V-N对中碳SiMn非调质钢显微组织的影响

用光学显微镜和透射电镜研究了0.130%V-0.021 5%N、0.130%V-0.0304%N和0.001%V- 0.020 7%N三种V-N含量的(%)0.37～0.38C、0.82～0.92Si、1.78～1.81Mn、0.06 Ti、0.015Nb非调质钢的组织,用Gleeble 1500热模拟机测定了该钢的应力-应变曲线,并用JMatPro 4.1软件计算了该钢的CCT曲线以及900℃和600℃平衡状态下钢中各相的含量。结果表明,该钢的组织为珠光体+先共析铁素体,随氮含量增加,珠光体增多,晶界铁素体变粗;随钒含量减少,珠光体数量显著增加,贝氏体及铁素体变粗;共析铁素体和先共析铁素体中的析出物尺寸≤3 nm;V和/或N含量高的钢,应变时应力大。     

Effect of Nb-V Microalloying on Microstructures and Mechanical Properties of Medium Carbon Non-Quenched and Tempered Steel

Based on optical microscope(OM),transmission electron microscope(TEM) and mechanical performance measurement,the microstructures and mechanical properties of Nb-V micro-alloying non-quenched and tempered steels have been studied.The results showed that the microstructure consists of ferrite and pearlite,in which there exists a lot of intragranular ferrite.Niobium carbide is the main form of carbonitrides,Nb-enriched carbonitrides refine grains,V-enriched carbonitrides have precipitation strengthening effect,which promotes the toughness of the studied steel.The mechanical properties for steels 1,2 and 3 have met the standards required by high load automobile crankshaft,in which the comprehensive property for No.2 is the best.     

超高碳钢的回火组织及力学性能

用CM200型透射电子显微镜研究了超高碳钢双相区淬火 中、高温回火后的组织,用Instron型拉伸试验机测定了力学性能.结果表明:650℃的回火组织为等轴状的铁素体与球状的渗碳体,屈服强度σ0.2=1127MPa,抗拉强度σb=1 266 MPa,均匀伸长率δu=8.26%,总伸长率δt=9.71%,维氏硬度HV为397;450℃回火组织的铁素体保持淬火的形态,回火碳化物为ε碳化物在基体上以断续的片状析出,σ0.2=1 911 MPa,σb=2 028MPa,δu=δt=1.88%,HV为595;400℃回火组织中的铁素体保持淬火的形态,回火碳化物在位错处几乎呈网状析出,拉伸无塑性,HV为703.     

Study on Microstructure Refinement of Vanadium and Nitrogen Microalloyed Low Carbon Bainitic Steel

The effect of relaxation treatment after finish rolling on microstructure and mechanical properties has been investigated for a vanadium and nitrogen microalloyed low carbon bainitic steel.Finer lath bainite microstructure can be obtained in the plate with relaxation.The results of quantitative statistics show that in the plate without relaxation,80% of the total bainite lath bundles are in the range 5-15μm in length and 3-13μm in width,while in the plate with relaxation 80% of the total bundles are in the range 3-9μm in length and 1-7μm in width.The mechanical properties show that the plate with relaxation has higher impact energy,yield strength and hardness than the plate without relaxation,also the comprehensive performance after tempered at 650℃ is superior to the plate without relaxation.     

表面纳米晶化处理中碳钢的组织与力学性能

采用高能表面处理技术在40Cr钢的表面制备出具有纳米晶体特征的表面层.用扫描电子显微镜和透射电子显微镜研究了表面纳米层的微观结构,并利用纳米压入法测定了表面纳米层的硬度.结果表明,经过高能表面处理后,样品表面层的晶粒细化为纳米晶,平均晶粒尺寸约为11 nm,表面纳米层的硬度明显提高.     

Effect of Cooling Patterns on Microstructure and Mechanical Properties of Hot-Rolled Nb Microalloyed Multiphase Steel Plates

 The effect of the run-out table cooling patterns on the microstructure and mechanical properties of Nb microalloyed steel plates was investigated by hot rolling experiment. The results showed that the mixed microstructure containing ferrite, bainite and significant amounts of retained austenite can be obtained through three kinds of cooling patterns on the run-out table under the same hot rolling condition. Three kinds of cooling patterns possess different austenite transformation kinetics, which leads to variations in microconstituent characteristics. The yield strength increases, the tensile strength decreases and the total elongation tends to increase as the cooling patterns Ⅰ, Ⅱ and Ⅲ were applied respectively. The yield strength, the total elongation and the product of tensile strength and ductility reach the maximum values (547 MPa, 37.2% and 28384 MPa·%, respectively) for the steel plate processed by cooling pattern Ⅲ.     

