TW201522661A - Austenitic stainless steel resistant to intergranular corrosion and a method for its production - Google Patents

Austenitic stainless steel resistant to intergranular corrosion and a method for its production Download PDF

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TW201522661A
TW201522661A TW103138169A TW103138169A TW201522661A TW 201522661 A TW201522661 A TW 201522661A TW 103138169 A TW103138169 A TW 103138169A TW 103138169 A TW103138169 A TW 103138169A TW 201522661 A TW201522661 A TW 201522661A
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stainless steel
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iron
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plastic deformation
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Juho Talonen
Hannu Haenninen
Antti Forsstroem
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Outokumpu Oy
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    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • C21D8/0273—Final recrystallisation annealing
    • C—CHEMISTRY; METALLURGY
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    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/004—Heat treatment of ferrous alloys containing Cr and Ni
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/46—Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/50—Ferrous alloys, e.g. steel alloys containing chromium with nickel with titanium or zirconium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese

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  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Heat Treatment Of Steel (AREA)
  • Heat Treatment Of Sheet Steel (AREA)

Abstract

The invention relates to an austenitic stainless steel having high resistance to intergranular corrosion. For good intergranular corrosion resistance the stainless steel thermomechanically processed having the fraction of special coincidence site lattice grain boundaries in the microstructure of the stainless steel at least 60%, preferably at least 80%, contains 0.03-0.5% C, 0.01-3% Si, 0.01-20% Mn, 10-30% Cr, 0.01-8% Ni, 0.01-3% Mo, 0.01-3% Cu, 0.03-0.5% N, 0.001-0.5% Nb, 0.001-0.5% Ti, 0.001-0.5% V, the balance of Fe and inevitable impurities., in which austenitic stainless steel carbon is utilised as an austenite forming element and an austenite stabilising element and a solid solution strengthening element. The invention also relates a method for producing the austenitic stainless steel in which method thermomechanical processing consists of at least one plastic deformation stage and at least one subsequent heat treatment stage.

Description

耐晶粒間腐蝕之沃斯田鐵系不銹鋼及其製造方法 Vostian iron-based stainless steel resistant to intergranular corrosion and manufacturing method thereof

本發明係關於一種可耐受由稱為敏化(sensitization)之現象所引起之晶粒間腐蝕的沃斯田鐵系不銹鋼。根據本發明之鋼與習知沃斯田鐵系不銹鋼之不同處在於其儘管包含大量碳仍不易受到敏化及晶粒間腐蝕影響。本發明亦關於一種製造沃斯田鐵系不銹鋼之方法。 The present invention relates to a Worthfield iron-based stainless steel which can withstand intergranular corrosion caused by a phenomenon called sensitization. The steel according to the present invention differs from the conventional Worthfield iron-based stainless steel in that it is not susceptible to sensitization and intergranular corrosion despite the large amount of carbon. The invention also relates to a method of making a Worthfield iron-based stainless steel.

由於鎳的波動價格，不銹鋼工業因而發展出針對含鎳沃斯田鐵系不銹鋼之低鎳及不含鎳的替代選擇。在此等鋼中，鎳因可穩定沃斯田鐵相而係重要的合金化元素。可利用若干種合金化元素來替代鎳，例如：錳、銅、氮及碳。在此等合金化元素中，通常使用錳、銅及氮。然而，碳因有形成碳化鉻的傾向而被視為不期望的雜質。碳化鉻尤其易於在鋼的晶界處形成，其導致此等區域中鉻之耗盡。此稱為敏化的現象係在材料易於形成碳化物之溫度(通常為約600-900℃)經足夠長時間時發生。敏化可例如在焊接期間發生。敏化因會導致快速的晶粒間腐蝕侵襲而係有害的。實務上，敏化的風險阻礙了使用碳作為合金化元素。而在新型不銹鋼中，最大容許碳含量通常低於0.03重量%。 Due to the fluctuating price of nickel, the stainless steel industry has developed an alternative to low nickel and nickel free for nickel-containing Worthfield iron-based stainless steel. Among these steels, nickel is an important alloying element for stabilizing the iron phase of the Vostian. Several alloying elements can be used in place of nickel, such as manganese, copper, nitrogen, and carbon. Among these alloying elements, manganese, copper and nitrogen are usually used. However, carbon is considered to be an undesirable impurity due to its tendency to form chromium carbide. Chromium carbide is particularly prone to form at the grain boundaries of steel, which results in the depletion of chromium in these regions. This phenomenon, known as sensitization, occurs at a temperature at which the material readily forms carbides (typically about 600-900 ° C) for a sufficiently long time. Sensitization can occur, for example, during welding. Sensitization is harmful because it causes rapid intergranular corrosion. In practice, the risk of sensitization hinders the use of carbon as an alloying element. In the new stainless steel, the maximum allowable carbon content is usually less than 0.03% by weight.

