形变热处理工艺对403Nb马氏体耐热钢组织和性能的影响

403Nb是一种马氏体耐热不锈钢,主要用于制作火电机组汽轮机叶片,该钢是在AISI 403不锈钢的基础上,通过添加一定质量分数的Nb和V 发展起来的。通过与传统热处理工艺对比,研究了形变热处理工艺(即高温固溶后在奥氏体亚稳态区变形后空冷)对马氏体耐热钢403Nb的组织和性能的影响。结果表明：形变热处理可以使403Nb钢组织明显细化,马氏体板条宽度由传统热处理的0.3 μm减小到0.1 μm,而且生成大量弥散的纳米级MX碳化物。形变热处理对403Nb钢组织改变的直接结果是可以大幅度提高403Nb钢的屈服强度,在常温拉伸时由传统热处理的800 MPa提高到1 180 MPa,在高温(700 ℃)拉伸时由246.5 MPa提高到341.4 MPa,其屈服强度分别提高了47.55%和38.5%。     

控冷工艺对微合金钢性能的影响

通过热轧模拟实验，研究了轧制过程中控制冷却工艺对含Nb－V微合金钢性能的影响。适当降低终轧温度，增加冷却速度，降低终冷温度，以控制Nb(CN),V(CN）析出行为，从而改善钢的性能。     

卷取温度对Ti-Nb微合金钢微观组织和力学性能的影响

利用试验轧机和热处理炉进行了低碳Ti-Nb微合金钢的模拟轧制和卷取试验,研究卷取温度对微观组织和力学性能的影响。结果表明,随着卷取温度的降低,钢的相变过程逐步由扩散型相变过渡到切变型相变,微观组织由等轴铁素体依次转变为多边形铁素体、粒状贝氏体、板条贝氏体;由于析出强化和相变强化的综合作用,卷取态试验钢强度先降低后升高,延伸率持续降低;卷取过程微合金碳氮化物的析出强化导致卷取态试验钢强度高于空冷态试验钢,且随着卷取温度的降低,卷取态试验钢较空冷态试验钢强度的增量逐步降低;Ti-Nb微合金钢的卷取温度设定在560～630℃时,钢屈服强度744～754 MPa,延伸率19%～20.9%,可获得良好的综合性能。     

N含量对Nb微合金化HRB400E钢筋组织与性能的影响

摘要：为了更好地发挥N元素在Nb微合金化钢筋中的作用,降低生产成本以及为钢筋成分设计提供理论依据。利用金相显微镜、扫描电镜、透射电镜、力学试验机对不同N含量的Nb微合金化高强抗震钢筋进行显微组织表征及力学性能测试,探究N含量对Nb微合金化钢筋的组织与力学性能的影响。研究表明,轧制过程中的奥氏体组织,随着N含量的增加,平均奥氏体晶粒有所减小;最终组织为铁素体和珠光体,随着N含量的增加,铁素体平均晶粒尺寸而减小,片层状珠光体的连续性增加,片层间距减小;析出相Nb(C,N)随着N含量的增大,沉淀析出的第二项颗粒体积分数增大,颗粒尺寸随之减小;在力学性能方面,屈服强度逐渐增加,抗拉强度先增加后减少。     

控轧控冷工艺对铌钛微合金钢组织和性能的影响

采用金相、图相仪、透射电镜和相分析等方法,系统地研究了不同控轧控冷条件对铌、钛复合微合金化低碳热轧钢板的组织和性能的影响规律;分析了不同工艺条件下铌、钛碳氮化物的析出行为;探讨了微合金钢的强化机制;提出了更佳的控轧控冷工艺参数。研究结果对开发高强度、高成形性能的汽车钢板具有参考价值     

微合金钢焊缝金属中夹杂物的研究

通过对微合金钢焊缝金属中夹杂物的研究发现 :夹杂物数量在焊缝中心最多 ,而在熔合线附近最少 ;随着焊接热输入的增加 ,夹杂物平均尺寸增大。约有 6 0 %夹杂物的平均尺寸都小于 0 .6 μm,而大于 1.0 μm的不足 10 %。夹杂物是由多个物相组成的复合物 ,组成夹杂物的物质 :Mn O2 、3Mn O· Al2 O3· Si O2 、Ti N、Ca O· 2 Al2 O3、Si O2 、Ca O· 2 Ti O2 和 θ- Al2 O3等。提供针状铁素体 (AF)形核的夹杂物尺寸约 93 %以上都集中在 0 .2～ 0 .6 μm范围内     

