Effect of Carbonitriding on the Susceptibility of Medium-Carbon Alloy Steels to Temper Brittleness

Metal Science and Heat Treatment - The effect of carbonitriding as a finishing operation of hardening of the thread of drill pipes on the properties of the matrix metal, its temper brittleness in...     

Boronitriding of Die Steels in Fluidized Bed

Processes of progressive and simultaneous boronitriding of die steels in fluidized bed are considered in comparison with conventional diffusion boronizing. A comparative analysis of the microhardness and wear resistance of die steels after boronitriding and boronizing is performed.     

Surface Hardening of Die Steels by Diffusion Boronizing, Borocopperizing, and Borochromizing in Fluidized Bed

Processes of diffusion boronizing, borocopperizing, and borochromizing of die steels in fluidized bed are considered. The microhardness, microbrittleness, and wear resistance of die steels after boronizing, borocopperizing, and borochromizing are studied.__________Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 3, pp. 27 – 30, March, 2005.     

Microstructural Characteristics and Mechanical Properties of Low-Alloy,Medium-Carbon Steels After Multiple Tempering

The microstructure and mechanical properties of NiCrMoV-and NiCrSi-alloyed medium-carbon steels were investigated after multiple tempering. After austenitising, the steels were hardened by oil quenching and subsequently double or triple tempered at temperatures from 250 to 500 °C. The samples were characterised using scanning electron microscopy and X-ray diffraction, while the mechanical properties were evaluated by Vickers hardness testing, V-notched Charpy impact testing and tensile testing. The results showed that the retained austenite was stable up to 400 °C and the applied multiple tempering below this temperature did not lead to a complete decomposition of retained austenite in both steels. It was also found that the microstructure, hardness and impact toughness varied mainly as a function of tempering temperature,regardless of the number of tempering stages. Moreover, the impact toughness of NiCrMoV steel was rather similar after single/triple tempering at different temperatures, while NiCrSi steel exhibited tempered martensite embrittlement after single/double tempering at 400 °C. The observed difference was mainly attributed to the effect of precipitation behaviour due to the effect of alloying additions in the studied steels.     

Single Treatment of Steel in Fluidized Bed

Results obtained by the author and his coworkers at the Vysokogorskii Mechanical Works in the city of Nizhny Tagil are presented. The effect of single treatment in fluidized bed on the mechanical properties of high-carbon and low-alloy steels is studied and the data are compared with the properties of these steels after toughening. A mechanized flow line for single treatment of parts from steel 40Kh in fluidized bed is described, and designs of electric furnaces/baths with fluidized bed are presented.     

Rapid Induction Heat Treatment of Articles from Plain and Low-Alloy Low-Carbon and Medium-Carbon Steels

A new method of rapid induction heat treatment (RIHT) of articles and semiproducts from plain and low-alloy low-carbon and medium-carbon steels is described. The method ensures a high ductility at a strength at least no lower than the initial one and a high strength at a ductility higher than the initial one. Examples of pipes from steels 15G2 and 20 are used to show the advantages of the RIHT method over traditional methods of heat treatment. __________ Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 6, pp. 20 – 23, June, 2005.     

Oxidation Kinetics of Ilmenite Powder in Fluidized Bed

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碳化硅纳米线合成及显微结构分析

利用悬浮床,以Si粉为原料,在0.2 L/min的高纯氮气中,维持反应温度1～600 ℃,悬浮反应30 min,在预先放置的收集器上得到了SiC纳米线,XRD结果表明所得SiC纳米线为部分结晶状态,结晶态晶型为六方6H型.SEM形貌观察结果表明,所得SiC为纳米线.进一步SEM观察发现,大量纳米线的端部有球状液滴存在,VLS机制为该纳米线的主要形成机制, 通过EDX能谱对比分析,纳米线端部球状液滴中相对纳米线本身含有较多的氧元素,因此,氧元素对于通过VLS机制形成SiC纳米线起到了促进作用.TEM观察显示,纳米线中存在大量的堆垛层错缺陷.     

