回火温度对贝氏体/马氏体复相海洋用钢的组织和性能影响

利用扫描电镜、透射电镜等实验方法,研究不同回火温度下试验钢的组织性能变化情况.结果表明:经控轧控冷获得了贝氏体/马氏体复相海洋用钢,其中贝氏体体积分数约占30%;随着回火温度的升高,试验钢的屈服强度先上升后又略有下降,在600℃达到最大值,为983 MPa,抗拉强度明显下降,延伸率先降低后升高,在600℃回火温度达到最大值为19.6%,之后又开始降低,冲击功在400℃和600℃出现明显回火脆性;在550℃回火温度试验钢取得最佳力学性能,其中抗拉强度和屈服强度分别为1050MPa和981 MPa,延伸率为16.6%,-40℃低温冲击功为19.9 J.分析认为,回火过程中马氏体板条断裂消失,贝氏体相互合并形成准多边形铁素体,析出物逐渐回溶和重新析出,造成力学性能的变化差异.     

硼对780 MPa低碳贝氏体钢组织和力学性能的影响

试验低碳贝氏体钢（/%:0.08C,0.11~0.13Si,1.10~1.20Mn,0.008~0.009P,0.002S,0.21~0.23Ni,0.020~0.021Ti,0.003~0.004Nb,0~0.0010B,0.000 7~0.0008O,0.0031~0.0033N）由50kg真空感应炉熔炼,轧成45mm钢板,并经930℃淬火,610℃回火。研究了0.0010%硼对780 MPa低碳贝氏体钢45mm板组织和力学性能的影响。结果表明,硼可显著提高试验钢的淬透性,不含硼试验钢淬火后得到粒状贝氏体,0.0010%硼试验钢淬火后得到板条贝氏体。硼明显改善试验低碳贝氏体钢的力学性能,含0.0010%硼试验钢淬、回火后的抗拉强度834MPa和屈服强度771MPa远高于不含硼试验钢的抗拉强度702MPa和屈服强度591MPa,实际生产中应加入适量硼可使低碳贝氏体钢得到板条贝氏体。     

gdl-1钢不同热处理状态下的显微组织与力学性能

对一种新型高强韧微变形钢(GDL-1)在七种热处理状态下的显微组织与力学性能进行了分析。结果表明,该钢在900℃保温1 h空冷回火后的显微组织以窄束状贝氏体+粒状贝氏体为主加少量马氏体,而油淬回火后的组织为回火马氏体;910℃加热奥氏体化1 h的晶粒度普遍在8～9级。在低温回火温度范围内,随着回火温度的升高,冲击韧性逐渐增大,屈服强度逐渐降低,硬度变化不大。     

Microstructure and Mechanical Properties of High-strength Micro-deformation Steel GDL-1

对一种新型高强韧微变形钢(GDL-1)在七种热处理状态下的显微组织与力学性能进行了分析.结果表明,该钢在900℃保温1h空冷回火后的显微组织以窄束状贝氏体+粒状贝氏体为主加少量马氏体,而油淬回火后的组织为回火马氏体;910℃加热奥氏体化1h的晶粒度普遍在8～9级.在低温回火温度范围内,随着回火温度的升高,冲击韧性逐渐增大,屈服强度逐渐降低,硬度变化不大.     

钛、铌、硼对低碳贝氏体钢组织与性能的影响

以C-Mn钢和700 MPa级低碳贝氏体钢成分为基础成分,通过调整微合金元素含量,实验室条件下熔炼浇注钢锭,并采用TMCP技术轧制钢板,研究了微合金元素钛、铌、硼对低碳贝氏体钢组织与性能的影响。结果表明,随着铌含量的增加,贝氏体含量增加,晶粒变细,材料的抗拉强度、屈服强度与韧性均增加;随着钛含量的增加,贝氏体含量增加,抗拉强度、屈服强度提高,韧性的变化与是否进行回火处理有关;硼有利于形成板条贝氏体组织,硼含量增加能提高强度,但有损韧性。     

