preferable to set the upper limit of the Nb content to 0.6%. Further, by including Nb, it is preferable to increase the above characteristics to 201213559, and it is preferable to contain Nb of 5% or more. The Nb content is preferably 0.15% to 0.55%. Molybdenum (Mo): 3.0% or less by mass%

Mo has a passivation film repair effect, which is a very effective element for improving financial touch. Further, by containing Mo together with Cr, there is an effect of effectively improving pitting resistance. Further, by containing the same as Ni, there is an effect of improving the rust resistance. However, when Mo is increased, workability is lowered and the cost is increased. Therefore, it is preferable to set the upper limit of the Mo content to 3. 〇%. Further, it is preferable to contain Mo which is 0.30% or more in order to improve the above-mentioned characteristics by containing 〇. The content of M〇 is 0.60. /. ~2.5°/. The best is better 〇 9% ~ 2.0%. Nickel (Ni): 2.0% or less by mass%

Ni has an effect of suppressing the active dissolution rate, and since the hydrogen overvoltage is small, the repassivation property is excellent. However, excessive addition of Ni deteriorates the workability and makes the ferrite iron structure unstable. Therefore, it is preferable to set the upper limit of the (10) content to 2% by weight. Further, in order to enhance the above characteristics by containing Ni, it is preferable to contain Ni of 5% or more. The Ni content is preferably 2%, preferably 0.2% to 1 _ 1% 〇 copper (Cu): 2% by mass or less.

Cu and Ni are not only capable of lowering the active dissolution rate but also promoting the effect of repassivation. However, excessive addition of Cu degrades workability. Therefore, when Cu is added, it is preferable to set the upper limit to 2 〇%. In order to enhance the above characteristics by containing Cu, it is preferable to contain 0.05% or more of Cu. The Cu content is preferably from 〇2% to 1.5%, more preferably 〇25. /. ~11%.鈒 (V) and / or wrong (Zr) · 〇 2〇 / by mass %. The following 12 201213559 V and Zr can improve weather resistance or crevice corrosion resistance. Also, if c is suppressed

The addition of V to the use of Mo also ensures excellent processability. In the absence of I 1 heat, excessive addition of V and/or Zr will reduce the workability, and the effect of improving the durability will be saturated. Therefore, the upper limit of the content of V and/or Zr is set to 〇2% or less. good. Further, it is preferable to contain V and/or Zr in order to increase the above characteristics to contain 0.03% or more of V and/or Zr. Further, the content of V and/or heart is preferably from 0.05% to 0.1%. Boron (B): 0.005°/〇 or less by mass% B is a grain boundary strengthening element which contributes to the improvement of brittleness of secondary processing, but excessive addition of solid solution-fortified ferrite iron ’ causes a decrease in ductility. Therefore, when B is added, the lower limit is made 0.0001%, and the upper limit is preferably 40.000%, and it is preferably 0.0002% to 0.0020%. EXAMPLES A test piece composed of a ferrite-based iron-based stainless steel having the chemical composition (composition) shown in Table 1 was produced by the method shown below. First, a cast steel in which the chemical composition (composition) shown in Table 1 was melted was vacuum-processed to produce a crucible having a thickness of a claw claw, which was further rolled to a thickness of 5 mm by hot rolling. Thereafter, heat treatment was carried out for 1 minute at a temperature of 800 to 1 Torr C according to the respective recrystallization behavior, and the rust removal was performed by grinding to remove a steel sheet having a thickness of 〇 8 mm by cold rolling. Thereafter, heat treatment was performed at a temperature of 8 〇〇 to 1 依据t according to each recrystallization behavior as a final annealing, and the rust scale on the surface was removed by pickling as a test material, and No. 1 to 28 was produced using the same. Test piece. Further, in the chemical composition (composition) shown in Table ,, the content of each element is expressed by mass%, and the remainder is iron and unavoidable impurities. The bottom line shows values outside the scope of the invention. 13 201213559

