Properties of tungsten - molybdenum high-speed steel with cobalt

Popandopulo, A. N.

doi:10.1007/bf00651789

Cited by 2 publications

(1 citation statement)

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“…The methods, which provide properties enhancement, affecting the solidification structure formation of high-speed steels, form the first group. The solidification processing variables that appear to influence cast structure formation may be identified as follows: alloying design of high-speed steels, [8][9][10][11][12][13][14][15] introduction of inoculant particles or surface-active additions into the melt, [16][17][18][19][20][21][22] pouring temperature of the melt and cooling rate of the tool castings, 15,23,24) purifying process of electroslag remelting, 25) including application of a magnetic field, 26,27) and so on. The processes of hot deformation 1,28) and heat treatment-mainly homogenizing annealing 23) and carburising of the tool castings [29][30][31][32] -belong to the technological methods, which impact greatly on solidification structure transformation.…”

Section: Introductionmentioning

confidence: 99%

Application of Bismuth for Solidification Structure Refinement and Properties Enhancement in As-cast High-speed Steels

Чаус

2005

ISIJ Int.

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In order to exhibit good all-round performance the impact toughness enhancement of as-cast high-speed steels is obligatorily needed. In general, different methods are used commercially to achieve cast structure refinement and, as a consequence, their properties are improved. Introduction into the melt of inoculant particles or surface-active additions is among most beneficial. However, the effect of modifying additions in as-cast high-speed steels has been studied insufficiently. In fact, a restricted number of modifiers is used for structure and properties improvement in the as-cast high-speed steels compared to the common cast alloys. In the present work several kinds of alloys including tungsten-molybdenum high-speed steels of M2 and T30 types and low-alloy tungsten-free 1.1C-5Mo-1.7V high-speed steel were melted to investigate the effect of bismuth on their structures and properties.It has been found that additions of bismuth produce a very fine cast structure and affect the shape of the matrix grains and the morphology of the eutectic carbides as well as the redistribution of the main alloying elements of high-speed steels between solid solution and eutectic carbides. The microstructural changes, induced by bismuth during solidification, are explained by the surface activity of bismuth, which segregates to liquid/solid interface, significantly blocking dendrite growth in the direction along certain crystallographic planes. It has been shown that during eutectic solidification, carbides are also exposed to the barrier effect of bismuth being surrounded in the melt by this element. The main metallographic features of the modified cast structure alongside with the purifying effect produced by bismuth are retained after full heat treatment affecting the final mechanical properties of as-cast high-speed steels. As a result, bismuth significantly increases impact toughness and wear resistance of as-cast high-speed steels but decreases their red hardness.

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