小行星架铸件热处理裂纹缺陷分析与消除

研究了小行星架铸件的铸造过程及热处理工艺,并对小行星架热处理过程中产生的裂纹进行了分析。结果表明,应力集中是小行星架产生裂纹的主要原因。降低加热过程中升温速度及增加加热过程中保温时间,可使应力集中减轻,大大降低了铸件的废品率。     

新型飞机用材——钛

<正> 最近钛材的需求正日趋升温,这是由于最新型的民用客机波音777的订货量呈上升趋势造成的。据推算一架波音777飞机至少需要约50t的钛材(非成品)。根据波音公司公布的数字来看,至1996年末波音777的确切订购量已达318架,1997年后半年计划以每月7架的速度交付使用。     

钨钼丝炉升温的控制方法

钨、钼材料的电阻温度系数相对较大,低温段电阻值较小,因此由钨、钼材料做发热体的电阻炉在冷态升温过程中,若不采用合适的控制方法极易产生过大的电流而损坏设备。本文分别介绍了手动升温、单温度闭环自动升温和温度、电流双闭环自动升温三种升温控制方法,以及如何有效地防止升温过程中产生过大电流。对于以上三种升温方法,本文分别针对在升温过程中电压、电流、功率等物理量的相互关系进行了分析,讨论了三种方法的控制性能及适应的电炉类型。     

如何选购不锈钢厨具

<正> 随着家庭装修热的升温,装修的重点之一——厨房,也越来越讲究,不锈钢厨具成为人们首选对象,如:不锈钢洗涮台、操作台、贮藏柜、吊柜、水池、存放架等。 因为不锈钢具有优异的化学稳定性、耐腐蚀、不生锈、易清洗,它的成型性好,可以加工成形态各异、规格多样、品种繁多的器械,它外观华丽,美观大方,可以满足各界人士的     

升温速率对P91钢管道局部焊后热处理温度场的影响及参数优化

升温速率是P91钢管道局部焊后热处理的关键参数之一,决定着热处理的效率和质量. 文中以?575 mm × 35 mm的P91钢管道为对象,进行79 ~ 479 ℃/h 之间的5个升温速率下的局部焊后热处理试验,并分析升温速率对实际升温时间(管道外壁温度达到稳态的名义升温时间+管道内壁温度达到稳态的滞后时间)、管道轴向和径向温度梯度的影响,然后建立P91钢管道焊后热处理有限元计算模型,优化升温速率参数. 结果表明,提高升温速率减小整个管道接头的实际升温时间,可以提高热处理效率. 当升温速率小于179 ℃/h时,提高升温速率明显缩短实际升温时间;当升温速率超过179 ℃/h时,提高升温速率缩短实际升温时间的作用减小. 升温速率的变化对径向温度梯度影响较小,对轴向温度梯度影响则较大. 基于轴向温度梯度控制准则和优化计算结果,得到了不同壁厚P91钢管道局部焊后热处理最大升温速率的计算公式,最后提出了工程上快速选取焊后热处理最大升温速率的应用方案.     

敞开式焙烧炉新型排烟架技术开发和应用

为解决敞开式焙烧炉传统排烟架压损大，压力分布不均的问题，通过开发新型排烟架，对排烟架的结构进行优化，保证排烟架内流场的均匀性，保证边火道的负压水平，从而降低排烟架压损。通过对新型排烟架的结构强度进行核验并对排烟架设备进行轻量化优化设计，做到了降低排烟架重量。生产实践采用新的排烟架技术，总管压力由-1200 Pa左右降低至-800 Pa左右，实现了节能降耗、提质增效目的。     

挤压铸造铝合金医用头架的研制

介绍了铝合金医用头架的挤压铸造工艺,所研制的头架毛坯显微组织细小、力学性能优良,实现了挤压铸造铝合 金头架代替锻铝头架的目标。     

行星架开裂原因分析

行星架是无级变速箱用粉末冶金件。某公司有多件行星架开裂。对开裂的行星架进行了宏观检查、硬度检测、化学成分分析、断口形貌分析。此外还检查了行星架的生产和磁粉探伤过程。结果表明：开裂的行星架的硬度和化学成分符合技术要求。但因其生产中操作不当，行星架产生了隐形裂纹，并由于磁粉探伤操作不规范隐性裂纹未被及时发现。     

焙烧参数对预焙阳极特性影响的实验研究

搭建了实验平台,采用实验的方法研究了升温速率和终焙温度对预焙阳极体积密度、气孔率、电阻率和挥发分析出率等参数的影响。结果表明,气孔率、电阻率和挥发分析出率都随升温速率的增大而增大,在升温速率较小时,体积密度随升温速率的增大快速减小,当升温速率超过80℃/h后,再增大升温速率,体积密度变化不大。体积密度、气孔率和挥发物析出率都随终焙温度的升高而升高,而电阻率则随终焙温度的升高而降低。     

铝电解用TiB_2阴极涂层固化、炭化的升温制度

采用DTG ,DDTA等热分析手段 ,研究了高温固化、炭化过程中 ,铝电解用TiB2 阴极涂层糊料的质量和能量的变化速率 ,制定了涂层的变速固化、炭化升温制度 ;在此基础上 ,研究了升温制度对TiB2 阴极涂层性能的影响。结果表明 :变速升温制度优于匀速升温制度 ,采用变速固化、炭化升温制度所制备的涂层形变小、无裂纹 ,其抗拉强度达 3.13MPa,电阻率为 2 3.2 μΩ·m ;而采用升温速度为 10 .3℃ /h的匀速固化、炭化升温制度制备的涂层形变大、裂纹多 ,抗拉强度小 (2 .6 9MPa) ,电阻率大 (2 8.6 μΩ·m)。     