一種稱為「晶界工程(grain boundary engineering)」之方 法係可用來降低材料對晶粒間腐蝕的敏感性。晶界工程涉及藉由包括在室溫下變形及隨後熱處理的熱機械處理來修飾晶界結構。晶界工程方法可涉及單一變形及熱處理、或若干個該等循環。藉由該晶界工程方法，一般無規的晶界係被高比率的特殊晶界(稱為重合位置晶格(CSL；coincidence site lattice)邊界)取代。若干專利公開案係關於沃斯田鐵系不銹鋼之晶界工程，例如，US 5817193、JP 2003-253401、EP 2112237 A1。 a method called "grain boundary engineering" The system can be used to reduce the sensitivity of materials to intergranular corrosion. Grain boundary engineering involves modifying the grain boundary structure by thermomechanical treatment including deformation at room temperature and subsequent heat treatment. The grain boundary engineering method can involve a single deformation and heat treatment, or several such cycles. By this grain boundary engineering method, a generally random grain boundary system is replaced by a high ratio of special grain boundaries (called CSL (coincidence site lattice) boundaries). A number of patent publications relate to the grain boundary engineering of the Worthfield iron-based stainless steel, for example, US Pat. No. 5,917,193, JP 2003-253401, EP 2112237 A1.

JP公開案2010-275569係關於一種具有經改良之耐晶粒間應力腐蝕龜裂性的沃斯田鐵系不銹鋼及其製造方法。該鋼具有三種類型的晶界，其中兩種類型的晶界為重合(CSL)邊界及一種類型的晶界為無規晶界。該沃斯田鐵系鋼包含0.001-0.1重量%碳、12-30重量%鎳及15-30重量%鉻。在該製造方法中，沃斯田鐵系不銹鋼在進行輥軋比為2-5%的冷軋後，在高於再結晶溫度之溫度(諸如1300K或更高(1027℃或更高))下熱處理30-180分鐘。 JP Publication No. 2010-275569 relates to a Worthfield iron-based stainless steel having improved intergranular stress corrosion cracking resistance and a method for producing the same. The steel has three types of grain boundaries, two of which are coincident (CSL) boundaries and one type of grain boundary is a random grain boundary. The Vostian iron-based steel comprises 0.001-0.1% by weight of carbon, 12-30% by weight of nickel and 15-30% by weight of chromium. In the manufacturing method, the Worthfield iron-based stainless steel is subjected to a cold rolling of 2-5% after the rolling ratio, at a temperature higher than the recrystallization temperature (such as 1300 K or higher (1027 ° C or higher)). Heat treatment for 30-180 minutes.

JP公開案2011-168819描述一種沃斯田鐵系不銹鋼及該鋼之製造方法。該鋼具有經改良的抗晶界腐蝕性及抗晶界應力腐蝕龜裂性。該鋼包含0.001-0.03重量%碳、8-30重量%鎳及15-30重量%鉻。該沃斯田鐵系不銹鋼在進行輥軋比為2-5%的冷軋後，在1200-1500K(927-1227℃)之溫度範圍內熱處理1-60分鐘，以獲致超過75%頻率的CSL晶界及40-80微米的粒度。 JP Publication No. 2011-168819 describes a Worthfield iron-based stainless steel and a method of manufacturing the same. The steel has improved resistance to intergranular corrosion and resistance to grain boundary stress corrosion cracking. The steel comprises from 0.001 to 0.03 wt% carbon, from 8 to 30 wt% nickel and from 15 to 30 wt% chromium. The Worthfield iron-based stainless steel is heat-treated at a temperature range of 1200-1500 K (927-1227 ° C) for 1-60 minutes after performing a cold rolling of 2-5% on a rolling ratio to obtain a CSL exceeding 75% of the frequency. Grain boundaries and particle sizes of 40-80 microns.