Influence of Vanadium on Fracture Splitting Property of Medium Carbon Steel

The fracture splitting property of medium carbon steel 37MnSiS microalloyed with V up to 0. 45% was investigated by using simulated fracture splitting test,for the development of new crackable medium carbon steel to manufacture high performance connecting rod. Conventional high carbon steel C70S6 was used for comparison. The results show that the volume fraction of both ferrite and V-rich M( C,N) particles increases,and the pearlite interlamellar spacing decreases with increasing V content,which in turn results in gradual increase of strength and decrease of ductility and impact energy. The fracture splitting property of the tested steel could be improved significantly due to the increase of V content mainly through the precipitation hardening mechanism of fine M( C,N) precipitates. The fraction of brittle cleavage fracture in the crack initiation area increases noticeably with increasing V content and full brittle cleavage fracture surface could be obtained when V content was increased to 0. 45%. It is concluded that medium carbon steel with V content higher than about 0. 28% possesses not only comparable or even higher mechanical properties with those of conventional steel C70S6,but also excellent fracture splitting property,and therefore,is more suitable to fabricate high performance fracture splitting connecting rod.     

Effect of Cyclic Annealing on Microstructure and Mechanical Properties of Medium Carbon Steel

The microstructure and mechanical properties of medium carbon steel after cyclic heat treatment were in-vestigated.The effects of cyclic numbers and long time annealing on the microstructure and mechanical properties of the experimental steel were compared.A short-duration (5 min)holding at 1 023 K (above A1 temperature)and a short-duration (3 min)holding at 893 K are adopted in each cyclic heat treatment.The spheroidization is accelerated during cyclic heat treatment,and the spheroidizing ratio grows with cyclic numbers.After 1 2-cycle heat treatments, there are few incompletely spheroidized regions in the specimens,and cementite lamellae mostly change into cement-ite particles.The morphological character of cementite for 12 cycles is similar to that undergoing annealing for 10 h at 973 K.The strength of the experimental steel after 5-cycle heat treatment is the lowest in the following cyclic heat treatment,but it is still higher than that of specimens with subcritical annealing over a long period (10 h).After 12-cycle heat treatment,the strength of the experimental steel is close to that of the normalized steel,and the plasticity is the best in all heat-treated specimens.     

组织细化对中碳Cr-Mo钢力学性能的影响

通过循环热处理和改变奥氏体化温度两种方法获得不同的原奥氏体晶粒尺寸,研究了不同晶粒尺寸对高温回火中碳Cr-Mo钢力学性能的影响.结果表明,当奥氏体化温度低于1 050℃时,实验钢的强度随奥氏体化温度的升高而提高.在相同的奥氏体化温度下,强度随着晶粒的细化而上升.在整个研究范围内,随着晶粒的细化,实验钢的韧性有一定的提高,塑性略有下降.晶粒细化显著提高了钢的低温冲击韧性.     

中碳钢球化退火行为和力学性能的研究

采用常规双相区球化退火和亚温球化退火工艺研究了常规轧制（CR）和控轧控冷（CRC）的中碳钢SWRCH35K的球化退火行为和力学性能。结果表明,与传统的双相区球化退火相比,亚温球化退火时碳化物球化进程明显加快,球化率高,且碳化物比较细小,具有良好的塑性和冷成形性,采用亚温球化退火处理可明显地缩短球化退火时间。控轧控冷的中碳钢线材尽管具有比较粗大的珠光体组织,但因有相当部分的珠光体发生退化,其球化退火进程要明显快于细珠光体组织。     

TRIP钢显微组织与性能关系的评述

概述了近20年来汽车材料中TRIP钢的研究进展情况。对影响TRIP钢强度和塑性的显微组织从其大小、形貌及含量等多方面进行了分析和比较，认为要使TRIP钢具优良的强度和塑性匹配，应优化该钢显微组织中各相含量的配比。     

热变形和加速冷却对低碳微合金钢组织的影响

利用Gleeble-1500热模拟实验机研究了热变形和加速冷却工艺对3种低碳微合金钢组织演变的影响,结果表明,在再结晶或未再结晶温区实施1道次变形的晶粒细化效果不如2道次形次的效果明显,在再结晶和再结晶温区实施4道次变形可以得到更细的组织,配合较高的冷却速度可以形成部分针状铁素体组织。随着冷却速度的提高,组织变得更细,并且针状铁素体的数量增加。在相近的变形和冷却条件下,碳、锰含量较高的试样具有更细的组织。     

低温时效对非调质钢组织和耐疲劳性能的影响

 紧固件工作失效多起源于疲劳,利用光学显微镜、透射电子显微镜、洛氏硬度仪和耐疲劳性能试验机等分析测试方法研究时效处理对减面率22.5%的非调质钢MFT8紧固件的组织、硬度和耐疲劳性能的影响。研究结果表明：与未时效处理试样相比,时效工艺为300℃×2h时,其硬度和耐疲劳极限达到最大值。时效强化和耐疲劳性能提高的主要原因是,在时效回复处理过程中,位错之间相互反应而湮灭或逐渐迁移而重排,引起位错墙或位错胞内部位错密度减少,形成具有稳定状态或亚稳定状态的组织结构或亚结构。     

