Effect of low-pressure carburizing and plasma nitriding on mechanical properties and fatigue endurance limits of low alloy sintered steels

ABSTRACT

Thermochemical treatments like plasma nitriding or surface carburizing are commonly used to enhance surface hardness of steel components. An important difference between these treatments is the temperature at which they are carried out. In the present paper, the surface carburizing was carried out following a recently reported non-isothermal low pressure carburizing (LPC) treatment. In order to gain a comparative view of the effect of different treatments on the microstructure, microhardness, fatigue and impact properties, materials with distinct hardenability and widely used in the industrial production were evaluated. Tests were also carried out using industrially processed components aimed to an application demanding high wear resistance. The microstructural evolution during case hardening was studied by optical and electron microscopy.     

The influence of cryogenic rolling on a transformation-induced plasticity steel

ABSTRACT

Here, a novel cryogenic rolling plus intercritical annealing process was applied to a transformation-induced plasticity (TRIP) steel with a low chemical composition of carbon and manganese. Compared with traditional cold rolling, obvious grain refinement was observed, due to a high amount of dislocations retained. In addition, austenite volume fraction was increased, because of a unique nucleation mechanism. Subjected to cryogenic rolling, strength and ductility were increased, due to the enhanced austenite stability, which provided continuous and active TRIP effect. Consequently, tensile strength was increased to 1030?MPa, and elongation was increased to 38.2%. Thus, a great mechanical combination was obtained in a steel with a relatively low chemical composition with carbon and manganese, only by cryogenic rolling process.     

冷轧螺纹钢筋的力学性能研究

介绍了冷轧螺纹钢筋的轧制原理,从屈服强度、抗拉强度、延伸率、冷弯条件等方面说明了冷轧螺纹钢筋力学性能标准(新技术的生产工艺),研究了冷轧螺纹钢筋的力学性能及其影响因素。     

蓬莱田横栈道维修加固技术

结合蓬莱田横栈道维修加固工程实例,介绍了针对滨海环境下不同的工程构件采取的不同的处理措施以及施工效果。     

20CrNi2MoA钢锻件去氢退火工艺的研究

分析了氢在钢中的存在状态,阐明了氢的溶解度与扩散系数之间的关系,据此,科学地设计了20CrNi2MoA钢锻件的去氢退火工艺,该钢退火前的氢质量分数为(1.50～1.90)×10-6,退火后的氢质量分数为(0.37～0.57)×10-6,回火索氏体组织,硬度212～229HB,满足标准要求,并获得显著经济效益.     

浅谈建筑施工扣件式钢管脚手架安全技术监理

文章主要阐述了对扣件式钢管脚手架施工的事前控制和过程检查的安全监理工作。     

深圳会议展览中心钢结构工程涂装工艺

结合工程实例，介绍了钢结构工程涂装工艺，从涂装工艺流程、涂装施工工艺等方面进行了论述，指出加强工艺的操作管理，以确保涂装质量。     

轻钢增层结构的设计与构造

通过对轻钢增层结构设计与构造方法的介绍，提出了轻钢增层结构中的关键技术问题，为轻钢增层结构的合理设计与研究提供参考。     

悬链线无铰拱拱轴系数m值的确定

以马鞍山大桥为例，运用计算机桥梁计算程序，按平面有限元分析，选取了无数组m值进行了各截面应力值的比较，得出一些有意义的结论，最终使各截面受力均匀，有利于截面尺寸及受力钢筋的控制，使其达到最为经济的状态。