800 MPa级CSiMnNb与CSiMnCr系冷轧双相钢组织与性能

在实验室采用CCT-AY-Ⅱ连续退火模拟器研究不同退火温度条件下800 MPa级CSiMnCr与CSiMnNb系冷轧双相钢的力学性能,并对其显微组织进行分析.结果表明：在同一成分试验钢中,770℃退火较790℃退火时所获得的强度高;钢中添加少量的Nb细化了铁素体与岛状马氏体组织,并且岛状马氏体更纯净,屈强比低,加工硬化指数n值更高.     

Discussion on the heat treatment process of cold rolled Q345 steel in laboratory

A new kind of DP steel with about 40％ martensite in matrix was developed from cold rolled Q345steel by continuous annealing simulation.Microstructure and mechanical properties obtained by conventional ...     

回火工艺参数对DP600热轧双相钢组织和性能的影响

采用低温回火实验模拟热轧双相钢实际生产过程中卷取后的冷却过程,分析回火温度与保温时间对0．09C-0．1Si-1．3Mn-0．5Cr-0．05P热轧双相钢组织及力学性能的影响。结果表明,回火过程中主要是碳原子通过扩散影响铁素体与马氏体中的微结构,从而对其组织和力学性能产生影响;200℃回火后双相钢基本保持原有的组织与性能,230℃以上随回火温度升高和保温时间延长,马氏体分解逐渐明显,铁素体中碳原子钉扎可动位错造成屈服现象的发生;在230～250℃温度范围回火时,保温时间的延长较温升对回火程度的影响更加明显。     

冷轧TRB薄板的连续退火工艺试验研究

为了探索连续退火工艺对TRB板组织与性能的影响,在实验室采用四辊可逆式冷轧机进行单厚度过渡区TRB板轧制,对轧制的DP590双相钢和22Mn B5热成形钢TRB薄板进行模拟连续退火试验,利用光学显微镜和扫描电镜,以及拉伸和硬度试验方法研究钢板退火后各厚度区的组织与力学性能差别.研究表明:TRB板变厚度区的最大厚度偏差为0.03 mm,长度误差1.0 mm.TRB板在连续退火的冷却段和过时效段,其薄区温度较过渡区和厚区的温度偏低57~20℃,导致DP590钢板薄区的抗拉强度和伸长率较高,屈服强度与厚区的相当,而22Mn B5钢TRB板的屈服与抗拉强度偏高.在TRB板的变厚度区内维氏硬度波动较小.根据厚区的厚度来制定冷轧DP590双相钢TRB薄板的连续退火工艺,将更有利于保证钢板的组织与力学性能,对22Mn B5热成形钢TRB薄板建议采用罩式退火.     

Relation of martensite-retained austenite and its effect on microstructure and mechanical properties of the quenched and partitioned steels

A two-step quenching and partitioning(QP) treatment was applied to low-carbon alloy steels. The relation of initial martensite- retained austenite- fresh martensite and its effect on microstructure and mechanical properties were investigated by experiments. The results reveal that the volume fraction of retained austenite can reach the peak value of 17%, and the corresponding volume fractions of initial martensite and fresh martensite are 40% and 43%, respectively, when the tested steel is treated by initial quenching at 330°C, partitioning at 500°C for 60 s and final quenching to room temperature. Moreover, the micromorphologies of austenite and martensite become finer with the increasing of initial martensite fraction. The elongation is the highest when the volume fractions of initial martensite and retained austenite are 70% and 11%, respectively, meanwhile, the yield strength increases and tensile strength decreases gradually with the increase of initial martensite fraction, which proves that the mechanical properties including elongation, yield strength and tensile strength are based on the comprehensive effect of the retained austenite fraction, the finer microstructure and austenite stability.     

高强度冷轧双相钢应变硬化行为

为了研究双相钢在变形过程中的应变硬化特性,采用Hollomon法与修正的Crussard Jaoul法分析了试验钢的应变硬化曲线,并利用力学测试与显微组织观察等手段研究了组织结构对应变硬化行为的影响机制.结果表明：三种试验钢,均表现出较高的初始加工硬化能力.具有岛状马氏体与类针状马氏体的双相钢表现出两个阶段的应变硬化特征,具有粗大块状马氏体的双相钢则表现出三个阶段的硬化特征.与类针状和粗大块状马氏体相比,含有岛状马氏体的双相钢表现出较强的加工硬化能力和强度与塑性的良好配合.块状马氏体较早的进入塑性变形,导致双相钢变形协调难度加大并在晶界周围产生孔洞而使塑性恶化.     

