SU1502656A1 - Method of gas nitriding of steel articles - Google Patents

Abstract

The invention relates to a method for the gas nitriding of steel products and can be used in mechanical engineering. The aim of the invention is to intensify the process and reduce gas consumption. The gas at each stage is carried out cyclically, and the gas at the beginning of each cycle is carried out for 3-4 hours with a degree of dissociation of 63-67%, then the gas supply is stopped and held for 1-2 hours without gas supply at a dissociation degree of 100%, the number of cycles in the second stage is repeated 4-8 times. 1 hp ff, 1 tab.

Description

The invention relates to the field of chemical heat treatment and can be used in the nitriding of steel products.

Depty of the invention is the intensification of the process and reduction of gas consumption,

The essence of the method is that according to the proposed method of nitriding steel products, including surface preparation of products, heating to the temperature of nitriding, soaking in a saturating gas and cooling, nitriding is carried out with a cyclic ammonia supply, and in the first cycle the gas is supplied in an amount that provides the degree of dissociation is 15-30%; in the second cycle, the process is carried out without supplying ammonia (the degree of dissociation of the remaining amount of ammonia is increased to 70-100%), repeat the cycles until a given crowd reaches us diffusion layer.

In the process of steel saturation in the atmosphere with the dissociation degree of ammonia 15-30%, a high nitride zone is formed, and when dissolved in a medium of more dissociated ammonia more than 70%, further diffusion of nitrogen into the layer without gas supply occurs. It was established experimentally that optimal results for reducing the duration of nitriding of cylinder liners in CHA-6.5.22.10 / 6M furnaces and reducing ammonia consumption are achieved when using a treatment scheme: the duration of the ammonia supply cycle (ammonia dissociation rate 15-30%) is 3-4 h, the duration of the processing cycle without the supply of ammonia (the degree of dissociation of 70%) 1-2 hours

An increase in the duration of the ammonia supply cycle leads to an increased consumption of process gas, and a decrease in this cycle, as well as an increase in the treatment cycle without the supply of ammonia

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Miak, leads to a decrease in uroyn saturation of the layer of nitrogen and surface hardness below the required 1-2 HRA.

The practical ratio of the duration of the cycles with the supply of ammonia and without the supply of hectares depends on the type of the furnace used in the furnace, the mass of the charge, the efficiency of the parts, and be taken from 1: 1 to 2: 1,

Example. Nitriding was carried out on 1 shchlindra of steel 38Kh2MYUL on the well-known and iredlagomu moms. Preliminary n-1-1eska processing, preparation of money surfaces for nitriding (chemical etching, glazing, drying, wiping) are carried out according to serial technology. Nitriding is carried out in a CHA-6.5 "22JO / 6M furnace in order to obtain a diffusion layer of 0.55-0.65 mm TOL1TSINO and 80 HRA surface hardness,

When nitriding in a manner known per se, gas is supplied continuously at a rate of 0.8-1.0. The degree of dsssociation is maintained at stage I (510+ + 10 s, 12 h) - 20–30%, at stage II (530–5 ° C, 52 h) - 50–60%. The nitriding time is sufficient to obtain a predetermined layer thickness.

When nitriding by the known method, the scheme of loading the products, their quantity, output to the mode are the same as in nitriding by the iFthTHONry method. Upon reaching the required temperature in stage I; (510 Л О С, 9 hours for 4 hours ammonia is supplied in the amount necessary to maintain the degree of dissociation {and 15-30%). Then the gas supply completely stops and after 1-2 hours the exposure is followed for 4 hours with gas supply When holding without gas supply, the degree of dissociation of ammonia increases to 70-100%. After the nitriding is completed from Q

Delhi oxJia vJ, aroT up to 300 C in the current aMMii aka, as well as by a known method.

The nitriding regimes according to the known and proposed methods are given in Table 1.

I.; 1 Nosotriation Quality Test (.: Products are elicited by witnesses who are made of the same thread that the cartridges. Dimensions, quantity, quality of preparation according to the surface) and the installation circuit. Lraztsov witnesses alike and obshu. cases x The thickness of the diffusion cross-section, the surface hardness HRA, passes-g is determined by pa samples-tests.ps x. metatlograficheskih did not eat the food of the panis,

P,) Kazatg: Is the quality: Nitriding according to the knowledge and the proposed methods are given in Table 2?