5 ¥ 5 5 ΐφί 魈兹-4 4 4 4 4 4 4 4 4 4 4 4 -Ο -id Street Gong κ- κ-£ ^ Φ Let φ φ φ φ Φ Φ φ ta_ t2_ tc_ t2_ 话 · Umbrella Cone cone cone wm ¥ m ¥ ¥ ¥ ¥ ¥ ¥ ¥ ¥ ¥ ¥ 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 CQ | 0.0007 I 1 0.0004 1 | 0.0008 I 1 o.ooio 1 | 0.20 I 0-15 1 | 0.44 I ! 0.50 0.39 0.39 云ο”21 | 0.15 1 | 0.28 I (N 〇0.40 I 0.25 1 1〇.25 IX) Ζ | 0.20 I 031 1 | 0.28 I | 0.18 ] | 0.22 I | 0.23 I | 0.25 1 0 45 1 | 0.25 1 1 °-21 1 10.51 1 Divination | 0.55 I 0.21 1 1 0.38 1 0.19 | 1 0.22 J LmlJ 1 0.36 1 | 0.18 I ο 1 0.52 1 C. 00 00 | 0.99 1 | 0.82 I | 0.95 I 055 1 00 ο 2.01 卜.56 1 0.008 1 1 0.007 1 | 0.012 I | 0.010 | | o.oi 1 | | 0.0 08 1 | 0.010 | | 0.010 | | o.oii | [0.009 1 | 0.009 1 | 0.009 I | 0.014 I | 0.006 I 0.008 I | 0.008 I 1 0.009 1 1 0.009 1 | o.oii | 1 0.014 1 | o. Oio | 0.012 1 0.009 1 o.oio 1 1 0.014 II ο.οπ 1 0.014 1 0.012 Λ ssm 〇(N 〇〇(N 〇S | 0.0002 I yn m 〇0.0004 IS 1 0.0009 1 inch 〇ο ο 〇\ ο 1 0.0015 0.0014 0.0019 oo ο ο 〇〇〇CD 〇c>〇〇〇c> 〇〇〇〇〇〇〇〇d ο ο d 〇〇〇d ο ο d 〇〇d ο ο ο 〇〇〇〇ο d ο ο ο ο I 0.20 I (Ν ο (N d 1 o.io 1 | 0.16 1 | 0.09 I 〇_^4l | 0.16 I md | 0.07 I 丨0_06” Lo.l^J 1 0.08 I 0.09 I 0.08 0.19 1 0.30 1 1 0.22 1 in ο 1 0.07 1 0.21 0.19 0.02 0.34 0.21 1 0.40 ο 0.21 < 1 0.04 I 1 0.06 1 I 0.04 I 1 0.03 1 | 0.03 I | 0.07 I 0.04 I | 0.04 I 1 0.05 I | o. Oi | 0.03 1 0.06 1 0.04 0.05 0.08 L〇j2 1 0.04 1 0.04 1 1 0.06 I 0.06 1 1 0.08 II 0.15 1 0.05 1 1 0.09 1 1 0.09 1 1 0.03 1 0.04 1 0.10 18.0 I —18.2 19.7 | 1 22.9 1 〇〇 22.5 | 丨19.0 I 8.4丨22.6 1 〇\ | 20.9 I σί 1 »7·5 1 1 19-4 1 00 1 23.0 1 丨19.2 1 卜 (Ν 7.6 1 | 23.8 1 23.0 1 18.5 (Ν 〇\ 17.9 1 18.0 1 | 23.5 Ο) I o.ooi 1 0.003 1 | 0.002 I 1 o.ooi 1 | o.ooi | | o.ooi | | 0.002 I | 0.002 I 1 0.003 1 | 0.002 I | o.ooi | 1 0.002 1 1 0.003 1 1 0.002 | 0.002 I 1 0.002 I 1 0.003 1 1 o.ooi 1 0.003J 1 0.003 1 1 0.002 I 0.003 0.002 0.003 I o.ooi 1 0.002 1 0.002 I 0.003 CL 0.007 I 0.015 1 | o.oii | 1 0.009 1 | 0.009 1 | 0.008 I | o.olo | | o.olo | 1 0.009 1 | o.olo | | 0.009 1 1 o.oio 1 1 0.020 o.oii I 0.008 I 0.022 I 1 0.020 1 1 0.007 1 0.008 1 0.020 1 1 0.015 II 0.030 I 1 0.015 1 0.020 1 1 0.025 1 1 0.020 1 0.002 I 0.018 1 1 Μη 1 d 0.20 1 0.20 I d 0.18 I 1 0.20 IL〇”aJ 〇00 d 1 Q-25 1 〇1 0.25 J 0.22 0.27 0.09 0.20 1 〇·2ΐ 1 0.14 (Ν Ο 1 0.25 1 0.28 I 0.20 0.21 1 0.22 ! 0.16 0.20 0.31 0.23 0.10 ο 1 0.09 I 1 o.io 1 d 0.08 1 o.io I 0 13 0.12 | 0.51 1 〇d 0.12 1 0.04 0.45 0.08 (Ν ο d ο d 0.12 I 0.62 1 0.09 I 0.25 0.65 0.20 0.26 1 0. 25 1.01 0.28 U 1 0.004 I 1 0.005 1 | 0.008 I 1 o.oii 1 | 0.012 I | 0.005 I 1 0.007 1 | o.olo | 1 0.004 1 | 0.007 I | 0.004 I 1 0.007 1 1 0.014 1 1 0.003 1 0.009 I 1 0.004 1 | 0.005 I 1 0.004 1 0.004 1 1 0.013 1 | 0.005 1 0.010 0.006 1 0.004 1 1 0.006 I 1 o.oio I 1 0.015 0.012 ο a (Ν ΓΛ 卜 00 as 〇 — (Ν 寸 00 CS (N (N N Ν Ν Ν Ν Ν Ν Ν Ν Ν Ν Ν Ν Ν Ν Ν Ν Ν Ν Ν Ν Ν Ν Ν Ν Ν Ν 00 00 00 00 00 00 00 TI TI TI TI TI TI TI TI TI TI TI TI TI TI TI TI TI TI TI ratio. Further, the No. 1 to 28 test pieces were subjected to the following humification test. "Splicing conditions" The TIG welding system performs butt welding of the same steel grade at a conveying speed of 5 〇cm/min and a heat input amount of 550 to 650 J/cm2. The shielding is applied to the torch side and the inside side using argon. The black spot generation length ratio is determined by the black spot generation length ratio as a reference indicating the amount of black spot generation after TIG welding. The black spot generation length ratio is calculated by dividing the length of the black spot generated in the welded portion by the length in the refining direction, and dividing the total weld length by the integrated value. The length of each black spot was measured by photographing the length of the weld of about 1 cm in length by a digital camera, and image processing was used to calculate the ratio of the total length of the black spots in the weld length to the length of the weld. "Corrosion test" The corrosion test piece used was an expanded TIG weld. The expansion condition was based on the Ayerson embossing test conditions of JIS 2247, and the side of the penetration test bead of the welded test piece was used as a surface, and a punch of 2 mm mm was used. However, the expansion height is stopped on the way due to the processing conditions. The stop height (expansion height) is unified to 6mm and 7mm. Corrosion evaluation was carried out in accordance with JIS z 2371, and a continuous spray test of 5/〇 NaCl was carried out, and evaluation was carried out with or without flow rust after 48 hours. In the processed material having an expansion height of 6 mm, the continuous rust test of 5 ° / 〇 NaCl was "good" when no rust was found in the welded portion, and the rust was not found as "excellent" in the processed material having an expansion height of 7 mm. . Flow generated under continuous spray test 15 201213559 When rust is used, it is "bad" in Table 2, which shows the BI value of the chemical composition of Table 1, the growth ratio of the black spot, and the result of the corrosion test.

