Recrystallization Behavior of Deformed Austenite in High Strength Microalloyed Pipeline Steel

 Using methods of single hit hot compression and stress relaxation after deformation on a Gleeble 1500D thermomechanical simulator, the curves of flow stress and stress relaxation, the microstructure and the recrystallization behavior of Nb V Ti high strength microalloyed low carbon pipeline steel were studied, and the influence of the thermomechanical treatment parameters on dynamic and static recrystallization of the steel was investigated. It was found that microalloying elements improved the deformation activation energy and produced a retardation of the recrystallization due to the solid solution and precipitation pinning. The deformation conditions such as deformation temperature, strain, and strain rate influenced the recrystallization kinetics and the microstructure respectively. Equations obtained can be used to valuate and predict the dynamic and static recrystallizations.     

Recrystailization Behavior of Deformed Austenite in High Strength Microalloyed Pipeline Steel

Using methods of single-hit hot compression and stress relaxation after deformation on a Gleeble 1500D thermomechanical simulator,the curves of flow stress and stress relaxation,the microstructure and the recrystallization behavior of Nb-V-Ti high strength microalloyed low carbon pipeline steel were studied,and the influence of the thermomechanical treatment parameters on dynamic and static recrystallization of the steel was investigated.It was found that microalloying elements improved the deformation activation energy and produced a retardation of the recrystallization due to the solid solution and precipitation pinning.The deformation conditions such as deformation temperature,strain,and strain rate influenced the recrystallization kinetics and the microstructure respectively.Equations obtained can be used to valuate and predict the dynamic and static recrystallizations.     

X120管线钢形变奥氏体的静态再结晶行为

通过在Gleeble-3500热模拟试验机上进行的两道次热压缩变形试验,对含铌微合金管线钢的静态软化行为进行了研究。采用应力补偿法计算了不同变形温度下的静态再结晶百分数。变形温度和弛豫时间对X120钢的静态再结晶影响很大。根据试验数据和静态再结晶动力学方程,计算出X120管线钢静态再结晶激活能为401.56kJ.mol-1。绘制了试验钢的析出动力学(PTT)曲线。     

低碳钢Q235形变奥氏体的静态再结晶

在Thermecmastor-Z热模拟试验机上进行了低碳钢Q235的双道次压缩试验,确定了该钢静态再结晶的动力学方程.结果表明,在大变形量下,即使变形温度较低(850～800℃),应变速率较高时,静态再结晶的速度仍然很快.通过静态再结晶可以将奥氏体晶粒尺寸细化至10～20μm.     

低碳钢热变形奥氏体的再结晶行为

对热变形奥氏体的再结晶动力学和微观组织演变进行了模拟计算,对晶粒尺寸的模拟值和实测值作了比较,分析了化学成分对动态再结晶率的影响以及残余应变与变形温度的关系.结果表明:在温度较高、应变速率较低的条件下容易发生动态再结晶,随着变形温度的降低,发生动态再结晶的几率减小,而静态再结晶在前几道次进行得比较充分,随后进行得不充分,增加碳和锰的含量可以促进动态再结晶的发生,残余应变随变形温度的降低而增大,晶粒尺寸的模拟值和实测值吻合较好,表明所选用的模型有一定的参考价值.     

Dynamic and Static Recrystallization Behavior of Low Carbon High Niobium Microalloyed Steel

 The recrystallization behavior of a low carbon high Nb microalloyed steel was investigated using Continuous and interrupted hot compression tests. The results showed that the onset of dynamic recrystallization (DRX) could be detected from inflection in the plot of the strain hardening rate θ against stress σ regardless of whether the stress peak appears or not. According to Zener-Hollomon parameter the activity energy of DRX (Qdef) was obtained, and a new modified expression calculating Qdef was proposed in consideration of the chemical composition of experimental steel. Applying the 2% offset method the static softening fraction was determined. The graphic representation of the softening fraction vs. interrupt time gave the information of the non-static recrystallization temperature (about 1000℃)and the relationship of precipitation-time-temperature. Static recrystallization kinetics follow Avrami’s law in high deformation temperature, and different values of the exponent n were given to illustrate the different effects of Nb element on static recrystallization at different deformation temperature.     

