Turning and drilling of parts made from sinter hardenable steel powders

Abstract

The constant demand for improved mechanical properties and lower production costs of PM parts has lead to the development of sinter hardenable steel powders. These powders produce fully martensitic microstructures by appropriately controlling the cooling rate during the sintering operation. Thus, the heat treatment operation (oil quenching) that would generally be required to obtain hardened parts can be eliminated. However, machining of the relatively hard sinter hardened parts is difficult.It then becomes critical to optimise the tool selection and the machining conditions, such as surface speed and feed. This paper presents guidelines for the turning and drilling of parts made with sinter hardenable powders, as well as a discussion on the effect of manganese sulphide particles and chip formation during turning.     

粉末冶金烧结钢的加工性

通过烧结和在铣床上切削加工的实验，研究了添加硫化锰和氟化钙的烧结钢的加工性。结果显示，添加不同的改善切削加工性的第二相颗粒后的粉末烧结制品，其切屑形态有很大差异。添加硫化锰或氟化钙，其切屑变小，利于从孔中排出。在雾化前加入硫化锰的烧结制品，其加工性最好，1个d9．5mm的高速钢钻头可在其中钻凿532个总深13．51m的孔而毋需更换。硫化锰和氟化钙在混料过程中会发生团聚现象，降低了切削加工性。改善硫化锰和氟化钙的分布，将会改善切削加工性。     

Fe-Cu-C及Fe-Cu-C-MnS烧结钢车削实验

研究了Fe－Cu－C及Fe－Cu－C－MnS烧结钢的车创加工性。通过对烧结钢车削力和刀具时用度的测试认为，采用不同原料铁粉制成的相同成分的Fe－Cu－C烧结钢车削力较大，刀具耐用度较低，因而其车削加工性较差；在Fe－Cu－C烧结钢中添加一定含量的MnS可以明显改善车削加工性。     

Effect of MnS powder additions and vibratory ball peening on corrosion resistance of sintered 316LSC stainless steels

Abstract

As sintered parts are to be machined after sintering, the MnS powder is usually added to improve the machinability. Vibratory ball peening is used for deburring and improving the surface finish of sintered components in local PM industries. The effect of the MnS powder content and vibratory ball peening on the corrosion resistance of the sintered 316LSC alloys was investigated. Experimental results show that the addition of MnS powder slightly decreases the sintered density. The weight loss rate of the sintered specimens immersed in the 10%FeCl₃ corrosion test solution increases slightly with increas- ing MnS content, but decreases with increasing sintering temperature. Vibratory ball peening effec- tively decreases the weight loss rate of the sintered stainless steels. The chromium atoms actively migrate across the phase boundary and diffuse into the MnS particles during sintering. This intensive chromium diffusion affects the corrosion performance of the sintered alloys with MnS added. The surface morphology of the as sintered and the ball peened specimens before and after the corrosion test were studied with a SEM.     

用烧结硬化工艺生产汽车分动箱链轮

烧结硬化工艺可利用通过烧结炉一次烧结生产强度与表观硬度高的粉末冶金零件。烧结硬化工艺省掉了烧结后的热处理，从而消除了与热处理相关的一些缺陷，诸如零件的扭曲变形、油污染及增大生产成本。为烧结硬化应用开发了低合金钢粉。这些低合金钢粉与可利用的装备有强化冷却能力的装置的烧结炉相结合，使烧结硬化对于因大小或形状难以淬火的零件特别有吸引力。Masco Tech Sintered Components最近开发的汽车分动箱链轮，就是成功应用低合金钢粉与烧结硬化工艺的一个范例。这篇论文阐述了粉末混合料配方与烧结参数对选择的可烧结硬化材料的力学性能的影响，和将链轮的主要生产线从传统的成形、烧结、精整及淬火的生产工艺改造成生产成本较低的成形与烧结硬化生产工艺采取的方法。     

Making better PM products

A two-day seminar dealing with machinability of PM parts is to be held in Dearborn, Michigan, in early December. The meeting at the Hyatt Regency on December 3-4 is designed to provide delegates with in-depth knowledge and understanding of both the fundamental and practical aspects of machinability in PM parts. Among the topics to be covered are improving operations to make higher quality parts, reducing costs, increasing productivity and greater profits.This is a short news story only. Visit www.metal-powder.net for the latest powder metallurgy industry news.     

