Recycling-Induced Copper Contamination of a 42CrMo4 Quench and Tempering Steel: Alterations in Transformation Behavior and Mechanical Properties

The transformation behavior and the mechanical properties of three laboratory produced steels are presented. To investigate the influence of copper contamination, the reference alloy 42CrMo4 is modified and alloyed with 0.5 and 1.0 wt% copper, respectively. The transformation behavior is investigated through dilatometry that yields continuous cooling transformation diagrams, while the mechanical properties are investigated by hardness measurements as well as Charpy-V-notch impact and tensile tests. Accompanying microstructure investigations by means of light optical, scanning electron, and transmissions electron microscopy and thermodynamic simulations (CALPHAD) are performed. It is demonstrated that copper contamination that will be unavoidable when increasing the overall steel recycling fraction may contain the potential for increasing the hardness as well the strength of standard high strength steels, although it is considered to be very detrimental during steel production. Together with reduced environmental footprints and production costs due to the utilization of lower grade scrap with more Cu-contamination, the development of alternative processing routes for Cu-contamination-tolerant high strength steels is pursued.     

深冷处理对NM500耐磨钢性能与磨损行为的影响

以一种自行设计的NM500级别耐磨钢为研究对象,利用冲击磨损试验,分析了深冷处理对其组织性能和磨损行为的影响。结果表明,NM500耐磨钢经深冷处理后,抗拉强度、硬度和冲击韧性均有提高,在淬火+深冷+回火处理后,最佳的综合力学性能可达抗拉强度1 910 MPa、硬度523HB、冲击韧性24.3 J/cm2,此时试验钢组织主要为马氏体,有Nb和Ti的碳化物析出。深冷处理通过残余奥氏体向马氏体转变,减少了不稳定相的含量,提升了试验钢的力学性能,从而使淬火+深冷+回火处理后的试验钢具有更高的耐磨性,此时的磨损机制以磨粒磨损为主,磨损形貌主要为犁沟、犁皱。而未经深冷处理的淬火+回火处理试验钢磨损机制以黏着磨损为主,磨损形貌主要为剥落坑和切削。     

301奥氏体不锈钢薄板拉伸强度与冷轧硬度之间的关系

 为对冷轧不锈钢薄板的产品硬度控制提供指导,尝试用一个新的方法来取代试轧,既达到控制冷轧板硬度的目的,又能降低成本、提高效率。对099mm厚的经过退火的301奥氏体不锈钢薄板进行冷轧减薄,并进行室温拉伸试验,测量其维氏硬度。通过观察金相和利用X射线衍射,验证了应变诱导马氏体相变是导致301奥氏体不锈钢冷轧和拉伸时产生加工硬化的主要原因。试验结果表明,冷轧和拉伸有着相似的加工硬化趋势,综合拉伸与轧制试验数据,确定了拉伸强度与冷轧硬度之间的关系,实现了通过拉伸强度来得到对应应变下的冷轧硬度,具有很好的预见性。冷轧可以提高301不锈钢的强度和硬度,显著改善其力学性能。     

Al元素对Q＆P钢连续冷却的相变及组织影响

Q＆P（Quenching and Partitioning）钢是一种超高强先进汽车用钢,具有优异的综合机械性能。据此,采用膨胀法结合金相-硬度法,在DIL-805热膨胀仪上测定了Q＆P钢的临界点。测定了不同冷却速度下连续冷却转变膨胀曲线,并对比Al元素的加入对Q＆P钢连续冷却转变产物的组织和硬度的影响。对制定C-Mn-Al系Q＆P钢的热处理工艺提供一定的参考依据。     

冷轧变形量对304不锈钢力学性能的影响

 研究304奥氏体不锈钢薄板的硬度随冷轧变形量的变化规律,为奥氏体不锈钢薄板工业生产提供指导。同时,采用金相显微镜、维氏硬度测量、X-射线衍射仪和透射电镜研究了不同变形量冷轧对304不锈钢显微组织和机械性能的影响。在室温对0.5mm厚退火板材进行冷轧,使冷轧变形量从10%增加到52%。结果表明,形变诱发马氏体相变是导致304不锈钢冷轧时产生加工硬化的主要原因,冷轧可以显著提高钢的强度和硬度。当冷轧变形至40%时,304不锈钢的维氏硬度是未变形时的2.2倍,屈服强度、抗拉强度分别增大到未变形时的4.2倍（880MPa）和1.8倍（1312MPa）。     

