Three Important Points that Relate to Improving the Hot Workability of Ledeburitic Tool Steels

Abstract

In this article, the importance of selecting the right process parameters for ledeburitic tool steels, i.e., casting temperature, cooling rate, and soaking temperature, which is needed to improve their intrinsic hot workability, is presented. The results were obtained from investigations in industrial practice and in the laboratory. It was found that inappropriate selection of these process parameters results in the occurrence of carbides that are not usually present in these types of steels, in terms of type, shape, fractions, and their distribution that decreases the steels' hot workability. In particular, a casting temperature that is too high and cooling rates that are too low result in the additional precipitation of carbides, which are not common in these steels, leading to cracking, predominately along these carbide stringers and consequently to a deterioration of the hot workability and the properties of the final products. It was also found that by selecting the proper soaking conditions, it is possible to decrease the negative influence of previous processing parameters on the hot workability.

Improving of hot workability and expanding the temperature range of safe hot working for M35 high-speed steel

“…In order to increase the economy of tool-steels production, both the improvement of their intrinsic hot deformability and the extension of temperature range of safe hot working are required. An improvement of the intrinsic hot workability of tool steels is related to the characteristics of carbides [1][2][3][4] that on the other hand have a large influence on the mechanical properties of tool steels that are used for the manufacture of various tools and dies usually subjected to high mechanical, temperature, chemical and tribological loads. [5][6][7] Referring to the scientific literature, it is known that initial deformations at upper temperature limit, as well as final deformations at lower temperature limit of hot working range, are characterized by considerably decreased hot deformability in comparison to temperatures within the mentioned range.…”

“…[5][6][7] Referring to the scientific literature, it is known that initial deformations at upper temperature limit, as well as final deformations at lower temperature limit of hot working range, are characterized by considerably decreased hot deformability in comparison to temperatures within the mentioned range. [1][2][3][4][8][9][10][11][12][13] The decreased hot deformability at the upper limit is attributed to the characteristics of carbides, i.e., to their type, size, shape, size-and/or spatial-distributions, fraction, melting point of eutectic carbides and/or other phases, etc. Also at lower temperature limit charac-teristics of carbides (i.e., with additionally precipitated secondary carbides) are responsible for pore deformability, where this is related also with the effect of a decreased recrystallization rate.…”

“…Moreover, the characteristics of the carbides are also influenced by the casting temperature and solidification rate. 3,[14][15][16][17][18][19][20][21][22][23] The appearance of cracks on areas that are most exposed during thermo-mechanical processing are thus related to similar conditions as described above for both limits of the safe hot working range. These areas are in combination with increased tensile strains additionally subjected to accelerated heating and/or cooling.…”

Evaluation of structural isotropy of Cr-V ledeburitic steel made by powder metallurgy of rapidly solidified particles

“…: +421 902 535 863; e-mail address: nemec1988@gmail.com works, which makes it impossible to use these materials in as-cast condition due to low toughness and ductility. The size of individual carbide particles as well as the thickness of eutectic networks (austenite + carbides) increase with the decreasing cooling rate during solidification, as quantified recently by Pirtovšek et al [1] and Kheirandish et al [2] for the AISI D2 and AISI D3 steel, respectively. To improve the mechanical properties, the materials are hot worked.…”

“…To improve the mechanical properties, the materials are hot worked. This procedure leads to fragmentation of carbide networks, however, resulting carbide particles are distributed parallel to the working direction in bands and agglomerates whereas the dimensions of the agglomerates depend on the quantitative characteristics of the initial as-cast microstructure of the steel [1]. In addition, spheroidization of the carbides and their coagulation and growth are occurring as a result of the effort of the material to minimize the surface energy of the particles [3,4].…”