管线钢控轧控冷组织与性能

研究超低碳管线钢控轧控冷显微组织及力学性能。对管线钢进行实验室控轧控冷,对轧后试样进行力学性能测试,用扫描电镜和透射电镜对显微组织进行观察。试验结果表明,采用制定的控轧控冷工艺轧制后的试验钢有较好的强度和优异的低温韧性。钢轧后显微组织主要由针状铁素体和粒贝组成;在铁素体板条的内部和品界处存在缠结、塞积、高密度的位错,显著提高了钢材的强韧性。     

硅锰弹簧钢的控轧控冷研究

以60Si_2Mn钢为例,对硅锰弹簧钢进行了控轧控冷研究,结果表明,60Si_2Mn钢经奥氏体再结晶区控轧,轧后以6～10℃/sec的冷速进行控制冷却,可获得球团细小的珠光体加少量铁素体组织,同时减少了脱碳,显著提高了硅猛钢材的热轧性能。     

高扩孔型铁素体/贝氏体双相钢组织性能研究

对540MPa级铁素体/贝氏体双相钢的组织性能进行分析研究。结果表明,试验钢的显微组织为85%左右的铁素体加上15%左右的贝氏体;铁素体晶粒尺寸细小,基体中有较高的位错密度和大量细小弥散的析出物;贝氏体在铁素体基体上分布均匀,以板条状为主,板条间分布有较多碳化物颗粒。通过合适的成分设计和控轧控冷手段获得的铁素体/贝氏体双相钢组织形态,可较好地保证材料所需的强度-拉伸凸缘性能匹配。     

轧后余热处理对37Mn5钢管组织和性能的影响

研究了控轧工艺参数对37Mn5钢(N80石油套管)组织和性能的影响,进而研究高温形变淬火—回火与轧后在线控制冷却(余热处理)工艺对组织和性能的影响。研究结果表明:高温形变淬火—回火钢的强度比普通调质工艺提高1～2个级别;在线控制冷却可获得全部索氏体,性能与API标准N80合格值相当。     

A36、DH36控轧控冷取代正火工艺生产实践

通过对A36、DH36钢板的控轧控冷工艺的实践研究。使控轧控冷工艺生产的A36、DH36具有良好和稳定的综合力学性能，成功实现高强度船板控轧控件取代正火工艺进行大规模生产。     

热处理对低锰高镍管线钢力学性能的影响

采用金相显微镜、扫描电镜观察和力学性能测试研究了650~850℃热处理对低锰高镍TMCP管线钢微观组织及力学性能的影响.结果表明:轧态钢板以针状铁素体组织为主,有良好的强韧性.经650℃高温回火后M/A岛分解并球化,贝氏体发生回复和部分再结晶,大量析出物弥散分布,强度稍有提高,韧性略有降低.经700~800℃双相区加热空冷后的显微组织由铁素体和不规则的M/A或贝氏体组成.700℃热处理抗拉强度升高到778 MPa,但-40℃冲击功依然高达132J,拉伸曲线表现出连续屈服行为.750℃热处理后强度降低,冲击功提高至302J,伸长率提高至22%,具有很好的塑韧性.850℃正火组织强度较低.选择650~750℃的热处理工艺,TMCP钢力学性能得到进一步改善.     

5CrNiMo钢热锻模强韧化处理的研究

本文研究了不同热处理工艺对5CrNiMo 钢的组织与性能的影响。结果表明,当淬火温度高于900℃时,其马氏体形态是以板条状为主;当回火温度高于450℃时,随着淬火温度的提高,钢的断裂韧性有明显的提高,其室温、高温冲击韧性略有下降。锻模在950～1000℃加热淬火,再高于450℃回火,比传统的热处理后有更好的强韧性。试验结果还表明,此钢臭氏体化后在230℃、280℃等温淬火后获得下贝氏体组织;回火下贝氏体比上贝氏体有较高的断裂韧性、冲击韧性和强度,在230℃等温淬火再500℃经回火后,它的强韧性还优于回火马氏体组织。因此,5CrNiMo 钢热锻模应获得回火板条状马氏体、回火下贝氏体或二者的复合组织为宜。     

调质处理对低碳贝氏体钢组织和性能的影响

通过对低碳贝氏体钢的调质处理工艺试验,研究不同的淬火介质、淬火温度及回火温度对实验钢组织和性能的影响。结果表明:经过930℃加热保温并10min油淬后,再选取500℃回火70min,实验钢的微观组织为细小的块状铁素体基体上分布着均匀的碳化物。实验钢的硬度由未调质处理前的260.7HV提高到322.2HV。     

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.     

热处理对高强度微合金钢组织与性能的影响

研究了不同热处理工艺对所设计的高强度微合金钢(屈服强度大于500 MPa)的组织与性能的影响.结果表明,通过适当的热处理工艺可以获得由多边形铁素体加一定含量针状铁素体的双相组织,既能显著提高钢的强度,还能保持较低的屈强比.     