钒,氮含量对耐磨钢NM400组织及性能的影响

在普通Cr-Mo-B系低合金耐磨钢成分基础上,通过添加适量的钒、氮元素,研究钒氮微合金化对轧后直接淬火(DQ)+低温回火耐磨钢板组织及性能的影响。结果表明:无钒氮钢板的微观组织为板条马氏体组织,-20℃冲击功为15 J,布氏硬度为443HBW。分别添加质量分数0.088%V-0.013%N和0.089%V-0.029%N的2种钒氮微合金化的钢板,板条马氏体组织明显细化,在组织中发现存在少量针状铁素体组织。2种钢板的-20℃冲击功分别提高至30和42 J,质量分数0.089%V-0.029%N的钢板强度、硬度与无钒氮钢板基本一致。低温轧制过程中析出的V(C,N)颗粒起到定扎奥氏体晶界、抑制晶粒长大作用。在860℃温度终轧及轧后弛豫过程中析出的V(N,C)粒子可以促进针状铁素体形成,它们起到分割奥氏体晶粒、细化马氏体板条束的作用。含质量分数0.089%V-0.029%N的耐磨钢板的综合性能最好。     

时效温度对贝氏体型冷作强化非调质钢力学性能的影响

 研究了时效温度对一种低碳Mn-B-Ti系贝氏体型冷作强化非调质钢力学性能的影响。结果表明：试验料的强度随时效温度的升高先是增加,并在250℃时存在一个峰值,随后强度又随时效温度的升高而降低,当温度升高到400℃以上时强度明显降低;试验料的塑性和屈强比则随时效温度的升高逐渐增加,其中后者增加的幅度更显著。与未充氢试样相比,试验料拉拔并充氢后的延迟断裂性能显著降低。随着时效温度的升高,充氢试样中的氢含量降低,缺口抗拉强度RBN和延迟断裂强度比R缓慢增加,当时效温度大于200℃时,RBN和R则明显增加。因此,在满足保载永久伸长变形量及强度和塑性要求的前提下,应选择合适的时效温度,以保证材料的延迟断裂性能。     

添加微米级ZrC颗粒的低碳微合金钢力学性能研究

真空条件下,在低碳微合金钢中添加体积分数为1.1%的微米级ZrC陶瓷颗粒,在φ450 mm热轧试验机上进行轧制,轧后钢板晶粒被细化到5.5μm,其抗拉强度和屈服强度分别达到635 MPa和517.5 MPa,维氏硬度(HV5)达到214.zrC颗粒对试验钢具有明显的强化作用,在试验钢凝固结晶和后期轧制过程中均起到细化晶粒的作用.热轧钢板的显微组织为铁素体,钢中夹杂物弥散分布.     

冷成型对低碳微合金钢拉伸行为及性能的影响

研究了冷成型对铁素体+珠光体组织类型低碳微合金热轧钢板拉伸行为及性能的影响。用弯曲和压平变形模拟高频直缝焊管制管及取样钢板所经历的冷成型过程。对冷成型前后材料拉伸行为和性能进行对比试验,结果表明,冷变形不同程度改变材料拉伸行为及性能,且这种变化是由冷变形方式和程度所决定;包申格效应试验分析结果表明,材料背应力随塑性应变增加而增大,且到达某一数值后当塑性应变继续增加,背应力增加幅度明显减小;有限元分析结果表明,冷成型导致的钢板性能变化是由包申格效应和加工硬化共同作用的结果,并给出了其形成机制。     

低碳贝氏体钢的组织类型及其对性能的影响

低碳贝氏体钢受控冷工艺的影响会得到不同类型的组织，在较慢速冷却时，在奥氏体中先形成针状铁素体，残余奥氏体会被包裹在铁素体之中，形成粒状贝氏体团。工业轧制试验表明．不同控制冷却工艺可得到两类组织，一类出现黑珠组织(富碳马氏体组织)．具有该组织的钢轧态冲击韧性低。另外一类为细化的板条贝氏体组织，具有该组织的钢轧态强度高，冲击韧性好，但伸长率不足。通过回火处理，存在黑珠组织钢的冲击韧性能得到提高，超细化板条贝氏体组织钢的伸长率也能得到改善，但后者屈服强度会比前者高100MPa左右。     

热轧温度参数对Nb-Ti和Nb-V微合金钢力学性能的影响

 设计了650 MPa级的Nb Ti和Nb V微合金钢的化学成分。采用正交实验方法考察了加热温度、终轧温度和终冷温度对这2种钢力学性能的影响。实验结果表明,加热温度和终冷温度是影响Nb Ti和Nb V钢力学性能的主要因素。2种钢的伸长率与屈服强度以及屈强比与屈服强度之间都具有明显的相关关系。