TWI722377B

TWI722377B - Fertilizer stainless steel

Info

Publication number: TWI722377B
Application number: TW108103350A
Authority: TW
Inventors: 中村徹之; 石川伸; 杉原玲子
Original assignee: 日商杰富意鋼鐵股份有限公司
Priority date: 2018-01-31
Filing date: 2019-01-29
Publication date: 2021-03-21
Also published as: JPWO2019151125A1; EP3719164A1; TW201934778A; CN111684092A; EP3719164A4; JP6624347B1; KR102508125B1; KR20200100833A; WO2019151125A1; US20210032731A1

Abstract

本發明提供一種耐潛變特性與熱疲勞特性優異之肥粒鐵系不鏽鋼。 The present invention provides a ferrous iron-based stainless steel with excellent creep resistance and thermal fatigue properties.

本發明之肥粒鐵系不鏽鋼具有如下之成分組成，即，以質量%計，含有C：0.020%以下、Si：0.1~1.0%、Mn：0.05~0.60%、P：0.050%以下、S：0.008%以下、Ni：0.02~0.60%、Al：0.001~0.25%、Cr：18.0~20.0%、Nb：0.30~0.80%、Mo：1.80~2.50%、N：0.015%以下、及Sb：0.002~0.50%，且滿足下式(1)，殘餘部包含Fe及不可避免之雜質。 The ferrous iron-based stainless steel of the present invention has the following composition, that is, in terms of mass%, it contains C: 0.020% or less, Si: 0.1 to 1.0%, Mn: 0.05 to 0.60%, P: 0.050% or less, and S: 0.008% or less, Ni: 0.02~0.60%, Al: 0.001~0.25%, Cr: 18.0~20.0%, Nb: 0.30~0.80%, Mo: 1.80~2.50%, N: 0.015% or less, and Sb: 0.002~ 0.50%, and satisfies the following formula (1), the remainder contains Fe and unavoidable impurities.

Nb+Mo：2.3~3.0%...(1) Nb+Mo: 2.3~3.0%...(1)

(式(1)中之Nb、Mo表示各元素之含量(質量%))。 (Nb and Mo in formula (1) represent the content (mass%) of each element).

Description

肥粒鐵系不鏽鋼 Fertilizer stainless steel

本發明係關於一種肥粒鐵系不鏽鋼，尤其係關於一種適宜用於汽車或機車之排氣管或轉換器箱、火力發電站之排氣導管等，於高溫下使用之排氣系統構件之具有優異之耐潛變特性與熱疲勞特性的肥粒鐵系不鏽鋼。 The present invention relates to a ferrite-based stainless steel, especially to an exhaust pipe or converter box suitable for use in automobiles or locomotives, exhaust ducts of thermal power stations, etc., which have exhaust system components used at high temperatures. Fertile iron-based stainless steel with excellent creep resistance and thermal fatigue properties.

對於汽車之排氣歧管或排氣管、轉換器箱、及消音器等排氣系統構件，要求優異之耐熱性。耐熱性有若干種類，可舉出熱疲勞特性、高溫疲勞特性、高溫強度(高溫耐力)、抗氧化性、潛變特性、高溫鹽害腐蝕特性等。其中，熱疲勞特性為特別重要之耐熱性之一。排氣系統構件伴隨引擎之起動及停止而反覆受到加熱及冷卻。此時，排氣系統構件與周邊之零件連接，故熱膨脹及收縮受到限制，素材自身產生熱應變。將因反覆受到該熱應變而導致破壞之低循環疲勞現象稱為熱疲勞。 Exhaust system components such as exhaust manifolds or exhaust pipes, converter boxes, and mufflers of automobiles require excellent heat resistance. There are several types of heat resistance, including thermal fatigue characteristics, high temperature fatigue characteristics, high temperature strength (high temperature resistance), oxidation resistance, creep characteristics, high temperature salt damage corrosion characteristics, and the like. Among them, thermal fatigue properties are one of particularly important heat resistance. The exhaust system components are repeatedly heated and cooled as the engine starts and stops. At this time, the exhaust system components are connected with the surrounding parts, so thermal expansion and contraction are limited, and the material itself generates thermal strain. The phenomenon of low-cycle fatigue that causes damage due to repeated exposure to this thermal strain is called thermal fatigue.

作為要求上述熱疲勞特性之構件中使用之素材，目前多使用如添加有Nb與Si之Type429(14%Cr-0.9%Si-0.4%Nb系)之肥粒鐵系不鏽鋼。然而，伴隨引擎性能之提高，若排氣溫度上升至超過900℃之溫度，則Type429中尤其無法充分地滿足所需之熱疲勞特性。 As the material used in the components requiring the above-mentioned thermal fatigue characteristics, the ferrous iron-based stainless steel such as Type429 (14%Cr-0.9%Si-0.4%Nb series) with Nb and Si added is currently used. However, with the improvement of engine performance, if the exhaust gas temperature rises to a temperature exceeding 900°C, the Type 429 in particular cannot fully satisfy the required thermal fatigue characteristics.

作為可應對該問題之素材，開發出例如添加有Nb與 Mo而使高溫耐力提高之肥粒鐵系不鏽鋼，即JIS G4305中規定之SUS444(19%Cr-0.5%Nb-2%Mo)、或添加有Nb、Mo及W之肥粒鐵系不鏽鋼等(例如，參照專利文獻1)。 As a material that can cope with this problem, we have developed, for example, the addition of Nb and Fertilized iron-based stainless steel with improved high-temperature endurance by Mo, that is, SUS444 (19%Cr-0.5%Nb-2%Mo) specified in JIS G4305, or ferrous iron-based stainless steel with addition of Nb, Mo and W, etc. ( For example, refer to Patent Document 1).

[先前技術文獻] [Prior Technical Literature] [專利文獻] [Patent Literature]

專利文獻1：日本專利特開2004-018921號公報 Patent Document 1: Japanese Patent Laid-Open No. 2004-018921

以應對近來之排氣限制強化或提高燃料效率為目的，有排氣溫度高溫化之趨勢，於SUS444等中亦出現耐熱性、尤其熱疲勞特性不足之情形。又，若排氣溫度超過900℃而高溫化，則不鏽鋼容易潛變變形，故耐潛變特性亦成為必要。 In order to cope with the recent exhaust gas restriction enhancement or to improve fuel efficiency, there is a tendency for the exhaust gas temperature to become higher. In SUS444, there are also insufficient heat resistance, especially thermal fatigue characteristics. In addition, if the exhaust gas temperature exceeds 900°C and the temperature increases, stainless steel tends to creep and deform, so creep resistance characteristics are also necessary.

SUS444於肥粒鐵系不鏽鋼中具有最高等級之耐熱性，但伴隨近年之排氣限制強化、燃料效率之提高而引起排氣溫度上升之情形時，未必可謂耐熱性充分。伴隨排氣溫度之高溫化，排氣系統構件於升溫時之熱膨脹變大，故因附加更加劇烈之熱應變而導致用於排氣系統構件之肥粒鐵系不鏽鋼變得容易熱疲勞破壞。進而，於長期保持在高溫域之情形時肥粒鐵系不鏽鋼容易產生潛變變形，若產生潛變變形，則會以因潛變變形而使厚度變薄之部分為起點而產生破壞，故亦必須提高耐潛變特性。 SUS444 has the highest level of heat resistance among fat-grained iron-based stainless steels. However, when the exhaust gas temperature rises due to the strengthening of exhaust gas restriction and the improvement of fuel efficiency in recent years, it may not be said to have sufficient heat resistance. As the exhaust temperature increases, the thermal expansion of exhaust system components increases when the temperature rises. Therefore, due to the addition of more severe thermal strain, the ferrous iron-based stainless steel used for exhaust system components becomes prone to thermal fatigue damage. Furthermore, when kept in a high temperature range for a long time, the ferrous iron-based stainless steel is prone to creep deformation. If creep deformation occurs, the part where the thickness becomes thin due to the creep deformation is the starting point and breaks. The creep resistance characteristics must be improved.

如此，於包含SUS444之習知之技術中，無法獲得於排氣溫度高溫化時熱疲勞特性亦充分之肥粒鐵系不鏽鋼。又，亦無法充分地對於排氣溫度超過900℃之情形時所特別需要之耐潛變特性進行評估。 As such, in the conventional technology including SUS444, it is impossible to obtain a ferrite-based stainless steel that has sufficient thermal fatigue characteristics when the exhaust gas temperature increases. In addition, it is not possible to sufficiently evaluate creep resistance characteristics that are particularly required when the exhaust gas temperature exceeds 900°C.

因此，本發明之目的在於解決該課題，提供一種耐潛變特性與熱疲勞特性優異之肥粒鐵系不鏽鋼。 Therefore, the object of the present invention is to solve the problem and provide a ferrous iron-based stainless steel with excellent creep resistance and thermal fatigue properties.