屈服强度785 MPa低碳含铜船板钢的组织和性能

 研究了一种屈服强度大于785 MPa的船板钢,测试了其动态连续冷却相变曲线（CCT）,研究了试验钢经控制轧制+直接淬火+回火（DQ- T）工艺处理后的组织性能。结果表明,直接淬火（DQ）钢板组织为板条马氏体（LM）,回火后铜、铌元素呈弥散析出。经500 ℃回火钢板的强度最高,冲击韧性（KV2）最低。钢板经710 ℃回火,其组织为二次马氏体（SLM）+铁素体,屈服强度（Re）为810 MPa,抗拉强度（Rm）为 1 066 MPa,伸长率（A）为17%,在-80 ℃下KV2为97 J,达到最佳强韧性匹配。     

C Si Mn Cr Nb钢双相组织性能的柔性控制

 根据C Si Mn Cr Nb试验钢的双道次变形和分段冷却热模拟试验结果,进行了试验钢控轧控冷试验,分析了工艺参数对试验钢组织和性能的影响,获得了具有不同力学性能的铁素体+马氏体或铁素体+贝氏体双相组织。结果表明,试验钢两段轧制分段冷却后550 ℃卷取获得铁素体+马氏体双相组织,屈服强度415 MPa,抗拉强度710 MPa,伸长率23.0％,屈强比0.59。500 ℃卷取得到铁素体加粒状贝氏体双相组织,与550 ℃卷取相比,屈服强度升高35 MPa,抗拉强度降低45 MPa,伸长率略微降低。     

调质低碳贝氏体钢的组织和性能

研究了C-Mn-Mo-Cu-Nb-Ti-B系低碳微合金钢915℃淬火和490~640℃回火的调质工艺对钢的组织及力学性能的影响.用扫描电镜和透射电镜对实验钢的组织、析出物形态和分布以及断口形貌进行观察,采用X射线衍射仪分析钢中残余奥氏体的体积分数.结果表明:调质后,实验钢获得贝氏体、少量马氏体及残余奥氏体复相组织,贝氏体板条宽度只有250 nm,残余奥氏体的体积分数随着回火温度的升高而降低,经淬火与520℃回火后残余奥氏体的体积分数为2.1%.调质后析出物的数量激增,6~15 nm的析出物占70%以上.实验钢经过915℃淬火与520℃回火后,其屈服强度达到915 MPa,抗拉强度990 MPa,-40℃冲击功为95 J.细小的析出物及窄的板条提高了钢的强度.板条间有残余奥氏体存在,改善了实验钢的韧性.      

贝氏体钢轨矫直前后回火的组织性能分析

利用TEM、磁性分析法和拉伸试验对矫直前后回火贝氏体钢轨显微组织、残余奥氏体含量、稳定性以及拉伸性能进行分析。结果表明:与矫直前回火相比,矫直后回火获得贝氏体钢轨的显微组织为无碳化物贝氏体+少量残余奥氏体和M/A+微量回火马氏体;抗拉强度平均提高139 MPa;屈服强度平均提高138 MPa;残余奥氏体机械稳定性明显提高;贝氏体钢轨强韧性优良。     

590MPa级压力容器用TMCP钢组织和性能的研究

通过OM、SEM、力学检测等方法研究了TMCP加回火型590MPa级压力容器用钢的组织形貌和性能.结果表明,试验钢的力学性能满足屈服强度ReL不小于470MPa,抗拉强度Rm不小于590MPa,伸长率A不小于17%,-20℃冲击功Akv不小于60J的设计要求,且具有良好的强韧性匹配.在TMCP状态下,试验钢组织为铁素体加贝氏体加少量马氏体,断口呈解理特征,回火后组织为铁素体加回火索氏体,断口呈韧窝特征,韧窝中夹杂物主要为Al2O3+MnS的复合夹杂物.随着回火温度的提高,试样断口韧窝变得大而深,分布更均匀,塑韧性得到明显改善,合理的回火温度为620～650℃.     

