THE MECHANICAL PROPERTIES OF SOME SINTERED MARAGING STEELS

Abstract

Maraging steels based on 18 and 12% nickel, and containing cobalt, molybdenum, silicon, copper, chromium, titanium, and aluminium in various proportions, were prepared in sintered form under varied processing conditions. The mechanical properties of the steels have been examined with particular reference to the effects of: (1) composition; (2) degree of shrinkage; (3) atmosphere, time, and temperature of sintering; and (4) compacting pressure. The influence of the type of iron-powder base was also studied.

The results demonstrate the possibility of producing, in the sintered and maraged condition and with only slight shrinkage on sintering, tensile strengths of the order of 95–110 kgf mm^?2 (60–70 tonf in^?2). Two compositions appear promising for further development as high-strength materials, and another to provide enhanced ductility. In all cases impact properties are similar to those characteristic of conventional sintered steels.     

INFLUENCE OF THIN OXIDE FILMS ON THE MECHANICAL PROPERTIES OF SINTERED METAL-POWDER COMPACTS

Abstract

The influence of thin oxide films, in the range 200–1200Å thick, on the mechanical properties of sintered iron, copper, and nickel powder compacts has been investigated. As the thickness of the oxide film on the metal powders increased, the properties studied, namely, densification parameter, hardness, and tensile strength improved and attained a maximum at a critical oxide-film thickness, the value of which was ～ 625 Å for iron and nickel and ～ 500 Å for copper. Further increase in thickness to ～ 1200 Å led to a gradual decline in the properties. The improvement in the properties obtained with powders having the optimum oxide thickness was independent of the sintering atmosphere. A probable explanation in terms of activated sintering is given.     

EVALUATION OF THE MECHANICAL PROPERTIES OF SINTERED LOW-ALLOY STEEL COMPONENTS

Abstract

When adopting low-alloy sintered steel components instead of traditional machined steel parts, it is misleading to attempt a direct comparison of the mechanical properties of the two products. Instead it is preferable to consider in each case the service conditions to which the parts are to be subjected and then to devise suitable mechanical tests under simplified loading conditions. The paper describes certain case histories illustrating this point and discusses briefly the definition of low-alloy “sintered steel”.     

复合添加剂对Fe-Cu-C烧结钢力学性能和切削加工性的影响

研究了新型复合添加剂（MnS＋S）、（MnS＋P）和（MnS＋Ca）对Fe－Cu－C烧结钢力学性能及切削加工性能的影响，通过添加（MnS＋S）、（MnS＋P）和（MnS＋Ca）复合添力口剂，可以明显地改善Fe－Cu-C烧结钢的切削加工性，同时保持或提高其力学性能，其中以（MnS＋Ca）效果最佳。     

THE MECHANICAL PROPERTIES OF SINTERED LOW-ALLOY STEELS

Abstract

An unacceptable degree of scatter in the values obtained in tensile tests of sintered parts may occur if their elongation does not exceed a few percent. To ensure the required elongation, the composition of the material selected must correspond to that of alloys made by melting which exhibit a certain minimum elongation in the forged and annealed condition. This minimum is a function of the density of the sintered compact and a knowledge of its value can be of assistance in choosing the correct composition. Values of Young’s modulus, Poisson’s ratio, and impact-resistance are also given as a function of density.     

THE MECHANICAL PROPERTIES OF HOT-RECOMPACTED IRON-NICKEL SINTERED ALLOYS

Abstract

Powder-metallurgy components which are to withstand high dynamic stress are frequently required to possess both high strength and great toughness. This combination of properties can best be achieved by increasing the density of the sintered component and one method of doing so is bot pressing.

This paper deals with the mechanical properties of sintered iron–nickel alloys produced by hot compacting in six stages, as follows:

(1) Preparation of the powder mix.

(2) Production of compacts under a pressure of 8 Mp/cm²

(3) Heating the compacts to 1000°C (1275 K).