再者，本發明之「耐潛變特性優異」係指於900℃下進行潛變試驗時之斷裂時間優於SUS444。又，「熱疲勞特性優異」係指具有優於SUS444之特性，具體而言，於200~950℃間反覆進行升溫與降溫時之熱疲勞壽命優於SUS444。 Furthermore, the "excellent creep resistance" in the present invention means that the breaking time when the creep test is performed at 900°C is better than that of SUS444. In addition, "excellent thermal fatigue characteristics" refers to the characteristics superior to SUS444. Specifically, the thermal fatigue life of SUS444 is better than that of SUS444 when the temperature is raised and lowered repeatedly between 200 and 950°C.

本發明者等人為了開發耐潛變特性與熱疲勞特性優於SUS444之肥粒鐵系不鏽鋼，而對各種元素對耐潛變特性及熱疲勞特性之影響反覆進行悉心研究。 In order to develop a ferrous iron-based stainless steel that has better creep resistance and thermal fatigue properties than SUS444, the inventors have repeatedly studied the effects of various elements on creep resistance and thermal fatigue properties.

其結果發現，以質量%計藉由含有Nb為0.30~0.80%、Mo為1.80~2.50%、及Nb與Mo之合計含量為2.3~3.0%，而於範圍廣泛之溫度域內高溫強度上升，熱疲勞特性提高。進而發現，藉由於0.002~0.50質量%之範圍內含有Sb而使耐潛變特性提高。 As a result, it was found that by containing 0.30 to 0.80% of Nb, 1.80 to 2.50% of Mo, and a total content of Nb and Mo of 2.3 to 3.0% in terms of mass%, the high-temperature strength increases in a wide temperature range. Improved thermal fatigue characteristics. Furthermore, it was discovered that the creep resistance property is improved by containing Sb in the range of 0.002 to 0.50 mass%.

根據以上見解，藉由形成Cr、Nb、Mo、Sb之全部以適量含有的特定成分組成而完成本發明。本發明中，上述元素較為重要，但為發揮本發明之效果而必須將所有必要元素調整為既定之含量。 Based on the above findings, the present invention has been completed by forming a specific component composition containing all of Cr, Nb, Mo, and Sb in an appropriate amount. In the present invention, the above-mentioned elements are more important, but in order to exert the effects of the present invention, all necessary elements must be adjusted to a predetermined content.

本發明係將以下所述作為主旨。 The present invention has the following as its gist.

[1]一種肥粒鐵系不鏽鋼，其具有如下之成分組成，即，以質量%計，含有C：0.020%以下、Si：0.1~1.0%、Mn：0.05~0.60%、P：0.050%以下、S：0.008%以下、Ni：0.02~0.60%、Al：0.001~0.25%、Cr：18.0~20.0%、Nb：0.30~0.80%、Mo：1.80~2.50%、N：0.015%以下、及Sb：0.002~0.50%，且滿足下式(1)，殘餘部包含Fe及不可避免之雜質，Nb+Mo：2.3~3.0%...(1) [1] A ferrous iron-based stainless steel having the following compositional composition, that is, in terms of mass %, containing C: 0.020% or less, Si: 0.1 to 1.0%, Mn: 0.05 to 0.60%, and P: 0.050% or less , S: 0.008% or less, Ni: 0.02~0.60%, Al: 0.001~0.25%, Cr: 18.0~20.0%, Nb: 0.30~0.80%, Mo: 1.80~2.50%, N: 0.015% or less, and Sb : 0.002~0.50%, and satisfies the following formula (1), The remainder contains Fe and unavoidable impurities, Nb+Mo: 2.3~3.0%...(1)

[2]如[1]之肥粒鐵系不鏽鋼，其中上述成分組成以質量%計，進而含有選自Ti：0.01~0.16%、Zr：0.01~0.50%、Co：0.01~0.50%、B：0.0002~0.0050%、V：0.01~1.0%、W：0.01~5.0%、Cu：0.01~0.40%、及Sn：0.001~0.005%中之1種或2種以上。 [2] The ferrous iron-based stainless steel as in [1], wherein the above-mentioned component composition is calculated by mass%, and further contains selected from Ti: 0.01~0.16%, Zr: 0.01~0.50%, Co: 0.01~0.50%, B: One or more of 0.0002~0.0050%, V: 0.01~1.0%, W: 0.01~5.0%, Cu: 0.01~0.40%, and Sn: 0.001~0.005%.

[3]如[1]或[2]之肥粒鐵系不鏽鋼，其中上述成分組成，以質量%計，進而含有選自Ca：0.0002~0.0050%、及Mg：0.0002~0.0050%中之1種或2種。 [3] The ferrous iron-based stainless steel as in [1] or [2], wherein the above-mentioned component composition is calculated by mass %, and further contains one selected from Ca: 0.0002~0.0050% and Mg: 0.0002~0.0050% Or 2 kinds.

[4]如[1]至[3]中任一項之肥粒鐵系不鏽鋼，其被用於因來自引擎之排氣而升溫至700℃以上之排氣歧管。 [4] The ferrous iron-based stainless steel as in any one of [1] to [3], which is used in an exhaust manifold whose temperature rises above 700°C due to exhaust from the engine.

根據本發明，可提供一種具有優於SUS444(JIS G4305)之耐潛變特性與熱疲勞特性之肥粒鐵系不鏽鋼。因此，本發明之肥粒鐵系不鏽鋼可適宜用於汽車等之排氣系統構件。 According to the present invention, it is possible to provide a ferrous iron-based stainless steel with creep resistance and thermal fatigue characteristics superior to that of SUS444 (JIS G4305). Therefore, the ferrous iron-based stainless steel of the present invention can be suitably used for exhaust system components of automobiles and the like.

圖1係說明潛變試驗片之圖。 Figure 1 is a diagram illustrating the creep test piece.

圖2係說明熱疲勞試驗片之圖。 Figure 2 is a diagram illustrating a thermal fatigue test piece.

圖3係說明熱疲勞試驗之溫度及約束條件之圖。 Figure 3 is a diagram illustrating the temperature and constraint conditions of the thermal fatigue test.

以下，對本發明之實施形態進行說明。再者，本發明並不限定於以下之實施形態。 Hereinafter, embodiments of the present invention will be described. In addition, the present invention is not limited to the following embodiments.

本發明之肥粒鐵系不鏽鋼以質量%計，含有C：0.020%以下、Si：0.1~1.0%、Mn：0.05~0.60%、P：0.050%以下、S：0.008%以下、Ni：0.02~0.60%、Al：0.001~0.25%、Cr：18.0~20.0%、Nb：0.30~0.80%、Mo：1.80~2.50%、N：0.015%以下、及Sb：0.002~0.50%，且滿足下式(1)，殘餘部包含Fe及不可避免之雜質。 The ferrous iron-based stainless steel of the present invention contains C: 0.020% or less, Si: 0.1 to 1.0%, Mn: 0.05 to 0.60%, P: 0.050% or less, S: 0.008% or less, Ni: 0.02% by mass%. 0.60%, Al: 0.001~0.25%, Cr: 18.0~20.0%, Nb: 0.30~0.80%, Mo: 1.80~2.50%, N: 0.015% or less, and Sb: 0.002~0.50%, and satisfy the following formula ( 1) The residue contains Fe and unavoidable impurities.

Nb+Mo：2.3~3.0%...(1) Nb+Mo: 2.3~3.0%...(1)

本發明中，成分組成之平衡非常重要，藉由形成如上所述之成分組成之組合，可獲得耐潛變特性與熱疲勞特性優於SUS444之肥粒鐵系不鏽鋼。上述成分組成中只要有一個必要元素(C、Si、Mn、Ni、Al、Cr、Nb、Mo、N、Sb)之含量範圍發生偏離，即無法獲得所需之耐潛變特性與熱疲勞特性。 In the present invention, the balance of the component composition is very important. By forming the above-mentioned component composition combination, a ferrous iron-based stainless steel with creep resistance and thermal fatigue properties superior to that of SUS444 can be obtained. As long as the content range of one essential element (C, Si, Mn, Ni, Al, Cr, Nb, Mo, N, Sb) deviates from the above composition, the required creep resistance and thermal fatigue properties cannot be obtained .

其次，對本發明之肥粒鐵系不鏽鋼之成分組成進行說明。以下，只要未特別說明，則成分之含量之單位%係表示質量%。 Next, the composition of the ferrous iron-based stainless steel of the present invention will be described. Hereinafter, unless otherwise specified, the unit% of the content of the ingredients means mass %.

C：0.020%以下 C: Below 0.020%

C係可有效提高鋼之強度之元素，但若含有超過0.020%之C，則韌性及成形性之降低變得顯著。又，與本發明中重要之Nb結合產生之碳化物量變多，由此導致下述Nb之使熱疲勞特性與耐潛變特性提高之效果變小。由此，將C含量設為0.020%以下。再者，根據確保成形性之觀點，C含量較佳設為0.010%以下。更佳為，C含量設為0.008%以下。又，根據確保作為排氣系統構件之強度之觀點，C含量較佳設為0.001%以上。更佳為，C含量設為0.003%以上。進而較佳為，C含量設為0.004%以上。 C is an element that can effectively increase the strength of steel, but if it contains more than 0.020% of C, the decrease in toughness and formability becomes significant. In addition, the amount of carbides produced by combining with Nb, which is important in the present invention, increases, and this leads to a decrease in the effect of the following Nb in improving thermal fatigue properties and creep resistance properties. Therefore, the C content is set to 0.020% or less. Furthermore, from the viewpoint of ensuring formability, the C content is preferably set to 0.010% or less. More preferably, the C content is set to 0.008% or less. In addition, from the viewpoint of ensuring the strength as an exhaust system member, the C content is preferably set to 0.001% or more. More preferably, the C content is set to 0.003% or more. More preferably, the C content is set to 0.004% or more.

