Effect of annealing cooling rate on microstructure and mechanical property of 100Cr6 steel ring manufactured by cold ring rolling process

Pre-heat treatment is a vital step before cold ring rolling and it has significant effect on the microstructure and mechanical properties of rolled rings.The 100Cr6 steel rings were subjected to pre-heat treatment and subsequent cold rolling process.Scanning electron microscopy and tensile tests were applied to investigate microstructure characteristic and mechanical property variations of 100Cr6 steel rings undergoing different pre-heat treatings.The results indicate that the average diameter of carbide particles,the tensile strength and hardness increase,while the elongation decreases with the decrease of cooling rate.The cooling rate has minor effect on the yield strength of sample.After cold ring rolling,the ferrite matrix shows a clear direction along the rolling direction.The distribution of cementite is more homogeneous and the cementite particles are finer.Meanwhile,the hardness of the rolled ring is higher than that before rolling.

Effect of Controlled Cooling on Microstructure and Mechanical Properties of H-Beam

Based on ANSYS, an analytical model was established for H beam during controlled cooling. The tempera-ture fields during controlled cooling and air cooling were analyzed and the microstructure and mechanical properties for different parts of H-beam were discussed in detail. After the H-beam was controlled cooled for 4.5 s, its mean surface temperature decreased from 850 to 460 ℃, and the lowest and the highest temperatures were measured at edge of flange and at R corner, respectively. Whereas, for the H-beam air cooled for 30 s, the mean temperature at R corner and web was 700 and 540 ℃, respectively. The microstructures for different parts of H-beam consisted of ferrite and pearlite, and the grain size at R corner was coarser than those at flange and web. The difference of yield and tensile strengths of web, flange and R corner was within 30 MPa, and the elongation was similar. The changes of microstructure were in good agreement with that of temperature field. In addition, the results show that the uni formity of microstructure and mechanical properties can be improved by increasing water flow rate at R corner.

Influence of Controlled Rolling and Cooling Process on the Mechanical Properties of Low Carbon Cold Forging Steel

In the present paper,controlled rolling and cooling processing was conducted by using a laboratory hot rolling mill.The influence of different processing parameters on the mechanical properties of low carbon cold forging steel was investigated.The results show that the faster cooling after the deformation (especially in low temperature rolling conditions) leads to the refinement of the ferrite grain.The specimen exhibits very good mechanical properties owing to the finer ferrite grains.The pearlite morphologies can also affect the mechanical properties of low carbon cold forging steel.The mechanical properties increase with decreasing final cooling temperature within the range from 650℃ to 570 ℃ due to the finer interlamellar spacing of pearlite colony.The mechanical properties of the specimens with fast cooling after the conventional rolling are not only better than those of the specimens with slow cooling after low temperature rolling,but also almost similar to those of the specimens with fast cooling after low temperature rolling.It is suggested that fast cooling after high temperature rolling (the conventional rolling) process would be of important industrial value.

Effect of Cooling Patterns on Microstructure and Mechanical Properties of Hot-Rolled Nb Microalloyed Multiphase Steel Plates

The effect of the run-out table cooling patterns on the microstructure and mechanical properties of Nb microalloyed steel plates was investigated by hot rolling experiment. The results showed that the mixed microstrueture containing ferrite, bainite and significant amounts of retained austenite can be obtained through three kinds of cooling patterns on the run-out table under the same hot rolling condition. Three kinds of cooling patterns possess different austenite transformation kinetics, which leads to variations in microconstituent characteristics. The yield strength increases, the tensile strength decreases and the total elongation tends to increase as the cooling patterns Ⅰ , Ⅱ and Ⅲ were applied respectively. The yield strength, the total elongation and the product of tensile strength and ductility reach the maximum values （547 MPa, 37. 2% and 28 384 MPa% respectively） for the steel plate processed by cooling pattern Ⅲ.

