Microstructure and Properties of Superplastic Welding between 4OCr and CrWMn Steels

Superplastic welding of tool steel and structural steel was investigated. The welding between 40Cr and CrWMn steels was carried out under the conditions of temperature 750～780°C, strain rate 2×10-4 s-1, compressive stress 50～90 MPa for 3～5 min. The joints show similar strength to that of 40Cr steel and the good metallurgical joining is formed. The structural change occurring during superplastic welding was analyzed by metallography and distribution of carbon content in the vicinity of the welding joint was also determined. The mechanism of superplastic welding for steels is proposed to be the disappearance of original bond interfaces caused by atomic diffusion and the grain sliding.     

Preview:HSLA Steels ''''90

The conference,which is organized by The Chinese Society of Metals,is being activelysupported by the following co-sponsors:ASM INTERNATIONAL(USA),AssociacaoBrasileira De Metals(Brazil),Association Technique de la Siderurgie Francaise(France),Associazione Italiana di Metallurgia(Italy),Societe Francaise de Metallurgie(France),The Indian Institute of Metals,The Institute of Metals,(UK),The Iron and Steel Instituteof Japan,The Iron and Steel Society of AIME(USA),The Japan Institute of Metals,The Minerals,Metals,and Materials Society(USA),Verein Deutscher Eisenhüttenleute(F.R.Germany),Institute of Metals and Materials Australia.     

Stretch Formability in HSLA and IF Steels

Stretch formability of steel sheets can be evaluated by the strain hardening exponent. Cold rolled High Strength Low Alloy (HSLA) and Interstitial Free (IF) steels having different compositions and processing histories have been studied. Steels were subjected to controlled strains and the values of strain hardening exponents, microstrains and residual stresses were measured. It was found that a linear correlation exists between residual stresses and the strain hardening exponents. A possible mechanism for work hardening in the presence of misoriented grains is proposed taking in account the smrage of elastic strain energy and the dislocation movements. A strain interval (10.15%) is proposed for stretch forming operations to minimize residual stresses.     

Fuzzy Modeling of Strength-Composition-Process Parameter Relationships of HSLA Steels

The effect of composition and process parameters on the mechanical properties of high-strength low-alloy (HSLA) steels is modeled by the application of fuzzy systems viz. Sugeno and Mamdani types. The fuzzy inference systems are found to be capable of interpreting the metallurgical relations between composition and process variables and yield strength described through some if-then rules. The predictability of the fuzzy inference systems is found to be moderate.     

Preliminary Announcement for the Second International Conference on HSLA Steels

General Information The Chinese Society of Metals ispleased to announce that The SecondInternational Conference on HSLA Steels(HSLA '90) will be held in Beijing, Chinain October, 1990. Much progress in researchand development of HSLA steels has beenachieved by the world's metallurgical andmaterials community since the previousInternational Conference HSLA Steels '85     

高碳钢超塑性形变组织的研究

本文研究了高碳钢在893k 温度下超塑形变过程中组织结构的变化。尽管含碳1.2wt％的钢形变前的原始组织中存在一些片层状珠光体,但以0.31mm/min 的速度拉伸后仍获得了442％的延伸率。由于这些片层状珠光体在形变过程中迅速球化,因而对钢的超塑性能无明显妨害。在形变中,球状渗碳体发生彼此相连,含碳1.6wt％的钢中的渗碳体形成沿晶界的条状和网状,考虑到钢的室温力学性能,作者建议用于超塑成形的钢的含碳量选择在0.8～1.2wt％范围。     

Surface Hardening of High-Strength Low Alloy Steels (HSLA) Dual-Phase Steels by Ball Burnishing Using Factorial Design

Burnishing is used increasingly as a finishing operation which gives additional advantages such as increased hardness, fatigue strength, and wear resistance. Experimental work based on 3⁴ factorial design was carried out to establish the effects of ball burnishing parameters on the surface hardness of high-strength low alloy steels (HSLA) dual-phase (DP) steel specimens. Statistical analysis of the results shows that the speed, feed, lubricant and ball diameter have significant effect on surface hardness.     