As shown in Table 2, the chemical composition (composition) is the range of the present invention, and the 81 value is 〇8, and the lower part of the test piece No. 1 to 21, the dark spot generation length ratio is small, and the dark spot after the TIG fusion is 16 201213559. Less generation. In No. 1 to 15, 18, and 19 in which the BI value is 0.6 or less, generation of dark spots is further suppressed, and in Nos. 1 to 13 having a BI value of 0.4 or less, the generation length is approximately 10% or less. Inhibit its production. Further, in the test pieces No. 1 to 21 of the expansion height of 6 mm, the rust of the welded portion was not found in the 5% NaCl continuous spray test in the analytic test piece after the processing by the Love absorbing concave tester. Further, in the test pieces No. 1 to 21 in which the more severe expansion height was 7 mm, the rust of the welded portion was not found in the test piece having a BI value of 〇.4 or less, and rust was observed in the test piece of more than 0.4. On the other hand, in the test pieces No. 22 and 24 in which the BI value was more than 0.8, the black spot generation length ratio after the TIG welding was large, and the rust from the welded portion was confirmed in the corrosion test. After the rust generating portions of the test pieces N〇 22, 24, and 26 to 28 were magnified by a magnifying glass, peeling was observed at the boundary between the black spots and the welded bead portions. Al, Ti, Si, and Ca are No. 22, 26, 27, and 28 having a predetermined concentration or higher. Further, in the test piece No. 23 of the test piece having a composition ratio of Cr of less than 16% and having a composition ratio of less than 0.05%, the occurrence of ore was found in the test of the rot. "Experimental Example 1" In the same manner as in the production method of the test piece of Ν〇·ι, except that the ferrite-based iron-based stainless steel having the chemical composition (composition) shown below was formed by cold rolling into a steel sheet having a thickness of a paw. Manufacture of test materials. Use it to obtain test piece A and test piece B 「 "Chemical composition (composition)"

Test piece A 17 201213559 C 0.007/〇' N : O.oi ι〇/〇, g· : 012% ' Mn : 0.18% ' P : 〇 22%, S . _1%, Cr: 19.4%, A1 : 〇 · 〇 6%, Ti: 0.15%, Ca. O.GGG5/〇, the remainder: iron and unavoidable impurities.

