Microstructure and texture evolution of cold-rolled deep-drawing steel sheet during annealing

In accordance with experimental results about the annealing microstructure and texture of cold-rolled deep- drawing sheet based on the compact strip production （CSP） process, a two-dimensional cellular automation simulation model, considering real space and time scale, was established to simulate recrystallization and grain growth during the actual batch annealing process. The simulation results show that pancaked grains form during recrystallization. （111} advantageous texture components become the main parts of the recrystallization texture. After grain growth, the pancaked grains coarsen gradually. The content of （111} advantageous texture components in the annealing texture increases from 55vo1% to 65vo1%; meanwhile, the contents of {112}〈110〉 and {100}〈110〉 texture components decrease by 4% and 8%, respectively, compared with the recrystallization texture. The simulation results of microstructure and texture evolution are also consistent with the experimental ones, proving the accuracy and usefulness of the model.

Study on the bendability and toughness of a 1 500 MPa cold-rolled martensitic sheet steel

Cold rolled martensitic sheet steels are achieving more and more applications in car-making because of their ultra-high strength and potential for weight reduction. The relatively low plasticity of ultra-high strength martensitic steels might be a drawback for the applications in the aspects of forming and safety protection function and should be significantly noted. A 1 500 MPa grade cold rolled martensitic sheet steel has been studied to investigate the bendability at 90 degree bending and impact toughness as well as fracture surface morphology at various temperatures. Some discussions have been made basing upon the experiment data to get some understanding on the performance of the materials under various conditions and on how to make use of this kind of ultra high strength steel properly.

Effect of water quenching processing parameters on the mechanical properties of a cold-rolled C-Mn-containing steel sheet

Cold-rolled advanced high-strength steel sheets have become the material of choice for the automotive industry because of their unique attributes of high strength and balanced mechanical properties.High-hydrogen gas jet cooling and water quenching are the most commonly used ultrafast cooling technologies for producing martensite-containing high-strength steel sheets.The water quenching technology ensures the fastest industrial cooling rate of 1 000 K/s;therefore,it has the highest potential with respect to saving alloys.In this study,the water quenching of a C-Mn-containing steel sheet is simulated during continuous annealing to investigate the effect of water quenching and tempering parameters on its mechanical properties.The results reveal that at low quenching temperatures,the strength of the steel sheet decreases as the soaking temperature increases.However,at high quenching temperatures,a high soaking temperature corresponds to increased strength after quenching,regardless of whether the material was austenitized in the single austenite zone or the inter-critical zone.Therefore,a high quenching temperature always results in a high strength and a high yield ratio after quenching.Low-temperature overaging(tempering) considerably influences the yield strength and yield ratio,and the extent of this influence is correlated with the soaking temperature.

Effect of annealing parameters on mechanical properties of cold-rolled martensitic steel sheets

Cold-rolled martensitic steel sheets produced on continuous annealing lines with water quenching facility,have advantages of high strength and low alloying element contents.These are in good accordance with the trend of light-weighting and fuel saving for automotive steel.In this article,a cold-rolled martensitic steel is studied to investigate the effect of annealing parameters on its mechanical properties.It is found that the quenching temperature and the slow cooling speed as well as the overageing temperature have significant influence on the strength of the experimental steel.The temperature zone at which the austenite decomposition is slow or has not started may be chosen as the quenching temperature to ensure the steel’s strength stability.The slow cooling speed also influences the steel’s strength greatly.A high cooling rate will lead to significantly higher strength.Tempering would decrease the steel’s tensile strength but would increase its yield strength.

