V-N微合金化CSP带钢中的析出物研究

利用Gleeble 1500D热力模拟实验机,在实验室模拟了V-N微合金化CSP钢带的生产过程.实验结果显示,在连铸初期,TiN基本全部从钢中析出,而随着铸坯温度的降低,V开始以TiN为核心或单独形核析出,在铸坯均热后,大部分单独形核的V(C,N)趋于溶解,未溶解的则开始长大,而以TiN为核心的(Ti,V)(C,N)中的V部分溶解于钢中,V在粒子中的含量减少.在CSP连轧中,V(C,N)不断从钢中析出,全部析出物起阻碍奥氏体晶粒长大的作用,而含V颗粒还促进铁素体的形核,提高奥氏体/铁素体相变比率,细化最终的铁素体组织.     

CSP流程钛微合金化高强钢的第二相粒子析出行为

采用光学显微镜、扫描电镜、透射电镜、物理化学相分析等方法并结合热力学计算,分析了CSP工艺生产的钛微合金化高强钢的析出物特征及析出规律.研究发现:屈服强度700 MPa级高强钢中存在大量球形的纳米级TiC和Ti(C,N)粒子及少量不规则形状、100 nm以上的Ti₄C₂S₂粒子,TiN在连轧前完成析出,TiC主要在卷取和空冷时析出.不含钼钢和含钼钢(0.1% Mo)中MC相的质量分数为0.049%和0.043%,由于钼的加入,含钼钢中Ti的析出量较少,但析出粒子更为细小,并定量得到了不含钼钢和含钼钢的析出强化效果分别为126 MPa和128 MPa.      

铁素体基Ti-Mo高强钢连续冷却相变及组织性能

摘要：为了深入了解铁素体基Ti-Mo高强钢在连续冷却相变过程中组织及硬度的变化及其原因,通过热膨胀法、金相及硬度等实验研究了Ti-Mo微合金钢在连续冷却条件下组织及性能的变化,探讨了冷却速率对组织、硬度及相变行为的影响机理,揭示了（Ti,Mo）C在奥氏体和铁素体中Ti/Mo原子比变化的原因。结果表明,随着冷却速率由0.06℃/s增加至17.9℃/s,组织依次为多边形铁素体+珠光体→多边形铁素体+粒状贝氏体→粒状贝氏体,硬度由144HV逐渐增大至228HV。当冷速由0.14℃/s增大至0.90℃/s时,组织中多边形铁素体比例不断增大,珠光体比例不断降低,硬度的提高主要来自于铁素体晶粒尺寸的细化及纳米级（Ti,Mo）C粒子的增多;当冷速由1.79℃/s增大至17.9℃/s时,组织中多边形铁素体比例不断降低,贝氏体比例不断提高,硬度的提高主要是由于贝氏体组织的细化及其比例的增加。（Ti,Mo）C粒子主要有2类：一类是奥氏体中析出的10～20nm的粒子,Ti原子数分数约为88%,另一类是铁素体中析出的小于10nm的粒子,Ti原子数分数约为68%,EDS测量结果与计算结果大致相当。     

氮在非调质钢中的作用

了氮在非调质钢中所起的有益作用。在Ｎｂ,Ｖ,Ｔｉ三咱微合金化元素中,钒有较高的溶解度,钒有较高的溶解度,是非调质钢最常用也是最有效的强化元素。钒在钢中通过形成细小析出相起细化晶粒和沉淀强化作用。与碳相比,氮与钒有更强的亲和力,且氮化物更稳定,因此,氮对控制钒的析出起更重要的作用。大量研究结果表明,非调质钢中增氮改变了钒在相间的分布,促进Ｖ（Ｃ,Ｎ）析出,使析出相的颗粒尺寸明显减小。因而氮增强了非调     

轧制工艺对V-N-Ti钢焊接粗晶热影响区组织和韧性的影响

摘 要: 为了分析大线能量焊接下接头低温韧性的影响因素,研究轧制工艺对V-N-Ti钢粗晶热影响区(CGHAZ)组织和韧性的影响。试验结果表明,当终轧温度从950降低到800 ℃,且t_8/5(从800冷却到500 ℃的时间)为180 s时,CGHAZ中铁素体面积百分数从91.2%降低到53.9%,贝氏体面积百分数从0%增加到31.1%,-20 ℃冲击功从182降低到92 J。上述现象是由于终轧温度影响了母材中尺寸为30~70 nm的富Ti-(Ti,V)(C,N)粒子的成分。与低温终轧相比,高终轧温度条件下母材中富Ti-(Ti,V)(C,N)粒子的V元素含量较高,这使其在焊接加热过程中更易发生溶解,并在焊接冷却过程中以细小富Ti-(Ti,V)(C,N)析出,钉扎奥氏体晶界;焊接冷却过程中,富Ti-(Ti,V)(C,N)可以作为V元素的析出核心促进VN的析出,提高了其铁素体形核能力,改善了CGHAZ组织和韧性。     

