Kinetics of static strain aging after temper rolling of low carbon steel

Abstract

In this study, static strain aging behaviour of cold rolled steel strips was considered with emphasis on the distribution of residual hydrostatic stress developed during temper rolling. In order to assess residual stress distribution produced by the temper rolling, a three-dimensional model was first employed. Then, samples were rolled at a reduction of 4% under single and double pass rolling programmes and the kinetics of static strain aging phenomenon as well as the required activation energies were then evaluated using hardness and tensile tests on the deformed samples. Considering the predicted residual hydrostatic stress distribution, it was found that tensile hydrostatic stresses promote the kinetics of the static strain aging process and alter the activation energy required for the phenomenon. In addition, it was revealed that different positions of the rolled steel show different aging behaviour owing to non-uniform distribution of residual stresses after temper rolling.     

异步冷轧工艺对IF钢织构的影响

对异步轧制IF钢的冷轧织构进γ行了测试分析,并与同步轧制的IF钢板的冷轧织构组分进行了比较.实验结果表明：随着冷轧压下量的增加,快、慢辊侧的γ织构组分均明显增强;异步轧制的速比显著影响γ织构组分的强弱,速比大时快、慢辊侧的组分的差异更加明显.     

Recrystallization and texture formation in cold-rolled dysprosium sheet

The primary recrystallization of dysprosium can be characterized by an apparent activation energy of 13.4 ±1.4 kcal/mole when specimens are isothermally annealed at temperatures between 400 and 600°C. At temperatures between 300 and 400°C recrystallization is strongly retarded, possibly by precipitation, and the activation energy associated with the process is increased to 31.4 ±4 kcal/mole. The deformation texture of dysprosium sheet following a cold reduction of 50 pct can be described as (0001)<1010> with a rotational spread of 15 to 20 deg about the rolling direction. Annealing the rolled sheet produces a recrystallization texture which is composed of two components related to the deformation texture by 27 deg rotations about a common 1010 direction. Within the scatter of the data this texture can be represented by the ideal orientation l5l6 (1010).     

冷轧工艺对双取向硅钢磁性和成品织构的影响

研究“交叉轧制法”试制立方织构双取向硅钢时的冷轧压下工艺,发现冷轧纵横向压下率比对成品磁性能的影响很大。当纵横向冷轧压下率比控制在1．380-1．450时,最利于最终成品中强而锋锐的立方织构{100}〈001〉形成。     

Effect of hot rolling on the dendritic texture of directionally solidified steel ingots

Directionally solidified ingots of three commercial steels—AISI 1010, Fe-3.4 pct Si, and Type 430 stainless steel—were hot-rolled at 1850°F in order to study the effect of hot deformation on the as-cast dendritic texture. The strong dendritic (100) orientation of both the Fe?Si and Type 430 alloys was completely destroyed by the heavy reductions typical of the commercial hot rolling of ingots. The primary effect of hot rolling is to eliminate the texture present in the ingot, and to create certain new textures. These new textures are in every case weak. For example, the AISI 1010 steel, which had very little of the dendritic <100> orientation in the ingot stage, has a combination of two weak textures after hot rolling: (100) [011] and (110) [110]. Likewise, with the other two materials, which had a strong dendritic <100> orientation in the ingot stage, hot rolling resulted in weak textures: (110) [001] with a rotation of this orientation of ±45 deg about the [001] rolling direction, followed by (110) [001] rotated ±35 deg about the [110] in the transverse direction.     

Formation of surface microtopography in the temper rolling of auto-industry steel sheet

A model is proposed for the formation of the surface microtopography in the temper rolling of cold-rolled steel sheet as function of the microtopography of the blank and the working rollers. In the model, temper rolling is treated as a linear system with several inputs and a single output. The results of simulation are compared with experimental data, and the model proves adequate.     

平整机组的断带与控制

通过冷轧平整过程中张力的变化说明了掉张与断带的关系。重点针对断带的主要原因带钢厚度错误进行分析，给出了它的数学模型，同时简要分析了断带的其它常见原因，并介绍了相应的控制措施。     

Effect of alloying elements on the formation of rolling texture in Mg-Nd-Zr and Mg-Li alloys

The effect of alloying on the texture of Mg-Nd-Zr and Mg-Li alloy sheets is studied using pole and inverse pole figures. The basal texture intensity in rolling of Mg-Nd-Zr alloys is shown to be substantially decreased due to the precipitation of dispersed intermetallic Mg₁₂Nd phase particles. As a result, the workability characteristics during deep drawing can be increased. Lithium alloying causes the formation of a prismatic rolling texture, which is unusual for magnesium alloys, as a result of the phase transformation of the lithium-based bcc phase into the magnesium-based hexagonal close-packed phase that obeys the Burgers orientation relationships.     

Recovery of heavily cold-rolled aluminum: Effect of local texture

Commercial-purity aluminum, AA1200, was cold-rolled to a true thickness strain of 2 and annealed at low temperatures. The microstructural evolution and the changes of the rolling, cube, Goss, and other texture components were characterized thoroughly by transmission electron microscopy. Both the deformation microstructure and the annealing behavior were found to be texture dependent. In the deformed structure, texture components other than the rolling, cube, and Goss showed a broader orientation spread as well as a larger content of stored energy. Structural coarsening took place during the annealing and depended on the local texture environment. Other texture components showed more pronounced coarsening than the rolling components. The orientational heterogeneity in the deformed structure influenced the heterogeneous structural coarsening during the recovery.     