低合金耐磨钢的组织与性能

低成本、高性能耐磨钢的需求增长及其开发都在进行中．本研究根据对耐磨钢性能的要求,试制了三种不同合金化方式的低合金耐磨钢,利用金相显微镜、透射电子显微镜、洛氏硬度计、万能材料试验机、夏氏冲击试验机和磨粒磨损实验机研究了其组织和性能,讨论了它们问的关系．结果表明：0．25C钢经不同工艺热处理后均获得了马氏体组织,并发生不同程度的自回火现象,硬度均大于45HRC,屈服强度大于1000MPa,抗拉强度大于1500MPa,并具有一定的塑性和韧性;在860℃淬火或920℃淬火并250℃回火后,实验钢的硬度、强度、塑性和韧性有最佳的配合,耐磨性最佳;V微合金化对钢的组织和性能没有明显影响．0．33C钢860℃或920℃奥氏体化后以等于或大于2．0％／s的冷速连续冷却或风冷至室温,回火或不回火即可得到由贝氏体与马氏体组成的混合组织,硬度超过50HRC,屈服强度大于900MPa,抗拉强度大于1500MPa,有一定的塑性和韧性,耐磨性良好,与商用淬火一回火耐磨钢类似;但由于具有高的加工硬化能力和良好的冲击韧性,在冲击条件下的耐磨性会优于商用钢．不同工艺热处理后的试验钢的磨损率随砂纸粒度和载荷增大而增大,载荷的影响较大,而磨粒的影响较小．     

低合金高强度双相耐磨钢热处理工艺研究

采用光学显微镜、电子显微镜和万能力学试验机对热处理后的低合金高强度双相耐磨钢试样进行组织观察和力学性能测试。结果表明,水淬后的试样微观组织为贝氏体-马氏体双相组织;250℃回火后的试样微观组织为回火马氏体和贝氏体;450℃和600℃回火后的试样微观组织分别为回火马氏体和贝氏体。水淬250℃回火后的试样具有最佳强度和塑性配比,其抗拉强度和屈服强度分别为1491.4 MPa和1264.6 MPa,HRC硬度为43,延伸率为9.42%。     

7．9Mn－1．4Si－0．07C钢高强韧机理研究

通过热轧、温轧、奥氏体化、两相区退火处理得到7．9Mn－1．4Si－0．07C钢板,该材料的拉伸强度及塑性随奥氏体化温度不同而具有显著差异．奥氏体化温度降低,室温下奥氏体含量升高,综合力学性能提高．当奥氏体化温度由900℃降低为800℃时,所得到钢板的奥氏体体积分数由15％增加到28％,拉伸强度由1150MPa提高到1340MPa,塑性由21％提高至27％．实验钢优异的力学性能源于其中大量的超细铁素体及奥氏体,细晶强化使其具有超高强度,铁素体基体及变形过程中奥氏体向马氏体相变提供了良好的塑性．基体组织中的位错强化,形变诱导马氏体转变的TRIP效应等是增强该钢板加工硬化能力的主要因素．     

空冷高硅中碳低合金钢的组织与性能

研究了高硅中碳低合金钢空冷态和空冷＋回火态的显微组织和力学性能.试验钢在860℃保温0.5 h奥氏体化后空冷处理,随后分别在250℃和400℃保温1 h回火.结果表明：试验钢空冷后组织为贝氏体/马氏体和残余奥氏体的混合组织,硬度约为41 HRC;而250℃回火后组织变化不大,硬度明显升高,约为49 HRC,韧性明显增加,由44 J/cm2增加到66 J/cm2,抗拉强度、屈服强度和延伸率明显下降.回火温度进一步增加对力学性能影响不大.     

残余奥氏体及其机械稳定性与钢强韧性关系的研究

钢中残余奥氏体发生应变诱发马氏体相变的百分量与拉伸应变量的对数呈线性关系,用直线斜率的倒数Ks值可表示残余奥氏体机械稳定性的大小。提高钢中残余奥氏体量及其机械稳定性是改善钢强韧性的有效途径之一。残余奥氏体发生应变诱发马氏体相变吸收能量是提高钢韧性的主要原因。在低碳贝氏体钢中,以M—A岛形式存在的残余奥氏体因受岛中马氏体的强化作用使屈服强度保持较高水平,而残余奥氏体在拉伸的均匀塑性变形阶段因应变诱发相变形成的马氏体使钢的抗拉强度提高。     

淬火配分工艺对高强Q&P钢织构和性能的影响

对试验用淬火配分（Quenching and Partitioning,Q&P）钢在一步淬火配分工艺中不同淬火温度（220 、260 、300 ℃）和淬火时间（60 、120 、180 s）下组织、织构、力学性能及拉伸断口特征进行研究. 结果表明:试验用Q&P钢在一步淬火配分中获得的最大残余奥氏体体积分数为7.12%;随着淬火温度升高,板条马氏体的宽度增大;随着淬火温度和配分时间升高,织构的最大强度逐渐降低,抗拉强度逐渐减少;屈服强度和延伸率呈相反的变化趋势.     

