Modification of Cr-Mo low alloyed steels by addition of Mn via mechanical milling (original) (raw)
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Modification of Low Alloyed Steels by Manganese Additions
Materials Science Forum, 2007
The efforts to increase the potential PM market [makes necessary to accept new challenges to develop new products. To address this question, we can consider modifying the pores system or the material composition and at same time, the cost of the alloying elements and the compromise between strength, tolerances and cost. The present study examines the sintering behavior and effect of manganese addition, both mechanically-blended and mechanically alloyed, on Cr-Mo low alloyed steels to enhance the mechanical properties. Mn sublimation during sintering results in some specific phenomena to occur which facilitate the sintering of alloying elements with high oxygen affinity. To benefit from the Mn sublimation effects, small Mn particles must be homogenously added in order to increase the specific surface available to sublimate. First, the milling time is optimized to attain a master alloy with 50% of Mn that is diluted in Fe-1.5Cr-0.2Mo water atomized prealloyed powder by normal mixing. ...
Archives of Metallurgy and Materials, 2014
The effects of processing parameters on the microstructure and mechanical properties of Fe-Mn-Cr- Mo-C PM steels are described. Pre-alloyed Astaloy CrM and Astaloy CrL, low-carbon ferromanganese and graphite powders were used as the starting materials. After pressing in rigid die, the compacts were conventionally and high temperature sintered at 1120 and 1250°C, respectively. Sintering was carried out for 60 minutes in atmospheres with different H2/N2 ratios. Cooling rate from sintering temperature was 65°C min-1 (convective cooling). The specimens were subsequently tempered at 200°C for 60 minutes in air. All specimens were tested for tensile strength (UTS), elongation (A), offset yield strength (R0:2), transverse rupture strength (TRS), impact toughness and apparent surface hardness (HV 30). After mechanical tests the microstructure of Fe-Mn-Cr-Mo-C PM steels was studied by optical microscopy. These investigations have shown that, by sintering in inexpensive and safe nitrogen-rich...
PM Manganese Steels for Powder Metallurgy Parts
2012
The ferrous PM industry continues to develop and expand its use of nontraditional PM alloying elements. Price, environmental, and recyclability concerns with Mo, Ni and Cu have driven this expansion. Manganese is a relatively inexpensive, yet effective, alloying element in wrought steels. Nevertheless, oxygen sensitivity has limited the use of manganese in PM steels in the past. The current nitrogen-hydrogen sintering atmospheres with low partial pressures of oxygen now permit its use. The combination of Mn with a moderate level of Mo results in PM steel alloys with mechanical properties approaching those of FD-0405. Equally important, these alloys can be processed under typical, industrial sintering conditions. At higher carbon contents these manganese steels can be used as lean alloy, sinter-hardening grades. These materials are copper-free and nicke-free.The benefits of these ferrous PM alloys containing manganese will be discussed.
HOW PROCESSING VARIABLES INFLUENCE MECHANICAL PROPERTIES OF PM Mn STEELS?
Ni and Cu and in some cases Mo are the alloying elements which have traditionally been used in sintered steels. High performance of PM heavy duty structural parts made from Fe powders is reached mainly by the alloying of Ni. The use of Mn in Fe-base PM structural parts have been avoided because of the high affinity of this element to oxygen. It makes it difficult to sinter steels containing Mn, without oxidation, in industrial atmospheres. However, the powder metallurgy industry also follows 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 has been introduced as an alloying element in Fe based structural parts, on a laboratory scale and also for pilot scale production. In this paper the factors that contribute to the structure and mechanical properties of PM Mn steels are summarised. INTRODUCTION Most powd...
Hardenability of PM Steel Alloyed Using Tailored Master Alloys
HTM Journal of Heat Treatment and Materials, 2023
The ferrous powder metallurgy industry is facing major upheavals currently, which, however, also offer opportunities. New materials and concepts, made possible by tailored design, are a way to prepare for new challenges. Alloying of PM steel through the master alloy route is a concept that combines efficient usage of alloying elements, also of such with high oxygen affinity, with accelerated homogenization via liquid phase sintering. Thus, improved properties can be attained while maintaining dimensional precision, which makes the PM route more attractive. In the present study, different master alloys containing Fe, Si, C, Cr and / or Mn have been admixed to plain iron base powder, the mixes then being consolidated by pressing and sintering. The materials thus produced are compared to two commercial sinter hardening PM steel grades in terms of hardenability. CCT diagrams are presented for all materials, and hardness data from quenching dilatometer experiments are compared to the hardness values achieved by sinter hardening in the lab furnace as well as by a classical quench-and-temper treatment.
Archives of Metallurgy and Materials, 2014
The object of the study was the evaluation of the effect of production parameters on the microstructure and mechanical properties of Cr and Cr-Mo PM steels. The steels were processed from commercial Höganäs pre-alloyed powders: Astaloy CrA, Astaloy CrL and Astaloy CrM with carbon, added in the form of grade C-UF graphite powder in amounts of 0.4 and 0.8 wt. %. Following Turbula mixing for 30 minutes, green compacts were single pressed at 660 MPa according to PN-EN ISO 2740 standard. Sintering was carried out in a laboratory horizontal furnace at 1120°C and 1250°C for 60 minutes in a 5%-95% hydrogen-nitrogen atmosphere. After sintering, the samples were tempered at 200°C for 60 minutes in air. Mechanical tests indicate that the steel based on Astaloy CrA pre-alloyed powder could be an alternative material to steels based on Astaloy CrM. Steels sintered at the higher temperature revealed better mechanical properties.
Study on the effect of alloying elements on the hardenability of PM steels
2018
The hardenability of steels is dependent on the type and amount of alloying elements present. Ni and Cu are commonly used in PM industry and can boost the hardenability of PM steels resulting in improved mechanical performance. In this study the effect of Cu or Ni additions on the hardenability of material grades pre-alloyed with Cr is investigated by generating and comparing the respective CCT diagrams. Results from mechanical testing from a previous study as well as metallographic investigation are used for getting a full picture regarding the hardenability of those steels. These results can be a useful tool for designing and controlling the heat treatment of PM steels.
2013
Manganese is the main alloying element used in the production of high manganese TRansformation-Induced Plasticity (TRIP) and TWinning-Induced Plasticity (TWIP) steels. These types of steels require low concentrations of the impurities such as P, N, C to show their unique properties. Since manganese is introduced to these steels through the application of manganese alloys, the impurity concentrations in the manganese alloys have to be at acceptable levels. In the present study, the purity requirements for ferromanganese and silicomanganese alloys for making TRIP and TWIP steels are studied. It is indicated that the levels of C, P and N in these ferroalloys are relatively high. The removal of these impurities in manganese alloys production and refining involves specific challenges to be responded. The alternative processes for removing these impurities are evaluated and it is shown that impurities removal requires the improvement of the charge materials for the Mn alloys production, o...
Archives of Metallurgy and Materials, 2014
The paper presents the effect of sintering conditions on the microstructure and mechanical properties of low-carbon Mn-Cr-Mo PM steels. It was proved there is no effect of tempering temperature on the properties of Astaloy CrL-base steels, sintered at 1250°C in 5%H2-95%N2 mixture as compared with the properties of those sintered at 1120°C. The properties of Astaloy CrM-based steels, sintered at 1250°C in air were comparable or higher to Astaloy CrL-based steels. The addition of lump of ferromanganese was not sufficient for metal oxides reduction. The structure investigation confirmed the earlier observations that Mn-Cr-Mo PM steels have predominantly martensitic or martensitic/bainitic microstructure.