两次冷轧法轧制的无取向硅钢{001}〈210〉织构的发展

在元取向硅钢中，{001}〈210〉织构具有良好的磁性，而采用两次冷轧法（中间退火温度为640℃）能够坩强这种织构。利用电子背散射图形（EBSP），测量退火过程中亚擞织构的变化来研究两次冷轧法生产的无取向电工钢{001}〈210〉奴构的形成机理。中间退火钢板的再结晶份数为60％，主要由〈111〉／／ND小等轴再结晶晶粒和〈110〉／／RD伸长变形晶粒组成．在最终退火期间，再结晶晶粒〈111〉／／ND方向的长大被抑制。晶粒在{001}晶面〈210〉晶向上的长大使〈111〉／／ND方向的再结晶晶粒被消耗。这是由于再结晶晶粒中第二次冷轧在〈111〉／／ND方向引入的应变所造成的。所以，最终退火钢板的结构主要为{001}〈210〉织构。     

Correlation Between Pre-annealing Temperature and {110}〈001〉 Annealing Texture in C- and Al-Free Fe-3 Pct Si-0.1 Pct Mn-0.002 Pct S Electrical Steel

In C- and Al-free electrical steel, the increase in primary grain size with increasing pre-annealing temperature causes the transition in annealing texture after final annealing from {110} + {100} to {110}. The strip pre-annealed at 1073 K (800 °C) shows a low magnetic induction B₈(T) of 1.784 T after final annealing. The strip pre-annealed at 1223 K (950 °C) shows a sharp {110}〈001〉 Goss texture, producing a high magnetic induction B₈(T) of 1.914 T comparable to that of the conventional electrical steels.     

Observation of 〈001〉 dislocations and a mechanism for transgranular fracture on {001} in FeAl

Transmission electron microscopy of iron-rich, B2-structure, FeAl alloys which had been compressed at room temperature revealed the presence of 〈001〉 dislocations, in addition to APB-coupled 〈111〉 dislocations which are normally observed at room temperature. It appears that the 〈001〉 dislocations form through the interaction of the 〈111〉 dislocations. This reaction to produce 〈001〉 dislocations is outlined and shown to be energetically favorable. The production of these 〈001〉 dislocations on {100} planes is suggested to be a cause of transgranular cleavage on {100} in B2 alloys deforming by 〈100〉 slip.     

Formation of Edge Crack in 1.4%Si Non-oriented Electrical Steel during Hot Rolling简

Microstructure evolution, dynamic recrystallization, high temperature oxidation and hot ductility of 1.4 % Si non-oriented electrical steel sheets were investigated to reduce edge cracking. The causes of cracking were found to be coarse as-cast microstructure, grain boundary oxidation in reheating furnace, lack of dynamic recrystallization during hot rolling and increase of temperature, resulting in reduced hot ductility in strip edge region. Countermeas- ures against the edge crack are proposed accordingly. Lowering reheating temperature and reducing holding time re- duced oxidation and decarburization. Hot charging temperature was increased to decrease reheating temperature. And using an edger can refine microstructure in strip edge region. Finally, edge heater can be added to increase edge re- gion formability by inducing dynamic reerystallization and ductility by increasing temperature.     

Effect of temperature and shear direction on yield stress by {11\bar 22}〈\overline {11} 23〉 slip in HCP metals23〉 slip in HCP metals

The yield shear stress τ _y due to {11 $\bar 2$ 2}〈 $\overline {11} $ 23〉 second-order pyramidal slip system in cadmium, zinc, and magnesium hcp crystals increased with increasing temperature. This result is interpreted by two thermally activated processes as follows: (1) the dissociation of a (c+a) edge dislocation with a Burgers vector of 1/3〈 $\overline {11} $ 23〉 into a c sessile dislocation and an a glissile basal dislocation, and the subsequent immobilization of the (c+a) edge dislocation; (2) consequently, the double-cross slip of (c+a) screw dislocations must be activated thermally by an increment of applied stress to increase propagation velocity of slip band width. Moreover, τ _y is affected strongly by a direction of applied shear force due to second-order pyramidal slip in zinc as well as in cadmium. The anomalous behaviors of yielding would be caused by the nonsymmetrical core structure of the (c + a) dislocation due to the lattice heterogeneity in hcp metals.     