添加MnS对烧结铁基材料切削性能的影响

论述了添加ＭｎＳ对粉末冶金材料的压制性、力学性能和切削性能的影响。添加ＭｎＳ后材料压缩性降低１５％，冲击韧性降低２１％，抗拉强度降低５％，延伸率降低２９％。但改善了材料的切削性能，切削力下降１９２％，切削刀具的磨损明显减少。     

铜铁预合金粉末对铜基摩擦材料摩擦磨损性能的影响

利用粉末冶金方法制备了含不同质量分数铜铁预合金粉末的铜基摩擦材料,并在不同温度下对材料摩擦性能进行测试。结果表明:铜铁预合金粉末的引入使得铁元素在烧结后铜基体中及铜基体与其他组元界面处析出,阻碍了烧结,导致材料密度下降。存在于界面处的铁以及反应生成的珠光体成为硬质强化相,使得材料的磨损机理从纯铜基体时的黏着磨损向添加铜铁预合金粉末之后的磨粒磨损转变,导致摩擦系数先下降后上升。200～250 ℃为摩擦系数保持稳定的临界温度。当超过临界温度时,摩擦表面铜软化,其自润滑作用使得摩擦系数下降。含30%铜铁预合金粉末的铜基摩擦材料（质量分数）的摩擦磨损性能最佳,这是由于此时摩擦材料兼具铜良好的塑性以及生成的适量硬质相能够强化摩擦表面。     

Factors influencing the machinability of sintered steels

The machinability of powder metallurgy materials is considered to be poor. The main factors that deteriorate the machining of PM parts are introduced in this work. They are those which participate in different ranges and modes in the formation of a sintered body with required mechanical and other characteristics. The effect of base iron powders, alloying systems, and alloying elements, as well as the effect of processing routes, especially solid-state sintering, are mentioned. The characteristic heterogeneous microstructures are presented. The effect of porosity in terms of interrupted and deformation cutting theories is discussed and demonstrated. The main measures to improve machinability of PM materials are described.     

Ultrasound-assisted drilling of copper and pre-alloyed powder metallurgy steels

Powder metallurgy (PM) steel components are generally considered ‘difficult’ to machine when compared with their wrought counterparts. Thus, efficient and cost effective machining strategies have to be devised. This paper summarises the results obtained by utilising ultrasounds to improve the machining behaviour of copper and sinter-hardenable PM steels. The effect of ultrasonic assisted drilling on tool life with and without admixed MnS is discussed as well. These results are compared to conventional machining methods and show that, for FC-0208 PM copper steels, tool life is increased by 180% and can be several thousand per cents higher if used in combination with admixed MnS. At the same time, the use of ultrasounds permitted to increase productivity by 86%, owing to the possibility of using higher feed rates. Similarly, for FLNC-4408 pre-alloyed PM steels, tool life was increased by 130% and productivity was 60% higher than when no ultrasounds were used.     

氧化锰矿和硫化铜矿酸浸生产海绵铜与化学二氧化锰的研究

氧化锰矿粉在酸性水溶液中有很强的氧化性，锰难以直接溶出，为达到溶浸目的，应有电极电位较低的还原剂存在。作者就氧化锰和硫化铜矿粉直接酸浸制取海绵铜和化学二氧化锰（ＣＭＤ）新工艺进行了试验探讨     

Improved Precision of Sintered Steel Components Made from Partially Prealloyed Copper—Iron Powders

Abstract

An improvement in the dimensional tolerances of sintered components by at least one ISO grade was obtained in field tests comprising several thousand parts by using a partially pre-alloyed copper-iron powder instead of an elemental mix. This effect is explained by the fact that segregation of the constituents is minimized. Further tests have shown that sintered components made from partially prealloyed powders have a more even microstructure and better distribution of the alloying elements, resulting in components with fewer defects in the microstructure, than do components made from the corresponding elemental mixes.     