HSLA钢连续冷却过程的相变与组织研究

在Gleeble-1500热模拟试验机上研究了20SiMn3NiA钢在不同连续冷却条件下相和组织变化,用热膨胀法测定了该钢的连续冷却转变曲线(动态CCT曲线)。研究结果表明,20SiMn3NiA钢中的Mn、Ni、Si等合金元素能有效地阻止铁素体和珠光体的形成,故20SiMn3NiA钢的过冷奥氏体连续冷却转变曲线只有马氏体和贝氏体相变区。当临界冷却速度大于1℃/s时,20SiMn3NiA钢就可以获得板条状马氏体组织,且随着冷却速度的增大,马氏体组织变得越来越细。与静态CCT曲线相比,形变使动态CCT曲线的Ms点升高,奥氏体稳定性降低,形变细化了马氏体和贝氏体组织,使20SiMn3NiA钢在1℃/s的冷却速率下产生较高的强度。     

喷射成形超高碳钢超塑性变形后的微观组织

研究了喷射成形超高碳钢的超塑性及其变形前后的显微组织.变形前,喷射态超高碳钢的组织为典型珠光体组织,而变形后,珠光体中的条状碳化物逐渐发生碎化和球化,并弥散分布于晶界处,此外,在铁素体基体中以及碳化物颗粒周围出现了高密度位错亚结构,而基体铁素体晶粒也有所伸长.喷射成形超高碳钢超塑性微观机制是以晶界滑动为主,晶内变形以及位错蠕变起了协调作用.     

Deformation and Failure of Single-Packets in Martensitic Steels

A three-dimensional multiple-slip dislocation-density-based crystalline formulation, and specialized finite-element formulations were used to investigate dislocation-density evolution and crack behavior in single-packet lath martensite in high strength martensitic steels. The formulation is based on accounting for variant morphologies and orientations, and initial dislocations-densities that are uniquely inherent to martensitic microstructures. The effects of loading plane with respect to the orientation o the habit plane are investigated. Furthermore, the formulation was used to investigate single-packet microstructure mapped directly from SEM/EBSD images of maraging and ausformed martensitic steel alloys. This analysis underscores that shear pipe effects in martensitic steels, where the long direction of the laths is aligned with specific slip-directions, can result in shear-strain localization along specific variants. Furthermore, the results indicate that the strength and ductility are higher for the loading plane parallel to the habit plane as compared to those normal to the habit plane.     

锰对一种HSLA钢的组织和性能的影响

把一种含碳量为0．06％的低碳钢,通过真空感应熔炼把锰的含量由1．3％提高到2．0％,通过对未提高锰含量和提高锰含量之后的钢的组织和性能的比较,分析锰对一种低合金高强度钢的强化机理,并初步确定锰的强化方式,为综合分析合金元素对高强度低合金钢组织和性能的影响奠定基础。     

微观组织演变对细晶Mg-Y-Nd合金超塑性性能的影响

在初始应变速率为2×10^-2~4×10^-4 s^-1,温度为683~758 K的条件下,对用水下搅拌摩擦加工制备的细晶Mg-Y-Nd合金进行高温拉伸实验,研究了微观组织演变对其超塑性性能的影响。结果表明:因为具有细小均匀的微观组织和良好的热稳定性,Mg-Y-Nd合金在733 K和3×10^-3 s^-1初始应变速率下表现出最大的伸长率(967%),在758 K和2×10^-2 s^-1条件下表现出最优的高应变速率超塑性(900%)。在高温下暴露时间过长导致α-Mg晶粒和第二相颗粒显著长大,使试样的伸长率明显降低;因为第二相颗粒与镁基体之间有良好的变形协调性,在相界处不会产生明显的应力集中,裂纹主要在晶界生成。     

30CrMnSiA钢超塑流变中的力学行为和显微组织的研究

经两次调质热处理细化的30CrMnSiA 钢在770℃以■=2.78×10~(-4)·S~(-1)的应变速率拉伸下呈现了良好的超塑性:δ=867%,σ=34.3MN/m~2,m=0.41。在拉伸时,经预处理的非平衡组织会经碎化而变成微细等轴的晶粒组织,并具有两相体积分数近似相等的α+v 双相组织。这种组织在超塑性流变过程中具有很高的稳定性。此钢对空洞的敏感性比较低,但在变形后期,由于空洞的形成、长大和连接而导致试样呈空洞型沿晶断裂。     

