WH70B高强钢TMCP工艺研究

主要对高强度钢WH70B进行工艺研究,并对工艺进行优化。WH70B主要采用C-Mn-Nb-B成分,不添加过多合金元素及复杂的后续热处理,通过合适的TMCP轧制,钢板具有高强度、高韧性、低焊接裂纹敏感性等特点。     

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℃.     

TMCP工艺对高性能桥梁钢Q370qE-HPS组织性能的影响研究

为了研究TMCP工艺对Q370q E-HPS高性能桥梁钢组织和性能的影响,达到替代正火工艺的目的,对终轧温度、开冷温度、返红温度及冷却速率等TMCP关键工艺参数与组织、力学性能的关系进行分析。结果表明:采用两阶段控轧控冷工艺生产Q370q E-HPS钢时,随终轧温度升高、开冷温度降低、返红温度升高及冷却速度降低,铁素体晶粒尺寸增大,珠光体含量增加,屈强比降低。通过工艺参数优化,可获得合适尺寸和体积分数的铁素体和珠光体,实现Q370q E-HPS钢良好的强韧性匹配和较低的屈强比。     

采用TMCP工艺开发低成本高强钢Q550

采用中碳高Mn的微合金化设计,在4 300 mm中厚板轧机上采用TMCP工艺生产铁素体珠光体高强钢Q550,并对其性能和组织进行分析。结果表明：采用TMCP工艺在两阶段轧制和加速冷却条件下生产的高强钢Q550的性能全部符合GB/T16270-1996的要求,同时节约了大量昂贵合金的加入、降低了成本、减少了热处理环节、缩短了交货期,提升了高强钢产品的市场竞争力。     

Q460MD钢板TMCP工艺及组织性能研究

根据GB/T 1591-2018《低合金高强度结构钢》标准要求设计Q460MD钢的化学成分,采用TMCP工艺生产不同厚度的Q460MD低合金高强度钢板,并对不同厚度的钢板进行力学性能检测和组织观察。结果表明:12～40 mm厚度Q460MD钢板的各项力学性能指标均满足GB/T 1591-2018标准中有关Q460MD钢种的要求,Z35厚度方向性能优异;钢板不同部位的力学性能稳定,且具有较大的富余量;不同厚度钢板的组织不同,20 mm及以下厚度Q460MD钢板的组织由铁素体、珠光体和贝氏体组成,厚度20 mm的Q460MD钢板组织为铁素体和珠光体。     

采用TMCP工艺生产700MPa级低碳贝氏体钢

以微合金化结合控轧、控冷工艺生产非热处理高强度钢,本文通过对700MPa级低碳贝氏体钢轧制工艺的研制分析,制定合理的轧制工艺,成功开发出TMCP工艺下700MPa级低碳贝氏体钢     

TMCP工艺对低碳Ni-Nb钢组织转变和力学性能的影响

 为了研究TMCP工艺对低碳Ni-Nb钢显微组织转变类型和晶粒尺寸的影响规律,研究了不同TMCP工艺下的显微组织特征及其对力学性能的作用机理。结果表明,在未变形轧制情况下,当冷却速度小于5 ℃/s时,显微组织为铁素体和珠光体,铁素体晶粒尺寸随着冷却速度的增大而减小;在变形轧制情况下,随着冷却速度的增加,组织中的铁素体晶粒尺寸明显减小;当冷却速度增大到5 ℃/s时,微观组织中出现了大量粒状贝氏体。试制钢板试验表明,当冷却速度为4 ℃/s时,试验钢的组织为准多边形铁素体,可以有效提高钢的低温韧性;当冷却速度达到6 ℃/s时,试验钢微观组织中出现大量粒状贝氏体,明显降低钢的低温韧性。     

TMCP工艺对车轮钢组织及扩孔性能的影响

采用TMCP(Thermo Mechanical Controlled Process)实验,研究了不同冷却方式对汽车车轮用低碳FB钢的组织及扩孔性能的影响,以及FB钢扩孔时的断裂类型及断裂机理。结果表明,采用连续冷却的实验钢,得到了针状铁素体＋贝氏体组织,针状铁素体明显降低了两相硬度比,改善了扩孔性能。FB钢在扩孔过程中的断裂机理为微孔聚集的韧性断裂。实验结果可为进一步研究低碳FB钢在车轮上的应用提供实验依据。     