热处理工艺对电子束选区熔化Ti-48Al-2Cr-2Nb合金组织性能的影响

对电子束选区熔化Ti-48Al-2Cr-2Nb合金热处理后的组织演变和力学性能进行研究。结果表明：随着热处理温度的提高,Ti-48Al-2Cr-2Nb合金的细小双态组织和等轴γ条带组织逐渐发生粗化,并且向层片组织转变。当热处理工艺为1290℃/4 h、1315℃/1.5 h和1335℃/0.5 h时,合金的主要组织分别为双态组织、近层片组织和全层片组织。其中,等轴γ条带的平均宽度由沉积态的28.5μm分别增大至115.5、291.4、332.5μm。组织粗化使得纵向试样的平均抗拉强度由沉积态的698MPa分别下降至541、461、390MPa,延伸率无明显变化。此外,所有热处理工艺下横向试样的力学性能均优于纵向试样,这是由于粗化的等轴γ条带与基体中双态组织的界面结合强度较弱。随着热处理温度的升高,横向试样与纵向试样抗拉强度的差值逐渐增大,在1335℃/0.5 h时达到最大值102 MPa。     

Mo对Nb—Mo微合金钢的动态再结晶的影响

本文研究了Mo对Nb微合金钢动态再结晶的影响。初始奥氏体晶粒尺寸,固溶体中微合金元素的数量以及变形条件（温度和应变率）都影响着Nb钢和Nb—Mo钢的动态再结晶动力学。微合金奥氏体的动态再结晶行为采用连续扭转实验来进行证明,实验后将样品再次加热到1100℃和1460℃之间的不同温度,这就会产生一个很宽的初始奥氏体晶粒尺寸,即从22μm到805μm之间。实验发现Zener—Hollomon参数值下降,初始晶粒尺寸促进动态再结晶。固溶体中的Mo元素推迟动态再结晶过程,提高了和值,这都受Mo含量的影响。这就意味着对于Nb钢,Nb—Ti钢和Nb—Mo钢产生最高的应变值存在唯一的关系。     

Effect of Heat Treatment Process on Properties of 1000 MPa Ultra-High Strength Steel

 Two types of steel, C-Mn-Cr-Mo-B microalloyed steel and C-Mn-Mo-Nb-Cu-B microalloyed steel, are designed to develop 1000 MPa ultra-high strength steel. Two kinds of processes, thermomechanical controlled process (TMCP) combined with traditional off-line quenching and tempering (QT) process versus controlled rolling process (CR) combined with direct quenching and tempering (DQ+T) process, are applied. The effect of heat treatment processing mode on the microstructure and mechanical properties is studied. The relationship between microstructure and mechanical properties is investigated by SEM and TEM. After tempering at 450 to 550 ℃ for 1 h, the steel produced by TMCP+QT process shows combination of excellent strength and low temperature toughness. The yield strength is above 1000 MPa, elongation above 15% and impact energy at -40 ℃ more than 30 J. After tempering at 450 ℃, a large number of ε-Cu particles precipitated in C-Mn-Mo-Nb-Cu-B steel produced by CR+DQ+T process lead to a significant increase in yield strength. And after tempering at 500 to 600 ℃, the yield strength of the steel is further improved to 1030 MPa because of precipitates, such as nitride or carbide of niobium, carbide of molybedenum and vanadium. When the tempering temperature is increased above 620 ℃, the yield strength is still higher than 1000 MPa and elongation is above 20% and impact energy at -40 ℃ is more than 35 J. After tempering at above 500 ℃, the toughness of the steel treated by TMCP+QT process is superior to that of steel by CR+DQ+T process.     

Effect of Annealing Time on Microstructure and Mechanical Properties of Cold-Rolled Niobium and Titanium Bearing Micro-alloyed Steel Strips

Effects of annealing time on microstructure of cold-rolled niobium-titanium bearing micro-alloyed steel strips were investigated by optical microscopy, scanning electron microscopy, electron back-scatter diffraction (EBSD) and transmission electron microscopy. The complete recrystallization annealing temperature of 670 °C and complete annealing time of 9 min were determined using Vickers-hardness testing and EBSD analysis. The ferrite microstructure with spheric cementite particles and nano-scale precipitates of Nb(C, N) in matrix was obtained. The kinetics of the ferrite grain growth is lowered due to ferrite grain boundaries pinned by the cementite particles, so the ferrite grain size of 5. 5 μm remains unchanged among the annealing time ranging from 9 to 30 min. In addition, the strength of tested steel also keeps unchanged with the increase of annealing time. The higher yield strength of approximately 420 MPa can be obtained by grain refinement and precipitation hardening and the higher elongation of approximately 40% and work-hardening exponent of approximately 0. 2 can be gained due to grain refinement and presence of cementite particles, indicating that the balance of strength, ductility and forming property is realized.     

