Effect of continuous annealing temperature on microstructure and properties of ferritic rolled interstitial-free steel

In this report,the microstructure,mechanical properties,and textures of warm rolled interstitial-free steel annealed at four different temperatures(730,760,790,and 820°C)were studied.The overall structural features of specimens were investigated by optical microscopy,and the textures were measured by X-ray diffraction(XRD).Nano-sized precipitates were then observed by a transmission electron microscope(TEM)on carbon extraction replicas.According to the results,with increased annealing temperatures,the ferrite grains grew;in addition,the sizes of Ti_4C_2S_2 and Ti C precipitates also increased.Additionally,the sizes of Ti N and Ti S precipitates slightly changed.When the annealing temperature increased from 730 to 820°C,the yield strength(YS)and the ultimate tensile strength(UTS)showed a decreasing trend.Meanwhile,elongation and the strain harden exponent(n value)increased to 49.6%and 0.34,respectively.By comparing textures annealed at different temperatures,the intensity of{111}texture annealed at 820°C was the largest,while the difference between the intensity of{111}<110>and{111}<112>was the smallest when the annealing temperature was 820°C.Therefore,the plastic strain ratio(r value)annealed at 820°C was the highest.

Effect of Typical Elements on the Heredity of Hot-rolled and Annealed Texture in Non-oriented Electrical Steel

Macroscopic texture and microscopic orientation in hot-rolled and annealed sheets of nonoriented electrical steel were studied by XRD and EBSD techniques. The microstructure of hot-rolled and annealed samples was studied by OM. Experimental results indicate that a strong heredity is observed in texture evolution between hot-rolled texture and annealed texture. Typical elements have a large effect on the recrystallization microstructure and texture distribution. The texture distribution through thickness is highly affected by recrystallization in hot rolled sheets. The recrystallization is boosted by Si and Al. Goss grains originate from cracked initial 〈100〉 columnar grains. {110}〈112〉, {112}〈111〉 and {111}〈112〉 grains are related to Goss grains. In subsurface lay of hot rolled sheets, Al can strengthen Goss texture and weaken copper-type texture. {112}〈111〉 texture and {110}〈112〉 texture are strengthened by Si. In the central layers, {100}〈001〉 texture and {111}〈121〉 texture are weakened by Al. {100}〈011〉 texture is increased by Al. Si can increase the proportion of γ-fiber texture and decrease that of {100}〈011〉 texture. In annealed texture, {100}〈001〉 texture and Goss texture are decreased by Al and Si. γ-fiber texture is increased by Si and {111}〈121〉 texture is preferentially increased by Al. The recrystallized grain size is increased and iron loss of annealed sheets is reduced by Al and Si, which means that the magnetic properties are optimized by the Al and Si content.

Texture evolution during semicontinuous equal-channel angular extrusion process of interstitial-free steel

Semicontinuous equal-channel angular extrusion（ SC-ECAE） is a novel severe plastic deformation technique that has been developed to produce ultrafine-grain steels. Instead of external forces being exerted on specimens in the conventional ECAE,driving forces are applied to dies in SC-EACE. The deformation of interstitial-free（ IF） steel w as performed at room temperature,and individual specimens w ere repeatedly processed at various passes. An overall grain size of 0. 55 μm w as achieved after 10 passes. During SC-ECAE,the main textures of IF steel included { 111} ,{ 110} ,{ 112} ,{ 110} ,and { 110} At an early stage,increasing dislocations induce new textures and increase intensity. When the deformation continues,low-angle boundaries are formed betw een dislocation cell bands,w hich cause some dislocation cell bands to change their orientation,and therefore,the intensity of the textures begins to decrease. After more passes,the intensity of textures continues to decrease w ith high-angle boundaries,and the sub-grains in dislocation cell bands continuously increase. The present study reports the evolution of textures during deformation; these w ere examined and characterized using high-resolution electron backscattered diffraction（ EBSD） in a field emission scanning electron microscope. The mechanisms of texture evolution are discussed.

