FTSR轧制含Nb钢的组织演变

 结合FTSR薄板坯连铸连轧自身的特点,设计了FTSR轧制含Nb钢BG510L的化学成分和轧制工艺,通过轧卡试验进行了组织演变的观察与分析,结果表明：FTSR薄板坯连铸连轧生产线轧制的BG510L钢的组织较为细小,粗大的铸坯组织经一道次轧制后发生了充分的再结晶,奥氏体晶粒明显细化,在FTSR工艺中,没有出现明显的混晶组织,表明该工艺可以轧制更高级别的钢种。     

薄板坯连铸连轧流程V微合金化技术研究

本文基于薄板坯连铸连轧流程物理冶金特征,系统地研究了V的析出规律和V微合金钢的强化机理.结果表明,均热前铸坯中有大量细小V析出物,均热过程中部分析出物溶解,颗粒略有长大;铸坯中的细小析出物对抑制变形奥氏体再结晶晶粒长大有明显的作用,使试验钢具有晶粒尺寸为3～4μm的超细晶组织;组织超细化是导致薄板坯连铸连轧流程V微合金钢强度提高的主要原因.采用薄板坯连铸连轧流程V微合金化技术开发了屈服强度550MPa级HSLAS-F80高强钢,其组织均匀、晶粒超细化、强度高、成型性能和焊接性能优良.     

薄板坯连铸连轧低温卷取生产双相钢的工业试验

在薄板坯连铸连轧生产线上,利用微合金元素Nb、Ti析出抑制再结晶发生,加工硬化奥氏体加速铁素体相变,轧后连续快速冷却至低温卷取,利用细晶强化和相变强化生产低成本高强度热轧双相钢。在FTSR生产线上进行工业试验。结果表明,在终轧800～820℃,快速冷却至卷取温度300℃以下,可以得到铁素体和马氏体双相组织,屈服强度400MPa以上,抗拉强度超过650MPa,屈强比低于0.70,伸长率大于20%。     

薄板坯流程连铸连轧过程中的细晶化现象分析

研究了薄板坯连铸连轧工艺的铸坯凝固组织特征和钢带的组织演变规律。通过化学相分析、微观组织分析研究发现，微细AIN粒子在薄板坯连铸过程中可沉淀析出，铸坯经20～30min均热后AIN仅部分溶解。对AIN析出的热力学和动力学分析也证实了AIN在铸坯上沉淀析出的合理性。这些在连轧开始前原始奥氏体中析出的AIN沉淀是抑制变形奥氏体再结晶晶粒长大，细化奥氏体组织，并最终使钢带组织细化的主要原因；同时，薄板坯连铸连轧流程冷却辊道短、冷却强度大等因素也是导致薄板坯连铸连轧过程中Al镇静钢组织细化的主要原因。     

FTSR线钛微合金化Q345B/C的工艺与组织性能

通钢依托薄板坯连铸连轧生产线（FTSR）的工艺特点,充分利用控轧控冷技术优势,改善结构热轧钢板的组织和性能。本项目通过攻关,将钢中的锰含量由1.10%降低至0.45%,大幅度地降低了合金消耗;并通过钛微合金化工艺,解决了钢板带状组织严重的问题;采用新工艺生产的结构热轧钢板低温冲击性能良好。该项目在低成本条件下达到了提高品质的目标,具有广阔的应用前景。     

珠钢电炉-薄板坯连铸连轧流程VN微合金钢组织性能研究

阐述了珠钢电炉-薄板坯连铸连轧流程VN微合金钢钒的析出规律、微观组织特征和强化机理。研究表明：在电炉-薄板坯连铸连轧流程采用VN微合金化,铸坯中析出以钒（C,N）为主,并有少量TiN或（Ti,V）（C,N）复合析出,平均粒度大约为40nm,热连轧开始前铸坯中大量存在的钒（C,N）能够抑制后续热连轧过程中变形奥氏体再结晶晶粒长大,使铁索体组织超细化;强化机制以细晶强化为主、沉淀强化为辅;采用VN微合金化技术开发的550MPa级VN微合金钢组织细化至3．0—4．0μm,产品具有良好的综合性能。     

温度参数对铌微合金高强度结构钢组织性能的影响

通过控轧控冷试验,力学性能检验和组织的光学显微观察,研究了温度参数对铌微合金钢组织性能的影响。结果表明:两阶段控轧及控冷所获晶粒尺寸明显小于常规轧制+快速冷却的晶粒尺寸;随冷却速率的增大或终冷温度的降低或精轧开轧温度的降低,试验钢晶粒细化,混晶程度加重,强度增大,塑性降低;精轧低温开轧利于韧性提高;铁素体混晶可能源于因铸坯中Nb(C,N)的不均匀分布造成的原始奥氏体混晶,粗轧大压缩比轧制可以消除这种混晶现象。     