Development and application of Baosteel's cold-rolled martensitic steel sheets

Cold-rolled martensitic steel sheets are becoming widely applied in the automotive industry because of their ultra-high strength,which may result in satisfactory weight reduction. The grades of martensitic steel sheets are classified based on their tensile strength,which ranges from 980 to 1 700 MPa. The main applications include a series of structural parts of uniform cross-section or simple shape,such as bumper beams,door beams and door sills,etc. The study and development of cold-rolled martensitic steel sheets date back to 2007 in Baosteel,and some grades became commercially available in 2009. By 2015,Baosteel had commercially supplied thousands of tons of these steel sheets with tensile strength up to 1 400 MPa. Currently,1 500 MPa martensitic steel sheet is commercially available and 1 700 MPa martensitic steel sheet has been successfully produced. The process technology and application guides of Basoteel ＇s cold-rolled martensitic steels are summarized and analyzed in order to assist ongoing research and ensure correct applications of these ultra-high strength steel sheets.

Properties of ultra-low carbon,cold-rolled sheet steels containing titanium or boron for use in enameling

Ultra-low carbon（ULC）,cold-rolled sheet steels for porcelain enameling containing alloys of titanium and boron are studied. The microstructure,mechanical properties,inclusions,and precipitates of the sheet steels are analyzed. The hydrogen permeation time of the sheet steels as-annealed and after skin-passed or cold-rolled at different reductions are measured. It is show n that the sheet steels possess different features of enameling properties in hydrogen permeability,fishscale resistance,and pinhole resistance.

Formation mechanism and control of aluminum layer thickness fluctuation in embedded aluminum-steel composite sheet produced by cold roll bonding process

The influences of rolling reduction and aluminum sheet initial thickness(AIT)on the thickness fluctuation of aluminum layer(TFA)of embedded aluminum?steel composite sheet produced by cold roll bonding were investigated,the formation mechanism of TFA was analyzed and method to improve the thickness uniformity of the aluminum layer was proposed.The results showed that when the reduction increased,TFA increased gradually.When the reduction was lower than40%,AIT had negligible effect on the TFA,while TFA increased with the decrease of AIT when the reduction was higher than40%.The non-uniformities of the steel surface deformation and the interfacial bonding extent caused by the work-hardened steel surface layer,were the main reasons for the formation of TFA.Adopting an appropriate surface treatment can help to decrease the hardening extent of the steel surface for improving the deformation uniformity during cold roll bonding process,which effectively improved the aluminum thickness uniformity of the embedded aluminum/steel composite sheets.

Research on the design of cold rolled ultra high strength sheet steel

This study researches cold rolled ultra high strength martensitic steel processed by water quenching. It is found that both the quenching and overageing temperatures greatly influence the mechanical properties of martensitic steel. A tensile strength of 1500 MPa can be obtained from 0.2% C-1.8% Mn steel by soaking at 840℃,quenching at 700℃ and overageing at 200℃ for several minutes. The continuous cooling transformation （CCT） diagram reveals that full martensite can be obtained at a cooling rate of 100℃/s or higher; and at a cooling rate of 3 - 10℃/s,austenite barely decomposes at 700℃. For steel with 0.2% carbon and less manganese, austenite decomposition occurs before it is cooled to 700℃ at a cooling rate of 3 - 10℃/s, which leads to lower tensile strength. It is possible to reduce the manganese content of the 1500 MPa martensitic steel by increasing the quenching temperature. To increase the quenching temperature,the control of flatness during water quenching becomes a major concern.

Research and application on the automatic measuring device for testing transverse thickness difference of cold-rolling steel sheet

Many advanced technologies have been applied in developing the automatic measuring device for testing transverse thickness difference of cold-rolling steel sheet,such as the technologies of automatic control,sensor measurement,marking identification,photographic location,computer application and information transmission.This measuring device can measure the transverse thickness difference of the steel plate accurately and quickly,with a high detection level of automation.It is an effective detection equipment for transverse thickness control of steel plate.Horizontal width of steel plate measuring 0.8-1.4 m, horizontal measurement point positioning accuracy±0.02 mm,thickness range 0.2-2.0 mm, measurement accuracy within±1μm.