Si：0.1~1.0% Si: 0.1~1.0%

Si係用於抗氧化性提高所必要之重要的元素。為確保高溫化之排氣中之抗氧化性而需要含有0.1%以上之Si。另一方面，含有超過1.0%之過剩之Si時，會使室溫下之加工性降低，故將Si含量之上限設為1.0%。較佳為，Si含量設為0.20%以上。更佳為，Si含量設為0.30%以上。進而較佳為，Si含量設為0.40%以上。又，較佳為，Si含量設為0.90%以下。更佳為，Si含量設為0.60%以下。 Si is an important element necessary for improving oxidation resistance. In order to ensure the oxidation resistance in the high-temperature exhaust, it is necessary to contain more than 0.1% of Si. On the other hand, if excess Si is contained in excess of 1.0%, the workability at room temperature will decrease, so the upper limit of the Si content is set to 1.0%. Preferably, the Si content is set to 0.20% or more. More preferably, the Si content is set to 0.30% or more. More preferably, the Si content is set to 0.40% or more. Furthermore, it is preferable that the Si content is set to 0.90% or less. More preferably, the Si content is set to 0.60% or less.

Mn：0.05~0.60% Mn: 0.05~0.60%

Mn具有藉由提高氧化鏽皮之耐剝離性而使熱疲勞特性提高之效果。為獲得該等效果，必須含有0.05%以上之Mn。另一方面，過剩地含有超過0.60%之Mn時，於高溫下容易產生γ相，使耐熱性降低。由此，將Mn含量設為0.05%以上且0.60%以下。較佳為，Mn含量設為0.10%以上。更佳為，Mn含量設為0.15%以上。又，較佳為，Mn含量設為0.50%以下。更佳為，Mn含量設為0.40%以下。 Mn has the effect of improving the thermal fatigue properties by improving the peeling resistance of the oxide scale. In order to obtain these effects, it must contain 0.05% or more of Mn. On the other hand, when Mn is contained excessively in excess of 0.60%, the γ phase is likely to be generated at a high temperature and the heat resistance is lowered. Therefore, the Mn content is set to 0.05% or more and 0.60% or less. Preferably, the Mn content is set to 0.10% or more. More preferably, the Mn content is set to 0.15% or more. Furthermore, it is preferable that the Mn content is set to 0.50% or less. More preferably, the Mn content is set to 0.40% or less.

P：0.050%以下 P: Below 0.050%

P係使鋼之韌性降低之有害之元素，較理想為儘可能地減少。由此，將P含量設為0.050%以下。較佳為，P含量為0.040%以下。更佳為，P含量為0.030%以下。 P is a harmful element that reduces the toughness of steel, and it is better to reduce it as much as possible. Therefore, the P content is set to 0.050% or less. Preferably, the P content is 0.040% or less. More preferably, the P content is 0.030% or less.

S：0.008%以下 S: less than 0.008%

S亦為有害元素，其使伸長率或r值降低，對成形性造成不良影響，並且使作為不鏽鋼之基本特性之耐蝕性降低，故而較理想為儘可能地減少。由此，本發明中，將S含量設為0.008%以下。較佳為，S含量為0.006%以下。 S is also a harmful element, which reduces the elongation or r value, and has a bad influence on the formability. It also reduces the corrosion resistance, which is the basic characteristic of stainless steel, so it is better to reduce it as much as possible. Therefore, in the present invention, the S content is set to 0.008% or less. Preferably, the S content is 0.006% or less.

Ni：0.02~0.60% Ni: 0.02~0.60%

Ni係使鋼之韌性及抗氧化性提高之元素。為獲得該等效果，將Ni含量設為0.02%以上。若抗氧化性不充分，則由氧化鏽皮之產生量變多導致素材截面積減少、或由氧化鏽皮之剝離導致熱疲勞特性降低。另一方面，Ni係強力的γ相形成元素，故若過剩地含有Ni，則於高溫下產生γ相，使抗氧化性降低並且熱膨脹係數變大，由此使熱疲勞特性降低。由此，將Ni含量之上限設為0.60%。較佳為，Ni含量為0.05%以上。更佳為，Ni含量為0.10%以上。又，較佳為，Ni含量為0.40%以下。更佳為，Ni含量為0.30%以下。 Ni is an element that improves the toughness and oxidation resistance of steel. In order to obtain these effects, the Ni content is set to 0.02% or more. If the oxidation resistance is insufficient, the increase in the amount of scale produced will reduce the cross-sectional area of the material, or the peeling of the scale will reduce the thermal fatigue properties. On the other hand, Ni is a strong γ-phase forming element, so if Ni is contained excessively, γ-phase is generated at high temperature, oxidation resistance is reduced, and thermal expansion coefficient is increased, thereby degrading thermal fatigue characteristics. Therefore, the upper limit of the Ni content is set to 0.60%. Preferably, the Ni content is 0.05% or more. More preferably, the Ni content is 0.10% or more. Furthermore, it is preferable that the Ni content is 0.40% or less. More preferably, the Ni content is 0.30% or less.

Al：0.001~0.25% Al: 0.001~0.25%

Al係具有使抗氧化性提高之效果之元素。為獲得該效果，必須含有0.001%以上之Al。另一方面，Al亦係提高熱膨脹係數之元素。若熱膨脹係數變大則熱疲勞特性降低。進而，鋼顯著地硬質化而導致加工性降低。由此，將Al含量設為0.25%以下。較佳為，Al含量為0.005%以上。更佳為，Al含量為超過0.010%。進而較佳為，Al含量為超過0.020%。又，較佳為，Al含量為未滿0.20%。更佳為，Al含量為未滿0.08%。 Al is an element that has the effect of improving oxidation resistance. In order to obtain this effect, it must contain 0.001% or more of Al. On the other hand, Al is also an element that increases the coefficient of thermal expansion. If the coefficient of thermal expansion increases, the thermal fatigue characteristics decrease. Furthermore, steel is significantly hardened, resulting in a decrease in workability. Therefore, the Al content is set to 0.25% or less. Preferably, the Al content is 0.005% or more. More preferably, the Al content is more than 0.010%. More preferably, the Al content is more than 0.020%. Furthermore, it is preferable that the Al content is less than 0.20%. More preferably, the Al content is less than 0.08%.

Cr：18.0~20.0% Cr: 18.0~20.0%

Cr係可有效使作為不鏽鋼之特徵之耐蝕性、抗氧化性提高之重要的元素，但於Cr含量未滿18.0%時，於超過900℃之高溫域無法獲得充分之抗氧化性。若抗氧化性不充分，則氧化鏽皮產生量變多，伴隨素材之截面積之減少，熱疲勞特性亦降低。另一方面，Cr係於室溫下使鋼固溶強化、硬質化及低延展化之元素，若Cr含量超過20.0%，則上述弊害變得顯著，熱疲勞特性亦反而降低，故將Cr含量之上限設為20.0%。較佳為，Cr含量為18.5%以上。又，較佳為，Cr含量為19.5%以下。 Cr is an important element that can effectively improve the corrosion resistance and oxidation resistance that are the characteristics of stainless steel. However, when the Cr content is less than 18.0%, sufficient oxidation resistance cannot be obtained in the high temperature range of over 900°C. If the oxidation resistance is not sufficient, the amount of scale produced will increase, and the thermal fatigue characteristics will also decrease as the cross-sectional area of the material decreases. On the other hand, Cr is an element for solid solution strengthening, hardening and low ductility of steel at room temperature. If the Cr content exceeds 20.0%, the above-mentioned disadvantages become significant and the thermal fatigue characteristics are also reduced. Therefore, the Cr content is reduced. The upper limit is set at 20.0%. Preferably, the Cr content is 18.5% or more. Furthermore, it is preferable that the Cr content is 19.5% or less.