固溶温度对022Cr22Ni5Mo3N双相不锈钢组织和性能的影响

试验研究了1000℃ 4h和1060℃ 4h固溶处理后022Cr22Ni5Mo3N钢中ϕ75 mm材的组织和力学性能。结果表明,022Cr22Ni5Mo3N钢ϕ75 mm材终锻温度970℃空冷的组织（体积分数)约为铁素体31% ,奥氏体 56%,析出物13%;1 000℃ 4 h固溶后为铁素体38% ,奥氏体60% ,析出物2%;1060℃ 4h固溶后铁素体50%,奥氏体50%,该钢通过釆用1060℃固溶后,拉伸断裂强度731MPa延伸率38%,冲击功AKV(-40℃ ）76~81 J,满足标准要求。     

Precipitation Strengthening by Nanometer-sized Carbides in Hot-rolled Ferritic Steels

The mechanical properties of the hot-rolled plates of Ti steel and Ti-Mo steel after isothermal transformation in a temperature range of 600 700 ℃ for 60 min have been tested, and the microstructures of the matrix and the characteristics of precipitated nanometer-sized carbides have also been examined by scanning electron microscopy and transmission electron microscopy. The precipitation regularity of nanometer-sized carbides has been studied by thermodynamic method and the contributions of corresponding strengthening mechanisms to the total yield strength have been calculated. The tensile strength of hot-rolled Ti-Mo ferritie steel can achieve 780 MPa with an elongation of 20.0% after being isothermally treated at 600 ℃ for 60 rain, and the tensile strength of Ti steel is 605 MPa with an elongation of 22.7%, according to the results of tensile tests. The critical nucleation size of （Ti,Mo）C is smaller than that of TiC at a given isothermal temperature, but the nucleation rate of （Ti, Mo）C is larger than that of TiC. The grainrefinement strengthening and precipitation strengthening contribute the main amount of the total yield strength. The major increase in yield strength with the decrease of isothermal temperature results from the contribution of precipi tation strengthening. The contribution of precipitation strengthening to the yield strength of the steels has been esti mated. The ferrite phase can be strengthened by about 400 MPa through precipitation strengthening in Ti-Mo steel isothermally treated at 600 ℃ for 60 rain, which is about 200 MPa higher than that of Ti steel under the same conditions.     

Nucleation Behavior Analysis of Intragranular Acicu-lar Ferrite in a Ti-killed C-Mn Steel

By using a Gleeble 3500Dthermo-mechanical simulator,the nucleation behavior of intragranular acicular ferrites(IAF)was studied in a Ti-killed C-Mn steel.During continuous cooling transformation,the allotriomorphic ferrite(AF)and ferrite side plate(FSP)microstructures grew more rapidly with the temperature decreasing from800to 650℃,and the IAF microstructure was dominant within austenite grain with further cooling to 600℃.The diffusion bonding experiment and the effect of C,Mn and Si concentrations on the Ae3temperature by thermodynamic calculation confirm that Ti2O3itself absorbs neighboring Mn atoms to form Mn-depleted zone(MDZ),which promotes the nucleation of IAF microstructure effectively.High temperature holding tests indicate that the nucleation potential of IAF microstructure was lowered in the Ti-killed C-Mn steel when it was treated at high temperature(1 250℃)for a longer time,which is attributed to the saturated absorption degree of Mn atoms by titanium oxide.     

奥氏体化温度对Ti–Zr处理钢中针状铁素体转变的影响

Ti、Zr的复合氧化物可以有效诱导针状铁素体形核,从而细化晶粒。为了研究Ti–Zr处理钢中针状铁素体转变机理,使用25 kg真空感应炉中熔炼试验所需钢种,向低合金钢中添加了质量分数为0.038%钛和0.008%锆。利用高温激光共聚焦显微镜原位观察了奥氏体化温度对针状铁素体转变行为的变化,使用扫描电镜观察了Ti–Zr处理钢种的夹杂物成分和针状铁素体在夹杂物表面形核,使用光学显微镜观察不同奥氏体化温度下的微观组织变化差异。结果表明,随着奥氏体化温度从1250 ℃增加至1400 ℃,奥氏体晶粒尺寸从125.6 μm 增加至279.8 μm,针状铁素体开始转变温度和侧板条铁素体开始转变温度先增加,在1350 ℃条件下达到最大值,后又降低,针状铁素体的体积分数由39.6%增加至83.6%;Ti–Zr处理钢中核心为Zr–Ti–O,外部为Al–Ti–Zr–O的氧化物为核心表面析出MnS的复合氧化物主要集中在1.5～3 μm,可以有效促进针状铁素体形核,贫Mn区和夹杂物与铁素体之间的良好晶格关系为该型夹杂物能够促进针状铁素体形核机理。奥氏体晶粒尺寸的增加导致多边形铁素形核位点的减少和针状铁素体的形核空间的增加,钛锆复合处理形成大量的有效诱发针状铁素体形核的夹杂物,这共同导致了针状铁素体体积分数增加。      