Relationship Among Microstructure and Properties and Heat Treatment Process of Ultra-High Strength X120 Pipeline Steel

 The variation of heat treatments including directed quenching and tempering off-line after controlled rolling (DQT) and quenching off-line and tempering off-line after controlled rolling (RQT) with microstructure and mechanical properties of a low-carbon microalloyed steel was compared and analyzed. For DQT, the quenched steel was obviously banded microstructure, with increasing tempering temperature, lath martensite coarsened, the cusp carbide precipitated at grain boundaries, the yield strength fluctuated slightly, and the fracture-separation was obvious. The impact toughness was better in the steel tempered at 500 ℃ for 1 h. In RQT, with increasing tempering temperature, lath martensite degenerated, intragranular and intergranular finer precipitations with smaller than 30 nm precipitated and grew up and were distributed dispersedly, the stripe-like carbides were distributed at grain boundaries, and the yield strength and tensile strengthen decreased obviously. The impact toughness of RQT process was much better than that of DQT process, and the comprehensive mechanical properties were better for the steel tempered at 500 ℃ for 1 h of RQT process.     

Microstructure and Mechanical Properties of GMAW Weld Metal of 890MPa Class Steel

The relationship between microstructure and mechanical properties of gas metal arc weld metal with strength over 890 MPa is discussed. The microstructure of the weld metals is characterized with OM, SEM, TEM and EBSD. The microstructure of the weld metals is mainly composed of martensite and bainite. Experimental results show that the microstructure with predominant fine lath bainite possesses good toughness of 77 .l, while its yield strength is less than 800 MPa. The microstructure of coarse lath martensite and bainite has the lowest toughness of 43 J and its yield strength is 820 MPa. The mixed microstructure with fine martensite, bainite and retained austenite films bears good combination of toughness and yield strength （62 J and 880 MPa, respectively）. It is concluded that fine effective grain size and ductile phase of austenite films are two main factors to achieve good mechanical properties.     

40CrMnSiMoV弹簧钢热处理工艺与力学性能研究

通过端淬试验及经各种工艺热处理试验,对弹簧钢40CrMnSiMoV的淬透性及热处理工艺与力学性能进行了试验研究.试验结果表明:此钢种不仅淬透性良好,而且力学性能强、韧性水平高.     

热处理工艺对30MnSi PC钢棒力学性能的影响

针对30MnSi 预应力混凝土用钢棒(简称PC钢棒)在实际生产中抗延迟断裂性能差、力学性能不稳、屈强比高等问题,从生产PC钢棒的技术关键热处理制度入手, 通过调质处理得到回火屈(索)氏体组织,分别绘出了淬火温度、回火温度与抗拉强度、伸长率、屈强比的关系曲线.系统地研究了热处理工艺参数对钢棒的组织及强韧性的影响规律并进行了理论分析.摸索出了生产30MnSi PC钢棒的合理工艺制度:当加热时间一定时,淬火温度920～960 ℃,回火温度控制在390～430 ℃时,能获得较好的综合力学性能.     

Effects of Hot Bending Parameters on Microstructure and Mechanical Properties of Weld Metal for X80 Hot Bends

Mechanical properties of weld metal are the key factors affecting the quality of heavy-wall X80 hot induction bends. The effects of bending parameters on the mechanical properties of weld metal for hot bends were investigated by simulation conducted on a Gleeble 3500 thermal simulator. Continuous cooling transformation （CCT） dia- grams of the weld metal were also constructed. The influences of hot bending parameters （such as reheating temperature, cooling rate, and tempering temperature） on the microstructure and mechanical properties of weld metal were also analyzed. Results show that the strength of all weld metal specimens is higher than the value indicated in the technical specification and increases with the increase of reheating temperature, cooling rate, and tempering tempera ture. The impact toughness is apparently related to the variation of reheating temperature, cooling rate, and tempering temperature.     

新型T23无缝钢管热处理工艺试验研究

分析研究了热处理工艺对新型T23无缝钢管组织性能的影响。结果表明,在试验温度范围内,随着奥氏体化温度提高,硬度总体缓慢增加,晶粒长大,奥氏体化温度升高到1 050℃、30 min时,晶粒度达到理想的7~7.5级;随回火温度升高,强度、硬度均缓慢下降,但在770℃温度以后,组织性能已趋于相对稳定。因此,最佳热处理工艺为:1 050℃保温30 min正火,770℃保温120 min回火,可得到最佳的综合性能与组织状态。     

Ti对大线能量焊接焊缝组织和性能的影响

对不同Ti含量的气电立焊焊缝组织及力学性能进行了对比研究。结果表明,Ti的质量分数在0.028%~0.038%范围内时,焊缝中获得大量细小的针状铁素体,焊缝组织及低温韧性得以明显改善。当Ti过量时,焊缝中的针状铁素体减少,组织以贝氏体为主,低温韧性相应下降。焊缝组织中观察到块状和条状的M-A组元,随着焊缝Ti含量增加,其总量增加。焊缝夹杂物多为以氧化物为核心,外层包裹着MnS的复合夹杂物,并随夹杂物Ti含量的增加,由Mn-Si-Al-O型向Ti-Mn-Al-O型转变,有利于促进针状铁素体形成。而当焊缝中Ti过量时,主要夹杂物又转变为对针状铁素体形核无效的Ti-Al-O型,促进了贝氏体转变。