JP公開案2009-185313係關於用來製造具有相當於316型鋼之抗輻射性之鋼的沃斯田鐵系不銹鋼及製造方法。該鋼尤其包含0.04-0.08重量%碳、13.0-14.0重量%鎳及16.0-18.0重量%鉻。在該製造方法中，鋼在溶液熱處理後進行輥軋比為3%的冷軋，且隨後在 1380-1420K(1107-1147℃)之溫度範圍內熱處理3小時或更久，以達成超過80%之晶界密度。 JP Publication No. 2009-185313 relates to a Worthfield iron-based stainless steel used for producing a steel having radiation resistance equivalent to 316 steel and a method for producing the same. The steel comprises in particular 0.04-0.08 wt% carbon, 13.0-14.0 wt% nickel and 16.0-18.0 wt% chromium. In the manufacturing method, the steel is subjected to a cold rolling of a rolling ratio of 3% after the solution is heat-treated, and then Heat treatment in the temperature range of 1380-1420K (1107-1147 ° C) for 3 hours or more to achieve a grain boundary density of more than 80%.

然而，此等公開案皆非關於利用晶界工程以容許使用碳作為穩定沃斯田鐵並提供固態溶液強化之合金化元素。此等公開案皆未關於包含超過0.1重量%碳之鋼。因此，並無利用晶界工程之含高碳的沃斯田鐵系不銹鋼曾被揭示。 However, none of these publications relates to the use of grain boundary engineering to permit the use of carbon as an alloying element that stabilizes the Worth Iron and provides solid solution strengthening. None of these publications pertain to steels containing more than 0.1% by weight carbon. Therefore, the Vostian iron-based stainless steel which does not utilize the grain boundary engineering and contains high carbon has been disclosed.

本發明之目的係要防止先前技術之缺點，並製造具有良好機械性質、低合金化成本及高耐晶粒間腐蝕性之沃斯田鐵系不銹鋼。本發明亦係關於該不銹鋼之製造方法。本發明之基本特徵羅列於隨附之申請專利範圍中。 It is an object of the present invention to prevent the disadvantages of the prior art and to manufacture a Worthfield iron-based stainless steel having good mechanical properties, low alloying cost, and high resistance to intergranular corrosion. The present invention also relates to a method of producing the stainless steel. The essential features of the invention are set forth in the appended claims.

本發明係關於一種呈扁平或長形產品形式之沃斯田鐵系不銹鋼，該不銹鋼具有高強度、低合金化成本及高耐晶粒間腐蝕性。藉由根據本發明之製造方法達成該等期望性質的組合。 The present invention relates to a Worthfield iron-based stainless steel in the form of a flat or elongated product having high strength, low alloying cost and high resistance to intergranular corrosion. A combination of these desirable properties is achieved by the manufacturing method according to the invention.

根據本發明，該不銹鋼係包含0.03-0.5重量% C、0.01-3重量% Si、0.01-20重量% Mn、10-30重量% Cr、0.01-8重量% Ni、0.01-3重量% Mo、0.01-3重量% Cu、0.03-0.5重量% N、0.001-0.5重量% Nb、0.001-0.5重量% Ti、0.001-0.5重量% V、其餘為Fe及無可避免之雜質的沃斯田鐵系不銹鋼。 According to the invention, the stainless steel comprises 0.03-0.5% by weight C, 0.01-3% by weight Si, 0.01-20% by weight Mn, 10-30% by weight Cr, 0.01-8% by weight Ni, 0.01-3% by weight Mo, 0.01-3 wt% Cu, 0.03-0.5 wt% N, 0.001-0.5 wt% Nb, 0.001-0.5 wt% Ti, 0.001-0.5 wt% V, the balance of Fe and the inevitable impurities of the Worthite iron system stainless steel.

根據本發明之方法加工的不銹鋼係有利地呈扁平或長形產品形式，諸如板材、片材、條材、捲材、棒材、桿材或線材。 The stainless steel processed in accordance with the method of the present invention is advantageously in the form of a flat or elongated product such as a sheet, sheet, strip, coil, rod, rod or wire.