Structure and mechanical properties of sintered Ni free structural parts

Abstract

Ni, Cu and in some cases Mo are the alloying elements which have traditionally been used in sintered steels. High performance of powder metallurgy (PM) structural parts from Fe powders is reached mainly by alloying of Ni. The use of Mn in Fe base PM structural parts has been avoided because of its high affinity to oxygen. It is difficult to sinter Mn steel, without oxidation, in industrial atmospheres. However, the PM industry follows also possibilities in order to develop Ni free sintered steels which render as high mechanical properties as diffusion alloyed Ni containing sintered steels and further fulfil the requirements of health protection. In recent years Mn have been introduced as alloying element in Fe based structural parts, on laboratory scale and also for pilot scale production. In this paper the factors that contribute to the structure and mechanical properties of sintered Mn steels are summarised.     

Consolidation of diamond tools using Cu–Co–Fe based alloys as metallic binders

Abstract

The present work reports the results obtained on the evaluation of both the response of commercially available Cu–Fe–Co pre-alloyed powders during processing for the consolidation of diamond tools under several fabrication routes, and the performance of the tools during in field cutting operations. The new metallic binders look attractive since they combine good sinterability with adequate values of hardness and wear resistance, as observed from the cutting tests carried out on granite and marble. The consolidation routes under research were conventional hot pressing, pressureless sintering, and hipping after sintering. The amount of copper contained in these alloys leads to fully dense parts by hot pressing at temperatures approximately 150°C lower than those used for cobalt. Pressureless sintering experiments showed that full densification requires the application of hipping post-sintering treatments. During processing under non-reducing atmospheres, the presence of metallic oxides contained in the powder was observed to exert a direct influence on the degradation of the diamond grits.     

含硫齿轮钢20CrMnTiH中硫化物对切削性能的影响

在不同切削速度(200～230 m/min)和切削深度(0.5～2 mm)下试验研究了普通20CrMnTiH齿轮钢(0.006%S)和含硫20CrMnTiH齿轮钢(0.031%S)的切削性能。结果表明,随切削速度增大,刀具的磨损增大,在200 m/min,0.031%S钢是0.006%S钢刀具的使用寿命的2.8倍;在230 m/min,0.031%S钢是0.006%S钢刀具使用寿命的2.6倍;随切削深度增加,切削力增加,但在相同切削深度下,0.031%S钢的切削力低于普通0.006%S钢;由于0.031%S钢存在≤6μm的MnS夹杂,使切屑易断,并硫化物夹杂能够包裹Al₂O₃尖晶石夹杂,减少刀具磨损,提高钢材的切削性能。     

Iron based partially pre-alloyed powders as matrix materials for diamond tools

Abstract

The hardness and bend strength of diamond tool matrix materials prepared from partially pre-alloyed Fe–Cu powders and from elemental powder mixes of equivalent composition has been compared. After sintering at 890^oC, the hardness of the partially pre-alloyed powder matrix was 81.72?HRB, 9.3% higher than that of the mixed powders matrix; sintering at 870^oC gave the highest bend strength (634.85 MPa), 11.6% higher than that of the mixed powders matrix. The improved homogeneity of alloy elements distribution achieved in the matrix by pre-alloying was shown generally to increase the hardness and strength. The cutting performance of diamond tool segments prepared with the pre-alloyed matrix material met standard requirements; overall, the pre-alloyed material is felt to offer significant manufacturing and performance benefits.     