加热温度对微合金高强钢奥氏体组织及其再结晶的影响

 通过实验室模拟实际生产中的加热过程及单道次压缩热模拟试验,结合组织观察分析方法,回火硬度法研究了一种Nb V Ti微合金高强管线钢加热温度与奥氏体组织,合金元素溶解及析出的关系,并对不同温度加热后奥氏体的动态再结晶行为及其组织进行了研究。试验结果表明,随加热温度的升高,奥氏体晶粒尺寸逐渐增大,在1 200 ℃以上易出现粗大晶粒,加热温度过高形成的粗大奥氏体晶粒延缓了再结晶行为,容易造成混晶现象。     

Dynamic Recrystallization Behavior of Microalloyed Forged Steel

The dynamic recrystallization behavior of microalloyed forged steel was investigated with a compression test in the temperature range of 1 223-1 473 K and a strain rate of 0. 01-5 s^-1. Activation energy was calculated to be 305.9 kJ/mol by regression analysis. Modeling equations were developed to represent the dynamic recrystallization volume fraction and grain size. Parameters of the modeling equations were determined as a function of the Zener-Hollomon parameter. The developed modeling equation will be combined with finite element modeling to predict microstructural change during the hot forging processing.     

Ti对低碳Mn-V钢奥氏体动态再结晶的影响

采用Gleeble热模拟试验机和透射电镜、扫描电镜及定量金相等分析技术,就钛对低碳Mn-V钢奥氏体晶粒长大行为、奥氏体动态再结晶行为等进行了研究.结果表明,含钛钢中形成稳定的碳氮化钛,对阻止再加热奥氏体晶粒长大有利.含钛钢变形抗力比不含钛钢要高,其动态再结晶开始的临界变形量比不加钛钢的小,易于发生再结晶,且含钛钢的再结晶晶粒尺寸相对较细,再结晶晶粒长大速度也更慢.     

Recrystallization Modelling of Hot Deformed Si-Mn TRIP Steel

By means of hot compression single and double hit experiments, the kinetics of dynamic and static recrystallization in hot-rolled Si-Mn TRIP steel was studied, and the emphasis was put on the influence of high silicon content. The results show that the calculated parameters are consistent with the experimental ones, and addition of silicon retards both dynamic and static recrystallization as well as increases the flow stress of austenite, and the non-recrystallization zone can be enlarged by increasing the silicon contents.     

Nb-Ti微合金钢的静态再结晶行为

 通过双道次压缩试验研究了Nb-Ti微合金钢的静态再结晶行为,确定了应变诱导沉淀析出前Nb-Ti微合金钢的静态再结晶激活能,并建立了静态再结晶动力学模型。采用面积法及积分-能量法计算的软化率,很好地反映了微合金钢的静态再结晶行为及应变诱导沉淀析出行为。应变诱导沉淀析出的鼻尖温度在900～925℃之间,静态再结晶的临界温度（SRCT）高于950℃。     

高强度钢的动态再结晶行为研究

采用Gleeble1500热模拟实验机研究了高强度钢在不同条件下热变形时的动态再结晶行为以及晶粒尺寸的变化规律,确定了该钢的动态再结晶激活能为294096J/mol,建立了动态再结晶行为的数学模型,分析了变形工艺参数对再结晶行为以及晶粒尺寸的影响。变形温度和变形速率是影响动态再结晶的主要因素,一般在高的变形温度和小的变形速率下,动态再结晶才能发生。     

冷轧高强度汽车钢板的再结晶及组织

 为了改善冷轧后铌微合金高强度钢的力学性能需对其进行退火处理。笔者通过此钢在不同再结晶条件下的退火处理试验,研究其在退火过程中的微观组织,并建立了组织演变过程的数学模型,用于预测该钢的退火组织,以控制实际生产中钢的再结晶退火工艺。     

Dynamic and Static Recrystallization Behaviour of Coarse-grained Austenite in a Nb-V-Ti Microalloyed Steel简