Ti微合金化高强度热轧带钢组织性能及强化机理

The continuous cooling transformation behavior, the effect of coiling temperature on microstructure and mechanical properties, and strengthening mechanisms of Ti microalloyed high strength hot strip steel were systematically investigated by thermal simulation testing machine, laboratory rolling mill, SEM and HR-TEM. The dynamic CCT curve was established. The results show that the austenite to ferrite and pearlite transformation takes place when the cooling rate is less than 1??/s. The austenite to bainite transformation accompanied with austenite to ferrite and pearlite transformation takes place when the cooling rate is in the range of 5 ??/s to 10 ??/s. The bainitic transformation temperature is about 600??. The amount of granular bainite decreases, while the amount of lath bainite increases with the increase of cooling rate in the range of 20??/s to 50??/s. Furthermore, the study on the effect of coiling temperature on the microstructure and mechanical properties of experimental steel has shown that the strength and plasticity of tested steel are improved with decreasing the coiling temperature. When the coiling temperature is 550?棬the experimental steel possesses optimal mechanical properties owing to the grain refinement and precipitation of nano-scale TiC particles. And the tensile strength, yield strength and elongation of tested steel were 742MPa, 683MPa and 22??5%, respectively.     

汽车螺旋悬架弹簧用钢55SiCrA组织和性能研究

采用热膨胀法结合显微金相与硬度法,在LINSEIS L78 RITA相变仪上测定了55Si Cr A弹簧钢的临界点温度和连续冷却转变曲线,研究了冷却速度对组织和硬度的影响规律。在此基础上,进行了控轧控冷工业试验。结果表明,当冷速≤2℃/s时,转变产物为少量铁素体、珠光体,珠光体硬度随冷速增大而增大;当冷速≥5℃/s时,转变产物为珠光体、马氏体;当冷速≥20℃/s时,转变产物为马氏体,硬度随冷速增大而增大;现场控轧控冷的试验钢抗拉强度达到1 163 MPa,伸长率为13%,面缩率为49%,综合力学性能良好,满足了用户的使用要求。     

硫含量对极低屈服点钢组织与性能的影响

摘要：采用Gleeble 3800热模拟试验机、OM、TEM与Vickers 硬度计，研究了不同变形温度下S含量对极低屈服点钢析出相、晶粒尺寸与硬度的影响；结合拉伸和冲击试验考察了S含量对实验室试轧钢板力学性能的影响。结果表明，不同变形温度下，当S质量分数由0.0018%提高至0.0077%，钢中晶粒尺寸发生粗化，硬度降低，析出相的主要类型由TiC变为Ti4C2S2和TiS，析出粒子的尺寸随之增大，分布数量减小。S质量分数为0.0077%的试轧钢板较S质量分数为0.0018%的试轧钢板具有更低的屈服强度且塑韧性并未降低，其综合力学性能更优且完全满足极低屈服点钢的要求。     

热处理工艺对高碳贝氏体钢的组织与性能影响

以轴承用高碳贝氏体钢为研究对象,采用扫描电子显微镜、X射线衍射仪及硬度计等手段研究了不同奥氏体化温度对贝氏体钢组织形成及性能的影响,遴选出最优的奥氏体化工艺,同时对比了不同贝氏体等温转变后有无Ce元素添加的高碳贝氏体钢的力学性能.试验结果表明,950℃奥氏体化温度得到的组织中无明显的大颗粒未溶碳化物,组织尺寸和硬度性能...     

冷加工对316L不锈钢力学行为和组织的影响

采用室温拉伸及硬度测试研究了不同的冷变形量对316L不锈钢室温力学性能及硬度的影响,并通过OM、TEM对冷变形后组织结构的观察,分析讨论了不同变形后力学性能及硬度的变化机制.结果表明,冷变形使材料的强度和硬度得到大幅度提高,但塑性有所降低.冷变形量为25％时,钢的屈服强度可达到745 MPa,同时伸长率达到19.3％.随冷变形量的不同,该钢加工硬化能力不同.变形量低于2.5％时,强度、硬度增加的速度较快,而变形量高于约2.5％后,强度、硬度增加的速度却相对较小,其原因是变形机制不同.另外,冷变形后钢的屈服强度与硬度有着相似的变化规律,由此提出了由冷变形后硬度变化预测冷变形后拉伸屈服强度的方程.     