根據本發明之不銹鋼及其製造方法係基於利用晶界工程來修飾鋼的晶界結構。根據本發明，不銹鋼之晶界結構係藉由以至少一個塑性變形階段(較佳例如冷軋或拉伸應變)及至少一個後續之熱 處理階段所組成的至少一個熱機械加工來修飾。熱機械加工可重複若干次。於熱機械加工階段後，達成超過至少60%，及較佳至少80%之在不銹鋼微結構中之期望比率的特殊晶界。根據本發明之熱機械加工包含至少一個變形階段及至少一個後續的熱處理步驟。於單一變形階段中之變形程度視待處理不銹鋼之化學組成而定在0.1-40%之範圍內。後續熱處理係在800-1200℃之溫度範圍內進行，此處理之時間視先前變形程度及待處理不銹鋼之化學組成而定為1秒至72小時。當使用超過一個變形階段時，亦進行相等數目的後續熱處理階段。如熱機械加工係由一個變形階段及一個熱處理組成，則變形程度通常相當低，在0.1-10%左右，較佳1-6%，且後續熱處理係在所指示溫度範圍之較低區間及在所指示時間範圍之較高區間內進行。如熱機械加工係由若干個變形階段及熱處理組成，則單一變形階段期間之變形程度通常較高，熱處理溫度較高且熱處理期間較短。在兩個或更多個熱機械加工中之變形程度及各別的熱處理條件係相同，或在兩個或更多個熱機械加工中之縮減程度及各別的熱處理條件係彼此不同。 The stainless steel according to the present invention and its method of manufacture are based on the use of grain boundary engineering to modify the grain boundary structure of steel. According to the invention, the grain boundary structure of the stainless steel is obtained by at least one plastic deformation stage (preferably, for example, cold rolling or tensile strain) and at least one subsequent heat At least one thermomechanical process consisting of a processing stage is modified. Thermomechanical processing can be repeated several times. After the thermomechanical processing stage, a particular grain boundary exceeding at least 60%, and preferably at least 80%, of the desired ratio in the stainless steel microstructure is achieved. The thermomechanical processing according to the invention comprises at least one deformation stage and at least one subsequent heat treatment step. The degree of deformation in the single deformation stage is determined to be in the range of 0.1 to 40% depending on the chemical composition of the stainless steel to be treated. The subsequent heat treatment is carried out at a temperature ranging from 800 to 1200 ° C, and the treatment time is from 1 second to 72 hours depending on the degree of deformation and the chemical composition of the stainless steel to be treated. When more than one deformation stage is used, an equal number of subsequent heat treatment stages are also performed. If the thermomechanical processing system consists of a deformation stage and a heat treatment, the degree of deformation is usually quite low, about 0.1-10%, preferably 1-6%, and the subsequent heat treatment is in the lower range of the indicated temperature range and Performed within the higher interval of the indicated time range. If the thermomechanical processing system consists of several deformation stages and heat treatment, the degree of deformation during the single deformation stage is usually higher, the heat treatment temperature is higher and the heat treatment period is shorter. The degree of deformation in the two or more thermomechanical processes and the respective heat treatment conditions are the same, or the degree of reduction in the two or more thermomechanical processes and the respective heat treatment conditions are different from each other.

根據本發明之熱化學加工使得可利用碳作為沃斯田鐵穩定及沃斯田鐵形成元素，及利用碳作為提供固態溶液強化之合金化元素。因此，該不銹鋼包含0.03-0.5%碳(C)，較佳0.1-0.5%碳(C)。此高含量之碳由於兩項主要理由而有利：碳改良鋼之機械性質，且碳亦係使得能夠使用較少昂貴鎳之具成本效益的沃斯田鐵穩定元素。另一額外利益係在不銹鋼中容許較高碳含量可例如在成本高昂的氬-氧脫碳(AOD)製程中縮短製程時間，且亦能夠使用含碳鐵錳作為亦被利用作為具成本效益之沃斯田鐵形成元素之錳的來源。 The thermochemical processing according to the present invention makes it possible to utilize carbon as a Worstian iron stabilized and Worth iron forming element, and carbon as an alloying element for providing solid solution strengthening. Therefore, the stainless steel contains 0.03-0.5% carbon (C), preferably 0.1-0.5% carbon (C). This high level of carbon is advantageous for two main reasons: the mechanical properties of carbon-modified steel, and the carbon is also a cost-effective Worstian iron stabilizing element that enables the use of less expensive nickel. Another additional benefit is that allowing higher carbon content in stainless steel can, for example, shorten process times in costly argon-oxygen decarburization (AOD) processes, and can also be used as carbon-manganese as a cost-effective Worth Iron forms a source of manganese for the elements.