Correlation of morphological anisotropy and Lankford value of deep drawing sheets hot-rolled by compact strip production

Cold-rolled steel sheets in automotive applications require an excellent deep draw ability, which is characterized by the Lankford value （r-value）. In this study, a correlation was identified between r-value and pancake-shaped grain flatness which is indicated as the ratio of grain diameter in the rolling direction （RD） and normal direction （ND） of sheets （dr/dn）. A mathematical model （ r = e^0.345（dn^1/2-dr^1/2） ） was developed to calculate r-value by the microstructure of steel sheets hot-rolled by compact strip production （CSP）. It is shown that the r-value is higher, if the microstructure of steel sheet is of pancake-shaped grains elongated in the rolling direction. The calculated r-value is confirmed to fit exactly to the measured one from the large-scale production.

Surface Defects of Cold-Rolled Ti-IF Steel Sheets due to Non-Metallic Inclusions

Surface defects of the cold-rolled sheets of Ti-IF steel were studied and analyzed. After analyzing surface defects of cold-rolled sheets, such as shelling defects, holes and sliver defects by SEM/EDS, a variety of inclusions were found. In addition, the distribution of macro-inclusions in slabs was analyzed by MIDAS method. The results show the macroscopic inclusion bands of head slabs and normal slabs are in 1/8 slab thickness regions of both inner arc side and outer arc side. The formation process of the defects in the cold-rolled sheets was simulated with an experimental cold-rolling machine for comparison. The results show that there were three kinds of inclusions underneath the surface defects: Al2O3, SiO2 and particles from slag entrainment, which were the main reason for defect formation during cold rolling.

退火对AlSn20Cu-钢轴瓦复合板材组织与性能影响

采用电子扫描显微镜电镜、金相显微镜、显微硬度和弯曲等方法,研究了热处理工艺对冷轧AlSn20Cu-钢复合板材微观组织和力学性能的影响。结果表明:经退火处理后,铝合金中锡相由带状逐渐球化、聚集成网状,而钢侧微观组织无明显变化。铝合金硬度从轧制态的55 HV降低到退火态的33 HV,而钢层显微硬度无明显变化。复合板经过弯曲后,钢/铝界面无明显开裂和缺陷。

Annealing Response of Cold-Rolled Vanadium Microalloyed Sheet Steels

Vanadium microalloying is widely employed in hot-rolled HSLA products;because of its relatively high solubility in austenite,vanadium plays a special role in thin-slab cast hot-rolled products where reheating is limited prior to direct-rolling.In cold-rolled and annealed sheet steels,vanadium technology has been employed in bake-hardenable drawing-quality steels,and in HSLA products.Recent studies have investigated the continuous and batch annealing response of vanadium-containing cold-rolled HSLA steels,with an emphasis on aluminum and nitrogen variations (because of the special importance of nitrogen in vanadium microallyed steels,and interesting interactions between vanadium,aluminum and nitrogen).The present contribution reviews some key aspects of vanadium-microalloyed coldrolled sheet steels,and highlights the results of selected studies showing the influence of steel composition and processing.

Fe-12Mn-2Al-0.1C冷轧钢板冲压成形数值模拟与实验

以Fe^(-1)2Mn-2Al-0.1C冷轧钢板为研究对象,进行了扩孔成形实验,获得了不同冲压速度下的扩孔率,讨论了冲压速度对板料成形性能的影响机制。使用Dynaform 9.2有限元仿真软件对钢板扩孔成形过程进行了数值模拟,获得了该材料在不同虚拟凸模速度下的扩孔成形极限图、板料厚度以及扩孔率。通过数值模拟发现,扩孔率随着虚拟凸模速度的增加大体呈上升趋势,在虚拟凸模速度为15000 mm·s^(-1)时进行扩孔,既能保持冲压件板形,又可改善其扩孔性能。实验结果表明,扩孔率随着冲压速度的增大呈先上升后下降的趋势并在冲压速度为20 mm·min^(-1)时获得最大扩孔率50.90%;冲压成形过程中的冲压速度决定了相变诱导塑性(TRIP)效应中残余奥氏体的相变速率,从而决定了钢板的成形性能。

Research of cold-rolling oil for stainless sheet steel

The research & application of cold rolling oil for stainless sheet steel are introduced inthis paper. The results indicate that this oil has well properties of anti-wear, oxidation, emulsifyingand fine rust-preventing characteristics, it can meet the employable demands of SENDZIMIR highspeed rolling mill at all.

