SU1157086A1 - Coating for protecting steels from oxidation in hot plastic working - Google Patents

Abstract

COATING FOR PROTECTION OF STALB% OXIDATION AT HOT TREATMENT WITH PRESSURE, containing silver graphite and liquid glass, characterized in that, in order to increase the protective ability against oxidation at 1300-1400 C, it additionally contains manganese ore and water, and as liquid glass - soluble sodium silicate with a modulus of 2.2-2.5 in the following ratio of components, wt.%: Manganese ore 35-38 Graphite silver 29-35 Soluble silicate (P sodium with a modulus of 2.2-2.5 19-21 s Water Remains

Description

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E) .1 The invention relates to compositions for preventing metal from oxidation and decarburization by heating it before hot working with pressure and can be used to protect steels and alloys in the metallurgical and mechanical engineering industry from high temperature corrosion, mainly under process heating rolling, forging, stamping. The purpose of the invention is to increase the protective ability of the coating to oxidize at 1300-1400 ° C. The proposed coatings are prepared according to the following technology. The initial dry components of the fine fraction, the sifted j are weighed in the specified proportions, carefully transferred, the dissolved sodium silicate (, 3) is mixed with water in the specified ratios, and the specific gravity of the solution is 1.25-1.30 g / cm . The resulting solution is poured into the dry prepared components and, after thorough mixing, the coating is heated to. Prepared samples of steel 09G2S, previously cleaned of rust, oil, scale, are heated in a chamber furnace before and covered with a composition by dipping into a bath. The thickness of the coating is 4 mm, the coating consumption per 1 m of the protected surface is 5.0 kg. The coated samples are placed on a pallet and placed in an oven, where they are kept for 8–12 h at 1350 ° C, after which the loss of msta.Shla or scale formation is determined. Upon visual inspection it is established that in some variants the coating is dense without cracks. The coating, in accordance with the requirements of the technical process, is removed by breaking the air hammer and blown off with compressed air. During rolling and free forging, the cookings are coated. The compositions of the proposed coatings and known and their properties are presented in the table. As follows from the table, the incidence of the scale of the metal surface protected by coating 3 is absent. Satisfactory results are achieved with the use of coatings 2 and 4. The selected combination of components makes it possible to obtain sintered, dense without cracks, on metal that prevents it from oxidizing the furnace atmosphere during prolonged (up to 12 hours) exposure and at temperatures up to 1350 ° C. When the ratio of silicon oxide to sodium oxide in soluble sodium silicate, called a modulus and 2.2-2.5, in combination with water, a composition is formed which, in combination with manganese ore, in an acceptable ratio, is optimal for obtaining a dense sintered coating without cracks. Manganese compounds (Mn, O, Mnj O, MpO SiOj, Mn O, 3Hj O, and others) are found in manganese ore, decompose at a temperature of Bmmie, recovering in MpO, and with carbon contained in silver graphite in the required amount, form carbides, which contribute to the hardening of the coating and .. sintering with the base metal. Upon prolonged heating (12 hours), graphite in a given amount, evaporates, forms gas protection, as a result of which the released atomic carbon combines. It combines with oxygen in the furnace atmosphere and prevents the metal from oxidation. Using the spectrographic, X-ray diffraction, and differential-thermal research methods, we have established the optimal conditions for these processes, which are achieved if the proposed limits for the content of components are met. When a large amount of graphite, water and a small amount of soluble sodium silicate are contained in the coating 1, it is not possible to obtain a durable coating due to the high moisture content. As soon as the 1st flow flows down and forms a thin layer, which complicates the work, as a result, the oxygen of the furnace atmosphere penetrates the metal and oxidation occurs, which in the first 8 hours to 0.5 mm / h, and with further heating, the subsequent time (up to 12 hours) ) 0.2 km / h. With an increase in the manganese content and a decrease in water, the strength of the coating 5 decreases, resulting in embrittlement due to the high specific gravity of the liquid compound 3.11 suppressing, which leads to cracking of the coating.

The known coatings 6 and 7 have very low strength and are completely removed from the metal surface, which leads to oxidation. In this case, metal loss in the first 8 hours is 1.0-1.5 mm / h, and during the subsequent time up to 2.5 mm / d.

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Thus, the optimum composition of the coating 2-4 provides protection 570864

surface oxidation during hot working.

Thanks to the formation of hard-to-remove dross n 5 as a result, the labor intensity of finishing products, the losses from rejection due to going beyond the minus deviations in size, overheating, etc. are significantly reduced. to and improves the quality of the metal, reduces the cost of injected products.

Claims (1)

COATING FOR PROTECTION OF STEEL # FROM OXIDATION IN HOT PRESSURE TREATMENT, containing silver graphite and liquid glass, characterized in that, in order to increase the protective ability against oxidation at 1300-1400 ° C, it additionally contains manganese ore and water, and as liquid glass - soluble sodium silicate with a module of 2.2-2.5 in the following ratio of components, wt.%: Manganese ore 35-38 Silver graphite 29-35 ’ Soluble silicate. sodium with a module 2.2-2.5 19-21 Water Remaining ^) SU ,,, (157086 I '1157086 2