根據本發明之不銹鋼係有利地透過尤其包括在電弧爐 中熔融、AOD(氬氧脫碳)轉爐處理及澆斗處理、連續澆鑄、熱軋、可能的冷軋、退火及酸浸之習知的不銹鋼製程途徑來製得。於習知的例如藉由熱軋、冷軋、拉製、擠壓、鍛造將不銹鋼加工為扁平或長形製造產品後，藉由根據本發明之變形及後續熱處理將材料進行熱機械加工，以修飾不銹鋼之晶界結構。 The stainless steel according to the invention is advantageously permeated, inter alia, in an electric arc furnace Medium melting, AOD (argon oxygen decarburization) converter treatment and bucket processing, continuous casting, hot rolling, possible cold rolling, annealing and acid leaching of the conventional stainless steel process route. After the stainless steel is processed into a flat or elongated product by, for example, hot rolling, cold rolling, drawing, extrusion, forging, the material is thermomechanically processed by deformation according to the present invention and subsequent heat treatment. Modification of the grain boundary structure of stainless steel.

本發明參照以下圖式更詳細說明，其中圖1a顯示習知不銹鋼之微結構，圖1b顯示根據本發明之不銹鋼的微結構，圖2顯示習知不銹鋼及根據本發明之不銹鋼在Streicher試驗中在非敏化及敏化狀態中之腐蝕速率，圖3a顯示習知不銹鋼於Streicher試驗後之表面的掃描電子顯微鏡影像，及圖3b顯示根據本發明之不銹鋼於Streicher試驗後之表面的掃描電子顯微鏡影像。 The invention is illustrated in more detail with reference to the following figures, in which Figure 1a shows the microstructure of a conventional stainless steel, Figure 1b shows the microstructure of a stainless steel according to the invention, and Figure 2 shows a conventional stainless steel and a stainless steel according to the invention in a Streicher test. The corrosion rate in the non-sensitized and sensitized state, FIG. 3a shows a scanning electron microscope image of a surface of a conventional stainless steel after the Streicher test, and FIG. 3b shows a scanning electron microscope image of the surface of the stainless steel according to the present invention after the Streicher test. .

藉由進行各種冷軋及熱處理實驗來測試本發明之不銹鋼。未經任何熱機械加工之習知沃斯田鐵系不銹鋼的微結構實例顯示於圖1a中，及由縮減程度1%之冷軋及於947℃溫度下24小時之後續熱處理所組成之熱機械加工後之根據本發明之不銹鋼顯示於圖1b中。期望的特殊晶界以淺灰色顯示及無規晶界以深灰色顯示於圖1a及圖1b中。在根據本發明之不銹鋼中，期望特殊晶界之比率為82%，相較於習知鋼僅38%。 The stainless steel of the present invention was tested by performing various cold rolling and heat treatment experiments. A conventional example of the microstructure of a Worthian iron-based stainless steel without any thermomechanical processing is shown in Figure 1a, and a thermomechanical consisting of a 1% cold rolling reduction and a 24 hour subsequent heat treatment at 947 °C. The stainless steel according to the invention after processing is shown in Figure 1b. The desired special grain boundaries are shown in light gray and the random grain boundaries are shown in dark gray in Figures 1a and 1b. In the stainless steel according to the present invention, the ratio of the special grain boundary is expected to be 82%, which is only 38% compared to the conventional steel.