Nb-Ti微合金化对热轧0.5~0.7Cr铲斗刀板型钢组织和性能的影响

试验0.5~0.7Cr铲斗刀板型钢（/%:0.22~0.30C,0.25~0.45Si,0.95~1.20Mn,0.006~0.009P,0.008~0.010S,0.5~0.7Cr,0.015~0.065Nb,0~0.040Ti）由50kg真空感应炉熔炼,热轧成16mm厚板,终轧温度850~900℃,空冷。通过光学显微镜、扫描、透射电镜和力学性能测试研究了Nb-Ti含量（0.015Nb,0.035Nb-0.010Ti,0.065Nb-0.040Ti）对热轧态铲斗刀板钢组织和力学性能的影响。结果表明,试验钢组织为F+P,随Nb-Ti含量增加,钢板的晶粒细化,珠光体片层间距降低,（Nb,Ti）C和（Nb,Ti）(C,N)析出物增多,强度增加,0.065Nb-0.040Ti钢板的力学性能为屈服强度632MPa,抗拉强度916MPa,延伸率17.7%,K_AV40 J,HB硬度值234。     

等温温度对低碳齿轮钢带状组织的影响

通过计算铁素体形核孕育期和形核率探讨了等温温度对带状组织的影响机理,并观察了齿轮钢SAE8822H(/%:0.22C、0.20Si、0.98Mn、0.60Cr、0.46Ni、0.36Mo)在管式炉经930℃10 min降至703～579℃等温1h空冷,或710～570℃等温处理2 h炉冷后钢中带状组织演变。结果表明,贫、富溶质区铁素体形核孕育时间差和铁素体形核率差异是造成等温转变时产生带状的原因;等温温度降低时,贫、富溶质区的孕育期时间差缩短,相对形核率减少,带状减轻;齿轮钢SAE8822H在570℃等温可使带状组织消失,这时相对形核率为6.3%。     

Influence of Mo on Growth and Coarsening of Nanometer-sized Carbides in Low-alloy Ferritic Steels Containing Ti

By optical microscopy, transmission electron microscopy and energy dispersive spectroscopy, the changes with aging time in size, composition and distribution of nanometer-sized （Ti, Mo）C precipitated in Ti-Mo low-alloy ferritc steel have been studied in comparison with that of nanometer-sized TiC precipitated in Ti low-alloy ferritc steel. It was found that the growth rate of （Ti,Mo）C in Ti-Mo steel was less than that of TiC in Ti steel. Nanometer- sized carbides formed at 650 ~C （or 550 ~C） for 55 h were at transitional stage from growth to coarsening. When aging time reaches 55 h, the coarsening rates of nanometer-sized carbides in Ti and Ti-Mo steel tend to be the same and in- variable. The influence of Mo on growth and coarsening of nanometer-sized carbides tends to decrease with increasing aging time, and Mo contents in nanometer-sized carbides with the same size at different aging time were different.     

温度和变形量对27SiMn钢组织影响的热模拟研究

采用Gleeble 1500热模拟试验机研究了煤机用钢27SiMn(/%:0.27C,1.20Si,1.25Mn,0.015Mo,0.021Ti)热轧Φ190 mm棒材的变形量(10%~50%)和温度(850~1 000℃)对钢中珠光体、铁素体尺寸和比例的影响。结果表明,随变形量和变形温度的增加,钢中晶粒尺寸减小,尺寸均匀度增加;当27SiMn钢在950℃进行30%形变时,珠光体晶粒尺寸为18~42μm,平均尺寸为28μm,珠光体占54%。     

Effect of sulphur content on precipitates and properties of DH36 structural steel

In the current research, the influences of sulphur content on precipitates and properties were investigated through thermodynamic calculation and microstructural analysis. The results show that the precipitates of DH36 structural steel are mainly (Nb, Ti)C and Ti(C,N), the size of which ranged from 7 to 220?nm. Plenty of nanoscale MnS was observed by transmission electron microscopy using carbon film replicas with 0.002% S. This is because the temperatures of maximum nucleation rate and fastest precipitation of MnS are much less than soaking temperature when S content is 0.002%, which is the main reason for the formation of nanoscale MnS. What is more, the pinning effect of nanoscale MnS can also refine the grain size. Consequently, ultra-low content of sulphur can be used to optimise the properties of DH36 structural steel.     

