55SiCr弹簧钢盘条组织偏析对拉拔断裂的影响

针对Φ14 mm规格55SiCr弹簧钢盘条在拉拔过程中发生断裂的问题,采用金相显微镜、扫描电镜、微区成分检验对断裂试样进行了分析.此外,采用微区成分分析法对国内外具有代表性的3个厂55SiCr弹簧钢成分进行电子探针检验,对衡量弹簧钢组织偏析程度与拉拔断裂之间关系的偏析指数进行了归纳总结,结果表明,当Mn、Cr偏析指数达1.50以上,Si偏析指数达1.40以上会加大弹簧钢拉拔断裂倾向.     

熔剂颗粒在烧结过程中的特征演变及影响

 对烧结现场生产进行全流程取样,分析熔剂颗粒在烧结过程中的演变规律,及其对烧结过程的影响。结果表明,在烧结混合料制粒过程中,小于0.5 mm熔剂颗粒较铁矿粉颗粒更容易黏附至核颗粒表面形成新的颗粒,从而相对均匀地分布至混合料各粒级中。大于0.5 mm粒级熔剂颗粒作为核黏附一定厚度的黏附层形成新的颗粒,黏附层厚度均小于1 mm,因此,新颗粒直径仅在原始颗粒粒径基础上增大不超过2 mm。同时由于熔剂原始颗粒粒级较细,导致制粒后大于5 mm粒级混合料中熔剂含量较少。而在烧结台车布料过程中粒级存在偏析,大颗粒向下分布,最底层大于5 mm粒级颗粒分布最多,从而导致熔剂的偏析,混合料中大于5 mm粒级颗粒增多加大了熔剂的偏析,混合料中3~5 mm粒级颗粒增多减弱了熔剂的偏析。料层粒级偏析使烧结料层,最底层混合料中熔剂总量变少,大颗粒熔剂增多,熔剂颗粒数量减少,导致熔剂分布点变少,熔剂分布不均匀程度增加,局部高碱度环境变少,液相产生的难度增加。同时,由于颗粒的偏析,最底层混合料中大颗粒铁矿粉增加,出现更多的未熔原矿,最终导致烧结料层最底层烧结矿质量变差。     

提高布料质量的途径

论述了台车上横向、纵向混合料容积密度及粒度的合理分布 ,偏析指数和混合料容积密度的关系 ,提出了改善台车上混合料容积密度 ,加大混合料粒度偏析 ,降低边缘效应及提高料面平整度的布料途径。     

改善烧结布料质量的方法

叙述了烧结台车上横向、纵向混合料容积密度及粒度的合理分布，偏析指数和混合料容积密度的关系，提出了改善台车上混合料容积密度，加大混合料的粒度偏析，降低边缘效应及提高料面平整度的布料方法。     

烧结混合料偏析布料方法的研究

通过模型试验，研究了反射板角度、给料速度、矿槽开度及采用条型反射板等对混合料粒度偏析度和固定碳偏析度的影响。并通过烧结试验研究了混合料偏析对烧结矿产质量的影响。研究结果表明：混合料粒度和固定碳在料层高度方向上的合理分布，是强化烧结过程，提高烧结矿质量、降低烧结能耗的重要措施。     

铬铁铸锭的成分偏析

本文论述了铬铁合金偏析的影响因素和各种铬铁的成分偏析情况，并简述了偏析在铬铁生产的实际应用及控制方法。     

新型烧结机布料设备——第三代烧结机多辊布料器

专利号 :992 5 775 1 9钢铁研究总院与北京庆妫机械厂合作开发的第三代多辊布料器 ,是在总结原北京燕妫机械厂生产的第二代多辊布料器使用中发现的一些问题 ,对多辊布料器的结构重新优化设计 ,重新编排加工工艺 ,于 2 0 0 1年初投产的新一代多辊布料器。第三代多辊布料器 ,控制混合料偏析的功能进一步提高 ,设备运行的故障率大大降低。使用多辊布料器向烧结机台车布料 ,具有松散混合料 ,将部分小粒级混合料筛分到料层表面 ,通过控制布料辊转速控制混合料偏析程度的功能。烧结混合料经多辊布料器布到烧结机台车上 ,不仅混合料粒度偏析适宜 ,…     

