GCr18Mo轴承钢的下贝氏体组织转变

利用光学显微镜和透射电镜观察和分析了GCr18Mo轴承钢的下贝氏体组织形貌和精细结构,探讨了下贝氏体组织转变机理。借助于图像分析仪分析了下贝氏体转变动力学。结果表明,GCr18Mo轴承钢等温淬火后生成的下贝氏体呈针状或竹叶状,且堆聚成簇,下贝氏体中的铁素体为条状,空间呈双透镜状,由许多更小的铁素体亚条平行排列构成;GCr18Mo轴承钢的下贝氏体转变机理符合类平衡切变长大模型,其形成过程是孕育成核和快速长大的过程,它的转变动力学方程为y=1-exp(2.2×10-12t3.22)。     

球墨铸铁的塑性变形及奥贝组织研究

利用Gleeble-1500热力学模拟机、光学和透射电子显微镜对球墨铸铁变形前后以及等温淬火处理后的组织进行了分析。结果表明,球铁热塑性变形最佳温度在750—800℃区间,此时流变应力接近950℃时的流变应力;变形后球铁为三层组织结构“球状石墨＋蠕虫状石墨＋流线型石墨”;在透射电镜下清楚地观察到不同形状的下贝氏体和上贝氏体形貌以及典型的隐“M”型马氏体形貌。     

碳中和国际标准解析

2010年5月全球第一分碳中和国际标准发布,该标准作为企业最终实现低碳发展必经途径,迅速引起了消费类产品生产企业的关注.该文在简要介绍碳中和概念的基础上对其关键步骤进行了解释说明,为企业开展碳中和承诺提供借鉴作用.     

贝氏体等温温度对CMnAl-TRIP钢性能的影响

含有磷、铜的CMnAl-TRIP钢板在820℃温度退火2min,然后分别在450℃和400℃贝氏体区等温不同的时间,研究了不同贝氏体等温温度对显微组织、力学性能和残余奥氏体稳定性的影响.结果表明CMnAl-TRIP钢具有优异的力学性能和延展性,450℃等温处理时钢板的各项力学性能优于400℃等温处理,而400℃等温处理试样中残余奥氏体的碳含量高,稳定性高,马氏体总体转变率低,导致低的应变硬化指数n值、均匀伸长率和总体伸长率.     

冷却速率对直接淬火钢组织和性能的影响

对含微量硼的钢与无硼钢在不同冷速下直接淬火试样的组织进行了观察,分别测定了含硼钢与无硼钢的连续冷却转变(CCT)曲线,以及轧制后不同温度回火试样的拉伸强度.结果表明:硼的添加会使贝氏体转变Bs点降低,生成粗大的针状或板条状贝氏体组织,这种贝氏体组织越多,它的强度就越低;无硼钢在慢冷情况下(15℃/s),Bs点较高,易于形成粒状贝氏体组织,该组织与马氏体形成的混合组织使强度较高.为避免粗大贝氏体区,对于含硼钢,适宜采用快速冷却;而对于无硼钢,应尽量降低冷却速率.     

超高强度钢40CrNi2Si2MoVA贝氏体等温淬火工艺

对超高强度钢40CrNi2Si2MoVA进行贝氏体区短时间等温淬火,得到马氏体加下贝氏体和少量残余奥氏体的复合组织,考察了等温时间的变化对材料显微组织和力学性能的影响,并进一步得出了此条件下该钢的最佳热处理工艺.结果表明:当等温时间在100～150 s时,得到以马氏体为主,含20%左右下贝氏体和少量稳定残余奥氏体的组织.     

Modelling of transition from upper to lower bainite in multi-component system

A model for estimating the upper to lower bainite transition has been developed for the iron–carbon–manganese–chromium–silicon alloy system by comparing the time required to decarburise a supersaturated bainitic ferrite platelet and that needed for the start of cementite precipitation in the ferrite. The problem is treated as a competition between the decarburisation time and the kinetics of cementite precipitation. Lower bainite is induced when the latter process is faster. The time for forming a volume fraction of 0.01 of the equilibrium amount of cementite is taken as the precipitation start time. The model was calibrated using experimental data from the iron–carbon system, and verified with the iron–carbon–manganese–molybdenum system and an experimental steel currently being developed for high-strength applications.     

As cast acicular ductile aluminum cast iron

 The effects of 2.2% Ni and 0.6% Mo additions on the kinetics, microstructure and mechanical properties of ductile aluminum cast iron were studied in the as-cast and tempered conditions. Test bars machined from cast to size samples, were used for mechanical and metallurgical studies. The results showed that the addition of Ni and Mo to the base iron produces an upper bainitic structure resulting in an increase in strength and hardness. The same trend was shown when the test bars tempered from 300oC in the range of 300 to 400oC. The elongation increased with increasing the temperature from 300 to 400oC. The carbon content of the retained austenite also increased with increasing temperature. The results also showed that the kinetics, microstructure and mechanical properties of this iron are similar to Ni-Mo alloyed silicon ductile iron.     

用于铁道绝缘接头的高强-塑-韧性空冷贝氏体钢

以Mn系空冷贝氏体钢成果为基础,设计了新型B800贝氏体钢的成分和工艺,实现了高强-塑-韧性热轧态空冷贝氏体高精度扁钢的批量生产。B800钢制铁道绝缘接头的力学性能达到了Rm835～925 MPa-A21.5%～24.5%-A_(kv)38～64 J的水平,解决了在普通工业生产条件下,铁道绝缘接头同时具有高强度、高韧性、高断后伸长率的国际性难题。B800贝氏体扁钢具有高的性能价格比。     

New Microalloyed Steels for Forgings

Microalloyed steels for forging applications have been newly developed in order to increase strength and toughness properties which thereby give the possibility for light weight constructions.The properties of these steels are set up by a controlled cooling directly from the forging heat without an additional heat treatment.This aim can be achieved on the one hand by a further development of precipitation hardening ferritic pearlitic steels (AFP-steel) due to an extended use of microalloying elements (AFP-M steel) and on the other hand by microalloyed steels which employ a bainitic microstructure (HDB steel).To adjust the targeted microstructure the temperature control has to be assured down to approx.500℃ for the AFP-M steels and down to approx.300℃ for the HDB steels.