Test piece BC · 0.009%, N: 〇.〇1{)%, Si: 〇25%, Mn: 〇15%, p · 〇·21%, S · 0 001%, Cr: 20.2%, A1 : 0.15 %, Ti: 0.19%, Ca: 0.GG15%, and the rest: iron and audible impurities. The test piece A and the test piece B thus known were subjected to TIG welding under the same splicing conditions as those of the ι test piece, and the appearance of the black spots generated on the fun side of the TIG splicing was observed. This result is shown in FIG. 1A and FIG. 1B. Fig. 1A is a photograph showing the appearance of black spots generated on the inner side when T1G is welded. Further, Fig. 1B is a schematic view showing the appearance of a black spot generated on the back side during TIG welding, and corresponds to the pattern of the photograph shown in Fig. 1AiI. In the first and second diagrams, the left side is a photograph and a diagram of the test piece a having a BI value of 〇 49, and the photograph and the pattern of the test piece 8 having a BI value of 1.07 on the right side. As shown by the arrows in Fig. 1A and Fig. 1B, the test piece A having a BI value of 〇 49 and the test piece B having a BI value of ι·〇7 are scattered with speckled black spots. However, it can be seen that the test piece B (right photo) having a large BI value causes more black spots to be produced. Further, the Aegis electron spectroscopy (AES) measurement was performed on the welded bead portion and the black spot portion 2 of the test having a BI value of 1.07. This result is shown in the second figure and the 28th figure. In addition, in the AES measurement t, the Saki (four) FE Aojie electronic energy spectrum device, with the accelerating voltage l〇keV, the spot diameter of about 4 〇 nm, the hybrid speed of l5nm / min 201213559 conditions, the copper is fixed to almost no thorns oxygen Until the intensity. In addition, since the measurement point of AES is small, there is a case where an error occurs due to the measurement position, but this time, the display thickness is used. Fig. 2A and Fig. 2B show the results of measuring the element depth of the inner side of the test piece and the element depth analysis (concentration knife of the element in the depth direction) in the inner side of the test piece by AES. Fig. 2A shows the result of the molten bead portion. Fig. 2B shows the result of the black spot. As shown in Fig. 2A, the welded bead portion is mainly composed of butadiene, and contains an oxide of A1 and a thickness of several hundred A. On the other hand, as shown in Fig. 2B, the black spot is mainly composed of A1 and contains oxides having a thickness of several thousand A and a thickness of Ti, Si, and Ca. Further, from the black spot pattern shown in Fig. 2B, it was confirmed that the AH system is contained in the highest concentration in the black spot, and although Ca is contained in the steel in a small amount, it is contained in the black spot at a high concentration. "Experimental Example 2" was produced by the same manufacturing method as Test A: c: 〇·002-0.015%^N: 0.02 to 0.015% 'Cr: 16.5-23% 'Ni: 0-1.5%' Mo : 0 ~2.5% as a basic composition, and has a different content of various chemical components (compositions) such as Al, Ti, Si, Ca, etc., which are the main components of black spots, and the test materials for the ferrite-grained stainless steel. sheet. The plurality of test pieces thus obtained were subjected to TIG welding under the same welding conditions as those of the test piece of No. 1, and the black spot generation length ratio was calculated in the same manner as the test piece of N 〇. 19 201213559 The results showed that there was a tendency for the increase in the ratio of the formation of dark spots to a greater extent. These elements are particularly strong in affinity with bismuth. Among them, the effect of A1 is large, and it is found that although the content of steel in the steel is small, the effect on black spots is still large. This helps the formation of dark spots. It can be seen that when the amount of Al, Ti' Si, and Ca added is large, even if masking is performed, the possibility of black spots is large, especially the formation of black spots by A1 and ^. In addition, the enthalpy values shown in the following formula (1) are calculated for the plurality of test pieces, and the relationship between the length ratio of the black spots is investigated. BI=3Al+Ti+0.5Si+200Ca^ 0.8 (again In the formula (1), the content of each component in the steel of Ding, 5, and 4 [% by mass].) The result is shown in Fig. 3. The third figure shows the ratio of the Bi value to the length of the spot. The graph of the relationship. As shown in Fig. 3, it can be seen that the larger the BI value is, the larger the spot length ratio is. The corrosion test is performed on the test piece of the complex test piece and the Ncu, respectively. The result is shown in Fig. 4. The graph shows the relationship between the enthalpy value and the sealing evaluation result after the post-processing spray test. The double circle (10) in the figure shows excellent The result, circular (square) of the lines showed good results, the [chi] lines showed poor results. As shown in Fig. 4, no corrosion occurred in the test piece with a ΒΙ value of 〇8 or less and a projection height of 6 mm, especially at a test height of 7 mm or less, even at a test height of 7 mm. No corrosion was found in the middle, so it was very good. Industrial Applicability 20 201213559 The ferrite-based iron-based stainless steel of the present invention is used for external materials, building materials, outdoor equipment, water storage, hot water storage tanks, home appliances, bathtubs, kitchen appliances, and latent heat recovery gas hot water supply. The waste water collector of the device, its heat exchanger, various fusion pipes, etc., can be suitably used as a member requiring corrosion resistance in a structure formed by T1G welding in general use in other houses and houses. In particular, the ferrite-based stainless steel of the present invention is suitable for a member to be processed after TIG welding. Further, the ferrite-based stainless steel of the present invention is excellent in corrosion resistance and excellent in processability of the TIG dashed portion, and thus can be widely used in applications where processing is severe. [Simple description of the drawing] Fig. 1A shows a photograph of the appearance of the black spot generated on the inner side when the ΉG is welded. Fig. 1 is a schematic view showing the appearance of the black spots generated on the inner side when the ΤIG is welded, and corresponds to the pattern of the photograph shown in Fig. 1 . Fig. 2 is a graph showing the results of elemental depth analysis (concentration distribution of elements in the depth direction) of the welded bead portion in the inner side of the test piece by AES. Fig. 2 is a graph showing the results of elemental depth analysis (concentration distribution of elements in the depth direction) of dark spots in the inner side of the test piece by AES. Figure 3 is a graph showing the relationship between the ΒΙ value and the length of the black spot generation. Figure 4 is a graph showing the relationship between enthalpy and corrosion. The double circle (?) showed excellent results, the round (〇) system showed good results, and the X system showed poor results. [Main component symbol description] 21 201213559