铸坯成分偏析对线材冷加工性能的影响

结合生产合金钢线材时冷镦检验试样沿45°方向出现开裂的问题,在实验室作了检验分析。结果表明,冷镦开裂的原因是由于铸坯上存在成分偏析,在轧制中不能消除,遗传到线材上,形成轧后组织偏析,导致冷镦开裂。通过对试样偏析处的成分定量分析查明,合金钢线材偏析带的主要成分为Cr、Mn,偏析处的平均成分比正常部位成分分别高出49%和79%。     

料仓粘料对烧结混合料横向分布均匀性的影响

采用离散单元法建立了烧结布料过程中混合料在料仓内和烧结台车上的分布模型,分析了料仓内四种类型粘料对烧结混合料横向分布均匀性的影响。模拟结果表明,粘料会使料仓内混合料的堆高位置和料面倾角发生变化,改变混合料在横向上的分布特征。(即使不发生粘料,混合料的横向分布也是不均匀的);粘料位置不同,对料仓内混合料的横向粒度分布影响也不同。在混合料下落面中段位置发生粘料时,会减弱混合料的横向偏析,提高横向分布的均匀性;混合料在烧结台车与料仓内的横向分布特征具有继承性,偏析布料器对混合料横向分布的影响较小。     

VC的不同添加方式对WC-6%Ni(Cr_3C_20.9%）硬质合金组织的影响

本文研究了VC的不同添加方式对WC-6%Ni(0.9%Cr_3C_2)合金组织的影响,分别是在WC碳化阶段添加和在混合料球磨阶段添加。结果表明在混合料球磨阶段添加VC的样品烧结后表面出现麻面,实际是Ni聚集同时伴随Cr、V的偏析,另外在该样品内部也存在较多显微孔隙。     

电极感应气雾化法制备新型高硬度马氏体铁基合金粉末

利用正交试验研究了电极感应气雾化（electrode induction gas atomization,EIGA）制粉工艺参数（雾化压力、雾化气体温度和熔炼功率）对新型高硬度马氏体铁基合金粉末粒径分布、粉末流动性和收得率的影响规律。结果表明,粉末粒径分布及其特征主要取决于雾化压力,粉末流动性及收得率主要受雾化压力及雾化气体温度的影响。当制粉工艺参数为雾化压力1.5 MPa、熔炼功率15 kW、雾化气体温度40 ℃时,所得粉末的收得率最高,粒径大小在53～180 μm之间的粉末质量占比高达68.24%,兼具较好的粉末流动性及粉末粒度分布标准偏差,粉末形貌最佳。     

铜包铁粉的应用及制备

铜包铁粉是一种将铜包在铁粉表面形成包覆层的复合粉末,被用来改善铜铁混合粉末组织不均、成分偏析等问题。本文综述了铜包铁粉的应用及制备方法,介绍了机械球磨涂覆法、置换镀铜法、化学镀铜法等铜包铁粉制备技术的基本原理及研究进展,总结了铜包铁粉制备过程中存在的问题,并展望了铜包铁粉的发展方向。     

Structure and properties of Fe—Ni—Si—B and Co—Fe—Ni—Si—B alloys obtained by explosive compaction of amorphous powders

Hard (up to 16 GPa) amorphous-crystalline compacts of cobalt-based alloys and iron-based alloys are made by explosive compaction from powders at pressures of 12 and 15 GPa. Their magnetic properties correspond to the amorphous-crystalline state. X-ray investigations reveal pronounced segregation of the alloying elements as a result of plastic deformation due to the blast wave. The cobalt-based alloy is more resistant to crystallization during explosive compaction than is the iron-based alloy. This is consistent with data obtain in heating tests. The most amorphous phase is preserved when cobalt alloy powder with a fraction of 63–40 μm is compacted by a blast wave traveling at 4000 m/sec (pressure 12 GPa). Institute for Problems of Materials Science, Ukraine National Academy of Sciences, Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 1–2(405), pp. 54–61, January–February, 1999.     

Selection of Alloying Method to Produce Iron-Based Powder

There are different methods to produce low-alloyed iron-based powders. The properties of such powders depend on the method of alloying as well as on the characteristics of the basic grade of iron powder. A comparative experimental study to estimate the influence of the basic iron powders on low alloyed powder properties has been conducted. The method of co-reduction of powdered oxides that contain alloying elements and selected iron powder grades has been selected. Chemical and mass spectrometer analysis has shown satisfactory alloying element distribution. Tensile strength test of the sintered parts has shown that the best results are obtained for specimens produced from low alloyed powder of Indian “Blue Dus” concentrate as the basic iron powder grade. __________ Translated from Poroshkovaya Metallurgiya, Nos. 5–6(443), pp. 8–3, May–June, 2005.     