習知不銹鋼及根據本發明之不銹鋼的耐晶粒間腐蝕性 於圖2中比較。圖2呈現Streicher試驗(根據標準ASTM A262-85實務B)之結果。根據此腐蝕速率試驗，使材料於含有50%硫酸及25克硫酸鐵狀態之1公升錐形瓶中沸騰120小時，以確定材料中的敏化作用。敏化作用的量度係由於晶粒間腐蝕所致的重量損失，其係藉由測量間隔24小時的樣品重量來測定。圖2中呈現非敏化及敏化不銹鋼之結果。敏化測試樣品係藉由於745℃下30分鐘之熱處理來敏化。根據本發明之不銹鋼在敏化及非敏化狀態中皆明顯表現優於習知不銹鋼。在敏化狀態中，習知不銹鋼中的晶粒間腐蝕侵襲相當嚴重，以致樣品在樣品的初次稱重之前完全溶解。 Conventional stainless steel and intergranular corrosion resistance of stainless steel according to the invention Compare in Figure 2. Figure 2 presents the results of the Streicher test (according to standard ASTM A 262-85 Practice B). According to this corrosion rate test, the material was boiled in a 1 liter Erlenmeyer flask containing 50% sulfuric acid and 25 grams of ferric sulfate for 120 hours to determine the sensitization in the material. The measure of sensitization is the weight loss due to intergranular corrosion, which is determined by measuring the weight of the sample at intervals of 24 hours. The results of non-sensitized and sensitized stainless steel are presented in Figure 2. The sensitized test samples were sensitized by heat treatment at 745 ° C for 30 minutes. The stainless steel according to the present invention clearly outperforms conventional stainless steel in both sensitized and non-sensitized states. In the sensitized state, the intergranular corrosion attack in the conventional stainless steel is so severe that the sample is completely dissolved before the initial weighing of the sample.

習知不銹鋼(圖3a)及根據本發明之不銹鋼(圖3b)於暴露至Streicher試驗120小時後之表面顯示於圖3a及圖3b中。此等樣品在試驗之前未敏化。然而，可見習知不銹鋼在晶界處明顯地受到侵蝕，而根據本發明經熱機械加工之不銹鋼則未見腐蝕侵襲之跡象。 The surface of the conventional stainless steel (Fig. 3a) and the stainless steel according to the invention (Fig. 3b) after 120 hours of exposure to the Streicher test is shown in Figures 3a and 3b. These samples were not sensitized prior to testing. However, it is seen that conventional stainless steels are significantly eroded at the grain boundaries, while stainless steels that have been thermomechanically processed according to the present invention show no signs of corrosion attack.

Claims (15)