The dynamic recrystallization （DRX） and static recrystallization （SRX） behaviour of coarse-grained aus- tenite in a Nb-V-Ti microalloyed steel were studied by using a Gleeble thermomechanical simulator. Continuous and interrupted compression tests of coarse-grained austenite were performed in the temperature range of 1000-1 150 ℃ at a strain rate of 0. 1- 5 s 1. The peak and critical strains for the onset of DRX were identified with strain hardening rate analysis, and the ratio of critical strain to peak strain was found to be consistent with the one reported for fine- grained austenite. An equation of the time for 50% softening was proposed by considering the activation energy of steel without microalloying elements and the solute drag effect of microalloying elements. Strain-induced precipitation may not take place at the deformation temperature above 1000 ℃, which indicates that SRX of coarse-grained aus- tenite is mainly retarded by coarse grain size and Nb in solution during rough rolling.     

Determination of Optimal Recrystallization Annealing Temperature of Nb-Ti Microalloyed High Strength IF Steel

The Nb-Ti microalloyed high strength IF steel sheet was used to study the effect of annealing temperature on the microstructures,mechanical properties and textures.The experimental results show that experimental steel is incomplete recrystallization at 750℃ annealing,but complete recrystallization from 780℃ to 870℃ under experimental conditions.When the annealing temperature was increased,the yield strength and tensile strength would gradually reduce,the plastic strain ratio and yield point elongation would gradually increase.The yield strength,tensile strength,elongation,the plastic strain ratio and the strain hardening exponent were approximate 300MPa,410MPa,36.5%,1.7 and 0.22 respectively under annealing temperature 810℃ to 840℃.When the annealing temperature was increased,the α-textures and γ-textures were gradually weakened,and the α-textures have a trend to {111} texture.Therefore,the suggestion of the optimal recrystallization annealing temperature is about 810℃ to 840℃ in industrial production.     

Dynamic Recrystallization Behavior in Mn-Cr Gear Steel

In the deformation process of austenite,the dy-namic recovery and the recrystallization occur,andthe austenite grain changes.First of all,the grainselongate and dislocation densityincreases.The poly-gonization in elongated austenite grain takes placeand the subcrystal forms due to slipping and cli mb-ing of dislocations,i·e·,dynamic recovery(DRV).When the strain reaches a critical value,new grainswill nucleate by bulging of the grain boundaries[1,2].This is so-called dynamic recrystallizat…     

35K钢的动态再结晶模型研究

利用热模拟试验机通过单道次压缩变形试验研究了35K冷墩钢测定奥氏体区形变规律，确定了不同应变率和温度条件下的应力-应变曲线，研究了变形温度、变形速率对试验用钢再结晶行为的影响，建立了35K钢的动态再结晶模型。     

Evaluation of the Austenite Recrystallization by Multideformation and Double Deformation Tests

A high amount of deformation below the non‐recrystallization temperature (T_nr) is a common industrial practice to achieve a good combination of toughness and strength in microalloyed steels. To combine the industrially relevant optimum combination of high productivity and product quality, an accurate knowledge of T_nr and the recrystallization kinetics is required. Although a lot of literature data is available on the recrystallization behaviour of microalloyed steels, correlations are often difficult to be made due to the effect of different experimental set‐ups and test schedules used to obtain this data. Although it would significantly improve the knowledge about these steels, so far, no systematic comparison has been presented in literature to correlate the different techniques one to another. In this study, different hot rolling simulation techniques and testing schedules were compared, within the experimental constraints of the used equipment, to determine the T_nr temperature of two microalloyed steels. Good agreement was found between the results from different test equipment. Furthermore, the results from the multideformation tests under continuous cooling conditions could be correlated with the results from isothermal double deformation tests.     

FTSR轧制含铌钢的再结晶行为

 结合某钢厂FTSR薄板坯连铸连轧生产线轧制X46含Nb钢的工艺参数,在Gleeble 2000热/力模拟实验机上模拟了粗轧阶段该钢的组织演变,并研究了Nb含量对未再结晶温度的影响。研究结果表明：①粗轧阶段,粗大的铸态组织发生了充分的动态再结晶,有效地细化了奥氏体晶粒。②随着钢中Nb含量的增加,未再结晶温度逐渐升高,该生产线可有效进行控制轧制,避免轧制含Nb钢时混晶现象的发生。