Electron theory study on the effect of Mn on as-cast structure of Fe-C-Cr-Mn cast irons

The valence electron structure of alloying austenite of 3C-15Cr high chromium white cast iron with different Mn contents from 1% to 6% is analyzed by BLD method and EET. Results show that the addition of Mn has major influence on the valence electron structure of the alloying austenite, especially on that of Fe-C, Fe-C-Cr and Fe-C-Cr-Mn unit cells of it. The effect becomes weak when Mn content is over 4%. Based on the effect of n~, F~~, the weighting of each unit cell and the degree of undercooling on phase transition of the aus- tenite, we can calculate the retained austenite content of as-cast structure of the high chromium white cast iron. The calculation results coincide well with those of the experiment. The phase transition characters of the austenite in high chromium white cast iron can be forecasted through valence electron structure analysis of alloying austenite by BLD method and EET on the basis of Fe-C-Cr equilibrium phase diagram.     

投本刊“安全工程”栏目的文章将优先发表

为了进一步强化《河南理工大学学报（自然科学版）》的特色。本刊新开设了《安全工程》栏目。该栏目依托河南理工大学的“安全工程”省级重点学科。主要刊登与安全工程有关的各类科研成果．对该栏目的稿件。本刊将优先发表．欢迎全国安全专家向本栏目赐稿。     

Effects of Ti addition on low carbon hot strips produced by CSP process

Large quantity of fine Ti（C,N） particles, 15-30 nm in size, were observed in low carbon hot strips added to a small amount of Ti and produced by CSP process. The results showed that the precipitation of Ti（C,N） mostly took place during soaking and hot rolling, which is significantly different from that in the conventional production. These fine Ti carbonitride particles could be very effective on the austenite grain refinement by hindering grain growth of recrystallized austenite. Their precipitation behavior was discussed and compared with that of the steels produced in the conventional production.     

Precipitation and stability of reversed austenite in 9Ni steel

A new method was used to analyze the factors affecting the precipitation of reversed austenite during tempering. The samples were kept at various tempering temperatures for 10 min and their length changes were recorded. Then, the precipitation of reversed austenite which led to the length reduction was shown by thermal expansion curves. The results show that the effects of process parameters on the precipitation of reversed austenite can be determined more accurately by this method than by X-ray diffraction...     

Embrittlement Mechanism due to Slow Cooling During Quenching for M152 Martensitic Heat Resistant Steel

 The brittleness of M152 martensitic heat resistant steel due to slow cooling during quenching was experimentally investigated by means of mechanical property test, TEM and XRD analysis. The results showed that the nonreversal brittleness of M152 steel due to slow cooling during quenching was caused by the continuous precipitation of M23C6 along prior austenite grain boundaries and of M2C along prior residual austenite film. The residual austenite in the steel was unstable and may decompose due to the precipitation of second phase during the process of slow cooling after quenching. The low cooling rate in the temperature range from 820 to 660℃ has a strong effect on the impact toughness of the steel, the precipitation of second phase in the same temperature range results in nonreversal brittle.     

核电给水加热器不锈钢换热管的选用

不锈钢管具有优良的使用性能,核电厂给水加热器常采用不锈钢管作为换热管.不锈钢管的材质包括有奥氏体不锈钢管和铁素体不锈钢管.分析了不锈钢换热管的失效机理,并对采用不锈钢管给水加热器的运行经验进行了总结.在选择换热管材质时,需综合考虑耐腐蚀和耐冲蚀性能、力学性能、最高运行温度、潜在振动等方面的要求.     

中碳合金奥氏体内C-Me偏聚与异常分解

根据由固体和分子经验电子论提出的奥氏体内C -Me偏聚理论 ,利用奥氏体过冷分解转变的规律 ,通过控制冷却技术使中碳合金奥氏体发生异常分解     

卷取温度对热轧TRIP钢残奥及力学性能的影响

为了研究卷取温度对热轧TRIP钢的残余奥氏体和力学性能的影响,使用金相显微镜、扫描电镜、x-射线衍射、拉伸实验等方法对三种卷取温度下制备的热轧TRIP钢进行分析.结果显示,随着卷取温度的降低,残余奥氏体晶粒尺寸变小,残奥体积分数和碳的质量分数也变小.450 ℃和400 ℃卷取温度下制备的热轧TRIP钢的残奥形貌的圆整性相差不大,而350 ℃卷取温度下制备的热轧TRIP钢的残奥形貌较圆整.热轧TRIP钢的力学性能随着卷取温度的降低表现为高的屈服强度和低伸长率,450 ℃卷取温度下制备的热轧TRIP钢的综合力学性能最优.     

残余奥氏体的诱发相变对Cr12钢耐磨性的影响

利用金相、Ｘ射线、扫描电子显微镜等手段研究了Ｃｒ１２钢中残余奥氏体的形变诱发马氏体相变对耐磨性能的影响，探讨了强化机制．结果表明，Ｃｒ１２钢经１１５０℃淬火得到大量处于变塑状态的残余奥氏体，并在磨损过程中发生形变诱发马氏体相变，使表面硬度和耐磨性显著提高，超过常规的９８０℃淬火．残余奥氏体对耐磨性的强化，为逐层诱发马氏体的循环强化机制．