Pack Cyaniding of Steel 6Kh4M2FS in Order to Increase Heavily-Loaded Die Durability
- PDF / 574,653 Bytes
- 5 Pages / 594 x 792 pts Page_size
- 65 Downloads / 127 Views
669.14.018.258:621.785.533
PACK CYANIDING OF STEEL 6Kh4M2FS IN ORDER TO INCREASE HEAVILY-LOADED DIE DURABILITY N. A. Kostin1 Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 5, pp. 35 – 40, May, 2020.
Technology for low-temperature carbonitriding combined with high temperature tempering of cold-worked die steel 6Kh4M2FS (DI55) is proposed. The high efficiency of a paste-like coating based on amorphous carbon and nitrogen-containing components (carbamide and potassium ferricyanide) during die steel cyaniding in the temperature range from 500 to 580°C is demonstrated. The effect of thermochemical treatment regimes on diffusion layers formed on steel, their phase composition, and properties is investigated.
Key words: die steels, low-temperature carbonitriding, nitrogen-carbon containing paste, structure, phase composition, wear resistance, impact strength.
More suitable materials for heavily loaded cold deformation dies should be acknowledged as heat resistant steels with a reduced carbon content, developed at the end of the last century [9 – 11]. There is greatest interest in hypoeutectoid steels alloyed with chromium and molybdenum, type 6Kh4M2FS (DI55), 55Kh6V3MFS (ÉP569), and others, which after hardening for secondary hardness by analogy with high-speed steels have increased strength, i.e., sr > 900 MPa, and impact strength KC = 1.8 J/cm2 (impact strength of high-speed steel R6M5 KC » 0.05 J/cm2 ). These steels exhibit good production properties and have little sensitivity to a scale factor. The main disadvantage of these steels is the relatively low hardness obtained during heat treatment (56 – 58 HRC ), which is lower than in high-speed steels (62 – 64 HRC ). This may have an unfavorable effect on the die life due to rapid blunting and wear of their operating parts. In order to avoid this disadvantage it is expedient subject a component working surface to strengthening treatment. The of the present work is development and study for surface strengthening technology for the operating parts of heavily loaded cold deformation dies in order to improve their hardness and wear resistance.
INTRODUCTION One of the main factors governing productivity and efficiency of forging production is tool life, in particular heavily loaded dies for cold workpiece deformation made from contemporary materials with increased strength and stiffness [1, 2]. These dies operate under conditions of high dynamic loads and intense friction with significant warm-up in the working parts that causes degradation of the structure and material loss of strength, deformation (crumpling), and acceleration of forging tool wear during operation [3 – 6]. In order to provide a long life for heavily loaded dies made from these materials, alongside high hardness they should have satisfactory ductility, and also increased heat resistance since during operation such dies may warm up to temperatures of 300 – 400°C. High carbon (in order to provide high hardness) die steel types Kh, Kh12F1, Kh12M, Kh6BF, KhVG, and those similar to the
Data Loading...