Corrosion behavior of tempered dual-phase steel embedded in concrete

Dual-phase(DP) steels with different martensite contents were obtained by appropriate heat treatment of an SAE1010 structural carbon steel,which was cheap and widely used in the construction industry. The corrosion behavior of DP steels in con-crete was investigated under various tempering conditions. Intercritical annealing heat treatment was applied to the reinforcing steel to obtain DP steels with different contents of martensite. These DP steels were tempered at 200,300,and 400°C for 45 min and then coo...     

High performance low cost steels with ultrafine grained and multi-phased microstructure

Ultrafine grained ferrite was obtained through tempering cold rolled martensite with an average grain size of 200―400 nm in a low carbon and a microalloyed steel. Thermal and mechanical stability of the two steels was studied. Due to the pinning effect of microalloyed precipitates on the movement of dislocations and grain boundaries, the recrystallization and grain growth rate were retarded, and the thermal stability of ultrafine grained microstructure was improved. The ultrafine grained ferritic steel was ...     

合金元素Mo对冷轧双相钢组织的影响

分析Mo微合金冷轧双相钢和普通C-Mn冷轧双相钢在不同双相热处理工艺下微观结构,讨论Mo对冷轧双相钢组织变化规律的影响。实验结果表明：当两种双相钢以1700℃／s冷却时,均获得了铁素体、马氏体双相组织,马氏体均匀分布在铁素体基体上,随着加热温度的升高,普通C-Mn双相钢得到的马氏体体积分数多。当以5．4℃／s冷却时,Mo微合金双相钢得到的马氏体体积分数多;当加热到820℃保温结束后以5．4℃／s的速率冷却时,普通C-Mn钢的组织组成相为铁素体、珠光体、马氏体;Mo微合金钢的组织组成相为铁素体、贝氏体、马氏体;Mo对铁素体晶粒的细化作用不明显。     

Microstructure and mechanical properties of FGBA/BG air cooling bainitic steels containing niobium

The effect of different Nb additions on the mechanical properties and microstructure evolution of grain boundary allotriomorphic ferrite(F_(GBA)) / granular bainite(B_G) air cooling bainitic steels was investigated.The results indicate that the tensile strength and yield strength increase by 157 and 97 MPa,respectively with the addition of 0.02wt%Nb.The steel acquires superior strength and toughness with the addition of 0.06wt%Nb.The results of scanning electron microscopy and transmission electron micro...     

热轧TRIP钢的组织与力学性能研究

采用热轧后控制冷却的工艺制备了TRIP钢，拉伸试验表明，试验钢的性能为：σb=605 MPa，σs=440 MPa，δ=28．4％；对试验钢的组织进行了研究，定量金相检测结果表明，试验钢中残余奥氏体含量为5．6％．     

低碳钢铁素体显微结构研究

通过应用金相和电子显微分析,对含有微量非金属夹杂物的含钛低碳钢在不同冷却条件下的显微组织进行研究,发现铁素体精细的显微结构对钢的机械性能有显著影响。其中针状铁素体之间细小的马氏体的存在与数量对钢的抗拉强度和低温冲击韧性起关键作用。     

热处理工艺对1000MPa级低碳微合金钢组织和性能的影响

采用C-Mn-Cr-Mo-B和C-Mn-Mo-Nb-Cu-B两种成分的低碳微合金结构钢,研究了热机械控制处理后离线调质(TMCP+QT)工艺和控轧后直接淬火回火(CR+DQ+T)工艺分别对2种钢的组织和性能的影响,利用SEM和TEM分析了显微组织、析出与位错.结果表明:C-Mn-Cr-Mo-B钢经过TMCP+QT工艺,在450～550℃回火1 h可以得到最佳的强度与低温韧性组合,屈服强度大于1 GPa,延伸率大于15%,-40℃冲击功大于30 J,组织为回火马氏体.C-Mn-Mo-Nb-Cu-B钢在CR+DQ+T工艺条件下,回火温度在450℃以上时,ε-Cu粒子大量析出,导致屈服强度大幅上升;经500～600℃回火,由于Nb、V、Mo碳化物析出,使钢的屈服强度达到1 030 MPa;620℃回火后,屈服强度仍达到1 GPa,延伸率达到20%,-40℃冲击功大于35 J.     

Stress-strain partitioning analysis of constituent phases in dual phase steel based on the modified law of mixture

A more accurate estimation of stress-strain relationships for martensite and ferrite was developed, and the modified law of mixture was used to investigate the stress-strain partitioning of constituent phases in dual phase (DP) steels with two different martensite volume fractions. The results show that there exist great differences in the stress-strain contribution of martensite and ferrite to DP steel. The stress-strain partitioning coefficient is not constant in the whole strain range, but decreases with...