本文選題：馬氏體不銹鋼 + 電渣重熔��； 參考：《北京科技大學(xué)》2016年博士論文

【摘要】：國產(chǎn)刀剪在鋒利度、耐磨性、使用壽命等方面與進(jìn)口刀剪相比還存在明顯差距,而且國內(nèi)的有關(guān)研究,特別是高碳刀剪材料的研究,還比較有限。因此,本文以刀剪用高碳馬氏體不銹鋼7Cr17MoV為研究對象,針對其在生產(chǎn)過程中組織、碳化物及性能的演變開展模擬計算及實驗研究,以期為高品質(zhì)馬氏體不銹鋼刀剪材料的生產(chǎn)和應(yīng)用提供合理依據(jù)和指導(dǎo)。論文的主要研究內(nèi)容和結(jié)論如下：利用Thermo-calc軟件計算分析了7Cr17MoV不銹鋼凝固過程中各相的析出規(guī)律和演變行為,得到含鉻量為17%的Fe-C平衡相圖。隨著凝固的進(jìn)行,鐵素體、奧氏體、碳化物等各相中的元素含量不斷發(fā)生變化。M7C3碳化物從奧氏體中脫溶析出,隨后向M23C6碳化物轉(zhuǎn)變,碳化物中Cr含量不斷增加。7Cr17MoV不銹鋼平衡凝固過程最終組織為87%的鐵素體和13%的M23C6碳化物。通過電渣重熔7Cr17MoV不銹鋼實驗研究發(fā)現(xiàn),電渣重熔后,基體組織由馬氏體和網(wǎng)狀碳化物轉(zhuǎn)變?yōu)轳R氏體、殘余奧氏體和離散分布的碳化物,碳化物的形貌和分布獲得有效改善。通過調(diào)整渣系組成和渣量,提高了材料中夾雜物的去除效率。采用Gleeble-3500熱模擬試驗機(jī),研究了7Cr17MoV不銹鋼的熱壓縮變形行為。結(jié)果表明：隨著應(yīng)變的增加,應(yīng)力首先迅速增加,隨后緩慢增加,達(dá)到峰值后,緩慢下降趨于平穩(wěn)。高的變形溫度和低的應(yīng)變速率有利于動態(tài)再結(jié)晶的發(fā)生,峰值應(yīng)力隨著應(yīng)變速率的降低和變形溫度的增加而減小。隨著變形溫度的升高、變形速率的減小和冷卻速度的增加,材料的微觀組織細(xì)化。同時,建立了材料熱變形時的流變應(yīng)力本構(gòu)方程。軋制對7Cr17MoV中組織、碳化物及性能的影響研究表明,7Cr17MoV鋼軋制退火組織為珠光體和碳化物,熱軋板材中碳化物有明顯偏聚現(xiàn)象,冷軋后板材組織變得更加均勻和細(xì)化,碳化物偏聚現(xiàn)象明顯減輕。隨著冷軋厚度的減小,碳化物尺寸減小,數(shù)量增加,分布更加均勻。軋制不改變碳化物的類型。隨著冷軋厚度的減小,7Cr17MoV的抗拉強(qiáng)度和屈服強(qiáng)度先降低后增加,斷后延伸率顯著增加。拉伸斷口處可見韌窩和第二相粒子,第二相粒子主要是碳化物和氧化物夾雜。對7Cr17MoV不銹鋼冷軋薄帶熱處理的研究結(jié)果表明：隨著淬火溫度的升高,馬氏體長大,殘余奧氏體含量增加,未溶碳化物減少,材料硬度增加,耐蝕性能增加。當(dāng)淬火溫度增加到1150℃時,材料硬度下降明顯,耐蝕性能下降。淬火保溫時間對材料的組織性能影響較小。隨著回火溫度的升高,組織中殘余奧氏體分解,碳化物析出,材料硬度降低,抗拉強(qiáng)度下降,斷后延伸率先增加后降低,最終得出材料最優(yōu)熱處理工藝為：淬火溫度1050℃-1100℃,保溫時間大于15 min,隨后在200℃-250℃回火,材料的綜合性能最優(yōu)。熱處理后,材料的硬度值大于55 HRC,抗拉強(qiáng)度大于1800 MPa,規(guī)定塑性延伸強(qiáng)度大于1400MPa,斷后延伸率大于4%,自腐蝕電位大于-0.25 V,自腐蝕電流小于2.0×10-8 A/cm2。
[Abstract]:There is a significant difference in the sharpness, wear resistance and service life of the domestic knives and scissors compared with the imported knives and scissors, and the domestic research, especially the high carbon knife and scissors, is still relatively limited. Therefore, the high carbon martensitic stainless steel 7Cr17MoV is used as the research object in this paper, and the carbide and the carbide are organized in the process of production. The simulation calculation and experimental study are carried out to provide reasonable basis and guidance for the production and application of high quality martensitic stainless steel knife and scissors. The main contents and conclusions of this paper are as follows: the Precipitation Law and evolution behavior of each phase in the solidification process of 7Cr17MoV stainless steel are calculated and analyzed by Thermo-calc software. To the Fe-C equilibrium phase diagram with a chromium content of 17%, the content of elements in each phase of ferrite, austenite, carbide and so on is constantly changing with the solidification..M7C3 carbides are dissoluble from austenite, and then to M23C6 carbides, and the content of Cr in the carbides continuously increases the final microstructure of the.7Cr17MoV stainless steel in the equilibrium solidification process of 87% iron. Through the experimental study on the remelting of 7Cr17MoV stainless steel by electroslag remelting, it is found that the matrix microstructure is transformed from martensite and reticulate carbide to martensite, residual austenite and dispersed carbide, the morphology and distribution of carbides are effectively modified after remelting of electroslag remelting, and the material is improved by adjusting the