Effect of Coiling Temperature on the Evolution of Texture in Ferritic Rolled Ti-IF Steel

The effect of coiling temperatures on the evolution of texture in Ti-IF steel during ferritic hot rolling, cold rolling and annealing was studied. It was found that texture evolution at high temperature coiling is absolutely different from that at low temperature one. The hot band texture includes a strong α-fiber as well as a weak γ-fiber after ferritic hot rolling and low temperature coiling. Both of them intensify after cold rolling and a γ-fiber with peak at {111}〈112〉 is the main texture of annealed samples. However, the main component of the hot band texture after high temperature coiling is v-fiber. After cold rolling, the intensity of γ texture reduces; α fiber （except {111}〈110〉 component） intensifies and a strong and well-proportioned γ-fiber forms in the annealed samples.

Study on grain refinement of interstitial-free steel during continuous frictional angular extrusion

To explore the application of severe plastic deformation for grain refinement in steel production, a new method called continuous frictional angular extrusion （CFAE） was applied to refine the grain of interstitial-free steel. The deformation was carried out at room temperature and individual sheet specimens were processed in different number of passes. An overall grain size of 200nm was achieved after 8 passes and the proportion of high-angle boundaries to the total boundaries was more than 60%. Through the characterization of high resolution EBSD, X-ray diffraction （XRD） and hardness testing,this paper discussed the evolution of microstructures and textures during deformation and explored the development direction of the method.

Modeling texture development during cold rolling of IF steel by crystal plasticity finite element method

With the consideration of slip deformation mechanism and various slip systems of body centered cubic （BCC） metals, Taylor-type and finite element polycrystal models were embedded into the commercial finite element code ABAQUS to realize crystal plasticity finite element modeling, based on the rate dependent crystal constitutive equations. Initial orientations measured by electron backscatter diffraction （EBSD） were directly input into the crystal plasticity finite element model to simulate the develop- ment of rolling texture of interstitial-free steel （IF steel） at various reductions. The modeled results show a good agreement with the experimental results. With increasing reduction, the predicted and experimental rolling textures tend to sharper, and the results simulated by the Taylor-type model are stronger than those simulated by finite element model.＇Conclusions are obtained that rolling textures calculated with 48 { 110} 〈 111 〉＋ { 112 } 〈 111〉＋ { 123 } 〈 111 〉 slip systems are more approximate to EBSD results.

Texture of Hot Rolled Strip for Fe-3Si Steel Produced by Thin Slab Casting and Rolling

Fe-3Si steel strip was produced by thin slab casting and rolling （TSCR） process in the laboratory. The microstructure and texture of hot rolled strip by different total reduction and rolling schedules were observed through EBSD technique and X-ray diffraction method. The rule of texture density for the a,ε and γ fibers was analyzed. When the total reduction was increased from 82.9% to 97.1%, the gradient of microstrueture and texture for A steel surface layer and center layer was found, {001}〈110〉 texture had higher intensity, and {001}〈110〉texture was changed to { 110 } 〈 001 〉 and { 112 } 〈 111 〉. The texture distribution with different reduction schedules for B steel was basically similar, but the Goss texture orientation density and volume fraction for B steel were higher, the hot rolling reduction schedule of C1 was effective for the formation of Goss texture. The research work was useful theoretical basis and reference data to develop electrical steel by thin slab continuous casting and direct rolling technology.

Hot deformation behavior of a Cr-containing low carbon steel in the ferrite range

A low carbon steel with Cr addition of 0.46wt% combined with trace elements of Mn and Ti was studied. The apparent activation energy of deformation and the hot deformation equation of the steel in the ferritic range were determined by means of single hot compression tests. The hot-rolled strip of 3 mm in thickness rolled in the ferritic range was obtained using a laboratory hot rolling mill. The mechanical properties show that the values of yield strength and ultimate tensile strength are 230 and 330 MPa, respectively, and the elongation is 33%. The average r-value is 1.1. Large polygonal ferrite recrystallization grains with about 40 grn in size and the strong { 111 } recrystallization texture can be obtained in the hot-rolled strip.