Nb：0.30~0.80% Nb: 0.30~0.80%

Nb係使高溫強度上升而使熱疲勞特性、耐潛變特性提高之對於本發明而言重要的元素。含有0.30%以上之Nb時可看出此種效果。於Nb含量未滿0.30%之情形時，高溫下之強度不足，無法獲得優異之熱疲勞特性、耐潛變特性。然而，含有超過0.80%之Nb時，作為金屬間化合物之Laves相(Fe₂Nb)等容易析出，高溫強度降低，不僅熱疲勞特性與耐潛變特性反而降低，而且促進脆化。由此，將Nb含量設為0.30%以上且0.80%以下。較佳為，Nb含量為0.40%以上。更佳為，Nb含量為0.45%以上。進而較佳為，Nb含量為超過0.50%。又，較佳為，Nb含量為0.70%以下。更佳為，Nb含量為0.60%以下。 Nb is an important element for the present invention that increases high-temperature strength and improves thermal fatigue properties and creep resistance properties. This effect can be seen when Nb is more than 0.30%. When the Nb content is less than 0.30%, the strength at high temperature is insufficient, and excellent thermal fatigue characteristics and creep resistance characteristics cannot be obtained. However, when the Nb content exceeds 0.80%, Laves phase (Fe ₂ Nb), which is an intermetallic compound, is easily precipitated, and the high-temperature strength decreases. Not only does the thermal fatigue property and the creep resistance property decrease, but it also promotes embrittlement. Therefore, the Nb content is set to 0.30% or more and 0.80% or less. Preferably, the Nb content is 0.40% or more. More preferably, the Nb content is 0.45% or more. More preferably, the Nb content is more than 0.50%. Furthermore, it is preferable that the Nb content is 0.70% or less. More preferably, the Nb content is 0.60% or less.

Mo：1.80~2.50% Mo: 1.80~2.50%

Mo係可藉由於鋼中固溶使鋼之高溫強度提高而有效使熱疲勞特性、耐潛變特性提高的元素。於含有1.80%以上之Mo時會顯現該效果。於Mo含量未滿1.80%之情形時高溫強度不充分，無法獲得優異之熱疲勞特性、耐潛變特性。另一方面，含有過剩之Mo時，不僅會使鋼硬質化而導致加工性降低，而且與Nb同樣地作為Laves相(Fe₂Mo)析出，鋼中固溶之Mo量減少，故熱疲勞特性反而降低。又，於熱疲勞試驗中藉由作為粗大之σ相析出而成為破壞之起點，導致熱疲勞特性降低。由此，將Mo含量之上限設為2.50%。較佳為，Mo含量為1.90%以上。更佳為，Mo含量為超過2.00%。又，較佳為，Mo含量為2.30%以下。更佳為，Mo含量為2.10%以下。 Mo is an element that can effectively improve thermal fatigue properties and creep resistance properties by increasing the high-temperature strength of steel due to solid solution in the steel. This effect will appear when Mo contains more than 1.80%. When the Mo content is less than 1.80%, the high temperature strength is insufficient, and excellent thermal fatigue properties and creep resistance properties cannot be obtained. On the other hand, when excessive Mo is contained, it not only hardens the steel and lowers the workability, but also precipitates as the Laves phase (Fe ₂ Mo) like Nb, reducing the amount of dissolved Mo in the steel, resulting in thermal fatigue characteristics Instead, it decreases. In addition, in the thermal fatigue test, the coarse σ phase precipitates and becomes the starting point of failure, resulting in a decrease in thermal fatigue properties. Therefore, the upper limit of the Mo content is set to 2.50%. Preferably, the Mo content is 1.90% or more. More preferably, the Mo content is more than 2.00%. Furthermore, it is preferable that the Mo content is 2.30% or less. More preferably, the Mo content is 2.10% or less.

N：0.015%以下 N: 0.015% or less

N係使鋼之韌性及成形性降低之元素，若含有超過0.015%之鋼，則不僅韌性及成形性之降低變得顯著，而且由Nb氮化物之形成引起固溶Nb量降低，使耐潛變特性與熱疲勞特性降低。由此，將N含量設為0.015%以下。再者，根據確保韌性、成形性之觀點，較佳為儘可能地減少N，N含量較理想為未滿0.010%。 N is an element that reduces the toughness and formability of steel. If it contains more than 0.015% of steel, not only the reduction in toughness and formability becomes significant, but also the formation of Nb nitrides causes a decrease in the amount of solid solution Nb, which makes it resistant to potential Variation characteristics and thermal fatigue characteristics are reduced. Therefore, the N content is set to 0.015% or less. Furthermore, from the viewpoint of ensuring toughness and formability, it is preferable to reduce N as much as possible, and the N content is more preferably less than 0.010%.

Sb：0.002~0.50% Sb: 0.002~0.50%

Sb係本發明中用以使耐潛變特性提高之重要的元素。Sb於鋼中固溶，抑制高溫下鋼之潛變變形。Sb於高溫域中亦不會作為碳氮化物或Laves相析出，於長期使用後仍會固溶於鋼中，抑制潛變變形，故可使耐潛變特性提高。於含有0.002%以上之Sb時可獲得該效果。另一方面，含有過剩之Sb時，使鋼之韌性、熱加工性降低，故不僅於製造時易產生破裂，而且由於熱延展性降低而導致熱疲勞特性亦降低。因此，將Sb含量之上限設為0.50%。較佳為，Sb含量為0.005%以上。更佳為0.020%以上。又，較佳為，Sb含量為0.30%以下。更佳為，Sb含量為0.10%以下。 Sb is an important element for improving creep resistance in the present invention. Sb is dissolved in the steel to inhibit the creep deformation of the steel at high temperature. Sb will not precipitate as carbonitrides or Laves phases in the high temperature range, and will still dissolve in steel after long-term use, inhibiting creep deformation, so the creep resistance characteristics can be improved. This effect can be obtained when the Sb content is more than 0.002%. On the other hand, when excessive Sb is contained, the toughness and hot workability of the steel are reduced, so not only cracks are likely to occur during manufacturing, but also the thermal fatigue properties are also reduced due to the reduced thermal ductility. Therefore, the upper limit of the Sb content is set to 0.50%. Preferably, the Sb content is 0.005% or more. More preferably, it is 0.020% or more. Furthermore, it is preferable that the Sb content is 0.30% or less. more Preferably, the Sb content is 0.10% or less.

Nb+Mo：2.3~3.0%...(1) Nb+Mo: 2.3~3.0%...(1)

如上所述，Nb與Mo係可有效提高熱疲勞特性、耐潛變特性之元素。Nb與Mo分別含有0.30%以上、1.80%以上時可看出其效果。然而，為實現用以應對排氣之高溫化而於200~950℃間反覆進行升溫與降溫時之熱疲勞壽命優於SUS444之熱疲勞特性、耐潛變特性，須於既定之範圍含有兩元素，而且必須至少滿足Nb+Mo≧2.3%，即，使Nb+Mo之量(Nb與Mo之合計含量)為2.3%以上。於不滿足該條件之情形時，即便添加既定量之Sb，亦無法獲得優異之耐潛變特性。較佳為，Nb+Mo>2.5%。另一方面，若Nb+Mo之量過度增加，則鋼變脆，無法獲得優異之熱疲勞特性、耐潛變特性。因此，Nb+Mo之量之上限設為3.0%。較佳為，Nb+Mo之量為2.7%以下。 As mentioned above, Nb and Mo are elements that can effectively improve thermal fatigue properties and creep resistance properties. The effect can be seen when Nb and Mo contain 0.30% or more and 1.80% or more, respectively. However, in order to cope with the high temperature of exhaust gas, the thermal fatigue life of repeated heating and cooling between 200~950℃ is better than the thermal fatigue characteristics and creep resistance characteristics of SUS444. The two elements must be contained in the predetermined range. , And must satisfy at least Nb+Mo≧2.3%, that is, make the amount of Nb+Mo (the total content of Nb and Mo) be 2.3% or more. When this condition is not met, even if a given amount of Sb is added, excellent creep resistance properties cannot be obtained. Preferably, Nb+Mo>2.5%. On the other hand, if the amount of Nb+Mo is excessively increased, the steel becomes brittle, and excellent thermal fatigue properties and creep resistance properties cannot be obtained. Therefore, the upper limit of the amount of Nb+Mo is set to 3.0%. Preferably, the amount of Nb+Mo is 2.7% or less.

再者，上述式(1)中之Nb及Mo表示各元素之含量(質量%)。 Furthermore, Nb and Mo in the above formula (1) represent the content (mass %) of each element.

本發明之肥粒鐵系不鏽鋼中，殘餘部包含Fe及不可避免之雜質。 In the ferrous iron-based stainless steel of the present invention, the remainder contains Fe and unavoidable impurities.

本發明之肥粒鐵系不鏽鋼除上述必須成分外，進而可於下述範圍含有選自Ti、Zr、Co、B、V、W、Cu、Sn中之1種或2種以上作為任意成分。 In addition to the above-mentioned essential components, the ferrous iron-based stainless steel of the present invention may further contain one or more selected from Ti, Zr, Co, B, V, W, Cu, and Sn as optional components in the following range.

