利用Gleeble 3500热力模拟试验机对22MnB5板材进行高温拉伸试验,研究了该材料在变形温度为700、800和900℃以及应变速率为0.01、0.1、1和10 s–1下的高温变形行为.在同一温度下,22MnB5的断裂应变随应变速率增加而呈现增加趋势,温度升高加剧这种趋势.建立了耦合损伤基于位错密度的统一黏塑性本构模型,该模型考虑了高温变形中损伤的演化规律,能够描述了应力–应变曲线后期的陡降段.利用遗传算法确定并优化该本构模型中的材料常数,所得材料常数确定的本构模型能够较好地预测22MnB5高温拉伸变形下的流变应力,并能较好地描述材料损伤演化规律.

The hot deformation behavior of 22MnB5 steel was investigated through tension testing on a Gleeble-3500 thermal-mechanical simulator, over a range of temperature from 700 ℃ to 900 ℃ and a range of strain rate from 0.01 s-1 to 10 s-1. It is found that failure strain of the steel increases with the increase of strain rate, and this trend is intensified as the temperature rises. A unified viscoplastic constitutive model coupled with damage, based on dislocation density and incorporated effects of strain, temperature and strain rate, was established to mathematically describe the steep-fall stages of the stress-strain curves. Material constants in the model were determined and optimized by a genetic algorithm. The model can accurately predict the flow stress of the steel in hot stretch and can describe damage evolution in the material.

为了探索连续退火工艺对TRB板组织与性能的影响,在实验室采用四辊可逆式冷轧机进行单厚度过渡区TRB板轧制,对轧制的DP590双相钢和22MnB5热成形钢TRB薄板进行模拟连续退火试验,利用光学显微镜和扫描电镜,以及拉伸和硬度试验方法研究钢板退火后各厚度区的组织与力学性能差别.研究表明：TRB板变厚度区的最大厚度偏差为0.03 mm,长度误差<1.0 mm. TRB板在连续退火的冷却段和过时效段,其薄区温度较过渡区和厚区的温度偏低57~20℃,导致DP590钢板薄区的抗拉强度和伸长率较高,屈服强度与厚区的相当,而22MnB5钢TRB板的屈服与抗拉强度偏高.在TRB板的变厚度区内维氏硬度波动较小.根据厚区的厚度来制定冷轧DP590双相钢TRB薄板的连续退火工艺,将更有利于保证钢板的组织与力学性能,对22MnB5热成形钢TRB薄板建议采用罩式退火.

To explore the effect of continuous annealing on microstructure and properties of TRB sheet, a reversible four high cold rolling mill was used to roll a single variable gauge zone TRB sheet in laboratory. The differences of microstructure and mechanical properties of various thickness zones were investigated by continuous annealing experiments of cold rolled DP590 dual phase steel and 22 MnB5 hot forming steel TRB sheet, which were analyzed by optical microscope and scanning electrical scope and tested by tension and hardness experiments. Results show that the maximum thickness deviation in variable gauge zone of TRB sheet is less than 0. 03 mm, length deviation is less than 1 mm. The temperature of the thin zone of TBR sheet is below 57-20℃ than the variable thickness zone and thick zone during cooling and over-aging phase of continuous annealing. It leads to the higher tensile strength and elongation in thin zone than others, and the almost same yield strength as that of i

基于RCP（Rapid Cooling Process）快速冷却工艺＋不同模具淬火热处理工艺，对22MnB5钢板材的淬火力学性能及微观组织进行了研究，探讨了冷速、强度硬度之间的关系，建立了三者之间的硬度指数模型。结果表明，采用加入淬火前快速冷却及改变不同模具淬火温度可以有效实现梯度冷却速率控制，冷却速率实现了从6～40℃／s的变化，微观组织从铁素体与珠光体、上、下贝氏体逐渐向“残留奥氏体＋马氏体”组织过渡，对应的强度区间范围为700～1600 MPa。建立的冷速、强度硬度模型与试验数据拟合良好。

The quenching mechanical properties and microstructure of 22MnB5 steel were investigated based on the RCP ( rapid cooling process) and with different mold quenching temperature.The relationships between the cooling rates, strength and hardness were discussed and the exponential model among them was established.The results reveal that the gradient cooling rates can be controlled effectively by adding rapid cooling before quenching or changing the mold quenching temperature.While the transition of microstructure is from ferrite and pearlite, upper bainite, lower bainite, to retained austenite and martensite from the cooling rate of 6℃/s to 40℃/s and the related tensile strength is from 700 MPa to 1600 MPa.The cooling rates, strength and hardness exponential model fits the experiment data quite well.

通过高温热胀形特征分析，研究热冲压22MnB5合金在不同温度下的成形性，并利用Dynaform软件仿真验证。比较成形温度在800℃和700℃时样件的热胀形特征，结果表明，在800℃时成形，样件由于平面应变方向主应变过大，拉压应变区次应力为负值，造成拉伸破裂；在700℃下冲压成形的试件，各部分应变都处于安全区域，双向拉伸区域和拉伸-压缩复合区域的变形均匀，较前者成形性良好。另外，提出关于热成形先进高强度钢(Advanced high strength steel, AHSS)样件，其最佳成形温度不是现有文献报道的800～850℃的范围内，该结论为深入探索最佳成形温度、提高成形性提供了方向；建立成形前的快冷法(冷速不低于27℃/s)，降温到目标温度700℃左右冲压成形。试验证明：通过该方法，样件的成形性明显改善，微观结构更为致密。

Based on the high-temperature thermal expansion analysis, the formability at different temperature of hot-forming 22MnB5 is studied and also verified by Dynaform simulation. Comparing the thermal expansion characteristics at forming temperature 800℃ and 700℃, the results suggest that:Forming at 800℃, the sample results in a tensile rupture since the principal strain in plane strain direction is too large, while the secondary strain in tensile-compressive zone is negative; forming at 700℃, the formability is significantly improved since the strain of all parts remain in a safety area and sample has a uniform deformation in biaxial stretching region and tensile-compressive zone. In addition, this work puts forward that the optimized forming temperature of hot-forming advanced high strength steel(AHSS) sample is not in the range of 800℃ to 850℃ reported in present literatures. This conclusion provides directions for deep exploration of optimized forming temperature and imp