Texture Evolution in Ferritic Rolled Ti-IF Steel During Cold Rolling

The texture evolution of ferritic hot rolled Ti-IF steel during cold rolling was investigated in which the reduction was from 15% to 85 %. It was found that α fibre texture was monotonously intensified with the increase in the cold rolling reduction, while y fibre texture changed in a different way. When the cold rolling reduction was in the range of 15 % -- 35 % or 45 % -- 75 %, γ fibre texture was strengthened ; however, when the cold rolling reduction was 35 %- 45 % or 75 %- 85%, the intensity of 7 fibre was reduced. The 7 fibre displayed a maximum intensity for the reduction of 75%, and the highest average plastic strain ratio was simultaneously obtained owing to the favorable recrystallization texture.

Texture of Cold Rolled Strip of Fe-3Si Steel Produced by Thin Slab Casting and Rolling

The hot rolled strip of Fe-3Si steel was experimentally produced by thin slab casting and rolling（TSCR） process in the laboratory.The texture evolution rule was investigated during hot rolling and cold rolling.The texture distribution of cold rolled strips with four kinds of cold rolling reduction schedules was observed through X-ray diffraction method,and the orientation density variation of 1/16 layer,1/8 layer,1/4 layer,and 1/2 layer in thickness was analyzed.The cold rolled texture of steel A with four kinds of cold rolling reduction schedules was mainly composed of α and γ fibers.Cold rolling reduction ratio of 70% was more beneficial for obtaining more γ fibers.The γ fiber texture orientation density of {111}01-1 and {111}1-1-2 was the largest on the 1/8 layer and 1/4 layer and the least on the 1/16 layer and 1/2 layer for steel B.The texture orientation density of {001}-{223}11-0 in the α fibers for steel C was increased,but the texture orientation density of {332}-{110}11-0 was low.

Texture Evolution of Columnar Grains in Electrical Steel During Hot Rolling

Columnar grains in cast slabs of electrical steel show strong anisotropy in grain orientation and morphology and thus influence the subsequent microstructure and texture after hot rolling significantly. The texture evolution of hot rolled sheets containing initial columnar grains with their 〈100〉 directions approximately parallel to the rolling direction （RD）, transverse direction （TD） and normal direction （ND） of the hot rolled sheets was investigated by using EBSD technique. The results indicated that, whatever the initial texture of the columnar grains was, typical Goss, brass-type and copper-type shear texture component could develop in shear-deformed surface region. The copper-type texture formed under the maximum shearing force with the fine, sheared or dynamically recrystallized grains, and Goss grains were mainly elongated and deformed grains, while brass grains behaved between them. Ad- ditionally, the rotating relationship of the three types of shear textures was different due to the restriction of grain boundaries. In homogenously deformed center region, the RD sample contained more {112}〈110^-〉 grains, and TD sample was covered by {100} textures such as {100}〈011〉 and {100}〈021〉 with coarse grains, while the ND sample developed many {100}〈001〉 grains which were attributed to more {100} grains in the initial sample. Re- markable texture transition occurred on both sides of grain boundaries when {110} grains were adjacent to mfiber texture grains. It was found that significant texture gradient and preferred distribution of rotating axis existed in the soft orientation grains on the α- fiber when the grains neighbored hard grains on γ-fiber.

Correlation of surface features with corrosion behaviors of interstitial free steel processed by temper rolling

Temper rolling,as a final manufacturing procedure,brings the change of surface features and hence affects the corrosion behaviors of interstitial-free(IF)steel.This study investigates changes in residual stress,microstructure,and surface topography of IF steel using X-ray diffraction,electron backscatter diffraction,and optical interferometric microscopy.And the synthetic influence of surface features on the corrosion process of the steel was evaluated by damp heat tests and electrochemical measurements.Results showed that low tensile and compressive residual stresses are introduced to the surface of the IF steel.Some grains had a grain orientation spread(GOS)value greater than 0.50 after temper rolling.Moreover,temper rolling caused a slight change in the surface profile of the IF steel.The compressive residual stress had an overwhelming role at the macroscopic level,in retarding the corrosion evolution process of IF steel,as well as in decreasing the average corrosion rate.And corrosion was more likely to initiate and propagate in matrices with a high GOS value,which played the determinant role at the microscopic level.Moreover,the depth of valley in the surface profile could affect the diffusion process involved in the electrode reactions,which was more likely to exert an extra influence on the corrosion rate of IF steel.

