本文選題：BN + 夾雜物��； 參考：《北京科技大學》2017年博士論文

【摘要】：易切削鋼是一類重要的特殊鋼,被廣泛應(yīng)用于汽車工業(yè),機械加工等領(lǐng)域。目前市場上的易切削鋼主要是硫系和鉛系易切削鋼,這兩種鋼都含有對環(huán)境污染嚴重的易切削元素(S,Pb)。而且硫的使用造成鋼材質(zhì)量的下降。因此急需開發(fā)新型的高質(zhì)量環(huán)境友好型易切削鋼,提升鋼材附加值,減少環(huán)境污染。本文利用熱力學,動力學理論計算,結(jié)合實驗室熱態(tài)實驗,真空感應(yīng)爐實驗,切削實驗,機械性能測試實驗及熱塑性實驗,同時借助一系列表征手段,對以下四個方面的內(nèi)容進行了詳細研究:鋼中BN粒子形成機理研究;BN鋼切削性能與機械性能研究;BN-S復合易切削鋼夾雜物共存機理及復合易切削鋼性能研究;BN易切削鋼熱塑性研究。鋼中BN粒子形成機理研究表明:BN在鋼液凝固末端1380℃～1430℃范圍內(nèi)大量快速析出。B,N在凝固前沿大量富集,局部濃度增加,達到臨界濃度,BN勻質(zhì)形核析出,鋼液中存在成核點時,BN在其表面以異質(zhì)形核的方式均勻析出,鋼中的Al2O3,球形的MnS粒子可以作為BN的形核核心�；跀U散作用BN長大到2～3μm,后期以碰撞結(jié)合(自身碰撞或和其他粒子碰撞)的方式長大。根據(jù)實驗結(jié)果和理論分析,提出了基于顯微偏析和動力學的BN析出擴散長大模型,基于碰撞和凝聚作用的長大模型,模型計算結(jié)果與實際結(jié)果相符。BN鋼切削性能與機械性能研究表明:BN可以改善鋼的可加工性,控制BN粒子尺寸在2～4μm或12～14μm可達到優(yōu)異·的切削加工性能改善效果。納米探針壓痕實驗輔助揭示了BN改善鋼的切削性能機理:BN破壞基體的連續(xù)性,充當鋼基體內(nèi)部缺口,引起應(yīng)力集中以降低切削抗力;BN具有良好塑性變形能力,有助于刀具前面上的塑性流動,起到潤滑作用;BN可以包裹鋼中Al2O3,SiO2等超硬夾雜物質(zhì)點,減輕了刀具磨損;BN易切削鋼中含A1元素時,在刀具刀面上生成AlN覆蓋膜,減輕刀具的擴散磨損。鋼中的BN粒子對鋼的強度等常溫力學性能影響不大,但是對鋼的沖擊性能有所影響。BN-S復合易切削鋼火雜物共存機理及復合從切削鋼性能研究表明:BN與MnS析出溫度區(qū)間相差不大,不會阻礙彼此的析出。BN+MnS復合易切削鋼中,易切削粒子或單獨存在或復合存在。復合存在時,BN,MnS相互碰撞或彼此包裹。BN可以顯著改善鋼的切削性,1000ppm S和115ppmB,240ppm N的復合切削效果,包括鉆削和車削,皆優(yōu)于2000ppm S的效果。BN+MnS復合易切削鋼的屈服強度和抗拉強度高于MnS易切削鋼,但是復合易切削鋼的沖擊性能卻較MnS鋼有所降低。BN易切削鋼熱塑性研究表明:BN易切削鋼在實驗溫度700～1200℃范圍內(nèi)斷面收縮率基本皆在60%以上,較C45對比鋼有較大幅度的提高,BN易切削鋼拉伸試樣皆為韌性斷裂,而C45對比鋼主要為沿晶界脆性斷裂。提出了BN易切削鋼熱塑性改善機制:由于B原子較小,可快速偏聚到晶界,抑制晶界滑移,從而提高熱塑性;B優(yōu)先偏聚于晶界,占據(jù)了原本作為TiN,(Fe,Mn)S等第二相形核核心的空位,抑制了第二相在晶界的析出;B偏聚于晶界,抑制了晶界鐵素體的析出。熱加工過程中冷速對BN易切削鋼熱塑性影響較大。20℃/s的冷速條件下,800～900℃溫度范圍內(nèi)熱塑性惡化嚴重。因此冷速的控制是實現(xiàn)BN易切削鋼熱塑性改善的關(guān)鍵�？傊�,通過對BN粒子的生長機理及BN新型易切削鋼的系統(tǒng)性研究表明BN粒子作為易切削粒子生產(chǎn)BN系新型易切削鋼可行,BN粒子對鋼材切削性能改善作用明顯,對鋼材機械性能影響較小。因此,BN新型易切削鋼潛在商業(yè)價值巨大,對提高鋼材附加值,減少環(huán)境污染意義重大。
[Abstract]:Easy cutting steel is a kind of important special steel, which is widely used in the automotive industry, mechanical processing and other fields. At present, the most easy cutting steel in the market is mainly sulfur and lead based easy cutting steel. These two kinds of steel contain easy cutting elements (S, Pb) for serious environmental pollution. Moreover, the quality of steel is reduced by sulfur. Therefore, new type of steel is urgently needed to develop a new type of steel. The high quality and environment-friendly easy cutting steel improves the added value of steel and reduces environmental pollution. In this paper, we use thermodynamics, dynamics theory, laboratory thermal experiment, vacuum induction furnace experiment, cutting experiment, mechanical performance test and thermoplastic experiment, and use a series of characterization means to advance the contents of the following four aspects. The research on the formation mechanism of BN particles in steel, the research on the cutting properties and mechanical properties of BN steel, the coexistence mechanism of the inclusions in the BN-S composite free cutting steel and the study of the properties of the composite easy cutting steel, the study of the thermal plasticity of the BN easily machined steel. The study on the formation mechanism of BN particles in the steel shows that BN is fast in the range of 1380 C to 1430 C at the end of the solidification of molten steel. The precipitation of.B, N is enriched at the cutting edge, the local concentration increases, the critical concentration reaches the critical concentration, the BN homogeneous nucleation is precipitated, and when there is nucleation point in the molten steel, the BN is uniformly precipitated in the form of heterogeneous nucleation on the surface of the steel. The Al2O3 and spherical MnS particles in the steel can be used as the nucleation core of BN. The BN is grown to 2~3 u m based on the diffusion effect and the later collision binding ( According to the experimental results and theoretical analysis, the BN precipitation diffusion growth model based on microsegregation and dynamics is