Ti：0.01~0.16% Ti: 0.01~0.16%

Ti係固定C及N、提高耐蝕性或成形性、防止焊接部之晶界腐蝕之元素，本發明中，可視需要而含有Ti。由於Ti相較Nb優先與C及N 結合，故藉由含有Ti而可確保對於高溫強度有效之鋼中固溶Nb之量，亦可有效提高耐熱性。於含有0.01%以上之Ti時可獲得該等效果。另一方面，含有超過0.16%之過剩之Ti時，導致韌性降低，例如，因於熱軋板退火線上反覆受到之折彎-回彈而引起斷裂等，對製造性造成不良影響。又，容易以Ti之碳氮化物為核心而析出Nb之碳氮化物，故反而使對於高溫強度有效之鋼中固溶Nb之量減少，導致熱疲勞特性、耐潛變特性降低。由此，於含有Ti之情形時，將Ti含量設為0.01~0.16%。較佳為，Ti含量為0.03%以上。又，較佳為，Ti含量為0.12%以下。更佳為，Ti含量為0.08%以下。進而較佳為，Ti含量為0.05%以下。 Ti is an element that fixes C and N, improves corrosion resistance or formability, and prevents grain boundary corrosion in the welded portion. In the present invention, Ti may be contained as needed. Since Ti has priority over Nb and C and N Therefore, by containing Ti, the amount of solid solution Nb in the steel that is effective for high-temperature strength can be ensured, and the heat resistance can also be effectively improved. These effects can be obtained when the Ti content is more than 0.01%. On the other hand, when Ti is contained in excess of more than 0.16%, the toughness decreases. For example, the hot-rolled sheet annealing line is repeatedly subjected to bending and springback, which causes breakage, which adversely affects manufacturability. In addition, it is easy to precipitate Nb carbonitrides with Ti carbonitrides as the core, so on the contrary, the amount of solid solution Nb in steel that is effective for high-temperature strength is reduced, resulting in a decrease in thermal fatigue properties and creep resistance properties. Therefore, when Ti is contained, the Ti content is set to 0.01 to 0.16%. Preferably, the Ti content is 0.03% or more. Furthermore, it is preferable that the Ti content is 0.12% or less. More preferably, the Ti content is 0.08% or less. More preferably, the Ti content is 0.05% or less.

Zr：0.01~0.50% Zr: 0.01~0.50%

Zr係使抗氧化性提高之元素，於本發明中，可視需要而含有Zr。於含有0.01%以上之Zr時可獲得該效果。然而，若Zr含量超過0.50%，則Zr金屬間化合物析出，使鋼脆化。由此，於含有Zr之情形時，將Zr含量設為0.01~0.50%。較佳為，Zr含量為0.03%以上。更佳為，Zr含量為0.05%以上。又，較佳為，Zr含量為0.30%以下。更佳為，Zr含量為0.10%以下。 Zr is an element that improves the oxidation resistance. In the present invention, Zr may be contained as needed. This effect can be obtained when Zr is contained more than 0.01%. However, if the Zr content exceeds 0.50%, Zr intermetallic compounds are precipitated and the steel is embrittled. Therefore, when Zr is contained, the Zr content is set to 0.01 to 0.50%. Preferably, the Zr content is 0.03% or more. More preferably, the Zr content is 0.05% or more. Furthermore, it is preferable that the Zr content is 0.30% or less. More preferably, the Zr content is 0.10% or less.

Co：0.01~0.50% Co: 0.01~0.50%

Co係作為可有效提高鋼之韌性之元素而被周知。於含有0.01%以上之Co時可獲得該效果。另一方面，含有過剩之Co時，反而會使鋼之韌性降低，故將Co含量之上限設為0.50%。由此，於含有Co之情形時，將Co含量設為0.01~0.50%。較佳為，Co含量為0.03%以上。又，較佳為，Co含量為0.30%以下。 Co is well known as an element that can effectively improve the toughness of steel. This effect can be obtained when Co contains more than 0.01%. On the other hand, when excessive Co is contained, the toughness of the steel will decrease instead, so the upper limit of the Co content is set to 0.50%. Therefore, when Co is contained, the Co content is set to 0.01 to 0.50%. Preferably, the Co content is 0.03% or more. Furthermore, it is preferable that the Co content is 0.30% or less.

B：0.0002~0.0050% B: 0.0002~0.0050%

B係可有效提高鋼之加工性、尤其二次加工性的元素。於含有0.0002%以上之B時可獲得此種效果。另一方面，含有過剩之B時，會生成BN而導致加工性降低。由此，於含有B之情形時，將B含量設為0.0002~0.0050%。較佳為，B含量為0.0005%以上。更佳為，B含量為0.0008%以上。又，較佳為，B含量為0.0030%以下。更佳為，B含量為0.0020%以下。 B series can effectively improve the workability of steel, especially the element of secondary workability. This effect can be obtained when B contains more than 0.0002%. On the other hand, when excessive B is contained, BN is generated and the workability is reduced. Therefore, when B is contained, the B content is set to 0.0002 to 0.0050%. Preferably, the B content is 0.0005% or more. More preferably, the B content is 0.0008% or more. Furthermore, it is preferable that the B content is 0.0030% or less. More preferably, the B content is 0.0020% or less.

V：0.01~1.0% V: 0.01~1.0%

V係可有效提高鋼之加工性之元素，並且係亦可有效提高抗氧化性之元素。於V含量為0.01%以上時該等效果變得顯著。然而，含有超過1.0%之過剩之V時，會導致粗大之V(C、N)析出，不僅使韌性降低，而且使表面性狀降低。由此，於含有V之情形時，將V含量設為0.01~1.0%。較佳為，V含量為0.03%以上。更佳為，V含量為0.05%以上。又，較佳為，V含量為0.50%以下。更佳為，V含量為0.20%以下。 V is an element that can effectively improve the workability of steel, and it is also an element that can effectively improve the oxidation resistance. These effects become remarkable when the V content is 0.01% or more. However, when the excessive V content exceeds 1.0%, coarse V (C, N) will precipitate, which not only reduces the toughness, but also reduces the surface properties. Therefore, when V is contained, the V content is set to 0.01 to 1.0%. Preferably, the V content is 0.03% or more. More preferably, the V content is 0.05% or more. Furthermore, it is preferable that the V content is 0.50% or less. More preferably, the V content is 0.20% or less.

W：0.01~5.0% W: 0.01~5.0%

W與Mo同樣係藉由固溶強化而使高溫強度大幅提高之元素。於含有0.01%以上之W時可獲得該效果。另一方面，含有過剩之W時，不僅會使鋼顯著硬質化，而且於製造時之退火步驟中會產生牢固之鏽皮，故酸洗時之除鏽變得困難。由此，於含有W之情形時，將W 含量設為0.01~5.0%。較佳為，W含量為0.05%以上。又，較佳為，W含量為3.5%以下。更佳為，W含量為1.0%以下。進而較佳為，W含量為未滿0.30%。 W, like Mo, is an element that greatly improves high-temperature strength through solid solution strengthening. This effect can be obtained when W contains 0.01% or more. On the other hand, when excessive W is contained, not only will the steel be significantly hardened, but also a firm scale will be produced during the annealing step during manufacturing, so it becomes difficult to remove rust during pickling. Therefore, when W is contained, W The content is set to 0.01~5.0%. Preferably, the W content is 0.05% or more. Moreover, it is preferable that the W content is 3.5% or less. More preferably, the W content is 1.0% or less. More preferably, the W content is less than 0.30%.

Cu：0.01~0.40% Cu: 0.01~0.40%

Cu係具有使鋼之耐蝕性提高之效果之元素，於需要耐蝕性之情形時含有。於含有0.01%以上之Cu時可獲得該效果。另一方面，若含有超過0.40%之Cu，則氧化鏽皮容易剝離，抗反覆氧化特性降低。因此，於含有Cu之情形時，將Cu含量設為0.01~0.40%。較佳為，Cu含量為0.03%以上。更佳為，Cu含量為0.06%以上。又，較佳為，Cu含量為0.20%以下。更佳為，Cu含量為0.10%以下。 Cu is an element that has the effect of improving the corrosion resistance of steel, and is contained when corrosion resistance is required. This effect can be obtained when Cu contains 0.01% or more. On the other hand, if Cu is contained in excess of 0.40%, the scale will be easily peeled off and the anti-repetitive oxidation properties will decrease. Therefore, when Cu is contained, the Cu content is set to 0.01 to 0.40%. Preferably, the Cu content is 0.03% or more. More preferably, the Cu content is 0.06% or more. Furthermore, it is preferable that the Cu content is 0.20% or less. More preferably, the Cu content is 0.10% or less.

Sn：0.001~0.005% Sn: 0.001~0.005%

Sn係可有效提高鋼之高溫強度之元素。於含有0.001%以上之Sn時可獲得該效果。另一方面，含有過剩之Sn時，伴隨鋼之脆化，反而使熱疲勞特性降低。因此，於含有Sn之情形時，將Sn含量設為0.001~0.005%。較佳為，Sn含量為0.001%以上且0.003%以下。 Sn is an element that can effectively improve the high temperature strength of steel. This effect can be obtained when it contains more than 0.001% of Sn. On the other hand, when excessive Sn is contained, the embrittlement of steel will degrade the thermal fatigue properties. Therefore, when Sn is contained, the Sn content is set to 0.001 to 0.005%. Preferably, the Sn content is 0.001% or more and 0.003% or less.

本發明之肥粒鐵系不鏽鋼進而可於下述範圍含有選自Ca、Mg中之1種或2種作為任意成分。 The ferrous iron-based stainless steel of the present invention may further contain one or two selected from Ca and Mg as optional components in the following range.