Effects of Rolling Parameters on Texture and Formability of High Strength Ultra-Low Carbon BH Steel

The effects of hot rolling and cold rolling parameters on texture and r （ plastic strain ratio ） value of high strength ultra low carbon bake hardening （ ULC-BH ） steels are studied with orientation distribution function （ ODF ） structural analysis method.After hot rolling , the high strength ULC-BH steel sheet has weakγ-fiber with uniform orientation distributions , and weakα-fiber , of which { 445 } component forms a high intensity peak at coiling temperature of 750℃.After cold rolling , both { 111 } -{ 111 } intensity on theγ-fiber and{ 111 -}{ 112 } intensity on theα-fiber enhanced.As a result of substitutional solute elements Mn and P being added to the steel , strong { 112 } deformation texture component is observed onα-fiber , especially at 80%cold rolling reduction , and this leads to the strong { 111 } recrystallization texture after annealing.The increase of cold rolling reduction shifts the maximum intensity on theγ-fiber from { 111 } to { 111 } .After annea-ling , a very strongγ-fiber is obtained , with intensity peak at { 111 } component when cold rolling reduction reaches 80%.Increasing coiling temperature and cold rolling reduction improveγ-fiber intensity and r value , resulting in good deep drawability.

Diffusion behavior of Cr in gradient nanolaminated surface layer on an interstitial-free steel

Nanolaminated structures composed of low-angle grain boundaries(LAGBs) possess high thermal stability. In this paper, a gradient nanolaminated(GNL) surface layer with smooth finish was fabricated on an interstitial-free steel by means of surface mechanical rolling treatment. Microstructural observations demonstrated that the average lamellar thickness is about 80 nm in the topmost surface layer and increases with increasing depth. High thermal stability was confirmed in the GNL surface layer after annealing at 500℃. Diffusion measurements showed that effective diffusivity of Cr in GNL layer is 4–6 orders of magnitude higher than lattice diffusivity within the temperature range from 400 to 500℃. This might be attributed to numerous LAGBs or dislocation structures with a higher energy state in the GNL surface layer. This work demonstrates the possibility to advanced chromizing(or other surface alloying)processes of steels with formation of GNL surface layer, so that a thicker alloyed surface layer with a stable nanostructure is achieved.

热轧工艺对家电用热镀锌超深冲IF钢性能影响的研究

文章结合生产实践,研究了热轧关键工艺参数对家电用热镀锌超深冲IF钢性能的影响,分别开展了880℃和915℃两种精轧终轧温度、680℃和710℃两种卷取温度下试验钢的织构、金相组织及力学性能分析。研究结果揭示了不同热轧工艺参数与家电用热镀锌超深冲IF钢成品织构、金相组织及力学性能的相关性,为通过制定合理的热轧工艺来提高热镀锌超深冲IF钢产品性能提供了参考。

取向硅钢热轧板中纤维织构及Goss织构的形成和演变

在热轧过程中,取向硅钢热轧板形成了不均匀的微观组织和织构梯度,其中热轧板表层和次表层中的Goss织构对取向硅钢的磁性能有重要影响。因此,热轧板微观组织和织构沿厚度方向的形成和演变,特别是Goss织构的形成,仍然是一个值得讨论的课题。为了研究热轧板组织和织构的形成及其演变,使用光学显微镜和扫描电镜(SEM-EBSD)观察了热轧板不同厚度层(表层、次表层和中心层)组织,研究了热轧板组织形貌沿厚度方向的演变,并使用XRD测量了热轧板各厚度层(从表层s=1到中心层s=0)的宏观织构。结果表明,在高剪切力的作用下,热轧板表层s=1形成了大量等轴晶粒(晶粒长宽比为1.0~1.5)和具有一定随机性的织构。表层以下,随着剪切力从表层向中心层逐渐减小,等轴晶粒(晶粒长宽比为1.0~1.5)占比逐渐降低,再结晶晶粒的晶粒长宽比沿着厚度方向逐渐增大,再结晶晶粒形状倾向于沿轧向延伸和呈不规则状。最后,在中心层s=0中,一些大尺寸再结晶晶粒的晶粒长宽比可以达到3.0~6.5。在压缩力和沿厚度方向逐渐减小的剪切力的共同作用下,热轧板次表层s=0.5~0.9形成由众多特定取向组成的纤维织构,而中心层s=0~0.4形成典型的α纤维织构,纤维织构中的一些典型的特定位向包括{100}〈011〉、{112}〈111〉、{110}〈112〉、{213}〈364〉、{441}〈104〉和{110}〈100〉Goss。热轧板次表层s=0.5~0.9中的纤维织构沿厚度方向逐渐演变,并且在次表层s=0.5中有稳定的Goss织构形成。然而,次表层s=0.5中形成的高强度的Goss织构,而次表层中形成的Goss织构只是纤维织构的一小部分。