Ferrite recrystallization and austenite formation in cold-rolled intercritically annealed steel

The recrystallization of ferrite and austenite formation during intercritical annealing were studied in a 0.08C-1.45Mn-0.21Si steel by light and transmission electron microscopy. Normalized specimens were cold rolled 25 and 50 pct and annealed between 650 °C and 760 °C. Recrystallization of the 50 pct deformed ferrite was complete within 30 seconds at 760 °C. Austenite formation initiated concurrently with the ferrite recrystallization and continued beyond complete recrystallization of the ferrite matrix. The recrystallization of the deformed ferrite and the spheroidization of the cementite in the deformed pearlite strongly influence the formation and distribution of austenite produced by intercritical annealing. Austenite forms first at the grain boundaries of unrecrystallized and elongated ferrite grains and the spheroidized cementite colonies associated with ferrite grain boundaries. Spheroidized cementite particles dispersed within recrystallized ferrite grains by deformation and annealing phenomena were the sites for later austenite formation.     

Effect of prior austenitic grain boundary composition on temper brittleness in a Ni-Cr-Sb steel

Grain boundary segregation during temper embrittlement of an Sb-containing, Ni-Cr steel has been examined both by Auger electron analysis and by chemical analysis by neutron activation of residues of surface layers dissolved by etching intercrystalline fracture surfaces. No grain boundary segregation of either alloying additions or impurities was detected during austenitization or tempering. Redistribution of Cr, Ni, and Sb between carbide and ferrite was observed during tempering, but no grain boundary segregation was noted. Both Ni and Sb were observed to segregate to the boundaries during embrittling. The segregated Sb was shown to be uniformly distributed along the prior austenitic grain boundaries and to control the ductile brittle transition temperature of the alloy studied. Ni segregating to the prior austenitic boundaries during embrittling was shown to be localized in a phase other than the ferritic portions of the boundaries. A possible location was shown to be the ferritecarbide interfaces in the grain boundaries. Weakening of these normally tenacious carbide and ferrite interfaces could account for the change in mode of brittle failure from transcrystalline cleavage to intercrystalline along the prior austenitic grain boundaries that is observed in temper brittle steels.     

低碳贝氏体钢中织构的变化

用50 kg真空感应炉冶炼的钢锭,经1 150 ℃开轧,两阶段控制轧制,826 ℃终轧成12 mm钢板,驰豫为29 s,737 ℃进水快冷(冷速为30～35 ℃/s)后,低碳贝氏体钢组织主要是板条贝氏体,晶界以小角度晶界为主,占62 %～65 %.钢板厚度1/4处和心部织构差异大,1/4处(横向)晶粒取向主要趋向{110}、{221}面,而心部(横向)晶粒取向主要趋向{111}面,1/4处和心部的晶界夹角、晶粒尺寸基本上是相同的.     

Effect of aluminum on secondary recrystallization texture and magnetic properties of grain-oriented silicon steel

The slab low-temperature reheating grain-oriented silicon steel was prepared in the laboratory, and the high-temperature annealing interruption tests were carri...     

Influence of force variations in skin pass rolling on texture and surface reactivity of hot dip galvanised low carbon steel sheets

Abstract

In this research work, the skin pass rolling force was changed in the range of 50 to 200 kN in steps of 30 kN. The crystallographic orientation of the coatings was determined using X-ray diffraction, and texture parameters were calculated. Corrosion behaviour was assessed employing the Tafel polarisation test. It was concluded that by increasing the force the texture coefficient of the basal planes component in the coating would be decreased and conversely, other components such as prismatic planes components would be strengthened. Increasing skin pass force would also cause an increase in surface roughness and microcracks in the coating. Such increasing in prismatic component texture coefficient, roughness and microcracks of the coating would result in the decreasing of coating corrosion resistance.     

Kinetics of hydrogen reduction and the influence of gas composition on hot-rolled steel scale after temper rolling

For replacing the presently employed pickling method with a more environmentally friendly descaling method,hydrogen reduction of oxide scale formed during hot rolling was studied at 800 ℃ under a varied atmosphere.The hydrogen level and water vapor content in the reducing atmosphere were found to influence the reduction rate wherein increasing hydrogen level as well as decreasing water vapor content resulted in faster oxide reduction. The reduction reaction substantially obeyed a parabolic rate law. Oxide scale of a usual thickness( approximately 7micrometer) could be reduced almost completely in an atmosphere of 20 vol. % hydrogen with a water vapor content corresponding to a- 40 ℃ dew point at 800 ℃. When lowering the hydrogen level to 10% and increasing the water vapor content to a 10 ℃ dew point,quite a large extent of the oxide scale was retained,which might be attributable to the formation of an outermost dense layer of pure iron at the early stage of reduction.     

Grain growth in a low-loss cold-rolled motor-lamination steel

This article attempts to determine the mechanisms governing the grain growth process that occurs during lamination annealing of a cold-rolled, motor-lamination (CRML) steel. A new simulation approach linking a Monte Carlo model with electron backscatter diffraction (EBSD) scans used as input has been employed to incorporate the effects of crystallographic texture on the simulated grain growth process. The results from the texture analysis and the computer simulation of the grain growth process indicate that both stored energy driven grain growth and anisotropic grain boundary growth influence the overall grain growth occurring during lamination annealing.