Diffusion induced grain boundary migration of symmetric and asymmetric 〈011〉 {011} tilt boundaries during the diffusion of Zn into Cu

Diffusion induced grain boundary migration (DIGM) of symmetric and asymmetric 〈011〉{011} tilt boundaries during the diffusion of Zn into Cu bicrystals having misorientation angles θ ranging from 10° to 172° was studied over the temperature range from 623 to 773 K using light microscopy and electron probe microanalysis. All boundaries except for the low angle (θ < 15°) and coherent Σ3 twin boundaries exhibited DIGM with the migration being randomly distributed on both sides of the originally symmetric boundaries and in preferred directions for the asymmetric boundaries. Symmetric Σ19a boundaries exhibited a unique faceted form of DIGM in which all boundary migration resulted in triangular shaped alloyed regions having {111} and {113} habit planes in the neighboring grains. At 693 K the average migration rates of the grain boundaries during DIGM as well as calculated grain boundary diffusivities exhibited a strong dependence on misorientation angle with some coincident site boundaries such as the Σ9 boundaries exhibiting high migration rates and others such as the incoherent Σ3 twin boundaries exhibiting low migration rates. For asymmetric Σ19a boundaries the migration rate at 693 K was observed to increase with increasing asymmetry. Grain boundary diffusivity values calculated for Σ19a, Σ9 and 45° high angle grain boundaries over the temperature range from 627 to 773 K agreed well with the values reported for Zn tracer diffusion in stationary Cu grain boundaries.     

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. Additionally, 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}<011> grains which were attributed to more {100} grains in the initial sample. Remarkable texture transition occurred on both sides of grain boundaries when {110} grains were adjacent to α-fiber 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.     

Growth Process of Goss Grains during Secondary Recrystallization of Grain‐oriented Electrical Steels

The coarsening behaviour of Goss grains in grain oriented electrical steel during annealing after cold rolling was investigated. The results show that the coarsening resistance of fine second phase particles was reduced inside the surface grains. This induced particle coarsening and the reduction of particle density. The reduction of particle density was grain orientation dependent because of the elastic anisotropy of ferrite. Experimental results also revealed that some small surface Goss grains exhibited higher particle density than their neighbouring grains. This may account for the higher coarsening resistance of fine particles and be responsible for the stronger pinning effect on the migration of grain boundaries. Therefore, these Goss grains may have grown at the expense of smaller neighbouring grains and most were very unlikely to be consumed by large neighbouring grains during secondary recrystallization annealing. When their sizes became even larger, they consumed the large grains in turn and consequently formed a strong Goss texture.     

低温板坯加热取向硅钢形变和初次再结晶织构的演变规律

 采用取向分布函数和取向线分析方法对低温板坯加热取向硅钢从热轧到初次再结晶工艺阶段的织构进行了研究。研究表明：一次冷轧后各层的织构组分与热轧板各层面的织构组分存在着继承关系,次表层存在很强的{001}<110>织构,中心层的织构和热轧板的中心层相似,存在强的{001}<110>和{112}<110>织构;中间退火后发生再结晶,各织构组分的强度有所减弱,Goss织构组分再次出现;二次冷轧后沿厚度方向上的织构不均匀性不明显,{111}<112>织构强度最高,几乎是其他织构组分的1倍,{001}<110>织构大幅降低;初次再结晶后织构沿厚度方向没有明显的不均匀性,{111}<110>为最强的织构组分,并且具有一定强度的Goss位向。     

Effect of Hot Band Annealing on Magnetic Properties in 3% Si Grain‐oriented Electrical Steels

Hot band annealing is known to be a prerequisite for good magnetic properties irrespective of manufacturing methods in grain‐oriented Fe‐3 wt.% Si electrical steels. In this study, the effects of hot band annealing on magnetic properties were investigated in 3% grain‐oriented electrical steels of low soluble AI contents and one‐stage cold rolling. Microstructure and precipitate distribution were compared with hot band annealing conditions. Secondary recrystallization behaviour with hot band annealing condition was also discussed.     

Control of δ‐γ Transformation during Solidification of Stainless Steel Slabs in the Mould

In order to obtain satisfactory workability properties required for defect free slab and strip production, the parameters of the casting process, e.g. cooling rate at the initial solidification for the alloy in question must, on the one hand, be carefully adjusted. On the other hand, controlling the characteristics of the solidification structure by chemical composition then takes on particular significance. The main aims of the work were to find out the influence of the phase transformation δ‐γ during the initial solidification of different variants of AISI 304 slabs cast in the industrial process on the ferrite distribution on slab surface, and how this relationship could favour the improvements of the surface slab quality. This report contains the joint contributions of the collaborative ECSC project among Centro Sviluppo Materiali (CSM), Krupp Thyssen Nirosta (KTN) and the Department of Ferrous Metallurgy of Rheinisch Westfälische Technische Hochschule Aachen (RWTH).