(4) Re-pressing the hot compacts in a die heated to 300°C (575 K).

(5) Cooling in air.

(6) Sintering at optimum temperature and time under optimum furnace conditions.

The investigation covered the dependence of tensile strength, elongation at fracture, and Brinell hardness of alloys with Ni contents of 1–10% on the sintering temperature and time, on the furnace conditions, and on raw-material variables.

It was found that Fe–Ni powder-metallurgy parts with a maximum tensile strength of ～60 kp/cm² could be produced. The Brinell hardness reached 190 kp/mm² with 10% Ni content. Elongation at fracture was in the region of 45% with 1% Ni and remained comparatively satisfactory even with high Ni contents if very pure raw materials were used. Powder-metallurgy materials with a tensile strength of 60 kp/cm² and an elongation at fracture of 17% can be obtained by the process.     

烧结钕铁硼的力学性能研究现状

分析了烧结钕铁硼呈脆性的原因，介绍了烧结钕铁硼的力学性能研究现状以及研究烧结钕铁硼力学性能的重要性。     

SINTERED STAINLESS STEEL: II—THE PROPERTIES OF STAINLESS STEEL POWDERS SINTERED IN DISSOCIATED AMMONIA

Abstract

Powders having compositions selected in accordance with the results of earlier work have been processed under conditions simulating industrial practice. The properties that can be obtained under such conditions are described.     

石墨种类对烧结钢性能的影响

本文研究了不同种类石墨对烧结钢件性能的影响,分析了钢件尺寸力学性能随烧结温度升高的变化规律,考察了一种高品质的初生合成石墨的作用。结果表明:TIMREX石墨F10组烧结件中的化合碳比天然石墨组的多,且F10含灰份及水分含量低,从而用量更易控制,使钢件精度增高;F10组石墨有很好的扩散性、反应性及稳定性,有助于密度不同的工件减少尺寸及外形波动,提高了制品的强度及稳定性。     

低碳锰铌钢的工艺制度与组织性能的关系

对低碳锰铌钢的控制轧制和加速冷却工艺制度进行了实验研究,得出终轧温度为７８０±１０℃、终冷温度为６７０±１０℃、冷却速度为１０℃／ｓ的控轧控冷工艺,同时给出加大冷却速度对提高钢屈服强度和抗拉强度的定量影响数据。     

影响奥氏体烧结不锈钢性能的工艺因素

本文研究了原料粉末质量、压制压力、烧结工艺等对奥氏体烧结不锈钢材料收缩率、密度、极限拉伸强度、延伸率及抗腐蚀性能的影响。提出了以压制压力为588-700MPa;500-600℃预烧半小时;在氢气保护下于1300-1330℃烧结1-1.5小时;于冷却水套中冷却的工艺。用这种工艺生产的制品,可获得均匀、稳定的细晶粒奥氏体组织,从而具有良好的综合物理机械性能和抗腐蚀性能。     

热处理渗铜烧结钢的性能和组织

研究了不同原料铁粉，基体骨架铜含量以及不同淬火温度对渗铜钢热处理后密度，硬度和抗弯强度的影响。结果表明，采用水雾化铁粉添加少量铜中高碳基体骨架，溶渗后经淬火－冷处理－低温回火，其硬度大于ＨＲＣ４５，密度大于７．６０ｇ／ｃｍ＾３抗弯强度达１６００ＭＰａ，组织为回火马氏体加铜相；断裂主要是通过铜相的撕裂，显示出塑性断裂的特微。     

球磨参数对TiC基钢结硬质合金性能的影响

本实验研究了球磨方式和球磨时间对于钢结硬质合金致密化的影响 ,结果发现 :在一定的球磨时间里 ,行星式高能球磨相对于普通球磨方式而言 ,可以减少粉末在球磨过程中的氧化程度 ,促进钢结硬质合金在烧结过程中的致密化进程 ,提高材料的密度和强度。     

THE STRUCTURE AND PROPERTIES OF SOME INTERNALLY OXIDIZED ALLOY POWDER COMPACTS

Abstract

The advantages of internally oxidized structures produced by powder-metallurgical techniques are briefly reviewed and discussed. A metallographic survey of the structures of some internally oxidized copper alloy and nickel alloy powder compacts is presented, and the effect of pressing and sintering variables upon the density and hardness of the product is established. Hot-hardness data up to 800°C, and also some tensile data up to 620°C, are presented for certain alloys.