Ca：0.0002~0.0050% Ca: 0.0002~0.0050%

Ca係可有效防止連續鑄造時容易產生之Ti系介存物析出所致之噴嘴堵塞的成分。於含有0.0002%以上之Ca時可獲得該效果。另一方面，為了不產生表面缺陷而獲得良好之表面性狀，必須將Ca含量設為0.0050%以下。因此，於含有Ca之情形時，將Ca含量設為0.0002~0.0050%。較佳為，Ca含量為0.0005%以上。又，較佳為，Ca含量為0.0030%以下。更佳為，Ca含量為0.0020%以下。 Ca can effectively prevent nozzle clogging caused by precipitation of Ti-based intermediary substances that are easily produced during continuous casting. This effect can be obtained when Ca contains 0.0002% or more. On the other hand, in order not to produce surface defects and obtain good surface properties, the Ca content must be Set it to 0.0050% or less. Therefore, when Ca is contained, the Ca content is set to 0.0002 to 0.0050%. Preferably, the Ca content is 0.0005% or more. Furthermore, it is preferable that the Ca content is 0.0030% or less. More preferably, the Ca content is 0.0020% or less.

Mg：0.0002~0.0050% Mg: 0.0002~0.0050%

Mg係可有效使鋼坯之等軸晶率提高、使加工性或韌性提高之元素。於如本發明般含有Nb或Ti之鋼中，Mg亦具有抑制Nb或Ti之碳氮化物粗大化之效果。於含有0.0002%以上之Mg時可獲得該效果。若Ti碳氮化物粗大化，則會成為脆性破裂之起點，故韌性大幅降低。若Nb碳氮化物粗大化，則Nb之鋼中固溶量降低，故導致熱疲勞特性之降低。另一方面，若Mg含量超過0.0050%，則使鋼之表面性狀惡化。由此，於含有Mg之情形時，將Mg含量設為0.0002~0.0050%。較佳為，Mg含量為0.0003%以上。更佳為，Mg含量為0.0004%以上。又，較佳為，Mg含量為0.0030%以下。更佳為，Mg含量為0.0020%以下。 Mg is an element that can effectively increase the equiaxed crystal ratio of the billet and increase the workability or toughness. In the steel containing Nb or Ti as in the present invention, Mg also has the effect of suppressing the coarsening of carbonitrides of Nb or Ti. This effect can be obtained when it contains 0.0002% or more of Mg. If the Ti carbonitride becomes coarser, it becomes the starting point of brittle fracture, so the toughness is greatly reduced. If the Nb carbonitrides become coarser, the amount of Nb solid solution in the steel decreases, resulting in a decrease in thermal fatigue properties. On the other hand, if the Mg content exceeds 0.0050%, the surface properties of the steel deteriorate. Therefore, when Mg is contained, the Mg content is set to 0.0002 to 0.0050%. Preferably, the Mg content is 0.0003% or more. More preferably, the Mg content is 0.0004% or more. Furthermore, it is preferable that the Mg content is 0.0030% or less. More preferably, the Mg content is 0.0020% or less.

殘餘部係Fe及不可避免之雜質。於含有未滿上述下限值之上述任意成分之情形時，以未滿下限值之含量含有之任意成分係作為不可避免之雜質而含有。 The remainder is Fe and unavoidable impurities. In the case of containing the above-mentioned optional components below the above lower limit, the optional components contained in the content below the lower limit are included as unavoidable impurities.

其次，對本發明之肥粒鐵系不鏽鋼之製造方法進行說明。 Next, the manufacturing method of the ferrous iron-based stainless steel of the present invention will be described.

本發明之不鏽鋼之製造方法只要係肥粒鐵系不鏽鋼之通常之製造方法則可適當採用，並無特別限定。 The manufacturing method of the stainless steel of the present invention can be suitably adopted as long as it is a normal manufacturing method of ferrite-based stainless steel, and is not particularly limited.

例如，可由以下製造步驟而製造，即，於轉爐或電爐等公知之熔解爐中熔製鋼，或進而經過盛桶精煉或真空精煉等二次精煉而形成具有上述本發明之成分組成之鋼，利用連續鑄造法或造塊-分塊輥軋法形成鋼片(鋼坯)，其後，經過熱軋、熱軋板退火、酸洗、冷軋、最終退火及酸洗等各步驟而形成冷軋退火板。上述冷軋亦可設為1次或隔著中間退火之2次以上之冷軋，又，冷軋、最終退火及酸洗之各步驟亦可反覆進行。進而，亦可省略熱軋板退火，於要求鋼板之表面光澤或粗度調整之情形時，亦可於冷軋後或最終退火後實施調質軋製。 For example, it can be manufactured by the following manufacturing steps, that is, melting steel in a known melting furnace such as a converter or an electric furnace, or further undergoing secondary refining such as ladle refining or vacuum refining. Refining to form steel with the above-mentioned composition of the present invention, using continuous casting method or block-block rolling method to form steel sheet (steel billet), after which it undergoes hot rolling, hot-rolled sheet annealing, pickling, and cold rolling , Final annealing and pickling and other steps to form cold-rolled annealed sheets. The above-mentioned cold rolling may be performed once or two or more times of cold rolling via intermediate annealing, and the steps of cold rolling, final annealing, and pickling may be repeated. Furthermore, the annealing of the hot-rolled sheet may be omitted, and when the surface gloss or roughness adjustment of the steel sheet is required, the temper rolling may be performed after cold rolling or final annealing.

對上述製造方法中之較佳之製造條件進行說明。 The preferred manufacturing conditions in the above manufacturing method will be described.

熔製鋼之製鋼步驟較佳為，將於轉爐或電爐等中熔解之鋼藉由真空吹氧脫碳(VOD，vacuum oxygen decarburization)法或氬氧脫碳(AOD，argon oxygen decarburization)法等進行二次精煉，形成含有上述必要成分及視需要添加之任意成分之鋼。熔製後之熔鋼可由公知之方法形成鋼素材，但就生產性及品質面而言，較佳為由連續鑄造法形成。其後，鋼素材較佳為加熱至1050~1250℃，藉由熱軋而形成所需板厚之熱軋板。於製造上，熱軋板之板厚較理想為5mm以下。當然，亦可對板材以外進行熱加工。較佳為，上述熱軋板於其後視需要以900~1150℃之溫度實施連續退火，或以700~900℃之溫度實施分批退火後，藉由酸洗或研磨等進行除鏽，形成熱軋製品。再者，視需要，亦可於酸洗前藉由噴丸進行除鏽。 The steel making step of melting steel is preferably performed by vacuum oxygen decarburization (VOD, vacuum oxygen decarburization) method or argon oxygen decarburization (AOD, argon oxygen decarburization) method on the steel melted in a converter or electric furnace. Sub-refining to form steel containing the above-mentioned essential components and optional components added as needed. The molten steel after melting can be formed into a steel material by a known method, but in terms of productivity and quality, it is preferably formed by a continuous casting method. After that, the steel material is preferably heated to 1050 to 1250°C and hot rolled to form a hot-rolled sheet of the desired thickness. In terms of manufacturing, the thickness of the hot-rolled sheet is preferably less than 5mm. Of course, thermal processing other than the sheet can also be performed. Preferably, the above-mentioned hot-rolled sheet is subsequently subjected to continuous annealing at a temperature of 900 to 1150°C, or batch annealed at a temperature of 700 to 900°C, and then rust-removed by pickling or grinding. Hot rolled products. Furthermore, if necessary, rust can be removed by shot blasting before pickling.

進而，亦可將上述熱軋製品(熱軋退火板)經過冷軋等步驟而形成冷軋製品。該情形時之冷軋可為1次，但就生產性或要求品質方面之觀點而言，亦可設為隔著中間退火之2次以上之冷軋。1次或2次以上之冷軋之總軋縮率較佳為60%以上，更佳為70%以上。其後，經冷軋之鋼板較佳為，於較佳為900~1200℃、更佳為 1000~1150℃之溫度下進行連續退火(最終退火)，並進行酸洗或研磨，形成冷軋製品(冷軋退火板)。最終退火亦可於還原性氣體環境中進行，該情形時，亦可省略最終退火後之酸洗或研磨。進而，根據用途，亦可於最終退火後實施調質軋製等，進行鋼板之形狀、表面粗度及材質之調整。 Furthermore, the above-mentioned hot-rolled product (hot-rolled and annealed sheet) may be subjected to steps such as cold rolling to form a cold-rolled product. In this case, the cold rolling may be one time, but from the viewpoint of productivity or required quality, it may be cold rolling two or more times via intermediate annealing. The total reduction ratio of the cold rolling performed once or more than twice is preferably 60% or more, more preferably 70% or more. Thereafter, the cold-rolled steel sheet is preferably, preferably at 900~1200°C, more preferably Continuous annealing (final annealing) at a temperature of 1000~1150℃, and pickling or grinding to form cold-rolled products (cold-rolled annealed sheets). The final annealing can also be performed in a reducing gas environment. In this case, the pickling or polishing after the final annealing can also be omitted. Furthermore, depending on the application, temper rolling and the like may be performed after the final annealing to adjust the shape, surface roughness, and material of the steel sheet.