CSP流程VN微合金钢的冶金学特征

在薄板坯连铸连轧生产中，微合金元素的溶解与析出过程，以及微合金元素与变形奥氏体再结晶、γ-a相变间的关系与传统厚板坯连轧有较大的差异，这为薄板坯连铸连轧流程生产微合金钢带来了一定的困难。研究表明，V～N的冶金学特征比较适合于CSP技术的特定工艺流程。对0．05％C—1.5％Mn-0．12％V-0．020％N钢，连铸出坯后已有大量微细V（CN）析出，均热后仅有部分沉淀溶解。这些铸坯中的微细沉淀对抑制变形奥氏体再结晶晶粒长大有十分重要的作用。在工业试生产中，铁素体晶粒尺寸为3～4pm的V—N微合金化超细晶粒钢已经试制成功，在CSP流程V—N微合金钢中，V的沉淀强化作用也显著提高了试验钢的强度水平。通过对VN微合金钢的超细组织控制和沉淀强化控制，在CSP流程上可生产屈服强度达550MPa级的低碳贫珠光体高强度钢。     

V-Ti-N微合金钢的再结晶控轧与控冷

本文提出了一个称为再结晶控轧的新控轧方案及相应的合金化原则。再结晶控轧不要求分段轧制及在奥氏体未再结晶温度区轧制,从而避免了常规控轧所具有的两个主要缺点,即生产率较低及需要强力轧机。 对0.13V—0.017Ti微合金钢的研究表明,钒钛系微合金钢具有高的奥氏体晶粒粗化温度,低的奥氏体再结晶温度以及热变形后小的晶粒粗化速度。此外,这种微合金钢还表现出足够的过冷能力和铁素体内碳氮化合物析出硬化能力。这些特性使得钒钛微合金钢特别适于实施再结晶控轧。     

钛微合金化技术发展现状

介绍了单一钛以及铌钛、钒钛、锰钛、钼钛复合添加时的微合金化作用;着重分析了钛的析出热力学和钛的析出行为在薄板坯连铸连轧过程与传统连铸连轧过程中的差异,以掌握钛的析出规律;并提出了钛微合金化的技术要点,包括成分设计、冶炼技术和控轧控冷技术。对钛微合金化技术的分析将对钛微合金化的工业应用和技术发展具有一定指导意义。     

Effects of TMCP Schedule on Precipitation,Microstructure and Properties of Ti-microalloyed High Strength Steel

Using the similar compositions of the Ti-microalloyed high-strength steels produced by the thin-slab casting process of compact strip production(CSP),four thermo-mechanical control processes(TMCP)after the simulated thickslab casting,i.e.the two hot rolling routes and the two cooling processes,were designed,aiming at achieving the same mechanical properties as the thin strip products.The final microstructures after the four TMCP processes were examined by optical microscope(OM),scanning electron microscope(SEM)and transmission electron microscope(TEM).The tensile properties and Charpy impact energy were measured correspondingly.Strain-induced TiC precipitation was found in the two-stage rolling route with the finish rolling temperature at low levels,leading to grain refinement due to the pinning effect during austenite recrystallization.Precipitation hardening in ferrite was observed when a period of isothermal holding was applied after hot rolling.It could be concluded that both finish rolling temperature and the subsequent isothermal holding temperature were crucial for the achieved strength level due to the combined effect of grain refinement and precipitation hardening.At the same time,it was found that the isothermal holding led to poor impact toughness because of remarkable precipitation hardening.Therefore,it was suggested that the precipitation kinetics of titanium carbides in both austenite and ferrite should be investigated in future.     

关于薄板坯连铸连轧产品开发问题的探讨

分析了国内外薄板坯连铸连轧产品开发现状及发展趋势,探讨了转炉薄板坯连铸连轧生产HSLC钢的优势,薄板坯连铸连轧HSLA钢微合金元素的控制,薄规格及超薄规格热带产品开发,薄板坯连铸连轧生产冷轧用钢板的技术分析,薄板坯连铸连轧生产高性能、高附加值产品的技术探讨以及薄板坯连铸连轧产品开发的关键工艺技术等.     

