The method of machining of stainless maraging steels

 

(57) Abstract:

The invention relates to the field of mechanical engineering. The method of machining of stainless Maraging steels includes quenching and chemical-heat treatment in the melt containing, wt.%: potassium iodide 70, calcium iodide 30, combined with aging, followed by rubbing the surface with molybdenum disulfide. The method allows to improve the extreme pressure characteristics of a pair of friction, to reduce the coefficient of friction 2 times. table 2.

The invention relates to mechanical engineering and can be used to improve anti-friction and anti-wear characteristics of Maraging steels.

It is known (somyne C. H., Mackiewicz, S. L. Resistance of stainless steels against sudrania friction with lubrication. In Proc. of "Friction and wear in machines", Proc. of XIV, an SSSR, 1960, S. 185, 199. Birman, S. R. low-alloy Maraging steel. - M.: metallurgy, 1974, S. 12), stainless, including Maraging steels exhibit low friction characteristics and ability to adhesion of grease.

The technological process of heat treatment of Maraging steel consists of quenching and subsequent to casinosfree steel. - M.: metallurgy, 1974 S. 18).

Aging Maraging steels occurs in the temperature interval corresponding to the temperature of some types of chemical-thermal treatment.

The most common method of improving the anti-friction characteristics of stainless Maraging steels nitriding, combined with aging (Lakhtin Y. M., Kogan, J. D. Nitriding steel. - M engineering, 1976, S. 74) (prototype). However, the nitriding is a long process, many times longer than the aging time. Vigilant extract at a temperature of aging caused by the inverse of the transition leads to the weakening (rebuild) Maraging steel. Nitriding during the time of aging (e.g., 3 hours) antifriction characteristics of stainless steel does not improve. In addition, the nitriding does not increase the capacity stainless Maraging steels to the adhesion of the lubricant.

A method for machining stainless Maraging steels, including quenching and chemical-heat treatment, combined with aging, which is that the chemical-thermal treatment is carried out in the melt, consisting, wt.%:

potassium iodide - 70

The proposed method can improve the extreme pressure characteristics of friction and to reduce its coefficient of friction.

An example of the method. Processing was subjected stainless Maraging steel OONT. The technological process of heat treatment of this steel consists of hardening at a temperature of 1000oC and subsequent aging at a temperature of 480oC for 3 hours. After processing, the steel acquires a hardness of about 4400 MPa.

Processing was performed according to known (Lakhtin Y. M., Kogan, J. D. Nitriding steel. - M.: Mashinostroenie, 1976, S. 74) and the proposed methods.

Treatment by a known method. After quenching was performed simultaneous aging and nitriding steel OONT in an environment of ammonia, the degree of dissociation of 30-35% at a temperature of 480oC for 40 hours. After nitriding hardness decreased to 3400-3500 MPa.

Processing of the proposed method. After quenching spent aging in the melt, consisting of 70 wt.% of potassium iodide and 30 wt.% iodide of calcium at a temperature of 480oC and holding time of 3 hours (i.e., equal to the time of aging). Maraging steel OONT becomes maximum (about 4400 MPa) TBE the second operation - the rubbing-treated surface of the fine powder of molybdenum disulfide.

Anti-friction and anti-wear characteristics identified at sliding velocity of 0.04 m/s according to the scheme per partial insert. The samples made of stainless steel OONT. Processing the exposed shaft.

Treatment according to known (a) and proposed (b) methods (see tab. 1, 2)

Drawing on the nitrided surface friction molybdenum disulfide does not improve anti-friction and anti-wear characteristics of the friction pair. Application of the proposed method of treatment reduces the coefficient of friction 2-6,5 times and increases the pressure setting 2 times.

The method of machining of stainless Maraging steels, including quenching and chemical-heat treatment, combined with aging, characterized in that the chemical-thermal treatment is carried out in the melt, consisting, wt.%:

Potassium iodide - 70

Iodine calcium - 30

with the subsequent application to a surface by rubbing molybdenum disulfide.

 

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