一種具有高耐晶粒間腐蝕性之沃斯田鐵系不銹鋼，其特徵在於為獲得良好的耐晶粒間腐蝕性，該不銹鋼經熱機械加工成具有至少60%、較佳至少80%之在不銹鋼微結構中之特殊重合位置晶格晶界之比率，其包含0.03-0.5重量% C、0.01-3重量% Si、0.01-20重量% Mn、10-30重量% Cr、0.01-8重量% Ni、0.01-3重量% Mo、0.01-3重量% Cu、0.03-0.5重量% N、0.001-0.5重量% Nb、0.001-0.5重量% Ti、0.001-0.5重量% V、其餘為Fe及無可避免之雜質，在該沃斯田鐵系不銹鋼中，利用碳作為沃斯田鐵形成元素及沃斯田鐵穩定元素及固態溶液強化元素。 A Worthfield iron-based stainless steel having high intergranular corrosion resistance, characterized in that the stainless steel is thermomechanically processed to have at least 60%, preferably at least 80%, in order to obtain good intergranular corrosion resistance. Ratio of special coincident position lattice grain boundaries in the microstructure of stainless steel, which comprises 0.03 - 0.5 wt% C, 0.01 - 3 wt% Si, 0.01 - 20 wt% Mn, 10 - 30 wt% Cr, 0.01 - 8 wt% Ni, 0.01-3 wt% Mo, 0.01-3 wt% Cu, 0.03-0.5 wt% N, 0.001-0.5 wt% Nb, 0.001-0.5 wt% Ti, 0.001-0.5 wt% V, the balance is Fe and none To avoid impurities, in the Worthfield iron-based stainless steel, carbon is used as a Worthite iron forming element and a Worstian iron stabilizing element and a solid solution strengthening element. 如申請專利範圍第1項之沃斯田鐵系不銹鋼，其中，該不銹鋼包含0.1-0.5%碳。 The Vostian iron-based stainless steel of claim 1, wherein the stainless steel contains 0.1-0.5% carbon. 如申請專利範圍第1或2項之沃斯田鐵系不銹鋼，其中，該不銹鋼係呈扁平或長形產品形式。 For example, the Vostian iron-based stainless steel of claim 1 or 2, wherein the stainless steel is in the form of a flat or elongated product. 如申請專利範圍第3項之沃斯田鐵系不銹鋼，其中，該不銹鋼係呈板材、片材、條材、捲材、棒材、桿材或線材形式。 For example, the Vostian iron-based stainless steel of claim 3, wherein the stainless steel is in the form of a sheet, a sheet, a strip, a coil, a rod, a rod or a wire. 如申請專利範圍第1至4項中任一項之沃斯田鐵系不銹鋼，其中，該熱機械加工係由至少一個塑性變形階段及至少一個後續的熱處理階段所組成。 The Vostian iron-based stainless steel according to any one of claims 1 to 4, wherein the thermomechanical processing system consists of at least one plastic deformation stage and at least one subsequent heat treatment stage. 一種用於製造具有高耐晶粒間腐蝕性之沃斯田鐵系不銹鋼之方法，其特徵在於針對沃斯田鐵系不銹鋼進行熱機械加工，以獲致至少60%、較佳至少80%之在不銹鋼微結構中之特殊重合位置晶格晶界之比率，該沃斯田鐵系不銹鋼包含0.03-0.5重量% C、0.01-3重量% Si、0.01-20重量% Mn、10-30重量% Cr、0.01-8重量% Ni、0.01-3重量% Mo、0.01-3重量% Cu、0.03-0.5重量% N、0.001-0.5重量% Nb、0.001-0.5重量% Ti、0.001-0.5重量% V、其餘為Fe及無可避免之雜質，呈扁平或長形產品形式。 A method for producing a Worthfield iron-based stainless steel having high resistance to intergranular corrosion, characterized in that it is thermomechanically processed for a Worthfield iron-based stainless steel to obtain at least 60%, preferably at least 80% The ratio of the special coincident position lattice grain boundary in the stainless steel microstructure, the Vostian iron-based stainless steel contains 0.03-0.5% by weight C, 0.01-3% by weight Si, 0.01-20% by weight Mn, 10-30% by weight Cr , 0.01-8 wt% Ni, 0.01-3 wt% Mo, 0.01-3 wt% Cu, 0.03-0.5 wt% N, 0.001-0.5 wt% Nb, 0.001-0.5 wt% Ti, 0.001-0.5 wt% V, the balance being Fe and inevitable impurities, flat or Long product form. 如申請專利範圍第6項之方法，其中，該熱機械加工係由至少一個塑性變形階段及至少一個後續的熱處理階段所組成。 The method of claim 6, wherein the thermomechanical processing consists of at least one plastic deformation stage and at least one subsequent heat treatment stage. 如申請專利範圍第6或7項之方法，其中，該塑性變形階段係冷軋階段。 The method of claim 6 or 7, wherein the plastic deformation stage is a cold rolling stage. 如申請專利範圍第6或7項之方法，其中，該塑性變形階段係拉伸應變階段。 The method of claim 6 or 7, wherein the plastic deformation stage is a tensile strain stage. 如申請專利範圍第6至9項中任一項之方法，其中，該塑性變形階段中之變形程度係0.1至40%。 The method of any one of claims 6 to 9, wherein the degree of deformation in the plastic deformation stage is 0.1 to 40%. 如申請專利範圍第10項之方法，其中，該塑性變形階段中之變形程度係0.1至10%。 The method of claim 10, wherein the degree of deformation in the plastic deformation stage is 0.1 to 10%. 如申請專利範圍第10項之方法，其中，該塑性變形階段中之變形程度係1至6%。 The method of claim 10, wherein the degree of deformation in the plastic deformation stage is 1 to 6%. 如申請專利範圍第6至12項中任一項之方法，其中，在塑性變形階段之後的該熱處理階段係在800至1200℃之溫度範圍內進行1秒至72小時。 The method of any one of claims 6 to 12, wherein the heat treatment stage after the plastic deformation stage is carried out at a temperature ranging from 800 to 1200 ° C for from 1 second to 72 hours. 如申請專利範圍第6至13項中任一項之方法，其中，在兩個或更多個熱機械加工中之變形程度及各別的熱處理條件係相同。 The method of any one of claims 6 to 13, wherein the degree of deformation and the respective heat treatment conditions in the two or more thermomechanical processes are the same. 如申請專利範圍第6至13項中任一項之方法，其中，在兩個或更多個熱機械加工中之縮減程度及各別的熱處理條件係彼此不同。 The method of any one of claims 6 to 13, wherein the degree of reduction in the two or more thermomechanical processes and the respective heat treatment conditions are different from each other.
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