薄板坯连铸连轧铁素体轧制工艺

铁素体轧制工艺是经济地生产具有良好性能的超薄规格热轧板卷的一项有效的生产工艺。随着薄板坯连铸连轧技术市场的不断扩大，随着市场对超薄规格、良好深冲性能的热轧薄板需求的日益增长，铁素体轧制工艺将具有更广阔的市场前景。介绍了铁素体轧制工艺的发展和现状，分析了铁素体轧制工艺的特点、分类、适用范围、产品的组织性能和用途，说明了采用铁素体轧制工艺的制定以及在薄板坯连铸连轧机组上的应用。     

Slow Hot Rolling in Direct Linkage with Thin Slab and Strip Continuous Casting: Effect on the Evolution of Austenite Grain

This work was carried out in context with the development of strip casting with the single‐belt process. In this new process the hot rolling is performed in‐line with considerably lower velocity than in conventional hot rolling. It is of interest to study the effect of low rolling speed on the material properties. Based on a finite element model used to predict the thermomechanical behaviour of the strip in tandem mills, the microstructural evolution of austenite was computed. In order to take account of the non‐isothermal conditions in industrial hot rolling, the material equations for recrystallization and grain growth are modified. The parameter studies were carried out over a wide range of volumetric flow rate extending from that in thin slab casting to that in conventional finishing rolling. They demonstrate that the “slow hot rolling” can produce a fine grain of austenite. Austenite grain evolution was computed for conventional rolling with a seven stand mill and for in‐line hot rolling of strip produced by the single‐belt process. It is found that the final grain size of austenite is about the same for the two processes under the condition that strip thickness behind the last stand is the same.     

Study on Austenite Grain Growth Law of Ultra-High Strength Hot-Stamped 22MnB5 Steel During Thin Slab Casting and Rolling Process

Clarifying the austenite grain growth law in the thin slab casting and rolling (TSCR) process can provide theoretical guidance for the control of austenite grain in the slab. Starting with the austenite nucleation during solidification process, the growth law of austenite grains is methodically studied throughout the TSCR continuous casting and soaking process. The results show that the austenite growth is not interrupted during the TSCR continuous casting and soaking process. The austenite grain growth in the continuous casting process accounts for more than 70% of the total growth. The growth rate of austenite in the continuous casting cooling process is always faster than that when reheated to this temperature. Compared with the holding temperature and holding time, the final size of austenite grains in the TSCR process slab is most affected by the continuous casting cooling rate. In addition, compared with the traditional process, the growth rate of austenite in TSCR process is faster at the end of soaking.     

薄板坯连铸连轧流程Fe-3％Si钢冷轧板织构

在实验室按照薄板坯连铸连轧工艺流程试制了Fe-3％Si硅钢热轧板,按照四种冷轧变形制度将热轧板冷轧后采用X射线衍射方法观察了织构分布,分析了14／16层、H／8层、H／4层、H／2层的取向密度变化,研究了热轧和冷轧过程的织构演变规律。试验研究结果为开发薄板坯连铸连轧短流程生产电工钢技术提供理论依据和参考数据。     

热轧船板钢时奥氏体组织变化规律

奥氏体热变形时再结晶规律研究是制定合理控制轧制工艺的理论基础。在试验基础上就一般强度船板钢热变形时奥氏体再结晶百分数及晶粒尺寸与工艺参数的关系进行了研究。认为奥氏体再结晶百分数及晶粒尺寸在不同的温度区域有不同的变化规律，并借此讨论了制定控轧工艺时应注意的问题。     

薄板坯连铸连轧生产线工艺技术及应用

简单介绍了薄板坯连铸连轧技术特点、产品范围及工艺优劣势;还阐述了与传统热轧工艺相比,该薄板坯连铸连轧生产线生产(超)薄带钢、(超)低碳钢的优势以及相关产品质量保证的特点.     

Austenite Recrystallization and Controlled Rolling of Low Carbon Steels

The dynamic recrystallization and static recrystallization in a low carbon steel were investigated through single-pass and double-pass experiments. The results indicate that as the deformation temperature increases and the strain rate decreases, the shape of the stress-strain curve is changed from dynamic recovery shape to dynamic recrystallization shape. The austenite could not recrystallize within a few seconds after deformation at temperature below 900 ℃. According to the change in microstructure during deformation, the controlled rolling of low carbon steel can be divided into four stages： dynamic recrystallization, dynamic recovery, strain-induced ferrite transformation, and rolling in two-phase region. According to the microstructure after deformation, the controlled rolling of low carbon steel can be divided into five regions： non-recrystallized austenite, partly-recrystallized austenite, fully-recrystallized austenite, austenite to ferrite transformation, and dual phase.     

400 MPa级C-Mn钢控轧控冷生产过程组织-性能的预测

建立了C－Mn钢在控制轧制和控制冷却生产中微观组织演变和力学性能预测的物理冶金模型，模型包括加热、再结晶、相变和力学性能四部分，分别描述了带热轧及冷却过程中的物理冶金现象，根据现场数据，计算了轧制过程奥氏体晶粒尺寸和再结晶分数的演变，预测了在不同工艺条件下连续冷却转变各相的体积分数和铁素体的晶粒尺寸等显微组织参数和相关的力学性能，预测结果和实测值吻合较好。