Stability of iron-based powders with different phase compositions in biological media

Powder Metallurgy and Metal Ceramics - The interaction of iron-based powders with different phase compositions with model biological media is examined in experiments in vitro. The powders are...     

Testing of powders for sensitivity to air effect segregation

Abstract

A loss of blend homogeneity through handling operations can have a major influence on the mechanical properties of sintered products. Plant optimisation to minimise the potential for segregation of blends can be undertaken through an audit of handling operations combined with an evaluation of the materials that are handled through the process. The correct identification of the mechanism of segregation is essential to support strategies to implement the most efficient and cost-effective counter measures. In support of this type of industrial activity, a piece of test apparatus has recently been developed to provide measurements of segregation potential for powders (metal and mineral) that are prone to loss of homogeneity (by composition or particle size) when subjected to counter-directional air displacements through equipment. The test equipment is described and examples given of its output in industrial application.     

Predicting segregation of metal powders

Abstract

Close tolerances in powder quality are necessary for efficient production and control of these tolerances can be achieved only by detailed analysis of materials and processes. The quantification and identification of segregation effects has been a challenge, especially with the powders typically used in PM. An attempt to quantify segregation as a first step towards the predicting segregation behaviour of general powders is reported. Experiments have been undertaken using a lubricated iron alloy powder to analyse rolling segregation, and using am unlubricated powder to determine the effect of height of discharge on segregation. Bulk particulates characterised by small particle sizes, narrow size distributions, free flow, high particle densities and high inter-particle forces require careful experimental procedures to obtain repeatable results.     

Characterization of a Rapidly Solidified Iron-Based Superalloy

Rapidly-solidified powders of an iron-based superalloy were characterized before and after consolidation by hot isostatic pressing. Powders made by inert gas atomization were compared to powders made by centrifugal atomization. Although many of the powder characteristics were similar, the microstructures were not. The inert gas atomized powder structure is cellular while the centrifugally atomized powder structure is dendritic. In general the finer powder particles have the finer micro-structure with the effect more noticeable in centrifugally atomized powders. After consolidation, the differences in microstructure are more dependent on the consolidation temperature and post-consolidation heat treatment than in the powder type or size. Higher consolidation temperatures and/or post-consolidation heat treatment will result in transformation of the as-solidified microstructures. The transformed microstructure and the mechanical properties can in some cases be related to the as-solidified structure. Heat treatment is needed to obtain mechanical properties equivalent to those of ingot metallurgy processed material.     

THE PREPARATION OF CARBIDE-ENRICHED TOOL STEELS BY POWDER METALLURGY

Abstract

Two PM methods of increasing the carbide content of M2 high-speed steel have been investigated: (1) By the mechanical mixing of tool-steel powder with up to 15 wt.-% of either VC or TiC powders of two different size ranges. (2) By the production of fully prealloyed carbide-enriched powders by gas atomization.

The mixed powders were consolidated by either cold isostatic pressing or explosive compaction, and then vacuum-sintered. Fully dense specimens, however, could be obtained only by subsequent hot working. The pre alloyed powders could not be cold compacted and were densified by hot working the canned loose powders.

With the mixed powders, the carbide dispersion depended closely both on the relative sizes and amounts of the tool-steel and carbide particles and onthe total reduction during hot working. With the fully prealloyed powders a very fine uniform carbide dispersion was obtained in all samples. It was found that with proper composition control the new materials could be heat-treated in a manner similar to that applied to M2 tool steel; significant increases were thus obtained in hardness and wear-resistance. The preferred production methods would be to employ mixed powders for TiC-enriched materials and fully pre alloyed powders for VC-enriched materials.     

激光熔覆改性铁基合金涂层的硬度和耐磨性能研究

为提高石油钻井行业中工件表面涂层的硬度和耐磨性,提升工件使用寿命,本文设计开发了含Cr、V元素的三种铁基激光粉末,通过激光熔覆加工工艺进行涂层制备,对铁基激光涂层的物相、硬度和摩擦磨损性能检测,成功开发了硬度高达60 HRC,摩擦系数为0.6094,15分钟50N载荷条件下磨损量仅为0.0007 g的高耐磨铁基激光熔覆涂层,满足石油钻井行业对于高硬度、高耐磨、长寿命的涂层需求。