回火温度对Cu-Cr-Ti马氏体耐磨钢组织及强韧性的影响

摘要：矿山机械用耐磨钢构件服役环境恶劣而常常出现磨损失效，研究适用于复杂工况下的高耐磨钢成分、工艺与组织性能的关系，有利于提高耐磨构件的服役寿命并降低经济损失。利用SEM、TEM、洛氏硬度计、万能拉伸试验机及冲击试验机等，研究了160～400℃不同回火温度下Cu-Cr-Ti马氏体耐磨钢的组织形貌、强度硬度及-20℃冲击韧性的变化。结果表明，试验钢淬火态组织主要为板条马氏体，当回火温度为160℃时，马氏体板条依然清晰，但随回火温度升高到400℃，马氏体板条界渐渐消失，基体中出现大量片状或粒状渗碳体。EDS分析发现样品钢基体中含有纳米级Ti、Nb的碳氮化物。随回火温度升高，基体组织演变导致强化机制发生变化，回火温度为300℃，综合力学性能最佳，其抗拉强度为1500MPa，屈服强度1100MPa，伸长率为15.5%。随回火温度升高，-20℃冲击韧性由60J/cm2逐渐降低到36.3J/cm2。     

1800MPa级低合金超高强度工程机械用钢显微组织与力学性能

 设计了一种新型的超高强度工程机械用钢,在中试轧机上进行了不同工艺模拟轧制,对比研究了工艺1（80%变形量+直接淬火+250℃回火）、工艺2（90%变形量+层流冷却快冷至650℃/1h+空冷+250℃回火）和工艺3（90%变形量+空冷至650℃/1h+空冷+250℃回火）3种不同控轧控冷工艺对试验用钢的显微组织和力学性能的影响。结果表明：工艺1条件下试验钢的抗拉、屈服强度最高,塑韧性最好,分别可达到1816,1473MPa,伸长率为9.5%,断面收缩率为45%,室温冲击功为28J,-40℃冲击功为21J,硬度值达到50HRC,认为获得的是板条马氏体+残余奥氏体的复相组织和析出的复合微合金碳化物、ε-碳化物强韧化机制的综合作用;工艺2,3分别得到的是板条马氏体+块状贝氏体+残余奥氏体、板条马氏体+针状铁素体+片层状珠光体+残余奥氏体,力学性能下降明显;第二相析出物主要是Nb,V,Ti的复合析出颗粒。     

含钛中锰钢淬火-配分组织及力学性能

 为了研究淬火-配分含钛中锰钢的组织与力学性能,借助扫描电子显微镜,透射电子显微镜、电子背散射衍射技术与万能拉伸试验机、磨粒磨损试验机等,分析与测试了含钛中锰钢在165~240 ℃淬火380 ℃配分处理后组织、强度、塑性与磨粒磨损性能。结果表明,试验钢淬火-配分组织主要为板条状一次马氏体、块状二次马氏体及残余奥氏体,同时含有大量微米级TiN和纳米级(Ti,Mo)C及TiN-(Ti,Mo)C复合析出相。190 ℃淬火380 ℃配分后残余奥氏体体积分数最高为12.5%。试验钢不同温度淬火与配分后屈服强度均大于1 000 MPa,抗拉强度均大于1 500 MPa,硬度从482.5HV增大到542.2HV,伸长率范围为9.2%~14.5%,在165~190 ℃淬火-配分处理后其抗磨粒磨损性能优于220~240 ℃淬火-配分钢。磨损机制主要是塑性变形和疲劳破坏,磨损过程中残余奥氏体发生应变诱导马氏体相变(TRIP)效应,析出相颗粒阻断基体塑性变形过程犁沟的前进和刮削行为,含钛中锰钢通过淬火-配分引入一定体积分数的残余奥氏体,有利于提高钢的强塑性与抗磨损性能。结合力学性能指标,含钛中锰钢最佳淬火-配分工艺为900 ℃奥氏体化30 min,190 ℃淬火,380 ℃配分10 min。     