其後，以上述方式獲得之熱軋製品或冷軋製品根據各自之用途而實施切斷或彎曲加工、拉伸加工及拉拔加工等加工，成形為汽車或機車之排氣管、觸媒外筒材、火力發電站之排氣導管或燃料電池相關構件，例如間隔件、互連連接器或改質器等。於該等之中，本發明之肥粒鐵系不鏽鋼適宜用於排氣歧管或排氣管、轉換器箱、及消音器等排氣系統構件。尤其於使用時藉由來自引擎之排氣而升溫至700℃以上之情形時亦可獲得耐久性優異之排氣歧管為特徵之一。 After that, the hot-rolled products or cold-rolled products obtained in the above manner are subjected to cutting or bending, stretching, and drawing processing according to their respective uses, and are formed into exhaust pipes and catalysts for automobiles or motorcycles. Tubes, exhaust ducts of thermal power plants, or fuel cell-related components, such as spacers, interconnecting connectors or reformers, etc. Among them, the ferrite-based stainless steel of the present invention is suitable for exhaust system components such as exhaust manifolds or exhaust pipes, converter boxes, and mufflers. Especially when the temperature rises to 700°C or higher by exhaust from the engine during use, an exhaust manifold with excellent durability can be obtained as one of the characteristics.

該等構件之焊接方法並非特別限定，可應用金屬極鈍氣(MIG，Metal Inert Gas)、金屬活性氣體(MAG，Metal Active Gas)、鎢極鈍氣(TIG，Tungsten Inert Gas)等通常之弧焊接、或點焊接、縫焊接等電阻焊接、及電縫焊接等高頻電阻焊接、高頻感應焊接等。 The welding method of these components is not particularly limited. Common arcs such as Metal Inert Gas (MIG), Metal Active Gas (MAG), Tungsten Inert Gas (TIG), etc. can be used. Welding, or resistance welding such as spot welding, seam welding, and high-frequency resistance welding such as electric seam welding, high-frequency induction welding, etc.

[實施例] [Example]

以下，藉由實施例更詳細地說明本發明。 Hereinafter, the present invention will be explained in more detail with examples.

於真空熔解爐中熔製、鑄造具有表1所示之No.1~41、43、45~47之成分組成之鋼，形成50kg鋼塊，於1170℃下加熱之後，藉由熱軋而形成35mm厚之板片。將板片分成2個部分，將其中1個鋼塊加熱至1100℃，其次，進行熱軋而形成板厚5mm之熱軋板，於1000~1150℃之範圍之溫度下退火後，進行研削而形成熱軋退火板。繼而，進行軋縮率70%之冷軋，於1000~1150℃之溫度下進行最終退火後，藉由酸洗或研磨而除鏽，形成板厚1.5mm之冷軋退火板而供潛變試驗。再者，作為參考，對於SUS444(習知例No.28)，亦以與上述相同之方式製作冷軋退火板，供潛變試驗。關於退火溫度，於上述溫度範圍內確認組織並對各鋼決定溫度。 Melt and cast steel with the composition of No. 1~41, 43, 45~47 shown in Table 1 in a vacuum melting furnace to form a 50kg steel block. After heating at 1170°C, it is formed by hot rolling 35mm thick plate. Divide the plate into two parts, heat one of the steel blocks to 1100°C, and then perform hot rolling to form a hot-rolled plate with a plate thickness of 5mm. After annealing at a temperature in the range of 1000~1150°C, it is ground and ground. Hot rolled annealing board. Then, cold-rolled with a reduction ratio of 70%, final annealed at a temperature of 1000~1150℃, and then pickled or polished to remove rust to form a cold-rolled annealed sheet with a thickness of 1.5mm for creep test . Furthermore, for reference, for SUS444 (Conventional Example No. 28), cold-rolled annealed sheets were also produced in the same manner as above for creep test. Regarding the annealing temperature, confirm the structure within the above-mentioned temperature range and determine the temperature for each steel.

<潛變試驗> <Creep Change Test>

自以上述方式獲得之各冷軋退火板切下圖1所示之形狀之試驗片，於900℃下進行負載15MPa之應力之潛變試驗。根據斷裂前所花費之時間，以如下方式進行評估。關於作為比較而進行之SUS444(習知例No.28)，斷裂前所花費之時間為5.5hr。 A test piece of the shape shown in Fig. 1 was cut from each cold-rolled and annealed sheet obtained in the above manner, and a creep test with a stress of 15 MPa was carried out at 900°C. Based on the time taken before fracture, the evaluation is performed in the following manner. Regarding SUS444 (Conventional Example No. 28), which was performed as a comparison, the time taken before breaking was 5.5 hr.

◎：斷裂時間≧10hr ◎: Breaking time≧10hr

○：6hr≦斷裂時間<10hr ○: 6hr≦break time<10hr

×：斷裂時間<6hr ×: Breaking time<6hr

上述評估中，將◎與○設為合格，將×設為不合格。將所得之結果示於表1(參照表1中之潛變900℃)。 In the above evaluation, ⊚ and ◯ are regarded as pass, and × is regarded as unacceptable. The obtained results are shown in Table 1 (refer to the creep change of 900°C in Table 1).

其次，使用上述分成2個部分之板片之剩餘之1個，加熱至1100℃後，進行熱鍛造，形成30mm見方之各棒。其次，以1000~1150℃之溫度退火後，進行機械加工，加工成圖2所示之形狀、尺寸之熱疲勞試驗片，供下述熱疲勞試驗。退火溫度設為針對每一成分確認組織並完成再結晶後之溫度。再者，作為參考，關於具有SUS444之成分組成之鋼(習知例No.28)，亦以與上述相同之方式製作試驗片，供熱疲勞試驗。 Next, using the remaining one of the above-mentioned two-part plate, heated to 1100°C, hot forged to form each rod of 30mm square. Secondly, after annealing at a temperature of 1000~1150℃, mechanical processing is performed to process the thermal fatigue test piece with the shape and size shown in Figure 2 for the following thermal fatigue test. The annealing temperature is set to the temperature after confirming the structure for each component and completing recrystallization. Furthermore, for reference, regarding the steel with the composition of SUS444 (Conventional Example No. 28), test pieces were also made in the same manner as the above, and the heat fatigue test was performed.

<熱疲勞試驗> <Thermal Fatigue Test>

如圖3所示，熱疲勞試驗係於一方面以0.5之約束率約束上述試驗片，一方面於200℃與950℃之間反覆進行升溫、降溫之條件下進行。此時，升溫速度設為5℃/秒，降溫速度設為2℃/秒。而且，200℃、950℃下之保持時間分別設為30秒。再者，關於上述約束率，如圖3所示，約束率可表示為η=a/(a+b)，a為(自由熱膨脹應變量-控制應變量)/2，b為控制應變量/2。又，自由熱膨脹應變量係完全不賦予機械應力而升溫之情形時之應變量，控制應變量表示試驗中產生之應變量之絕對值。由約束而於材料中產生之實質的約束應變量為(自由熱膨脹應變量-控制應變量)。 As shown in Fig. 3, the thermal fatigue test is performed on the one hand with a constraint rate of 0.5 to constrain the above-mentioned test piece, on the other hand, it is carried out under repeated heating and cooling conditions between 200°C and 950°C. At this time, the temperature increase rate was set to 5°C/sec, and the temperature decrease rate was set to 2°C/sec. In addition, the holding time at 200°C and 950°C was set to 30 seconds, respectively. Furthermore, regarding the above-mentioned restraint rate, as shown in Fig. 3, the restraint rate can be expressed as η=a/(a+b), a is (free thermal expansion strain-control strain)/2, and b is the control strain/ 2. In addition, the amount of free thermal expansion strain is the amount of strain when the temperature is raised without applying mechanical stress at all, and the amount of control strain represents the absolute value of the amount of strain generated during the test. The substantial constraint strain produced in the material by the constraint is (free thermal expansion strain-control strain).

又，關於熱疲勞壽命，將於200℃下檢測出之負重除以試驗片均熱平行部(參照圖2)之截面積而算出應力，設為應力值相對於初始之循環(試驗穩定之第5循環)之應力值降低至75%的循環數，以如下方式進行評估。關於作為比較而進行之SUS444(習知例No.28)，熱疲勞壽命為650循環。 Regarding the thermal fatigue life, the stress is calculated by dividing the load detected at 200°C by the cross-sectional area of the parallel portion of the test piece (refer to Figure 2), and set the stress value to the initial cycle (the first stable test) 5 cycles) The number of cycles at which the stress value is reduced to 75% is evaluated in the following manner. Regarding SUS444 (Conventional Example No. 28), which was performed as a comparison, the thermal fatigue life was 650 cycles.

◎：1000循環以上(合格) ◎: More than 1000 cycles (qualified)

○：800循環以上且未滿1000循環(合格) ○: 800 cycles or more and less than 1000 cycles (pass)

×：未滿800循環(不合格) ×: less than 800 cycles (unqualified)

上述評估中，將◎、○設為合格，將×設為不合格。將所得之結果示於表1(參照表1中之熱疲勞壽命950℃)。 In the above evaluation, ⊚ and ◯ were regarded as pass, and × was regarded as unacceptable. The results obtained are shown in Table 1 (refer to the thermal fatigue life in Table 1 at 950°C).