TMCP厚板组织控制技术的最新进展和厚板产品的高性能化

TMCP工艺是通过控轧技术和控冷技术的结合，在线精确控制显微组织，从而获得优越机械性能的钢材制造技术体系。JFE自1980年在西日本制铁所首次成功的将厚板在线加速冷却装置（OLAC）应用到工业化生产以来，一直致力于提高TMCP水平。1998年，能够以接近水冷理论极限的最高冷却速度进行均匀加速冷却的Super-OLAC（超速加速冷却装置）开发成功并投入运行。2004年，在世界上率先投入使用了在线感应加热装置（HOP，在线热处理工艺）。通过这两种工艺的组合，使淬火-回火工艺生产的高强钢的显微组织细化，从而达到高性能化，并且进一步发现了中途停止冷却，然后再次加热的这种传统工艺从未设想过的热处理过程来控制显微组织的新方法，应用此方法正在积极开发新产品。对TMCP组织控制技术基础及TMCP的最新进展和厚板产品的高性能化进行了阐述。     

TMCP工艺生产E420海洋平台用钢板的组织与性能研究

介绍了E420海洋平台用钢板的成分性能要求,根据成分和工艺参数对力学性能的影响,对采用TMCP工艺生产的钢板组织与性能进行了研究,通过回火工艺验证,最终成功研发出组织和性能符合要求的E420钢板,为更高级别、更大厚度海洋平台用钢板的开发提供了技术储备。     

控轧控冷工艺生产海洋平台用钢的研究

在4 300 mm宽厚板轧机上进行了低碳海洋平台用钢E40-Z35工业试制,针对钢板心部铁素体晶粒粗大且出现混晶导致低温冲击功和裂纹尖端张开位移(CTOD)值不合的问题,采取增大层流冷却能力、降低终冷温度的措施,抑制心部晶粒长大,消除厚度方向组织差异,最终得到具有良好的低温韧性、抗层状撕裂性能和焊接性能的海洋平台用钢。     

TMCP对低碳锰钢组织和力学性能的影响

通过TMCP工艺实验,研究了终轧温度和卷取温度对低碳锰钢力学性能和微观组织的影响规律.结果表明,在形变诱导相变上限温度Ad3之上(850 ℃)终轧后快速冷却,组织主要由仿晶界型铁素体(GBA)和大量贝氏体组成,其中贝氏体铁素体呈板条状,塑性和韧性较高;当终轧温度降低到800 ℃(低于Ad3)时,得到的组织为等轴状铁素体和一定量的贝氏体,等轴铁素体的平均晶粒尺寸约为8 μm,强度较高,综合性能良好.终轧温度和卷取温度主要是通过改变实验钢的组织组成和晶粒大小来对其力学性能产生影响的.通过控制终轧温度和卷取温度,可以实现细晶强化、贝氏体相变强化和析出强化的复合强化,有利于低碳锰钢获得良好的综合性能.     

轧后加热温度对高Nb X80管线钢板组织性能的影响

 采用TMCP（热机械控制处理）工艺制造的高Nb成分X80管线钢板,在实验室进行了不同加热温度下的离线热处理试验研究,分析了轧后加热温度对高Nb管线钢组织性能的影响规律。结果表明：钢板在150~600℃温度范围内热处理时,钢板的显微组织、强度及DWTT（Drop Weight Tear Test,落锤撕裂试验）性能无显著变化,韧脆转变温度略有上升;650℃加热处理后,钢板的显微组织粗化、韧脆转变温度上升,DWTT性能明显下降。     

Evolution of Microstructure and Mechanical Properties of Thermomechanically Processed Ultrahigh-Strength Steel

In the present study, low carbon microalloyed ultrahigh-strength steel was manufactured on a pilot scale. Transformation of the aforesaid steel during continuous cooling was assessed. The steel sample was thermomechanically processed followed by air cooling and water quenching. Variation in microstructure and mechanical properties at different finish rolling temperatures (FRTs) was studied. A mixture of granular bainite and bainitic ferrite along with interlath and intralath precipitation of (Ti, Nb)CN particles is the characteristic microstructural feature of air-cooled steel. On the other hand, lath martensitic structure along with a similar type of microalloying precipitates of air-cooled steels is obtained in the case of water-quenched steel also. The best combination of strength (1440 to 1538 MPa) and ductility (11 to 16 pct) was achieved for the selected range of FRTs of water-quenched steel.     