Evolution of Texture in Grain Oriented Silicon Steels

Goss texture or （110）[100] crystallographic orientation of the grains is typical grain structure of grain oriented silicon steel used for transformer. This type of texture is one of the most important parameters determining the magnetic properties of the laminated steel plates. The furination and growth of Goss texture in three steel samples are investigated. Two of them are prepared under laboratory conditions and one under industrial conditions. The em- phasis is put on the effects of hot lamination temperature and time, primary and secondary recrystallization temperatures during cold lamination on developing of the Goss texture in correlation with other texture components. Also in all steel processing stages, the influence of the chemical composition on the occurrence of Goss texture is examined.

退火对单/双相区热轧无取向硅钢组织织构的影响

硅钢热轧后的退火处理对其组织织构具有显著的影响,通过控制热轧条件制备单相区和双相区热轧无取向硅钢试样,并对试样进行退火处理实验(900,1200℃退火15 min),研究退火对单相区和双相区热轧硅钢组织织构的影响。结果表明:热轧硅钢试样中的动态再结晶区域退火后进一步发生静态再结晶,而热轧后未发生动态再结晶的形变组织退火后仍未发生静态再结晶;本文退火条件下试样未发生明显的相变,总体上静态再结晶不利于{100}织构的提高,热轧过程中的剪切变形程度越大,越有利于退火后{100}织构的形成;单相区热轧试样中的动态再结晶是由剪切变形形成的,而双相区热轧试样中的动态再结晶主要是由铁素体-奥氏体相变形成的,由此导致单相区和双相区热轧试样在不同温度退火后的静态再结晶晶粒尺寸和主要织构组分等存在显著差异。

热轧板厚度对高牌号无取向硅钢磁性能的影响

基于高牌号无取向硅钢现场生产实验,将相同炉次的连铸板坯热轧至不同厚度(2.1,2.3,2.6 mm)的板卷,经常化均热工艺调控,获得晶粒较为均匀的常化板组织,再经85.7%~88.5%压下率冷轧,得到相同厚度(0.3 mm)的冷轧板,最终采用相同的退火工艺得到退火板;结合组织、织构和磁性能的相关检测分析,研究热轧板增厚对高牌号无取向硅钢产品磁性能的影响。结果表明:随高牌号无取向硅钢热轧板厚度的增加(在2.1~2.6 mm范围,即冷轧压下率降低),退火板组织中{111}晶粒占比提高,γ纤维织构强度逐渐增强,织构发生恶化;随热轧板厚度的增加,磁性能中铁损P_(1.0/400)线性增加,磁感强度B_(50)线性降低。热轧板厚度由2.1 mm增至2.3 mm时,P_(1.0/400)平均恶化0.20 W/kg,P_(1.5/50)平均恶化0.04 W/kg,B_(50)平均恶化0.005 T;热轧板厚度由2.3 mm增至2.6 mm时,P_(1.0/400)平均恶化0.24 W/kg,P_(1.5/50)平均恶化0.04 W/kg,B_(50)平均恶化0.009 T。

摩擦对钢退火织构及平面应变影响分析

为进一步提升钢材的轧制效果和质量,在对热轧工艺参数对钢结构影响机理研究的基础上,通过实验研究了摩擦对钢退火结构的影响,得出了润滑轧制工艺下主要成分为γ纤维织构,无润滑轧制工艺下主要为高斯织构。通过数值模拟仿真研究了不同摩擦系数对应板材的等效塑性变形、全塑性变形的变化,研究成果可指导后续实践生产。