不锈钢固溶化现象.ppt

中華民國九十七年四月一日,不銹鋼固溶化處理概述,金屬工業研究發展中心 曾博義,Called stainless because, in the presence of air, they develop thin hard film of chromium oxide that prevents corrosion. Types: Austenitic (200 and 300 series) steels: has Cr, Ni and Mn; non- magnetic and excellent corrosion resistance. Ferritic (400 series) steels: high Cr content (up to 27%); magnetic and good corrosion resistance but less ductile than austenitic. Martensitic (400 and 500 series) steels: do not contain Ni and are hardenable through heat-treatment; are magnetic with high strength, hardness and fatigue resistance but moderate corrosion resistance. Precipitation hardening (PH) steels: contains Cr and Ni along with Cu, Al, Ti and Mo; good corrosion resistance, ductility, and high strength at high temp. Duplex structure steels: have a mix of austenite and ferrite.,Stainless Steels,Austenitic Group,CF8,CF8M,Austenitic Grades Austenitic grades are those alloys which are commonly in use for stainless applications. The austenitic grades are not magnetic. The most common austenitic alloys are iron-chromium-nickel steels and are widely known as the 300 series. The austenitic stainless steels, because of their high chromium and nickel content, are the most corrosion resistant of the stainless group providing unusually fine mechanical properties. They cannot be hardened by heat treatment, but can be hardened significantly by cold-working.,Martensitic Grades Martensitic grades were developed in order to provide a group of stainless alloys that would be corrosion resistant and hardenable by heat treating. The martensitic grades are straight chromium steels containing no nickel. They are magnetic and can be hardened by heat treating. The martensitic grades are mainly used where hardness, strength, and wear resistance are required.,Ferritic Grades Ferritic grades have been developed to provide a group of stainless steel to resist corrosion and oxidation, while being highly resistant to stress corrosion cracking. These steels are magnetic but cannot be hardened or strengthened by heat treatment. They can be cold worked and softened by annealing. As a group, they are more corrosive resistant than the martensitic grades, but generally inferior to the austenitic grades. Like martensitic grades,these are straight chromium steels with no nickel. They are used for decorative trim-sinks, and automotive applications, particularly exhaust systems.,各系不銹鋼之特性,資料來源:日本TOYO,資料來源:日本TOYO,304及316系不銹鋼之特性,,,CF8,CF8M,Nickel— to stabilize the austenitic structure, improve forming properties, increase ductility, high temperature strength and corrosion resistance (particularly in industrial and marine atmospheres, chemical, food and textile processing industries).2. Silicon— to increase scaling resistance and resist carburizing at high temperatures.3. Manganese— to improve hot working properties, increase yield and tensile strengths (above 2%), partially replace nickel and stabilize the austenitic structure.,合金元素對不銹鋼之影響,4. Molybdenum— to increase corrosion resistance (particularly in sulfite, sulfate, acetic acid and acetate solutions and salt water atmosphere), increase creep resistance, increase strength at elevated temperatures, expand range of passivity and counteract tendency to pit.5. Titanium, Columbium-Tantalum— to prevent inter-granular corrosion by stabilizing the carbon as titanium or columbium carbides instead of chromium carbides, produce finer grain size, reduce stretcher strains from drawing and forming in Type 430.,合金元素對不銹鋼之影響,6. Sulphur, Phosphorus and Selenium—to improve machinability.7. Additional Chromium— to increase scaling, wear and corrosion resistance and increase tensile strength.,合金元素對不銹鋼之影響,固溶化熱處理的目的及方法,沃斯田鐵系不銹鋼目的:固溶Cr碳化物,除去內部應力,獲得耐蝕性最好之狀態.方法:進行固溶化處理(solution treatment),亦即加熱至鋼的合金成份可溶解於固溶體的溫度以上,保持充份時間,其後急冷,阻止碳化物之析出.例:SUS 304系(CF8)1.加熱時間:約1050℃2.保持時間:每厚25mm ,1小時3.冷卻:急冷至常溫,在900~500 ℃的區域,Cr碳化物易析出於晶界,所以此溫度範圍要急冷.,Heat Treatment,All castings shall receive a heat treatment at the temperature specified in Table 1, followed by a quench in water or rapid cool by other means except as noted.,,CF8M(SUS316), solution treated , water quenched,CF8(SUS304), As cast,CF8(SUS304), As-cast,CF8(SUS304), Solution treated,CF8M(SUS316) Solution treated, water quenched, sensitized,ASTM A262-02a,,,,,,段狀腐蝕,混合型腐蝕,槽狀腐蝕,島狀肥粒鐵 邊界腐蝕,樹支狀腐蝕,孔蝕型態I,孔蝕型態II,Observed in castings and welds.,,,,,,簡報結束 敬請指正,。