【摘要】：本文以SWRS82B珠光體鋼為研究對(duì)象,首先采用膨脹法和金相法繪制了實(shí)驗(yàn)SWRS82B珠光體鋼等溫轉(zhuǎn)變TTT曲線,研究了珠光體轉(zhuǎn)變動(dòng)力學(xué)相關(guān)內(nèi)容;其次,結(jié)合SWRS82B珠光體鋼等溫轉(zhuǎn)變TTT和連續(xù)冷卻CCT曲線,設(shè)定對(duì)比實(shí)驗(yàn),利用DIL-805A/D動(dòng)靜態(tài)相變儀進(jìn)行了精確的熱處理,研究了大過冷工藝的可行性;最后,采用鹽浴等溫等溫工藝替代了傳統(tǒng)鉛浴工藝,進(jìn)行了鹽浴大過冷實(shí)驗(yàn),通過OM、SEM及TEM組織形貌觀察,MTS Landmark拉伸性能試驗(yàn),Image tool軟件測(cè)量顯微組織(晶粒)尺寸,Origin軟件繪圖分析,SPSS軟件線性回歸分析等手段,全面系統(tǒng)研究了不同大過冷工藝參數(shù)下珠光體亞結(jié)構(gòu)組織及力學(xué)性能的變化,建立了珠光體微觀組織參量與力學(xué)性能及加工硬化指數(shù)之間的經(jīng)驗(yàn)性方程,并分析了三者之間的聯(lián)系,得到了以下主要結(jié)論:1)與傳統(tǒng)等溫處理相比,大過冷新工藝能明顯提高珠光體形核率,當(dāng)相對(duì)(瞬時(shí))過冷度增加250時(shí),珠光體(形核)體積提高了近50%,說明了大過冷工藝具有可行性。2)過冷溫度越低,過冷度增大,瞬時(shí)形核率提高,團(tuán)尺寸明顯細(xì)化,且易出現(xiàn)納米級(jí)滲碳體。隨過冷時(shí)間增加,團(tuán)尺寸和片層間距均增大,鐵素體和滲碳體兩相界面位錯(cuò)密度下降;而隨過冷時(shí)間進(jìn)一步延長,團(tuán)尺寸和片層間距又開始減小,珠光體亞結(jié)構(gòu)組織連續(xù)性變好,且出現(xiàn)少量下貝氏體組織。3)過冷溫度為300℃,過冷時(shí)間為3 s時(shí),珠光體團(tuán)尺寸和片層間距最小,分別為2.39μm和62.11 nm,且部分區(qū)域出現(xiàn)了55 nm左右的納米級(jí)滲碳體。力學(xué)性能主要受片層間距和團(tuán)尺寸影響,但具體還受納米級(jí)滲碳體、位錯(cuò)、亞結(jié)構(gòu)組織連續(xù)性以及下貝氏體等影響。4)大過冷工藝為300℃-3 s-550℃時(shí),珠光體亞結(jié)構(gòu)組織最細(xì)小,綜合力學(xué)性能較好,考慮到冷拉拔線材鋼絲的原材料以全珠光體鋼最佳,排除貝氏體相影響,并結(jié)合實(shí)際生產(chǎn)應(yīng)用,大過冷最優(yōu)工藝參數(shù)為300℃-3 s-550℃。5)珠光體微觀組織參量(晶粒尺寸)與力學(xué)性能及加工硬化指數(shù)的經(jīng)驗(yàn)性方程表明:抗拉強(qiáng)度和形變硬化指數(shù)主要受片層間距影響,同時(shí)受團(tuán)尺寸影響較大,幾乎不受晶粒尺寸影響;斷面收縮率主要受團(tuán)尺寸影響,較少受晶粒尺寸影響,基本不受片層間距影響。
[Abstract]:In this paper, SWRS82B pearlite steel is taken as the research object. Firstly, the isothermic transformation TTT curve of experimental SWRS82B pearlite steel is drawn by expansion method and metallographic method, and the related contents of pearlite transformation kinetics are studied. Secondly, combining the isotherm transformation TTT curve and continuous cooling CCT curve of SWRS82B pearlite steel, the comparative experiment is set, and the precise heat treatment is carried out by using DIL-805A/D dynamic and static phase transformation instrument, and the feasibility of large supercooling process is studied. Finally, the salt bath isotherm process was used instead of the traditional lead bath process, and the salt bath supercooling experiment was carried out. The microstructure (grain) size was measured by, MTS Landmark tensile property test, Image tool software through OM,SEM and TEM microstructure observation. The changes of pearlite substructure and mechanical properties under different supercooling process parameters were studied comprehensively and systematically by means of Origin software drawing analysis and SPSS software linear regression analysis. The empirical equation between microstructure parameters, mechanical properties and work hardening index of pearlite is established, and the relationship between them is analyzed. The main conclusions are as follows: 1) compared with traditional isotherm treatment, The new supercooling process can obviously improve the nucleation rate of pearlite. When the relative (instantaneous) undercooling degree increases by 250, the volume of pearlite (nucleation) increases by nearly 50%, which shows that the high supercooling process is feasible. 2) the lower the supercooling temperature, With the increase of undercooling, the instantaneous nucleation rate is increased, the cluster size is obviously refined, and nanometer cementite is easy to appear. With the increase of undercooling time, the cluster size and lamellar spacing increase, and the dislocation density at the interface between ferrite and cementite decreases. However, with the further prolongation of supercooling time, the cluster size and lamellar spacing began to decrease again, and the continuity of pearlite substructure became better, and a small amount of lower bainitic structure appeared. 3) when the undercooling temperature was 300 鈩，

本文編號(hào)：2475857