Effect of Cooling Rates in Coiling Process on Microstructures and Mechanical Properties in Al-Bearing Hot-Rolled TRIP Steel

In this study, the effect of cooling rates on microstructures and mechanical properties in a Al-bearing hot-rolled transformation- induced plasticity steel was investigated. The experiments were carried out using hot simulation machine and hot rolling mill, where the samples were cooled at different cooling rates. The results showed that with the increase in cooling rates, film-like retained austenite gradually disappeared and only blocky retained austenite was retained at higher cooling rates. The volume fraction of retained austenite was 9-11% at cooling rates of 0.05-1 ℃/s and 4-6% at cooling rates of 5-10 ℃/s. In addition, martensite/austenite island was observed because of the heterogeneous carbon distribution. The samples cooled at 0.05℃/s and 0.5 ℃/s exhibited excellent mechanical properties, with tensile strengths of 712 MPa and 726 MPa, total elongations of 42% and 36% and strength and ductility balances of 29.91 GPa% and 26.15 GPa%, respectively. During plastic deformation, the instantaneous work hardening exponent of the sample cooled at 0.05 ℃/s increased continuously until it reached the maximum value, while the instantaneous work hardening exponent of the sample cooled at 0.5℃/s remained stable.

Effect of Rolling Process on Microstructure and Properties of 95CrMo Drill Steel

In order to improve the strength and toughness of 95CrMo steel and explore a short flow process, a direct rolling process was employed, and the effect of finishing rolling process on microstructure and mechanical properties was investigated. The results show that, with the decrease of finishing rolling temperature, inter-lamellar spacing in- creases, the strength as well as hardness has a general increase, and secondary cementite is distributed uniformly but represents a remarkable decrease in size. Based on Hall-Petch type equation, an effective relationship of yield strength and pearlite structure parameters was established. The correlation coefficients between the measured and calculated strength were more than 0.95, which indicated a high reliability of the relationship. By analyzing the individual strength contributions of pearlite structures, yield strength was found to have a more great dependence on pearlite inter-lamellar spacing than colony size.

Effects of TMCP Parameters on the Microstructure and Mechanical Properties of Nb-Bearing Spring Steel

The effects of TMCP parameters,such as finish rolling temperature and cooling rate on the microstructure and mechanical properties of Nb-bearing spring steel were investigated by thermal simulation,quantitative metallography and tensile test.And the precipitation in Nb-bearing spring steel was analysis by electron microscopy.Experimental results indicate that the higher finish rolling temperature or the more rapid cooling rate in a given range,the less the proeutectoid ferrite content and the thinner the interlamellar spacing is.Reasonably higher finish rolling temperature followed by properly higher cooling rate is suggested to improve the mechanical properties of Nb-bearing spring steel.Micro-addition of niobium decreases the proeutectoid ferrite content and the interlamellar spacing and leads to forming degenerated pearlite.The precipitation of size range ～20-50 nm in Nb-bearing spring steel occurred at the lamellar ferrite of pearlite and the proeutectoid ferrite.

Study on Microstructure and Mechanical Properties of Hot Rolled Low Silicon Containing Phosphorus TRIP Steel

The effects of final air cooling temperature on the microstructure and mechanical properties of hot rolled 0.2C-1.9Mn-0.5Si-0.08P TRIP steel were studied by utilizing OM, SEM, TEM and tensile tests. Experimental results showed that in the multiphase microstructure of the investigated steel when the finish rolling temperature was about 820 ℃ and the final air cooling temperature was in the range of 630-700 ℃, the grain size of most of ferrite was finer (about 4 μm) and which had higher dislocation density, the bainite packets had chaotic orientations and lath boundaries of bainite were not quite straight, the retained austenite distributed in the ferrite grain boundaries or triradius was fine and dispersive, and their grain size was about 0.4-1.9 μm. With increasing the amount of ferrite, the volume fraction of retained austenite had a slight decrease. When the final air cooling temperature was 630 ℃, the steel had excellent mechanical properties, which was characterized by combination of continuous yielding, high strength (about 796 MPa) and high elongation (22.7%) as well as low yield/strength ratio (0.58); when the final air cooling temperature increased to 700 ℃, the matrix structure was bainite packets and the comprehensive properties were deteriorated.