终锻温度和锻压比对贝氏体非调质钢铁素体析出的影响

研究了终锻温度810～960℃和锻压比3～6对贝氏体钢(%:0.16C、0.91Si、1.98Mn、1.03Cr、0.17Mo、0.065V、0.001Ti)铁素体析出的影响。结果表明,贝氏体钢锻造过程中的变形提高了钢中奥氏体至铁素体相变的临界温度;在终锻温度为810～820℃时,钢中产生变形诱导铁素体相变,当锻压比由3增至6时,铁素体的体积分数由1.8%增至9.6%,铁素体由针状趋于演变为块状;终锻温度为940～960℃时,钢中铁素体主要为针状,随着锻压比由3增至6,钢中铁素体体积分数由3.0%降至0.6%。     

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The influence of heating temperature and holding time of different Ti content of microalloy high strength steel on austenite grain size and the influence of the precipitation characteristics on mechanical properties were quantificationally investigated through the methods of metallography, phase analysis and X-ray diffraction. The results show that, under the heating temperature of 1000-1150?? and the same soaking time,the steel B has small size of austenite grain. However when the temperature rises to 1150?? and above, austenite grain size in steel B increases fast, bulky containing Ti precipitates almost have no side effect on austenitic grain growth. With Ti content in steel increasing, MC precipitated phase in steel A and B respectively is 7. 5%, 159. 0% of the total M3C precipitated phase. When the ratio of MC/M3C increases, the corresponding strength of steel also increases. The mass fraction of less than 10nm precipitation phase in steel A and B is 2. 2% and 21. 7%.     

HRB500E抗震钢筋中钛化物析出热力学分析

 钢液凝固过程中钛化物在液相、固相的存在形态对固相组织的性能有着重要的影响,其第二相析出起到细化晶粒的作用。为分析HRB500E抗震钢筋钢中TiN、TiC、Ti(C,N)析出物的析出规律,对TiN、TiC、Ti(C,N)析出物进行热力学计算。结果表明,TiN、TiC在钢液成分均质状态下难以析出,TiC_0.19N_0.81在温度为1 843 K时析出;在凝固过程中,由于Ti、N在凝固前沿富集,TiN在凝固过程中具备析出的热力学条件,析出温度为1 745 K;在固相奥氏体中,TiN和TiC粒子具备析出热力学条件,TiC析出温度比TiN的低,铁素体中有TiC的析出。     

Austenite Grain Refinement and Isothermal Growth Behavior in a Low Carbon Vanadium Microalloyed Steel

The austenite grain refinement through control of the grain growth during reheating process after thermomechanical controlled process(TMCP)in a vanadium microalloyed steel was achieved.The formation of ultra-fine grained austenite was attributed to the high density of austenite nucleation at the ferrite/martensite structure and to the inhibition of austenite growth by(Ti,V)C particles at the relatively low reheating temperature.Corresponding with the precipitation behavior of(Ti,V)C with temperature,the growth behavior of austenite in the vanadium microalloyed steel could be divided into two regions.At lower reheating temperature,austenite grains grew slowly,and ultra-fine grained austenite smaller than 5μm was successfully obtained.By contrast,the austenite grains grew rapidly at high temperature due to the dissolution of(Ti,V)C particles.According to the measured and predicted results of austenite growth kinetics,two models were developed to describe the growth behavior of austenite grains in two different temperature regions,and the apparent activation energy Qappfor grain growth was estimated to be about 115 and 195kJ/mol,respectively.     

铌-钛微合金化0.36C-0.83Ni-1.2Cr-0.23Mo超高强度淬火-210℃回火马氏体钢组织与性能

利用拉伸试验机、冲击试验机、光学显微镜、透射电镜等研究了 Ni-Ti微合金化超高强度钢(/％:0.36C,0.45Si,0.63Mn,0.005P,0.002S,0.83Ni,l.2Cr,0.23Mo,0.04Nb,0.01Ti,0.0040N,0.002 0O)的组织与性能.200 kg真空感应炉冶炼的试验钢开轧温度...     

Mn-Mo-Nb-B低碳微合金钢的应变诱导析出

采用热模拟及透射电子显微镜结合纳米束能谱技术,研究了Mn-Mo-Nb-B系多元微合金钢奥氏体变形后等温过程中(松弛)的析出行为。实验结果表明:经变形后,在850℃和900℃保温过程中,Mn-Mo-Nb-B多元微合金钢析出颗粒尺寸在各个阶段均小于相同工艺下Nb-Ti钢中析出相的尺寸。统计结果显示,析出颗粒的尺寸均复合正态分布,并且峰位尺寸接近平均尺寸。析出相中Nb/Ti比随着松弛时间而增大。松弛阶段后期,Mo进入(Ti,Nb)(C,N)的晶格当中,其含量随着时间的延长而增加。