热穿-热轧法生产的新型贝氏体中空渗碳钢的组织和性能

用热穿-热轧法制备了新型贝氏体中空钢．研究了热处理对新型贝氏体钢和渗碳处理对中空钢组织和性能的影响．结果表明：新型贝氏体钢正火＋低温回火热处理后的组织为贝氏体铁素体和奥氏体,淬火＋低温回火后的组织由马氏体、贝氏体和奥氏体组成;正火或淬火＋低温回火后,新型贝氏体中空钢具有良好的强韧性．正火＋低温回火后,中空钢的组织为贝氏体铁素体和残余奥氏体组织．新型贝氏体中空钢渗碳后空冷,渗层的组织为高碳马氏体和残余奥氏体组织,非渗层为贝氏体铁素体和残余奥氏体组织,实体中空钢具有较好的强韧性和渗碳效果．     

Effect of cooling parameters on the microstructure and properties of Mobearing and Cr-bearing steels

To develop low-cost low carbon bainitic steel,Mo-bearing and Cr-bearing steels were melted in a vacuum induction furnace and were researched by thermal simulation and hot rolling at the laboratory.As the cooling rate increases from 0.2 to 50℃/s,the transformation temperatures of two steels lie between 650 and 400℃,and the final microstructures of them change from quasi-polygonal ferrite and granular bainite to lath bainite.Compared with cooling in air or by interrupted cooling,Mo-bearing and Cr-bearing steel plates cooled by sprayed water boast higher strength and superior toughness,for large-size islands are responsible for the poor mechanical properties.Compared to Mo,Cr is effective to isolate the bainitic reaction in low carbon steel,and the bainitic microstructure can also be obtained in Cr-bearing steel cooled at a wide range of cooling rate.     

Microstructure characteristics and mechanical properties of X80 pipeline steels

The relation between microstructure characteristics and mechanical properties of X80 pipeline steels was investigated using optical microscopy,scanning electron microscopy,etc.It is shown that the structure consists of polygonal ferrite(PF),quasi-polygonal ferrite(QPF),acicular ferrite(AF),and granular bainitic ferrite(GF).With increasing volume fraction of M-A islands(below 3%),the yield strength increases.With increasing content of higher angle grain boundaries(HAGBs),the yield strength,elongation,and DWTT properties at-15 ℃ increase,and the volume fraction of M-A islands reaches its highest point in the steel containing the most volume fraction of GF.     

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。     

Effect of controlled rolling on the martensitic hardenability of dual phase steel

The C-Mn and C-Mn-Nb steels were thermo-mechanically processed to develop dual phase steel and to study the effect of controlled rolling on the martensitic hardenability of austenite. The steel specimens were intercritically annealed at 790°C,rolled at that temperature to the reductions of 10%,23%,and 47% and immediately cooled at different rates. Quantitative metallography was used to construct the microstructure map,which illustrated that increasing deformation progressively reduced the proportion of new ...     

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.     

Stability of Ultra-fine Microstructures during Tempering

The stability of ultra-fine microstructure during tempering at 650℃ was investigated on a Nb-containing steel. The steel had undergone 5 passes controlled rolling, then was relaxed (air cooled) to 730 ℃ and cooled in water The evolution of microstructure was that, in early stage of tempering, no obvious change was detected by means of optical microscopy while dislocation cells were formed inside bainitic laths. With further tempering, bainitic laths started to coalesce in some regions. Finally, polygonal ferrite was formed while hardness decreased dramatically. Some samples taken from the same primary plate were reheated at 930 ℃for 0.5 h followed by quenching into water before tempering. Despite their lower original hardness, the reheated samples softened faster during tempering. Ferrite was quickly formed in the reheated samples. These results indicate that the evolution of microstructures towards equilibrium during tempering of the steel is mainly determined by whether dislocations are pinned rather than the dislocation density.     

Development of grain boundary allotriomorphic ferrite/granular bainite duplex steel

A new hot-rolled low alloy high strength steel with grain boundary allotriomorphic ferrite/granular bainite duplex micro-structure has been developed through novel microstructure and alloying designs without any noble metal elements such as nickel and molybdenum. Its as-rolled microstructure and mechanical properties, fatigue crack propagation behavior compared with single granular bainitic steel as well as continuous cooling transformation, were investigated in detail. The measured result of CCT (continuous cooling transformation) curve shows that such duplex microstructure can be easily obtained within a wide air-cooling rate range. More importantly, this duplex microstructure has much better combination of toughness and strength than the single granular bainite microstructure. It is found that the grain boundary allotriomorphic ferrite in this duplex microstructure can blunt the rni-crocrack tip, cause fatigue crack propagation route branching and curving, and thus it increases the resistance to fati     

Microstructures and properties of 550 MPa grade high strength thin-walled H-beam steel

The microstructures and mechanical properties of 550 MPa grade lightweight high strength thin-walled H-beam steel were experimentally studied. The experimental results show that the microstructure of the air-cooled H-beam steel sample is consisted of ferrite, pearlite and a small amount of granular bainites as well as fine and dispersive V（C,N） precipitates. The microstructure of the water-cooled steel sample is consisted of ferrite and bainite as well as a small amount of fine pearlites. The microstructure of the water-cooled sample is finer than that of the air-cooled sample with the average intercept size of the surface grains reaching to 3.5 gna. The finish rolling temperature of the thin-walled high strength H-beam steel is in the range of 750 ~C-850 ~C. The lower the finish rolling temperature and the faster the cooling rate, the finer the ferrite grains, the volume fraction of bainite is increased through water cooling process. Grain refinement strengthening and precipitation strengthening are used as major strengthening means to develop 550 MPa grade lightweight high strength thin- walled H-beam steel. Vanadium partially soluted in the matrix and contributes to the solution strengthening. The 550 MPa grade high-strength thin-walled H-beam steel could be developed by direct air cooling after hot rolling to fully meet the requirements of the target properties.