Correlation of Microstructure Feature with Impact Fracture Behavior in a TMCP Processed High Strength Low Alloy Construction Steel

The present article aims at elucidating the effect of thermo-mechanical controlled processing(TMCP), especially the finish cooling temperature, on microstructure and mechanical properties of high strength low alloy steels for developing superior low temperature toughness construction steel. The microstructural features were characterized by scanning electron microscope equipped with electron backscatter diffraction, and the mechanical behaviors in terms of tensile properties and impact toughness were analyzed in correlation with microstructural evolution. The results showed that the lower finish cooling temperature could lead to a considerable increase in impact toughness for this steel. A mixed microstructure was obtained by TMCP at lower finish cooling temperature, which contained much fine lath-like bainite with dot-shaped M/A constituent and less granular bainite and bainite ferrite. In this case, this steel possesses yield and ultimate tensile strengths of ~ 885 MPa and 1089 MPa, respectively, and a total elongation of ~ 15.3%, while it has a lower yield ratio of ~ 0.81. The superior impact toughness of ~ 89 J at-20 °C was obtained, and this was resulted from the multi-phase microstructure including grain refinement, preferred grain boundaries misorientation, fine lath-like bainite with dot-shaped M/A constituent.

农用收割机滚筒用440MPa冷轧钢带的研发与制备

针对农用收割机滚筒制造用钢提出的母材均质化、高强度、易成型的质量提级需求,采用低碳、低硅、高锰,加铌、钛的微合金化成分设计,配合控轧控冷及罩式退火工艺,成功研制开发了农用收割机滚筒用440MPa冷轧钢带。所得冷轧退火钢带组织以铁素体+点状(部分球状)渗碳体为主,屈服强度≥350MPa,抗拉强度≥450MPa,断后伸长率≥27%,钢带综合性能较好,保证强韧性的基础上,兼顾较好的折弯成型及焊接性,实现了低成本、高性能农用车制造专用钢带的批量制备,满足农用收割机滚筒制造加工要求。

在线加速冷却对热轧C-Mn无缝钢管组织及性能影响

文章介绍了包钢钢管公司460生产线上一种C-Mn热轧无缝钢管在线加速冷却工艺试验。试验结果表明,在线加速冷却工艺对试验钢组织、性能影响显著,在线控冷能够抑制两相区先共析铁素体的产生,细化了基体晶粒,晶粒度从非控冷状态下的6.5级提高到了8级,改善了钢的带状组织。钢管力学性能及冲击性能有明显提高,屈服强度达到300~345 MPa,抗拉强度达到485~545 MPa,纵向室温冲击功平均值达到102 J,纵向0℃冲击功平均值达到86 J,纵向-20℃冲击功平均值达到60 J。

控轧控冷工艺对Nb-V钢的组织性能析出行为的影响

采用光学、电子显微技术和力学分析等方法 ,系统地研究了不同控轧控冷条件对铌钒复合微合金化低碳热轧钢板的组织和性能的影响规律 ,提出了较佳的控轧控冷工艺参数 。

控轧控冷工艺对低碳铌微合金钢组织和性能的影响

用Gleeble-1500热模拟实验机测定了低碳铌微合金钢变形后的连续冷却转变曲线（CCT曲线），并在实验室对该实验钢采用不同的工艺进行了控制轧制和控制冷却的实验。研究了工艺参数对实验钢力学性能和微观组织的影响，分析了低碳铌微合金钢的强韧化机制。热模拟实验结果表明，实验钢在较宽的冷却速度范围（0．5～30℃／s）内可以获得贝氏体组织。控轧控冷的实验结果表明，实验钢的组织主要为铁素体和贝氏体。随着终轧温度的降低，组织得到细化，强度提高，但屈强比也随之增加；降低卷取温度使组织中的贝氏体含量略有增加，强度有所提高。初步探讨了贝氏体对实验钢性能的影响，为制定合适的生产工艺制度提供了依据。

