CSP热轧过程中氧化铁皮结构和厚度演变规律研究

介绍了CSP热轧生产过程中表面氧化铁皮的结构和厚度演变规律,建立了氧化动力学模型,对汽车大梁钢（510L）在CSP过程中氧化铁皮的厚度变化进行了数值模拟,模拟结果与现场实际吻合较好。降低开轧温度、合理控制终轧温度、卷取温度是控制氧化铁皮厚度和结构的有效手段。在此基础上进行现场工业试轧,试轧结果氧化铁皮以Fe3O4为主,其含量超过75%,氧化铁皮厚度11-14μm。冷弯实验表明氧化铁皮与钢板粘附性好,弯曲面铁皮呈细粉末状。     

辊底式高温固溶炉在线数学模型的开发及应用

为精确跟踪某公司新建辊底式高温固溶炉内钢板温度,详细研究了明火炉内炉气温度、钢板内部导热和炉内传热机制,建立了考虑炉段间耦合的炉气温度数学模型和钢板温度跟踪模型,采用FDM法对数学模型离散化,结合TDMA数值方法进行求解.在线应用结果表明所建立的数学模型简单、可靠,为钢板加热质量的控制提供了科学依据,提高了出炉温度命中...     

轧制工艺对耐大气腐蚀钢综合性能的影响

分析了轧制工艺参数对耐大气腐蚀钢综合性能的影响。结果表明,终轧温度、卷取温度和轧后冷速均对钢板力学性能有影响,卷取温度对钢板强度的影响高于终轧温度,钢板强度随卷取前冷却速度的提高而增加,冷速超过12℃/s后不再进一步提高。耐大气腐蚀性主要与成分有关。试验成品钢板强度高,屈强比低,具有良好的低温冲击韧性和冷弯加工性能及优良的耐大气腐蚀性。     

热带钢超快速冷却条件下的对流换热系数研究

建立了热带钢超快速冷却过程的导热微分方程,采用有限差分方法计算了薄带钢实现超快速冷却(对于4 mm以下的薄带钢,冷却速率可达300℃/s)所需的带钢表面对流换热系数.同时,在实验室条件下采用厚度为20 mm的钢板进行了超快速冷却试验,得到了超快速冷却条件下的带钢表面对流换热系数与冷却水流量的关系.结果表明,在一定水流量范围内随着冷却水量的增加,带钢表面换热系数逐渐增加;采用所确定的换热系数对不同厚度钢板得到的温降曲线与实测值吻合较好,具有较高的精度.     

热轧精轧轧辊摩擦和磨损研究

针对某厂热连轧机采用定值摩擦系数计算轧制力与实际值相差2 000～3 000kN的情况,采用BP神经元网络与NeuroShell2软件对摩擦系数进行预测与检验,建立了符合现场实际的摩擦系数模型,在实际应用中提高了轧制力的预报精度.并根据POMINI公司磨床的辊型曲线,分析了精轧轧辊磨损的基本规律,提出了减小轧辊磨损的具体措施.     

Austempering of hot rolled transformation-induced plasticity steels

Thermomechanical controlled processing (TMCP) was conducted by using a laboratory hot rolling mill. Austempering in the salt bath after hot rolling was investigated. The effect of isothermal holding time on mechanical properties was studied through examining of the microstructure and mechanical properties of the specimens. The mechanism of transformation-induced plasticity (TRIP) was discussed. The results show that the microstructure of these steels consists of polygonal ferrite, granular bainite, and a significant amount of stable retained austenite. Strain-induced transformation to martensite of retained austenite and TRIP occur in the hot rolled Si-Mn TRIP steels. Excellent mechanical properties were obtained for various durations at 400°C. Prolonged holding led to cementite precipitation, which destabilized the austenite. The mechanical properties were optimal when the specimen was held for 25 min, and the tensile strength, total elongation, and strength ductility balance reached the maximum values of 776 MPa, 33%, and 25608 MPa?%, respectively.     

Partial Inverse Grain Size Dependence of Strength in High Mn Steels Microalloyed With Nb

 Two steels without and with Nb addition were chosen to investigate the effects of Nb on the microstructures and the mechanical properties of Fe-Mn-Al-Si steels. The results revealed that Nb refined the grains markedly and both TRIP and TWIP effects occurred during deformation process. The Nb containing steel possesses higher yield strength and much lower tensile strength, the latter being explained by the suppression of TRIP effect due to the increase of stacking fault energy. This indicates grain refining is secondary for strengthening of steels when TRIP or TWIP effect exists during the deformation of low carbon and high Mn steels.     

High rate directional solidification and its application in single crystal superalloys

In the present paper there are two parts contributing to the discussion of high rate directional solidification and its application. The first part aims to characterize the high rate directional solidification of various kinds of alloys. It was found that the relevant cooling rate of the high rate directional solidification is defined to be within 1–10³ K/s (solidification rate is 10⁻⁴–10⁻¹ m/s as G_L=100 K/cm) and that it is located in the region between the near-equilibrium slow growth rate and the rapid solidification rate beyond the equilibrium condition, whilst at the same time there occurs a series of turning effects of interface stability and morphologies. With the increase in the growth velocity the interface with the plane front evolves to cells and dendrites at the stage of near-equilibrium and with a further increase in growth rate they transformed reversibly from dendrites to cell structure and then to the absolute stability of a planar interface. The change of solute segregation reveals the same from a low segregation, then increased and finally reduced again. An explanation based on effective constitutional supercooling about the evolution of interface morphologies with respect to the changes of growth rate is proposed.The second part is devoted to introducing experimental results for single crystal superalloys using the rate directional solidification principle. It is shown that the single crystal superalloys CMSX-2 and NASAIR 100 exhibit significant improvement in microstructure segregation and mechanical properties at high temperature both in the as-cast and after-heat-treatment conditions with the high rate directional solidification technique.     

Corrosion Behavior of Low-Alloy Pipeline Steel with 1% Cr Under CO2 Condition

Carbon dioxide corrosion behavior of low-alloy pipeline steel with 1% Cr exposed to CO₂-saturated solution was investigated by immersion experiment. SEM, EDX, TEM, EPMA and XRD were utilized to investigate the microstructure, corrosion morphologies, corrosion phases and elements distribution of corrosion scale. The results demonstrate that the microstructure of tested steel consists of ferrite and carbides. During the corrosion process, ferrite dissolves preferentially, leaving carbide particles behind. The residual carbide particles may promote the nucleation of FeCO₃ crystal. The phase comprising of the inner layer is Cr compound, and the one of the outer layer is FeCO₃. The formation process of corrosion scale can be illustrated as follows: Firstly, a thin scale consisting of thin inner layer and outer layer is formed, which represents poor corrosion resistance; then, the inner layer changes little, once it has been formed, and the outer layer becomes thick and compact, which demonstrates that a fine corrosion resistance is obtained. The chemical elements of chromium and molybdenum accumulate in the inner layer of corrosion scale. The corrosion behavior of low-alloy steel based on microstructure and morphology characterization is also discussed.