Spray formation of high-density alloy-steel powder blanks

Powder blanks with densities of 96–98% of theoretical have been made under laboratory conditions with a URS-40 gas spray apparatus. The masses of such blanks are up to S kg, and the forming time is 4 sec. They can have any shape (flat or cylindrical), and they can be used either as final products or employed for forming sheet strip by metallurgical forming. The bending strength of the material is 1. S times higher than that in cast material by casting in a mold. Parameters have been identified that need to be monitored during the forming in order to obtain blanks with a given structure.     

Carbonitriding of porous P/M blanks

Conclusions With increasing total blank porosity and decreasing powder particle size the fraction of open pores grows and consequently so does the thickness of the carbonitrided layer. Carbonitride zones were found to form on blank surfaces at a treatment temperature of 970°K. During short-time heating of carbonitrided blanks for HF their diffusion layers were found to undergo partial denitriding and decarburization. It was established that to preserve the quality of the carbonitrided layer it is necessary to perform heating for a short time at a low temperature and also employ a protective atmosphere.Translated from Poroshkovaya Metallurgiya, No. 1(265), pp. 36–40, January, 1985.     

Selection of powders for the production of porous blanks

Summary An analysis is made of experimental data on the relation between the porosity, particle size, filtration fineness, and coefficient of permeability of porous materials. A formula is derived for determining the coefficient of permeability from known values of porosity and particle size.Translated from Poroshkovaya Metallurgiya, No. 11 (47), pp. 9–13, November, 1966.     

Deformation and cracking behavior of preheated cylindrical powder blanks

Conclusions With increasing h_f/d_d the deformability of preheated powder blanks to the formation of the first cracks on their side surfaces grows and the mean density of forged blanks falls. The increase in the deformability of preheated powder blanks brought about by an increase in h_f/d₀ is a result of more intense transverse (tangential in the case of powder blanks of cylindrical shape) deformation of the powder particles located on their side surfaces. The tangential strain of the side surface of a powder blank e, which is due to the spreading of its central zone, is independent of the value of the h_f/d₀ ratio, and can be employed as a criterion for assessing the ductility of a porous powder material undergoing a forging test. A method of calculating the dimensions of starting powder blanks is proposed which makes it possible to ascertain whether a given part can be produced with the required transverse strain.Translated from Poroshkovaya Metallurgiya, No. 1(205), pp. 25–30, January, 1980.     

Properties of porous powder materials

Translated from Poroshkovaya Metallurgiya, No. 7(307), pp. 74–80, July, 1988.     

Moiré method of the stress-strain state of sintered porous blanks in stamping

Conclusions It is demonstrated that the Moiré method can be successfully employed for studying the stress-strain state produced in sintered porous materials by plastic working. The strained state in the stamping of impressions with a flat cylindrical punch in a porous solid is characterized by the existence of two impeded deformation zones (under the punch and at the bottom of the blank) and a nonuniform distribution of displacement rates of points in the solid, deformation rates, and deformation rate intensities H_i on a meridional section. With decreasing starting density all these phenomena become less pronounced, and at a starting density of 60% the impeded deformation zones practically vanish. The distribution of stresses on a specimen section in the initial stage of stamping an impression is characterized-by a marked nonuniformity. The nonuniformity of stress distribution diminishes with decreasing starting specimen density and on passing from upper to lower (bottom) specimen layers. Experimental contact normal and tangential stress distribution curves have enabled deforming loads to be calculated and the locations of tangential stress maxima to be determined. It has been established that tangential stresses have their maxima at the punch corners, which accounts for the increased wear of the punch edge. With increasing starting specimen density the deforming load in the stamping of an impression sharply grows. Calculated values of deforming load, Pcalc, are in good agreement with experimentally determined values, P_exp.Translated from Poroshkovaya Metallurgiya, No. 10(214), pp. 7–13, October, 1980.     

Energy and force conditions of hydrostatic pressing of blanks from powder materials

Conclusions An examination is made of the hydrostatic pressing of metal powders. The total work done in this process is made up of six components. Their determination and methods of calculating them are described. Equations are proposed for calculating the work done in overcoming friction in the gland of the hydrostatic pressure vessel plunger. The equations allow for the variation of the coefficient of friction in the gland, which is a function of pressure in the vessel. Energy expenditure in hydrostatic pressing determined by calculation is in accord with experimental data. This shows that the equations proposed can be employed for choosing plant in the development of new technological processes for the production of parts from metal powders by hydrostatic pressing.Translated from Poroshkovaya Metallurgiya, No. 6(222), pp. 32–36, June, 1981.     

Properties of high-speed steel blanks produced by hot exteusion of atomized powder

Conclusions Hot extrusion of high-speed steel powder enables metal of 100% density to be obtained. The quality of P/M 10R6M5K5 high-speed steel produced by hot extrusion of powder, as assessed by all the indicators investigated, is comparable to that of the same steel produced by hot gasostatic pressing followed by forging.Translated from Poroshkovaya Metallurgiya, No. 9(213), pp. 23–27, September, 1980.