proposed. The model based on the effect of collision and condensation is based on the impact and condensation. The results of the model calculation agree with the actual results of the.BN steel cutting performance and mechanical properties. The results show that BN can be improved. The machinability of steel can be achieved by controlling the size of BN particles at 2~4 mu m or 12~14 u m. The nano probe indentation test helps to reveal the mechanism of BN to improve the cutting performance of steel: BN destroys the continuity of the matrix, acts as the internal gap in the steel matrix, causes the stress concentration to reduce the cutting resistance; BN has good plasticity. The ability of sexual deformation helps to lubricate the plastic flow on the front of the tool and plays a lubrication role. BN can wrap the particles of superhard inclusions, such as Al2O3 and SiO2 in steel, and reduce the tool wear. When the A1 element in the BN free cutting steel is contained, the AlN cover film is formed on the cutter surface to reduce the spread wear and tear of the tool. The mechanical properties of the steel in steel and the strength of the steel are also reduced. The impact properties of the steel can not be affected, but the impact properties of steel have some influence on the coexistence mechanism of the.BN-S composite free cutting steel and the properties of the composite from the cutting steel. It is shown that the difference of the precipitation temperature range between BN and MnS is small, and it will not hinder the precipitation of.BN+MnS composite free cutting steel. MnS collisions or each other wrapping.BN can significantly improve the cutting properties of steel, 1000ppm S and 115ppmB, 240ppm N compound cutting effects, including drilling and turning, are superior to 2000ppm S, the yield strength and tensile strength of.BN+MnS composite Machinable steel are higher than that of MnS Machinable steel, but the impact properties of the composite easy cutting steel are more than that of MnS steel. The study on the thermal plasticity of.BN free cutting steel shows that the section shrinkage rate of the BN easily machined steel is basically above 60% in the range of 700~1200 C, compared with the C45 contrast steel, the tensile specimens of the BN easy cutting steel are all ductile fracture, and the C45 contrast steel is mainly brittle fracture along the grain boundary. The thermal plasticity of the easy cutting steel of BN is put forward. Improvement mechanism: because B atom is small, it can quickly get to grain boundary, inhibit grain boundary slip, inhibit grain boundary slip and improve thermal plasticity; B preferentially segregates at grain boundary, occupies the original space of the two phase nuclear core, which is originally as TiN, (Fe, Mn) S and inhibits the precipitation of the second phase in grain boundary; B biased at grain boundary, restraining the precipitation of grain boundary ferrite. The effect of speed on the thermal plasticity of BN easy cutting steel is larger at the cold speed of.20 C /s. The thermal plastic deterioration in the temperature range of 800~900 C is serious. Therefore, the control of the cold speed is the key to the improvement of the thermal plasticity of the BN easy cutting steel. In a word, the mechanism of the growth of BN particles and the systematic study of the BN new easy cutting steel show that the BN particles are the easy cutting particles. The production of BN new type of easy cutting steel is feasible, and the effect of BN particles on the cutting properties of steel is obvious, and the mechanical properties of steel are less affected. Therefore, the potential commercial value of BN new type of easy cutting steel is huge, which is of great significance to increase the added value of steel and reduce environmental pollution.
【學位授予單位】：北京科技大學
【學位級別】：博士
【學位授予年份】：2017
【分類號】：TG142.1