还原铁粉对Fe-1.1Ni-0.5Mo-0.5Cr合金组织与性能的影响

在惰性气体雾化法制备的Fe-1.1Ni-0.5Mo-0.5Cr预合金粉末中添加1.5％的Cu粉和0.6％的C粉(均为质量分数)以及还原铁粉(添加量分别为0、10％、20％和30％),混合均匀后在600 MPa压力下模压,在1 180℃烧结1h.烧结合金经180℃/1h回火处理后,进行密度、硬度、拉伸力学性能检测以及显微...     

硅黄铜预合金粉末在金刚石工具中的应用

采用气水耦合雾化法制备了含有质量分数0.4%稀土Ce的硅黄铜预合金粉末, 在680~720 ℃热压烧结预合金粉末, 获得了致密烧结体。通过洛氏硬度计测试烧结体硬度为HRB62~65, 使用万能力学实验机测试烧结体抗弯强度为530~550 MPa, 利用扫描电子显微镜观察烧结体基体微观组织为α相黄铜, 组织中还存在蠕虫状及花状的弥散银灰色(β'+γ)相。选择添加质量分数20%的硅黄铜预合金粉末配方(铁粉+铜粉+锌粉+预合金粉末)制备花岗岩切割用金刚石刀头, 与单质粉末混合配方(铁粉+铜粉+锌粉)制备的刀头相比, 添加硅黄铜预合金粉末的刀头硬度增加22%, 抗弯强度降低8%, 刀头锋利度和使用寿命整体提升, 胎体磨粒夹杂减少, 并出现大量排屑沟槽。     

适用于工业制造的烧结硬化解决方案

在粉末冶金零件生产中,烧结硬化被认为是替代后续热处理工序的一种经济易行的方案。近年来烧结硬化材料和工业应用已取得很大进展,其中Ni和Mo是最常用的合金元素,然而Ni和Mo价格的增长和剧烈波动使制造商面临巨大的成本压力。含Cr合金材料虽然具备合理的价格和良好的淬硬性,但对烧结气氛类型和质量的严格要求限制了其更广的应用。为拓宽烧结硬化的应用范围和增强粉末冶金工艺的竞争优势,市场强烈需求同时具备成本效益和高度稳定性的合金材料。通过在工业条件下生产典型的粉末冶金零件,对比了Ni-Mo和Cr-Mo体系的传统粉末冶金材料与新开发的低合金材料的力学性能以及尺寸稳定性,从而给出适应不同工业生产条件的材料选择方案。     

Manufacture of magnetic cores from various iron powders

Conclusions Coercive force measurements were made on grades PZh4M3, PZhCh3SV, PZhCh3MV, NC 100.24, PZhR(0) and PZhÉ iron powders and magnetic cores heat treated in the temperature range 750–1200°C. Iron powders of large specific surface are characterized by greater coercive forces compared with powders of small specific surface. Grades PZhCh3SV, PZhCh3MV, NC 100.24, and PZhR(0) iron powders are suitable for the manufacture of magnetic cores after they have been alloyed with elements decreasing internal stresses in alloys. Sintered magnetic cores from PZhÉ electrolytic iron powder meet all the requirements of TU 16-538.225-74 without alloying. The properties of grades EMP300M, PM282N, KiP 270.MS, and SC 100.26 iron powders were assessed. KiP 270.MS and SC 100.26 powders possess the same properties as PZhCh3SV, PZhCh3MV, and NC 100.24 powders, but in grade SC 100.26 powder high oxygen contents are not permissible. Consequently, magnetic cores made from this powder will exhibit high coercivity. Grades EMP300M and PZhR(0) iron powders are similar in all their properties, and the magnetic characteristics of cores made from them will therefore also be comparable. Grade PM282N iron powder is produced by the electrolysis of solutions and characterized by a dendritic particle shape. Owing to the large specific surface of the particles of this powder, its coercive force will be 25–30 A/m greater than that of PZhÉ. In the manufacture of magnetic cores from this powder recourse must therefore be had to alloying with silicon in order to decrease their coercivity.Translated from Poroshkovaya Metallurgiya, No. 6(234), pp. 73–78, June, 1982.