Pressureless sintered high-strength mullite from commercial powder

High-strength monolithic mullite ceramics were prepared from commercial-grade power by carefully controlled processing of the powder followed by pressureless sintering at 1700 °C. Mullite powder was mechanically and chemically dispersed, ball milled, and screened prior to slip casting. Specimens were sintered to 97% of theoretical density under pressureless conditions. The furnace ramp and soak schedule was an important variable. Four-point flexural strengths of 250 MPa were achieved, exceeding literature values for pressureless sintering of Baikowski mullite powder.[a] Pore sizes were small and were not strength limiting. Griffith calculations suggest a critical flaw size of 20 μm, in good agreement with the maximum observed crystal size in the microstructure.     

Cobalt capping: Why is sintered hardmetal sometimes covered with binder?

Some sintered hardmetal grades come out of the furnace covered with a thin layer of binder at the surface, while others do not. The layer can be beneficial for subsequent brazing, but it must be removed by grinding or etching if the hardmetal is to be coated. It would be beneficial to be able to control this “cobalt capping” during sintering by applying suitable sintering conditions. For this purpose, the mechanism of cobalt capping was investigated. The capping occurs on the cooling ramp, at the eutectic temperature of the binder. If the binder solidifies first in the interior, the contraction caused by the phase transition squeezes melt out of the exterior zones. The contraction of the specimen was verified with dilatometry. Conditions leading to cobalt capping are: higher carbon content in the surface than in the bulk (decrease of melting point), high binder content, especially in the surface zone, and a low cooling rate.     

Microscopic study on the interfacial strength of hydrogenated amorphous carbon coating systems

The microstructure and the adhesion strength of two hydrogenated amorphous carbon (a-C:H) coatings on steel substrates with a Cr adhesion layer were investigated by Rockwell C testing, Focused Ion Beam and High Resolution Transmission Electron Microscopy (HRTEM).Slight variation of the coatings in the ramp layer between Cr and a-C:H resulted in a good or poor adhesion behaviour. Both coatings exhibited in the ramp layer a quasi amorphous matrix structure with short-range ordered substructures. No crystalline chromium carbides could be detected in these regions. Focused investigations of the chemical gradients with Energy Filtered TEM (EFTEM) and Energy Dispersive X-Ray (EDX) spectrometry revealed a clear difference in the chemical composition of the ramp layers. Smooth gradients together with a nanocomposite structure seem to provide a high stability of the ramp layer against delamination.     

超大型热处理炉关键技术的应用

本文介绍了超大型热处理炉项目关键技术的应用情况,阐述了超大型台车式热处理炉的关键技术：采用了炉体供热和炉内气流循环技术,轻型防变形结构门框技术、炉车纵梁组合式焊接技术和工业炉专用控制系统。     

Reverberatory Furnace Practice at Noranda

Developments in reverberatory furnace practice at Noranda over the period 1928 to 1953 are described. Features of interest are increasing furnace tonnage from 700 to 2000 tons per furnace day, the use of the suspended basic roof, and improvements in furnace fuel ratio. Points of comparison and contrast between Canadian and American furnace practice are given.     

A thermal system model for a radiant-tube continuous reheating furnace

A thermal system mathematical model developed for a gas-fired radiant-tube continuous reheating furnace is discussed. The mathematical model of the furnace integrates submodels for combustion and heat transfer within the radiant tube with models for the furnace enclosure. The transport processes occurring in the radiant tube are treated using a one-dimensional scheme, and the radiation exchange between the load, the radiant-tube surfaces, and the furnace refractories are analyzed using the radiosity method. The continuous furnace operation is simulated under steady-state conditions. Model simulations of load surface temperature variation compare well with measurements in an industrial galvannealing furnace. The scope and flexibility of the model are assessed by performing extensive parametric studies using furnace geometry, material properties, and operating conditions as input parameters in the model and predicting the thermal performance of the furnace. The various parameters studied include the effects of load and refractory emissivities, load velocities, properties of the stock material, and variations in the radiant-tube designs.     

衬套类零件压铸模抽芯结构分析及其液压抽芯设计

通过对衬套类零件压铸模斜滑块抽芯、斜导柱抽芯、齿轮齿条抽芯、液压抽芯结构对比分析，提出液压抽芯可实现此类模具设计的通用化和系列化，并对液压抽芯设计做了进一步阐述。     

大型矿热电炉厂的供电设计

随着矿热电炉大型化的发展,电炉变压器容量的不断提升,矿热电炉的供电设计出现了一些新问题.通过在大型矿热电炉设计中的经验,阐述大型矿热电炉供电设计中所出现的新问题及处理方案.     

自预热式燃气烧嘴在大型箱式调质生产线的应用

在大型箱式调质生产线中使用高效率自预热烧嘴替代传统电阻加热,可达到与电阻加热一样的炉温均匀性,经济与环保指标大幅优于传统电阻加热方式。     

竖炉式电弧炉的发展与现状

叙述世界炼钢工业中竖炉式电弧炉的发展概况及特点，对竖炉的形式、结构、工艺操作和节能优势等方面进行了分析和探讨，并对竖炉发展趋势提出了看法。