热轧含钒微合金钢在加速冷却条件下的强化因素

讨论了含钒微合金钢在热轧及加速冷却条件下终轧温度、终冷温度、冷却速度对钢的力学性能的影响。加速冷却含钒钢的显微组织为细小的多边形铁素体和粒状贝氏体组织，由此获得相变强化。钒引起的碳化物析出强化，在加速冷却条件下得到加强，这是由于生成了大量的弥散细小的析出物，并且析出强化效果在６００℃冷却条件下最大。

优化控冷制度改善X120管线钢的组织和性能

研究了热轧后四种不同的冷却制度对X120级管线用钢组织、性能的影响。结果表明,该管线钢在相同的控轧制度下,以冷速61℃/s、终冷温度370℃的冷却制度,能得到以贝氏体为主且强度和韧性均达到X120各项性能指标的组织。

控轧控冷生产中高碳钢高速线材组织和性能的预测模型

建立了高碳钢高速线材在控制轧制和控制冷却生产中组织转变和力学性能的预测模型。该模型分为再结晶、相变、组织和力学性能四部分 ,分别考虑了在控轧控冷过程中的各种冶金现象。该模型的预测结果与现场实际测量结果比较一致 。

超快速冷却工艺对中低碳钢组织性能的影响

基于UFC-ACC设计理念,结合超快速冷却机理及其在中厚板产品处理过程中的技术实现,针对中低碳钢采用不同轧制方式,分析超快冷后钢板力学性能变化,得出较优超快冷冷却规程;同时,对比不同工艺条件下的金相组织,结合理论计算,总结出超快速冷却条件下中低碳钢组织性能演变规律.从分析结果看,中低碳钢冲击韧性明显提高,其他力学性能也有较大改善;此外,UFC-ACC冷后机体大部分为细小均匀的F+P组织,并能保持原奥氏体中的高密度位错,使钢板性能优于普通ACC处理后钢板.

HSLA钢板控轧控冷生产中组织性能的预测模型

建立了ＨＳＬＡ钢板在控制轧制和控制冷却生产中，组织演变和力学性能的预测模型。模型包括再结晶，析出，相变和力学性能四个子模型，分别考虑了发生在控轧控冷过程中的各种冶金学现象。模型的计算结果与两种Ｎｂ－Ｔｉ－Ｖ钢的控轧控冷实验所测得的结果比较一致。

控制冷却对管线钢X65组织细化与性能的影响

在实验室φ450热轧实验机上进行了微合金管线钢X65轧后控冷工艺的研究,以便为进一步工业化生产提供可靠的实验和理论依据.通过TEM分析可知,针状铁素体组织典型的形貌为非常微细的亚结构、高位错密度以及部分细板条铁素体,基体上弥散分布着M/A岛和渗碳体.实验表明,随卷取温度的降低和冷却速度的增加,显微组织明显细化,针状铁素体体积分数增加且力学性能得到提高.因而通过控制轧后冷却制度可以实现X65铁素体-少珠光体钢的柔性化轧制,细化组织,从而显著提高力学性能,达到甚至超过X70钢的级别.

工业生产Super-SS400钢组织性能分析

对工业轧制Super-SS400带钢的强度、延伸率和A_k值进行了测定,用OM、SEM、TEM等实验方法研究了不同工艺条件对带钢显微组织的影响。试验结果表明,当终轧温度在780℃～810℃范围内,卷取温度为450℃左右,控制精轧各道次的变形量,可使SS400热轧带钢的屈服强度高于400MPa,抗拉强度超过520MPa,延伸率达到30％。显微组织观察结果表明终轧温度较低时,在形变过程中产生了应变诱导铁素体。应变诱导相变、铁素体动态再结晶以及轧后加速冷却可使Super-SS400钢的组织均匀细小。卷取温度降低,贝氏体含量显著增加,并出现了马氏体。冲击试验结果表明,卷取温度降低时带钢的韧性较差。Super-SS400钢的强化机制包括4部分;细晶强化、固溶强化、亚结构强化和相变强化。