Claims (1)

201213559 VII. Patent application scope: 1. A ferrite-based iron-based stainless steel containing C·· 0.020% or less, N: 0.025% or less, Si: 1.0% or less, Μη: 1.0% or less, Ρ by mass% : 0.035% or less, S: 0.01% or less, Cr: 16.0 to 25.0%, Α1: 0.12% or less, Ti··0.05 to 0.35%, Ca··0.0015% or less, and the remainder is composed of Fe and unavoidable impurities. It is composed and satisfies the following formula (1). BI = 3 Al + Ti + 0.5 Si + 200 Ca ^ 0.8 - (1) ( Further, the content (% by mass) of each component in the Al, Ti, Si, and Ca-based steels in the formula (1)). 2. For example, the ferrite-based iron-based stainless steel of the first application of the patent scope includes Nb: 0.6% or less by mass%. 3. For example, the ferrite-based iron-based stainless steel of the first application of the patent scope includes Mo: 3.0°/ in mass%. the following. 4. For example, the ferrite-based iron-based stainless steel of the second application of the patent scope includes Mo: 3.0% or less in mass%. 5. The ferrite-based iron-based stainless steel according to any one of claims 1 to 4, which further comprises, in mass%, one or two selected from the group consisting of Cu: 2.0% or less and Ni: 2.0% or less. 6. The ferrite-based stainless steel according to any one of claims 1 to 4, which further comprises, in mass%, selected from V: 0.2°/. Hereinafter, Zr: one or two of 0.2% or less. 7. The ferrite-based iron-based stainless steel according to item 5 of the patent application, which further comprises, in mass%, one selected from the group consisting of V: 0.2% or less, Zr: 0.2% or less, or 23 201213559 - wearing a drooping · 8 The fat-grained iron-based stainless steel of any one of the above-mentioned items of the first aspect of the invention is further characterized by a 5% by mass: 0.005% or less. 9. The ferrite-based iron-based stainless steel according to item 5 of the patent application, which further contains Β: 0.005% or less in mass%. 1〇·If the ferrite-grained stainless steel of the sixth paragraph of the patent application is applied, it is further contained in the mass 〇/〇: 〇_〇〇 5% or less. U · The ferrite-based iron-based stainless steel according to item 7 of the patent scope of the application, which contains B: 〇_〇〇 5% or less in mass%. twenty four