Effect of Cooling Rate and Deformation on Microstructures and Critical Phase-Transformation Temperature of Boron-Nickel Added HSLA H-Beams

 Microstructures and critical phase-transformation temperature of boron-nickel added Nb-treated high strength low alloy (HSLA) H-beams cooled at different cooling rate, with different deformation were investigated. Continuous cooling transformation (CCT) diagram of this new type of steel was obtained by using Gleeble 1500 thermomechanical simulator. Microstructures and hardness, especially micro-hardness of the experimental steel were investigated by optical microscopy (OM), scanning electron microscope (SEM), Rockwell and Vickers hardness tests. Phase analysis was also studied by X-ray diffraction (XRD). The results indicated that with increase of cooling rate, microstructures of continuous cooled specimens gradually transformed from polygonal ferrite and pearlite, grain boundary ferrite and bainite, bainite and martensite to single martensite. The CCT diagram revealed that slow cooling was needed to avoid austenite-bainite transformation to ensure toughness of this steel. By plastic deformation of 40%, austenite-ferrite transformation temperature increased by 46 ℃, due to deformation induced ferrite transformation during continuous cooling, but Rockwell hardness has little change.     

热轧逆相变退火中锰钢的疲劳性能

 为了研究循环载荷对含奥氏体钢微观组织和力学性能的影响,对逆相变处理中锰钢进行了疲劳性能研究,采用SEM、EBSD、XRD等表征了微观组织,采用单轴拉伸试验表征了疲劳前后的力学性能。研究结果表明,在应力比R为-1的试验条件下,逆相变中锰钢中值疲劳极限为378 MPa,疲劳极限与抗拉强度之比σ-1/R_m为0.48;中锰钢超细晶粒尺寸特征有利于阻碍二次疲劳裂纹扩展,亚稳奥氏体的转变行为受应力幅影响较大;在中值疲劳极限的应力水平下,亚稳奥氏体和单轴拉伸性能受循环载荷影响不大。     

屈服强度700MPa级冷成形用热轧带钢的开发

 采用SiMnTiNb低C钢成分、运用TMCP技术在1450mm热连轧生产线上成功开发了一种屈服强度700MPa级热轧超高强冷成形用钢。测定了开发钢的连续冷却相变（CCT）曲线,研究了其析出强化规律,测试了带钢的力学性能和冷弯性能,研究了其焊接性能。结果表明,其组织为4~5μm细晶粒铁素体+贝氏体+少量马氏体,铁素体晶粒中含Nb-Ti沉淀相。超高强度的获得归功于细晶强化+相变强化+析出强化。所开发的热带钢冷弯成形性和焊接性能良好。     

预热对激光熔化沉积成形12CrNi2合金钢组织与性能的影响

使用高功率光纤激光器的快速成形系统和电磁感应加热设备,分别在未预热和预热的情况下成形12CrNi2合金钢.通过扫描电镜观察成形件微观组织、维氏硬度计测试不同部位硬度、万能材料试验机测试不同方向的拉伸性能,研究预热对激光熔化沉积12CrNi2合金钢不同方向的组织、硬度、拉伸性能的影响.结果表明:未预热条件下,单道熔池组织为板条马氏体,块状成形件熔池为回火马氏体与贝氏体混合组织,XOZ截面与YOZ截面组织没有明显的组织差别,但YOZ截面整体硬度大于XOZ截面,同时两个截面均出现了大尺寸宏观裂纹缺陷,力学性能差.在预热条件下,熔池由于温度梯度降低发生贝氏体转变,单道熔池呈现性能优异的下贝氏体组织;块状成形件熔池没有发生回火马氏体转变,主要为粒状贝氏体.截面硬度分布较未预热下更为均匀.在拉伸方向及搭接方向均呈现高强度、低塑性特征,抗拉强度可达1189 MPa,屈服强度为951 MPa,伸长率仅为2.8%,性能没有明显的各向异性.预热能够降低熔池中温度梯度,减小热应力,有效控制裂纹缺陷,促进组织均匀化,降低组织、性能的各向异性,提高合金钢成型件力学性能.      

Transformation Conditions ‐ Microstructures ‐ Mechanical Properties Relationship in 0.60%C Hypoeutectoid Steel

The relationship between transformation conditions, microstructures and mechanical properties were investigated on a 0.60%C hypoeutectoid steel, which has predominantly pearlitic microstructure. The steel had been austenized at 850‐1050 °C and then isothermally transformed at 570‐660 °C. Afterwards, the microstructures were analyzed by optical microscope, scanning electron microscope, and quantitative metallography. And the mechanical properties were determined. The results indicated that the interlamellar spacing, the pearlitic colony size and the proeutectoid ferrite content follow a linear relationship with the reciprocal of the undercooling, and the strength, the hardness and the toughness follow a Hall‐Petch type of relationship with the inverse of the square root of the interlamellar spacing. Besides, the stress condition should be taken into account during analyzing the effect of the interlamellar spacing on the mechanical properties. The results have been explained on the basis of transformation conditions ‐ microsturctures ‐ mechanical properties ralationship.     