Mathematical Simulation on Oxidation of Ilmenite in Fluidized Bed

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强化流态床淬火能力的研究

在分析传热机理的基础上,研制了一种采用半导体致冷的,床温低于室温的淬火流态床,系统研究了－３０℃流态床的综合淬火效果。     

流态床的传热学研究

对流太床的传热过程进行了分析，提出了计算流态床热传递过程的数学模型，运用本模型可测定不同工作状况上的流态床换热系数，为正确制定热处理工艺奠定基础。     

流态床渗氮工艺的研究

本文对３Ｃｒ２Ｗ８Ｖ，Ｈ１３及３８ＣｅＭｏＡｌ钢在刚玉流态床中进行了渗氮工艺的研究。结果表明，氨气在２５％－６５％范围内变化时，对渗氮结果无明显的影响，在流态床中渗氮可减少工件表面化合物层的形成和加快渗氮的速度。采用脉冲渗氮方法可获得与非脉渗氮同样的效果，同时可降低耗气量。     

石墨流态炉快速氮碳共渗工艺研究

对０８钢制碾米机筛片进行石墨流态炉快速氮碳共渗工艺研究。结果表明，以空气为流化气的石墨流态炉，添加适量活化气ＮＨ３及少量ＣＯ２进行奥氏体氮碳共渗１５￣４０ｍｉｎ，即可获得２０￣５５μｍ致密的ε化合物层。经２５０℃回火ε相低氮侧强烈时效，使渗层硬度高达８００￣１０００ＨＶ０．０２，与起缓冲作用的次表中等硬度淬火层回火产物相配合具有极高的耐磨性、抗蚀性及较小的脆性。工件表面呈均匀的蓝黑色。石墨流态炉作     

型砂对固定式沸腾冷却床工作参数的影响

运用流体力学知识,结合固定式沸腾冷却床的特点,提出了流化速度、床层压降、功率等工作参数的计算方法;分析了型砂大小、密度、粒度分布、床层高度等因素对工作参数的影响规律,在此基础上得出了沸腾床无法流化的原因和风压、风速之间的关系,并通过调整型砂参数得以解决。     

一种高效旧砂冷却设备——固定式沸腾冷却床

随着造型机械化自动化程度的不断提高，型砂需要量显著增加，旧砂的循环时间因而大大缩短，许多铸造厂为造型线供砂的砂处理系统中没有设置可靠的砂冷却设备，导致在炎热的夏季及在满负荷运行中出现了回用的旧砂温度过高的“热砂”问题。型砂温度过高会给造型生产造成一系列困难，如型砂性能不稳定，容易粘附模板，造成铸型损坏；粘附砂斗使型砂加砂受阻；铸型表面容易脱水进而导致铸件废品率上升以及劳动条件恶化等。造成型砂温度过高的原因主要是回用旧砂的温度过高，固定式沸腾冷却床正是针对旧砂的温度过高而设计的。     

用于激光再制造的沸腾式送粉器设计

针对激光再制造对粉末输送的要求,设计一种基于流化床原理的沸腾式送粉器。实验采用粒径为75～109μm的Ni基合金粉末,在干燥室内环境下进行,分别在送粉器结构尺寸不同、气动回路控制方法不同以及沸腾气体流量不同的情况下对送粉器进行实验。根据实验结果对送粉器结构、气动控制回路进行改进。研究表明:内部尺寸适当小的送粉器其最小送粉率可达1.7 g/min;沸腾气体流量的变化对送粉率影响显著,即送粉率随着沸腾气体流量的增大而增大,且两者存在一定的线性关系;沸腾式送粉器的稳定送粉范围为2.5～20 g/min。     

循环流化床锅炉风帽材料的选用

自20世纪80年代以来,新型节能环保锅炉--循环流化床锅炉发展迅速,这种锅炉具有可燃劣质煤、易于脱硫和燃烧后产生的灰渣有很好的综合利用价值等独特优势.目前,我国已运行35 t/h～1 025 t/h不同容量等级的循环流化床锅炉2 000多台,约占电力行业锅炉总台数的1/3.     

预测函数控制在流态化床配气系统上的应用

流态化床是一种生产超细碳化钨钴复合粉末的专用冶炼炉。配气系统是流态化技术生产中的一个重要环节,配气过程的波动,不但对流态化气体流量造成波动,而且对WC颗粒晶度变化起着重要的作用。本文根据流态化床配气系统气体浓度控制的需求,分析了流态化床工艺和配气系统的工作特性,研究了目前气体浓度配比控制的几种控制策略应用现状,提出了针对流态化床配气系统气体浓度控制的一种预测函数控制策略。理论研究主要从预测函数控制的基本原理出发,对预测函数控制进行算法推导和参数分析。在应用上,引入预测函数控制算法进行浓度控制,有针对性地进行了数学模型设计和仿真研究,并实际应用在流态化床配气系统的浓度控制之中。通过仿真研究和实际应用效果表明,相对常规PID控制方式,在流态化床配气系统上实施预测函数控制是有效可行的,证明了基于预测函数控制的先进控制系统具有较强的适应性和鲁棒性,同时具有较高的控制精度。该系统的现场应用取得了很好的效果,同时对同类系统具有很好的推广应用价值。