【參考文獻】

相關(guān)期刊論文 前10條

1 Yu-nan Wang;Yan-ping Bao;Min Wang;Le-chen Zhang;;Precipitation and control of BN inclusions in 42CrMo steel and their efect on machinability[J];International Journal of Minerals Metallurgy and Materials;2013年09期

2 王毓男;包燕平;王敏;張樂辰;;BN型易切削鋼的冶煉工藝及其切削加工性[J];北京科技大學學報;2013年07期

3 Yu-nan Wang;Yan-ping Bao;Min Wang;Le-chen Zhang;;Precipitation behavior of BN type inclusions in 42CrMo steel[J];International Journal of Minerals Metallurgy and Materials;2013年01期

4 ;A method for observing the three-dimensional morphologies of inclusions in steel[J];International Journal of Minerals Metallurgy and Materials;2012年02期

5 田樹生;易耀云;楊勇;;45B含硼鋼裂紋成因分析及改進[J];金屬材料與冶金工程;2010年05期

6 吳元徽;;淺析非調(diào)質(zhì)鋼的應(yīng)用前景[J];機械制造;2009年09期

7 韓孝永;;微合金非調(diào)質(zhì)鋼技術(shù)淺析[J];梅山科技;2009年02期

8 馬曉平;惠衛(wèi)軍;劉春明;于同仁;孫維;;碳含量對冷作強化非調(diào)質(zhì)鋼力學性能的影響[J];金屬熱處理;2006年12期

9 陳丙璇;鐘建華;宋婧;;易切削Bi黃銅機理的研究[J];特種鑄造及有色合金;2006年08期

10 閆靜;唐生渝;李文兵;趙楨;沈保羅;;含Bi易切削黃銅的研究[J];特種鑄造及有色合金;2006年04期

，

本文編號：2079323