30SiMnCrB5热成形钢的微观组织和力学性能

为了提高热成形钢的综合性能,设计了一种C-Si-Mn-Cr-B系热成形钢,采用热膨胀仪测定并研究了30SiMnCrB5热成形钢的连续冷却转变曲线和相变规律.分析了经轧制、退火及热成形模拟后钢板的微观组织形貌和力学性能,结合等密度线极图的方法,判定了热成形模拟后钢板中马氏体变体与母相的取向关系.30SiMnCrB5热成形钢具有较好的淬透性,临界冷速为5℃·s-1,有效抑制了珠光体和贝氏体的形成,完全马氏体组织的硬度可达600 HV以上.热成形模拟后的微观组织由板条马氏体和残余奥氏体构成,残余奥氏体主要以薄膜状分布在马氏体板条间,质量分数为6%~8%,抗拉强度为1800 Mpa左右,总伸长率可达10%以上,强度和塑性的匹配较好.热成形模拟后30SiMnCrB5热成形钢板中马氏体变体与母相的取向关系更接近N-W关系,12种变体没有都出现在原始奥氏体内.      

淬火工艺对铜沉淀强化UHS钢组织性能的影响

 超高强度钢不仅可以降低海洋装备本身质量，而且节约能源，但这类钢应用过程中要求具有良好的强韧性匹配，而淬火工艺显著影响其后续的相变和性能。采用Thermo Calc软件、光学显微镜、扫描电镜以及透射电镜等研究了淬火工艺对低碳(w(C)<0.05%)铜沉淀硬化超高强海工钢组织性能的影响。结果表明，910 ℃淬火、450 ℃时效处理后峰值硬度达到386HV，700 ℃时效后空冷可得到部分二次马氏体组织，峰值硬度为357HV。525 ℃以下时效，富铜相析出的平均半径约为5 nm，产生较高的强化增量。820~910 ℃淬火，随着淬火温度降低，细小的(Nb，Ti)C粒子能够有效抑制奥氏体晶粒的长大，细化晶粒和马氏体板条块，同时基体中小角度界面密度增加，强韧性提高。其中820 ℃淬火强度最高达到1 109 MPa，-80 ℃ V型冲击功为91 J。     

硅对Nb-V微合金化Si-Mn-Cr-Mo系贝氏体轨钢组织和性能的影响

研究了1250 MPa级Nb-V微合金化Si-Mn-Cr-Mo系贝氏体轨钢(/%:0.25 C,0.38-1.56 Si,1.69～1.76 Mn,1.34～1.37 Cr,0.32～0.33 Mo,0.034～0.036 Nb,0.11～0.12 V)硅含量对试验钢显微组织和力学性能的影响。试验结果表明:试验钢热轧后空冷,随着硅含量的增加,试验钢的铁素体+珠光体相变被抑制,室温组织中贝氏体、马氏体含量增加,影响钢的强度和硬度,硅含量由0.38%提高到1.56%时,试验钢的屈服强度由846 MPa增至903 MPa,抗拉强度由1 280 MPa增至1 355 MPa,HBW硬度值由353增至411。     

Effect of Microalloying Additions on the Microstructure and Mechanical Properties of Low Carbon Steel

Low carbon steels are characterized by good weldability,formability and fracture toughness properties.However,the low strength levels of these steel grades limit their wide applications.On the other hand,increasing the strength by increasing the carbon content and alloying elements deteriorates the other properties.In this study,the microalloying technique was used to examine the possibility of attaining low carbon steels with good combination of strength,ductility and impact properties.A low carbon steel microalloyed with single addition of vanadium and another one microalloyed with combined addition of vanadium and titanium were used in this investigation and their properties were compared with non-microalloyed low carbon steel having the same base composition.Furthermore,other two nonmicroalloyed and V-microalloyed steels with higher carbon,silicon and manganese contents were also investigated to reveal the effect of base composition.Tensile,hardness,room and zero temperature Charpy V-notch impact tests were conducted to evaluate the variations in the mechanical properties of low carbon hot forged steel containing vanadium and combinations of vanadium and titanium.In addition,the microstructures of the different investigated steels were observed using both optical microscope and scanning electron microscope.Furthermore,the hardness of the ferrite phase was also determined using micro-hardness technique.The results showed improvement of the mechanical properties of the investigated steels by both single V-and combined V + Ti-microadditions.Tensile,hardness and impact tests results indicated that good combinations of strength,ductility and impact properties can be achieved by V-microalloying addition.Steel with combination of V and Ti microaddition has much higher hardness,yield strength,ultimate tensile strength and impact energy at both room and zero temperatures compared with non-microalloyed and single Vmicroalloyed steels.Higher C,Si and Mn contents result in increasing the strength accompanied with decrea