直接淬火石油储罐用钢N610E的回火组织与力学性能

 N610E级石油储备罐用钢(12MnNiVR)常用加热调质处理工艺生产。利用OM、TEM等试验方法,研究了石油储罐用钢N610E直接淬火后,不同回火温度对组织和力学性能的影响。结果表明：直接淬火钢经655℃回火,钢板具有最佳综合力学性能,其抗拉强度640MPa,屈服强度570MPa,伸长率22%,－20℃冲击功273J,不同回火温度的N610E钢韧脆?湮露染冢?0℃以下。随回火温度的升高,板条贝氏体回复作用逐渐加强,位错通过运动、合并、重组,相邻板条合并,组织粗化;回火后钢的力学性能变化趋势的非单调性,归因于回火过程贝氏体中位错亚结构的回复软化与碳的脱溶及第二相的析出强化机制综合作用。     

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.     

Phase Transformation and Mechanical Properties of an Ultrahigh Strength Steel

The present study deals with the development of a low carbon high strength steel by thermomechanical controlled processing on a pilot scale.The continuous cooling transformation has yielded a flat top "C" curve with the phase field occupied by a mixture of bainite and martensite.The microstructure of water quenched steel essentially consists of highly dislocated lath martensite along with fine (Ti,Nb)CN precipitates and twins.High strength steel with 1217-1298 MPa yield strength and 1372-1513 MPa ultimate tensile strength along with 16-12% total elongation has been obtained in the range of 850 to 750℃ finish rolling temperature.The impact toughness value in the range of 45-72J was also achieved in the present steel.     

Structure and mechanical properties of tempered martensite and lower bainite in Fe−Ni−Mn−C steels

The structure and mechanical properties of tempered martensite and lower bainite were investigated in a series of high purity 0.25 pct C steels with varying amounts of nickel and manganese. The martensites in 0.25 C-5 Ni?Fe and 0.25 C-3 Mn?Fe alloys were mainly untwinned, while those in 0.25 C-5 Ni-7 Mn?Fe and 0.25 C-7 Mn?Fe alloys were heavily twinned. Manganese appears to promote carbide precipitation along the lath boundaries in tempered martensite. At equivalent yield and ultimate tensile strength levels, the tempered martensite of lower manganese steels showed better impact toughness than the tempered martensite of higher manganese steels. The impact toughness (compared at similar strength levels) of untwinned tempered martensite of 0.25 pct C steel with Widmanstatten precipitation of carbide was higher than that of lower bainite, which showed unidirectional carbides. The reasons for the difference in impact toughness between the alloys, and also between the structures are rationalized in terms of internal twinning, grain boundary precipitation and carbide morphology together with other microstructural features.     

回火温度对轧后直接水淬15CrMoV钢组织和力学性能的影响

试验用钢15CrMoV(%:0.15C、0.29Si、0.57Mn、1.01 Cr、0.37Mo、0.24V)16 mm板材的终轧温度为900～950℃,轧后在880～900℃水淬,并经670～800℃回火。结果表明,试验钢在线淬火后的组织为马氏体+贝氏体,随回火温度升高,钢中碳化物析出量增加,贝氏体板条束逐渐合并和减少,最终转化为碳化物+多边形铁素体组织;在730～780℃回火,15CrMoV钢具有良好的综合力学性能,抗拉强度680～760 MPa,冲击功55～130 J。     

The Effect of Nb on Mechanical Properties of Quenching and Partitioning Steels

In order to study the effect of alloy elements on mechanical properties of quenching and partitioning steels,the Q and P heat treatments on different chemical composition steels were carried on in lab.The tensile test results indicated the strength of Nb+Ti-bearing steel was not increasing as expected,but lower than that of the Nb+Ti-free steel,and the elongation was raised to 26% from 9%.The Nb+Ti-bearing steel microstructures after tensile test were detected by TEM and found a certain amount of twins in the deformed microstructure while the deformed microstructure mainly was lath martensite in Nb+Ti-free steel,which means the addition of Nb and Ti elements could cause the twinning induced plasticity by inhibiting the phase transformation from austenite to martensite.Based on above analysis,adding trace Nb element could greatly increase the stacking fault energy of the retained austenite,which is beneficial to the formation of twins,and the formation of twins would lower the strength slightly and raise the elongation drastically.