Ti-IF钢冷轧缺陷的形成分析

对某钢厂生产的Ti-IF钢冷轧板的表面缺陷进行研究,利用扫描电镜和能谱仪分析其缺陷部位微观形貌及夹杂物成分,在缺陷部位发现大量氧化铝、硅铝酸盐、氧化硅、镁铝尖晶石夹杂物。此外,对夹杂物含量较高的头坯试样进行轧制模拟试验,分析结果进一步证实了由于各类夹杂物的存在导致Ti-IF钢冷轧板的表面缺陷。

Ti-IF钢冷轧板罩式退火工艺研究

为提高Ti-IF钢的综合性能,在Gleeble-1500热模拟试验机上,研究了退火工艺对Ti-IF钢组织和再结晶结构的影响,结果表明:再结晶温度随保温时间的延长而降低,在实验室条件下,保温1 h的再结晶温度为650℃,保温3 h的再结晶温度为640℃;Ti-IF钢对退火升温速度不敏感,可以采用较高的升温速度,如60℃/h。根据罩式退火的特点,为保证钢卷的冷点和温度的均匀性,Ti-IF钢的退火控制温度应按罩式炉上限控制,并保证足够的保温时间。经过工业生产和用户使用表明,产品冲压性能优良,质量稳定。

超纯净Ti-IF冷轧薄板的组织与性能

选择本溪钢铁公司特有的纯铁原料炼制超纯净Ti IF钢并加工成板 ,探讨了不同工艺参数对板材显微组织和性能的影响·结果表明 ,适于本钢CDCM +罩式退火的Ti IF冷轧薄板的生产工艺为 :890℃终轧→ 6 80℃卷取→ 80 %压下率冷轧→ 710℃ ,Δhr退火 ,可使超纯Ti IF深冲钢板的屈强比σs/σb=0 3～ 0 4应变硬化指数n≥ 0 3·

CSP-低碳钢DC03冷轧板的组织和织构

研究了CSP工艺生产的0.04%C低碳钢DC032.9 mm热轧基板、0.9 mm的冷轧板和退火平整板的组织与织构。结果表明,热轧基板组织为铁素体+少量沿晶界分布的珠光体,铁素体基体中有少量40～100 nm MnS粒子,没有观察到AlN;冷轧板组织为含大量位错的带状铁索体-珠光体,{111}织构的择优取向较明显;退火平整板组织为铁素体和游离渗碳体,并观察到10～30 nm的析出相,{111}织构轴密度达5.15,{100}轴密度减为0.61。

冷轧压下率和退火工艺对St37-2G结构用冷轧钢板组织和力学性能的影响

研究了冷轧压下率和退火工艺对St37-2G结构用冷轧钢板显微组织和力学性能的影响,并优化了生产工艺。结果表明:试验钢板经不同压下率冷轧并经670℃×5h退火后的显微组织均由铁素体、少量渗碳体和微量珠光体组成,仍保留着渗碳体沿轧向呈纤维状分布的特征;随着冷轧压下率的增大,试验钢板的硬度先增大后减小,在冷轧压下率60%时达到最大值;随退火升温速率的增大,试验钢板的屈服强度、抗拉强度以及塑性应变比明显下降,伸长率和加工硬化指数变化不大;最优的冷轧和退火工艺为冷轧压下率40%～50%,退火温度670℃,升温速率20℃·h-1。