Effect of carbon in iron-carbon melts on the structure and composition of chromium-alloyed surfaces of cavityless-cast c
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EFFECT OF CARBON IN IRON-CARBON MELTS ON THE STRUCTURE AND COMPOSITION OF CHROMIUM-ALLOYED SURFACES OF CAVITYLESS-CAST CASTINGS V. B. Dement’ev,1 P. G. Ovcharenko,1 and A. Yu. Leshchev1 Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 9, pp. 27 – 29, September, 2012. The effect of carbon in iron-carbon melts on the structure, phase and chemical composition and thickness of chromium-alloyed surface layers of castings obtained by the cavityless method is studied.
Key words: alloying, chromium, cavityless casting.
INTRODUCTION
METHODS OF STUDY
Today steel parts with special properties are often produced using the methods of surface alloying in the process of cavityless casting. The methods of surface alloying are reduced to deposition of alloying elements in the form of paint, paste or powder directly on the specified regions of a consumable pattern from foam polystyrene [1] or to their introduction into the composition of anti-burning coatings [2]. Cavityless casting has some undeniable advantages. One of them is the fact that the precision of cavityless-cast castings is close to that of investment-cast ones [3], while the cost of the production is much lower. The use of methods of surface alloying in cavityless casting gives castings with specified properties of the surface. This method lowers considerably the consumption of alloying elements and reduces the time of additional treatment (carburizing, nitriding, chromizing, etc.) of the surface of cast steel parts. One of the main factors providing specified properties in cavityless casting in addition to appropriate choice of alloying elements for coatings is the content of carbon in the initial iron-carbon melt. If we understand the method of surface alloying in cavityless casting as a counterpart of heat treatment, the composition of the alloying coating and the carbon content in the melt will determine not only the phase composition of the alloyed surfaces but also their structure, thickness, physicochemical, physical and mechanical properties [4]. The aim of the present work was to study the effect of carbon in iron-carbon melts on the structure, thickness, phase and chemical compositions of chromium-alloyed surfaces of castings from steels 10, 45 and U8 in cavityless casting.
Cavityless casting was performed using consumable patterns from foam polystyrene 30 mm wide, 30 mm long and 50 mm high. The alloying element was chromium powder with particle size 0.01 mm from which we prepared a paste by mixing it with an alcoholic solution of an adhesive for foam polystyrene to obtain the needed consistency. The ready chromium-containing paste was deposited with a spatula onto one side of a specimen from foam polystyrene with a thickness of 0.8 – 0.10 mm. Then the paste layer was dried. After this parts of a gating system were glued to the foam polystyrene patterns. The pattern blocks were stained with a gas-permeable burning-resistant coating and dried. To obtain castings the stained specimens with gating system were placed into a f
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