composition of slag system and the amount of slag. The thermal compression deformation behavior of 7Cr17MoV stainless steel was studied by Gleeble-3500 thermal simulation test machine. The results showed that with the increase of strain, the stress first increased rapidly, and then slowly increased, after reaching the peak, the slow descent tended to be stable. The high deformation temperature and low strain rate were beneficial to the dynamic re junction. The peak stress decreases with the decrease of the strain rate and the increase of the deformation temperature. With the increase of the deformation temperature, the decrease of the deformation rate and the increase of the cooling rate, the microstructure of the material is refined. At the same time, the constitutive formula of the rheological stress in the thermal deformation of the material is established. The rolling of the microstructure, carbides and properties in 7Cr17MoV The study shows that the microstructure of 7Cr17MoV steel annealed is pearlite and carbide, and the carbide has obvious segregation phenomenon in hot rolled sheet. The structure of the plate becomes more uniform and refined after cold rolling, and the segregation phenomenon of carbide decreases obviously. With the decrease of the cold rolling thickness, the size of carbide decreases, the quantity is increased and the distribution is more uniform. Rolling is not changed. The type of carbide. With the decrease of the cold rolling thickness, the tensile strength and yield strength of 7Cr17MoV first decrease and then increase, and the elongation after fracture increases significantly. The second phase particles are mainly carbide and oxide inclusions at the tensile fracture. The results of the study on the heat treatment of the cold rolled strip of 7Cr17MoV stainless steel show that: As the quenching temperature increases, the martensite grows, the retained austenite content increases, the undissolved carbide decreases, the material hardness increases, and the corrosion resistance increases. When the quenching temperature increases to 1150 C, the hardness of the material decreases obviously and the corrosion resistance decreases. The heat preservation time has little effect on the fabric properties. With the increase of tempering temperature, the microstructure of the material is increased. The residual austenite decomposition, carbide precipitation, material hardness and tensile strength decrease, the elongation after fracture first increases and then decreases. Finally, the optimum heat treatment process of material is: quenching temperature 1050 -1100 C, heat preservation time greater than 15 min, and then tempering at 200 c -250 C, the material has the best comprehensive performance. After heat treatment, the hardness value of the material More than 55 HRC, tensile strength is greater than 1800 MPa, the specified plastic extension strength is greater than 1400MPa, the elongation after fracture is more than 4%, the corrosion potential is greater than -0.25 V, and the corrosion current is less than 2 x 10-8 A/cm2.

【學(xué)位授予單位】：北京科技大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2016
【分類號】：TG142.71;TG335;TG161

【參考文獻(xiàn)】

相關(guān)期刊論文 前1條

1 張愛梅;;非金屬夾雜物對鋼性能的影響[J];物理測試;2006年04期

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本文編號：1895967