It is concluded that although dispersion-hardened structures can be prepared by the pressing, sintering, and internal oxidation of appropriate alloy powders, and although the methods described offer a valid comparison of the properties of the various alloys studied, optimum mechanical properties are undoubtedly developed only after the powders are hot worked. The latter treatment densifies the product, removes any porosity in the structure, and increases the stored energy in the material.     

爆炸处理消除焊接残余应力对奥氏体不锈钢焊接接头机械性能的影响

对爆炸处理消除奥氏体不锈钢焊接残余应力前后焊接接头常规机械性能进行对比试验研究，发现爆炸处理在显著消除焊接残余应力的同时，对材料机械性能影响不大。     

粉末冶金高强度烧结钢的疲劳特性

通过测定N-110烧结钢旋转弯曲疲劳下的S-N曲线、疲劳裂纹扩展速率da/dN以及疲劳门坎△K_th,对烧结材料的疲劳特性进行了探讨,初步阐明了孔隙的存在对各种疲劳性能的影响规律以及热处理状态与疲劳性能之间的关系。     

STRUCTURAL AND MECHANICAL PROPERTIES OF SINTERED MAGNESIUM PRODUCTS AT ELEVATED TEMPERATURES

Abstract

The use of products sintered from pure magnesium or a magnesium alloy is envisaged for certain structural components in the field of nuclear technology. The mechanical properties at elevated temperatures (up to 525°C) of sintered compacts of oxidized Mg-Zr or Mg-MgO of various particle-size ranges (～20–800 μm) are discussed. Comparison of the tensile properties and of the values of the creep parameters in tension and compression emphasizes the direct dependence of the increase in mechanical strength at elevated temperatures on the content and distribution of the oxide and on the particle-size distribution of the oxidized powders. Metallographic examination of the various materials confirms these observations. The ductility varies with the size of the original particles.

Finally, data are presented for comparison on a material obtained by sintering magnesium-zirconium and magnesium-aluminium cuttings. In this case hardening occurs as a result of the formation of intermetallic compounds between the zirconium and the aluminium.     

中高碳量粉末锻造钢的综合性能

研究了中高碳量Fe-2Ni-0.5Mo-xC及Fe-2Cu-xC粉末锻造钢经淬火-回火热处理后的综合力学性能。由4600合金粉制造的Fe-2Ni-0.5Mo-0.6C成分和由水雾化铁粉制造的Fe-2Cu-0.5C成分的粉末锻造钢具有良好的综合力学性能。前者抗拉强度达1570MPa,硬度为HRC45.2,冲击韧性为31.4J/cm2。后者抗拉强度达1090MPa,硬度为HRC40.7,冲击韧性为38.0J/cm2。可以满足要求具有高强度、良好韧性以及较高耐磨性的结构零件的需要。     

稀土元素对烧结铜钼钢性能的影响

研究了稀土元素对烧结铜钼钢性能的影响。探讨了稀土在烧结铜钼钢中的作用机理。结果表明:适量加入混合稀土,可明显提高烧结铜钼钢的机械性能,特别是抗拉强度与冲击韧性;含0.6％混合稀土的F0212J烧结铜钼钢,当用于生产中高强度结构零件时,可减轻重量约12％,降低成本25％～30％。作者认为,稀土具有脱氧保碳、细化晶粒、改变孔隙形态与分布、变质夹杂物之作用。