根據表1，顯示本發明例之No.1~27之肥粒鐵系不鏽鋼(以下，將肥粒鐵系不鏽鋼簡記為鋼)於潛變試驗及熱疲勞試驗中均優於SUS444(習知例No.28之鋼)之特性。 According to Table 1, it is shown that the ferrous iron-based stainless steels of No. 1 to 27 of the present invention (hereinafter, the ferrous iron-based stainless steel is abbreviated as steel) are superior to SUS444 in the creep test and the thermal fatigue test (the conventional example) No. 28 steel) characteristics.

No.29之鋼中，Nb+Mo含量未滿2.3質量%，潛變斷裂時間與熱疲勞壽命不合格。No.30之鋼中，Ni含量超過0.60質量%，熱疲勞壽命不合格。No.31之鋼中，Cr含量未滿18.0質量%，熱疲勞壽命不合格。No.32之鋼中，Mo含量未滿1.80質量%，潛變斷裂時間、熱疲勞壽命不合格。No.33之鋼中，Nb含量未滿0.30質量%，潛變斷裂時間、熱疲勞壽命均不合格。No.34之鋼中，Si含量未滿0.1質量%，於潛變試驗、熱疲勞試驗之任一者中均顯著地發現氧化，潛變斷裂時間、熱疲勞壽命均不合格。No.35之鋼中，Ti含量超過0.16質量%，潛變斷裂時間、熱疲勞壽命均不合格。No.36之鋼中，Cr含量超過20.0質量%，伴隨鋼之脆化，熱疲勞壽命變得不合格。No.37之鋼中，Mn含量未滿0.05質量%，於熱疲勞試驗中產生氧化鏽皮之剝離，熱疲勞壽命不合格。No.38之鋼中，C含量超過0.020質量%，伴隨鋼中Nb量之降低，潛變斷裂時間、熱疲勞壽命均變得不合格。No.39之鋼中，N含量超過0.015質量%，伴隨由Nb氮化物之析出引起鋼中Nb量之降低，潛變斷裂時間、熱疲勞壽命變得不合格。No.40之鋼中，Sb含量超過0.50質量%，伴隨熱軋展性之降低，熱疲勞壽命變得不合格。No.41之鋼中，Mo含量超過2.50質量%，熱疲勞試驗中粗大之σ相(Fe-Cr系金屬間化合物)析出，熱疲勞壽命不合格。又，潛變斷裂時間亦不合格。No.43之鋼中，Sn含量超過0.005質量%，熱疲勞壽命不合格。No.45之鋼中，不含有Sb，潛變斷裂時間、熱疲勞壽命均不合格。No.46之鋼中，Nb含量超過0.80 質量%，潛變斷裂時間、熱疲勞壽命均不合格。No.47之鋼中，Nb+Mo含量超過3.0%，潛變斷裂時間、熱疲勞壽命均不合格。 In No.29 steel, the Nb+Mo content is less than 2.3% by mass, and the creep rupture time and thermal fatigue life are unqualified. In No. 30 steel, the Ni content exceeds 0.60 mass%, and the thermal fatigue life is unqualified. In the No. 31 steel, the Cr content is less than 18.0% by mass, and the thermal fatigue life is unqualified. In No.32 steel, the Mo content is less than 1.80% by mass, and the creep rupture time and thermal fatigue life are unqualified. In No. 33 steel, the Nb content is less than 0.30% by mass, and the creep rupture time and thermal fatigue life are all unqualified. In the No. 34 steel, the Si content is less than 0.1% by mass, and oxidation is notably found in any of the creep test and thermal fatigue test, and the creep rupture time and thermal fatigue life are all unqualified. In No. 35 steel, the Ti content exceeds 0.16 mass%, and the creep rupture time and thermal fatigue life are all unqualified. In the No. 36 steel, the Cr content exceeds 20.0% by mass, and the thermal fatigue life becomes unacceptable due to the embrittlement of the steel. In No. 37 steel, the Mn content is less than 0.05% by mass, and peeling of oxide scale occurred in the thermal fatigue test, and the thermal fatigue life was unqualified. In the No. 38 steel, the C content exceeds 0.020% by mass. As the amount of Nb in the steel decreases, the creep rupture time and thermal fatigue life become unacceptable. In the steel of No. 39, the N content exceeds 0.015 mass%. As the Nb content in the steel decreases due to the precipitation of Nb nitrides, the creep rupture time and thermal fatigue life become unacceptable. In the steel of No. 40, the Sb content exceeds 0.50% by mass, and the thermal fatigue life becomes unacceptable due to the decrease in hot rolling ductility. In No.41 steel, the Mo content exceeds 2.50% by mass, the coarse σ phase (Fe-Cr series intermetallic compound) precipitates in the thermal fatigue test, and the thermal fatigue life is unqualified. In addition, the creep rupture time is also unqualified. In No. 43 steel, the Sn content exceeds 0.005 mass%, and the thermal fatigue life is unqualified. No.45 steel does not contain Sb, and the creep rupture time and thermal fatigue life are all unqualified. In No.46 steel, the Nb content exceeds 0.80 Mass%, creep rupture time and thermal fatigue life are all unqualified. In No.47 steel, the Nb+Mo content exceeds 3.0%, and the creep rupture time and thermal fatigue life are all unqualified.

(產業上之可利用性) (Industrial availability)

本發明之肥粒鐵系不鏽鋼不僅適宜作為汽車等之排氣系統構件用，亦可適宜用作要求相同特性之火力發電系統之排氣系統構件或固體氧化物類型之燃料電池用構件。 The ferrous iron-based stainless steel of the present invention is not only suitable for exhaust system components of automobiles, but also suitable for exhaust system components of thermal power generation systems requiring the same characteristics or components for solid oxide fuel cells.

Claims

一種肥粒鐵系不鏽鋼，其具有如下之成分組成，即，以質量%計，含有C：0.020%以下、Si：0.1~1.0%、Mn：0.05~0.60%、P：0.050%以下、S：0.008%以下、Ni：0.02~0.60%、Al：0.001~0.25%、Cr：18.0~20.0%、Nb：0.30~0.80%、Mo：1.80~2.50%、N：0.015%以下、Sb：0.002~0.50%，且滿足下式(1)，殘餘部包含Fe及不可避免之雜質，Nb+Mo：超過2.5%且2.73%以下...(1)(式(1)中之Nb、Mo表示各元素之含量(質量%))。 A ferrous iron-based stainless steel, which has the following composition, that is, in terms of mass%, it contains C: 0.020% or less, Si: 0.1 to 1.0%, Mn: 0.05 to 0.60%, P: 0.050% or less, and S: 0.008% or less, Ni: 0.02~0.60%, Al: 0.001~0.25%, Cr: 18.0~20.0%, Nb: 0.30~0.80%, Mo: 1.80~2.50%, N: 0.015% or less, Sb: 0.002~0.50 %, and satisfies the following formula (1), the remainder contains Fe and unavoidable impurities, Nb+Mo: more than 2.5% and 2.73% or less... (1) (Nb and Mo in formula (1) represent each element The content (mass%)).

如請求項1之肥粒鐵系不鏽鋼，其中，上述成分組成，以質量%計，進而含有選自Ti：0.01~0.16%、Zr：0.01~0.50%、Co：0.01~0.50%、B：0.0002~0.0050%、 V：0.01~1.0%、W：0.01~5.0%、Cu：0.01~0.40%、Sn：0.001~0.005%中之1種或2種以上。 For example, the ferrous iron-based stainless steel of claim 1, wherein the above-mentioned component composition is calculated by mass%, and further contains selected from Ti: 0.01~0.16%, Zr: 0.01~0.50%, Co: 0.01~0.50%, B: 0.0002 ~0.0050%, One or more of V: 0.01~1.0%, W: 0.01~5.0%, Cu: 0.01~0.40%, Sn: 0.001~0.005%.

如請求項1或2之肥粒鐵系不鏽鋼，其中，上述成分組成，以質量%計，進而含有選自Ca：0.0002~0.0050%、Mg：0.0002~0.0050%中之1種或2種。 For example, the ferrous iron-based stainless steel of claim 1 or 2, wherein the above-mentioned component composition is calculated by mass%, and further contains one or two selected from Ca: 0.0002 to 0.0050% and Mg: 0.0002 to 0.0050%.

如請求項1或2之肥粒鐵系不鏽鋼，其被用於因來自引擎之排氣而升溫至700℃以上之排氣歧管。 For example, the ferrous iron-based stainless steel of claim 1 or 2 is used in exhaust manifolds that heat up to 700°C or higher due to exhaust from the engine.

如請求項3之肥粒鐵系不鏽鋼，其被用於因來自引擎之排氣而升溫至700℃以上之排氣歧管。 Such as the ferrous iron-based stainless steel of claim 3, which is used for exhaust manifolds that heat up to 700°C or higher due to exhaust from the engine.