高级别管线钢板的组织特征与析出强化

利用扫描电镜、透射电镜对炉卷轧机生产的高级别X70,X80管线钢板的显微组织与析出相进行了观察与分析,并对管线钢板组织中碳氮化物析出相的成分、相结构以及粒度分布进行了定量分析,并采用Ashby-Orowan修正模型对析出粒子的强化贡献进行了理论计算.结果表明:X70,X80管线钢板的组织以针状铁素体为主,其高密度位错与交叉分布的大角度晶界特点保证了管线钢的高强韧性;X70,X80管线钢板中的析出相主要有两种类型,一种为尺寸较小的NbC析出相(1～30 nm),另一种为尺寸较大的(Ti,Nb)(C,N)复合析出相(50～300 nm),两种类型均为面心立方结构;生产工艺对析出相的粒度分布有明显影响,避开900～950 ℃碳氮化物的快速析出温度区间,以及适当增加冷却速度可以有效提高20 nm以下的析出粒子体积分数,细化析出物尺寸,从而提高析出强化对屈服强度的贡献.     

Investigations on the Effect of Ball Burnishing Parameters on Surface Hardness and Wear Resistance of HSLA Dual-Phase Steels

Surface finish has a vital influence on most functional properties of a component like fatigue life, wear resistance, corrosion resistance, etc. This has given birth to processes such as lapping, honing, burnishing, etc. Burnishing is a fine finishing operation involving the cold working plastic deformation of surface layers to enhance the surface integrity and the functional utility of a component. The present study has been carried out to establish the effect of burnishing parameters viz. feed rate, speed, force, ball diameter and lubricant on surface hardness, and wear resistance of HSLA dual-phase steel specimens. The result indicates that burnishing parameters have significant effect on the surface hardness and wear resistance.     

奥氏体化温度对900 MPa级HSLA钢显微组织和晶体学演变的影响

采用OM和SEM研究了奥氏体化温度对HSLA钢组织演变和低温韧性的影响.结果 表明:奥氏体化温度由850℃升高至950℃(实验钢的AC3温度为819℃)并保温30 min后,奥氏体的平均晶粒尺寸由7.22 μm增大到17.39 μm,在850～950℃淬火后的显微组织均为板条马氏体,屈服强度和抗拉强度均呈下降趋势,延伸...     

超快速退火对Nb+Ti-IF钢组织和织构的影响

研究了超快速退火对一种冷轧变形量为94.2%的Nb+Ti-IF钢的微观组织和织构的影响。结果表明:超快速退火(升温速度为300℃/s)提高了钢的再结晶完成温度,整个再结晶退火可在短至0.41 s内完成。与普通退火(升温速度为20℃/s)后钢的再结晶组织相比,超快速退火处理后晶粒平均尺寸由12.98μm细化到10.12μm,晶粒长大速度由～3μm/s提高到～23μm/s,且再结晶晶粒内存在大量缠结位错。在极短时间内,超快速退火再结晶织构仍以均匀、锋锐的{111}//ND有利深冲性能的γ织构为主,且避免了其它α织构的生成,有利于使退火板具有良好的成形性能。     

抽油杆钢材的发展和抽油杆的服役失效

抽油杆可以把地面抽油机动能传递给抽油泵,是石油生产中重要的工件之一.随着采油工程向腐蚀井、深井、超深井发展,普通抽油杆的耐蚀性、抗拉强度和疲劳强度等性能已不能满足生产要求.本文综述了C级、D级、KD级和H级抽油杆的分类标准、制备方法、应用环境及面临的挑战.抽油杆钢服役失效包括腐蚀、疲劳、机械磨损等.分析发现,抽油杆的失效主要是疲劳断裂或腐蚀疲劳断裂.在腐蚀性环境条件下,抽油杆会发生表面电化学腐蚀,形成腐蚀坑,而腐蚀坑是疲劳裂纹的主要萌生源.在拉-拉或拉-压载荷的作用下,抽油杆发生疲劳断裂.本文简单介绍了抽油杆在各油田中的服役环境及抽油杆的发展史,通过对比抽油杆不同热处理工艺所产生的微观组织,探索其防腐蚀、防氢脆、防疲劳的机理,同时分析了抽油杆在使用过程中常见的腐蚀、疲劳、磨损等失效原因和机制,最后对未来开发高性能抽油杆的可行途径进行了探讨.