Microstructure and Mechanical Properties of Ultrafine-Grained Interstitial-Free Steel Processed by ECAP

Equal-channel angular pressing (ECAP) of interstitial-free (IF) steel at equivalent strain, ε_vm = 12 has been employed to develop ultrafine-grained (UFG) microstructure with high fraction of low angle grain boundaries, that enhances strength significantly with reduced tensile ductility. ECAPed IF steel has been deformed further by cold rolling/cryorolling at ?50 °C to >90 % reduction in area. It is observed that the UFG structure gets refined with an improvement in high angle grain boundary fraction and heavily stressed non-equilibrium grain boundaries in cryorolled state resulting in significant strengthening. However, the decrease in grain size to an ultrafine level with the increased lattice strain lowers the work hardening ability of the material that limits its ductility. Hence, the rolled samples are flash annealed at 675 °C in order to recover the ductility of the material by achieving partially recrystallized structures. Consequently, the increased subgrain size as well as the grain size, the reduced residual lattice strain, lower hardness and strength with marginal recovery of ductility is maintained in order to attain the yield strength 2–3 times compared to that of as-received coarse-grained IF steel.     

Effects of TMCP Parameters on the Microstructure and Mechanical Properties of Nb-Bearing Spring Steel

The effects of TMCP parameters,such as finish rolling temperature and cooling rate on the microstructure and mechanical properties of Nb-bearing spring steel were investigated by thermal simulation,quantitative metallography and tensile test.And the precipitation in Nb-bearing spring steel was analysis by electron microscopy.Experimental results indicate that the higher finish rolling temperature or the more rapid cooling rate in a given range,the less the proeutectoid ferrite content and the thinner the interlamellar spacing is.Reasonably higher finish rolling temperature followed by properly higher cooling rate is suggested to improve the mechanical properties of Nb-bearing spring steel.Micro-addition of niobium decreases the proeutectoid ferrite content and the interlamellar spacing and leads to forming degenerated pearlite.The precipitation of size range ～20-50 nm in Nb-bearing spring steel occurred at the lamellar ferrite of pearlite and the proeutectoid ferrite.     

960 MPa Grade High Performance Weldable Structural Steel Plate Processed by Using TMCP

To develop high strength, good toughness, and weldable steel plate, a steel composition was designed. It was an uhra-low-carbon microalloyed steel. TMCP (thermal mechanical control process) and RPC (relaxation pre-cipitation control) were employed to ensure fine lath bainite microstructure. This kind of microstructure could induce higher strength and better toughness.     

Effect of Tempering Temperature on Microstructure and Properties of E690 Offshore Plate Steel

 A new kind of Mn-Mo-Nb-Cu-B bainite steel which satisfied mechanical demands of E690 offshore plate steel was designed. The effect of two processes——thermomechanical control process (TMCP)+tempering (T) and thermomechanical control process (TMCP)+reheating and quenching (RQ)+tempering (T)——on microstructure and mechanical properties were studied by means of scan electron microscope (SEM), transmission electron microscope (TEM) and electron back scatter diffraction (EBSD). The results showed that optimal mechanical properties were available when tempering at 550 ℃ for both processes. The microstructure of the TMCP+T treated sample tempering in the range of 450 to 550 ℃ for 1 h did not change dramatically yet the lath in the TMCP+RQ+T treated sample merged together and transformed into polygonal ferrite. At the same time, the sub-structure of grain bainite transformed from lath to cell-shape to refine grains with tempering temperature mounting. Lots of sub-grain boundaries were located within bainite and adjacent bainite grain boundaries were high angle.