【摘要】：雙相不銹鋼由鐵素體(δ)和奧氏體(γ)兩相組成,兼有鐵素體不銹鋼和奧氏體不銹鋼的優(yōu)點(diǎn),具有優(yōu)良的力學(xué)和耐蝕的綜合性能,目前被廣泛應(yīng)用于石油化工、海洋、造紙和能源等行業(yè),在石油化工、造紙、食品加工等行業(yè)雙相不銹鋼需要在高溫環(huán)境下服役,而雙相不銹鋼中加入較多的合金元素,在500-1000℃下等溫過(guò)程中易產(chǎn)生σ相、氮化物、χ相等金屬間相,對(duì)材料的沖擊韌性和耐腐蝕性能有很大影響。鎳在雙相不銹鋼中大量使用增加了成本,本文嘗試用低成本的錳代替鎳,研究錳對(duì)22%Cr雙相不銹鋼時(shí)效析出行為的影響,為節(jié)鎳型雙相不銹鋼的開發(fā)以及高溫環(huán)境下加工和使用提供參考。本論文從合金元素和時(shí)效溫度對(duì)22%Cr雙相不銹鋼的組織和力學(xué)性能進(jìn)行了系統(tǒng)的研究。采用光學(xué)顯微鏡(OM)、X射線衍射(XRD)、掃描電鏡(SEM)、透射電鏡(TEM)、析出動(dòng)力學(xué)和夏比沖擊試驗(yàn)等分析儀器和手段,重點(diǎn)研究了 Mn對(duì)雙相不銹鋼500℃、600℃、700℃和800℃時(shí)效不同時(shí)間的析出行為的影響。本文主要研究結(jié)果如下:固溶處理結(jié)果表明:固溶溫度從1040℃、1120℃升至1220℃,22%Cr雙相不銹鋼奧氏體相比例減小,沖擊韌性下降,固溶溫度1040℃時(shí),實(shí)驗(yàn)鋼兩相比例較均衡,沖擊韌性較好。時(shí)效析出行為研究結(jié)果表明:雙相不銹鋼時(shí)效析出行為主要發(fā)生在δ/γ晶界上和δ相內(nèi),時(shí)效溫度升高可促進(jìn)析出行為,不同時(shí)效溫度析出相類型也不同:500℃時(shí)效溫度下,析出相主要是為針狀相和χ相,針狀相隨時(shí)效時(shí)間延長(zhǎng)變得細(xì)小,最后完全轉(zhuǎn)化為塊狀χ相;600℃時(shí)效溫度下,析出相主要是χ相、σ相和γ2相,析出機(jī)制為:δ→2 + σ(χ),細(xì)小的χ相在晶界處最先析出,γ2相和σ相共析狀析出相隨后析出;700℃和800℃時(shí)效溫度下,析出相主要是γ2相、σ相和M23C6碳化物,按照δ→γ2+ M23C6和δ→γ2 + σ的機(jī)制析出。錳元素對(duì)χ相和σ相的析出均有促進(jìn)作用:500℃時(shí)效溫度下,實(shí)驗(yàn)鋼錳含量增加,χ相中錳含量遞增,鉬含量遞減,錳原子替代鉬原子改變了 χ相的晶格常數(shù)導(dǎo)致χ相與鐵素體共格,使χ相可在500℃時(shí)效溫度下大量析出并穩(wěn)定存在;600℃時(shí)效溫度下,χ相錳含量較低,錳元素更易富集于σ相中,促進(jìn)σ相析出;700℃和800℃時(shí)效溫度下,實(shí)驗(yàn)鋼錳含量越高,M23C6碳化物析出越早,σ相析出提前,σ相最大析出量也越大。析出動(dòng)力學(xué)結(jié)合沖擊實(shí)驗(yàn)分析結(jié)果表明:錳含量和時(shí)效溫度都會(huì)影響δ相分解動(dòng)力學(xué)參數(shù)。相同時(shí)效溫度下,錳含量增加,反應(yīng)常數(shù)k和時(shí)間指數(shù)n均增大,δ相分解時(shí)間提前,分解速率加快;相同成分下,隨著時(shí)效溫度增加,k值顯著增大,時(shí)效溫度從600℃增至800℃,δ相分解時(shí)間提前。少量δ相分解對(duì)試樣沖擊韌性影響不大,δ相分解體積分?jǐn)?shù)超過(guò)3%會(huì)導(dǎo)致試樣的沖擊韌性迅速降低。時(shí)效初期δ相分解數(shù)量較少,沖擊韌性主要受雙相不銹鋼兩相組織的影響,錳含量較高的試樣奧氏體相比例較大,沖擊韌性較好;時(shí)效中后期,試樣韌性主要受σ相影響,錳含量較高的試樣σ相數(shù)量更多,沖擊韌性較差。
[Abstract]:The duplex stainless steel consists of two phases of ferrite and austenitic stainless steel, has the advantages of ferrite stainless steel and austenitic stainless steel, has excellent mechanical and corrosion-resistant comprehensive performance, and is widely used in the fields of petrochemical, ocean, paper and energy, in that proces of petrochemical, paper and food processing, the two-phase stainless steel needs to service in a high-temperature environment, and the two-phase stainless steel is added with more alloy elements, The impact toughness and the corrosion resistance of the material can be greatly affected. In this paper, the effect of manganese on the aging and precipitation behavior of 22% Cr duplex stainless steel is studied by using low-cost manganese instead of nickel, and the reference is provided for the development of the nickel-type duplex stainless steel and the processing and use in high-temperature environment. The microstructure and mechanical properties of 22% Cr duplex stainless steel were studied in this paper. The analytical instruments and methods such as optical microscope (OM), X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), precipitation kinetics and Charpy impact test were used. The effects of Mn on the precipitation behavior of two-phase stainless steel 500 鈩，

本文編號(hào)：2503518