As it is shown from the data of the table, the thickness of the layers and hardness (in both cases, they were obtained in the required tfedelah. Metallographic analysis of the samples-descalers and measurement of the forms, 1diotized nitrided gas was found that nitration was This method does not reduce the quality of the diffusion layer and does not reduce the deformation of the products. At the same time, the process acceleration was reduced by 9 hours by about 40% compared to the known nitriding method.

FORUMUA AND 3 ABOUT IT AND L

 ;. The method of gas nitriding of steel products, including an exposure in two stages; 1 associated ammonia, characterized in that, in order to intensify the process and reduce gas consumption, the gas date at each stage is carried out cyclically, and the gas at the beginning of each cycle is conducted for 3-4 hours with the degree of its dissociation 63-67% I then the gas supply is stopped and the shutter speed is carried out for 1-2 hours without gas supply at a dnsocia1 degree. 100%.

2. The method according to claim 1, wherein t and h and y and II so that the number of gas supply cycles in the second stage is repeated 4-8 times.

Compiled by A. Petrov Editor A. Shandor Tehred L. Oliynyk Proofreader O. Tsiple

Order 50 49/37

Circulation 942

VNIIPI State Committee for Inventions and Discoveries under the USSR Committee on Scientific and Technical Information 113035, Moscow, F-33, Raushsk nab. D. 4/5

Production and publishing plant Patent, Uzhgorod, st. Gagarin, 101

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Claims (2)

Claim 1, A method of gas nitriding of steel products, comprising holding in two stages in dissociated ammonia, characterized in that, in order to intensify the process and reduce gas consumption, the gas supply at each stage is carried out cyclically, and the gas supply at the beginning of each cycle is carried out for 3-4 hours with a degree of dissociation of 63-67% ₍ then the gas supply is stopped · and holding for 1-2 hours without gas at a degree of dissociation. 100%. 2, The method of π. 1, the fact that the number of gas supply cycles in the second stage is repeated 4-8 times. Stage I Stage IT Duration h ----------------------------------- I Duration of the process - Tempera- Time, Consumption Tempeo In r me Gus move stages of nickel, h thenia, h ---------- tour, * C h gas m ’/ h round, ° C h ha <a ₍ H ³ / h. _____ from. gas supply without G1oD.CHP gas with gas supply I stage + II stage without feeding Total Ammonia Consumption - Process 1 »mJ J. Of weight tnmy way 5 10 * 10 12 1,0 5 30 * 5 32 0.3 Method 64 - 5 10 + 10 9 1,0 5 3'3 * 5 0 5 0.8 4 2 * 8 * 30-38 17 55,2 5 5 32 In the first cycle of R.'lder: a cell without gas supply is equal to I hour _________ table 2 Nasva time NII, h Тп / и ^ ina layer, mm of specimen-witnesses Hardness HRa By a known method / 0 0.60 0.60 0.60 2χ55 0.55 0.60 0.55 0.55 0.55 0.55 0.60 81 83 8 g * 82 R3 8 3 * 85 81 81 * 83 ’84 70 Οχ ™ 0.60; 0.60 0.55 2x? 5 0.55 0.55 2x55 0.60 0.60 82 * 82, 84 82 84 81 84 83 83 81 81 * 64 0.55 0.60 0.60 0.55 0.6 (1 0.60 0.55 0.55 0.55 0.55 0.60 80 80 80 80 80 80 * 80 83 * 80 80 * 80 64 0, 60 0.60 0.60 0.60 0.65 0.65 0.65 0.60 0.60 0.60 0.65 81 80 80 * 80 82 82 * 83 * 80 80 * 83 82 0.55 0.60 0.60 0.60 * 84 80 ** 81 81 0.55 0.60 0.60 0.55 82 * ' 84 80 82 0.60 0.60 0.60 0.60 80 80 82 80 0.65 0.65 0.65 0.65 80 81 * 81 80 According to the proposed method 53 0.55 0.55 0.60 0.55 0.60 0.60 ' 0.55 0 _A 60 0.60 0.60 0.60 82 84 82 83 83 ** 83 * 84 8? 83 83 * 83 ** 55 0.60 0.60 0.60 0.60 0.60 0.60 0.60 (L 60 0.60 0.60 0.60 80 81 81 * ' 80 80 81 ' 81 * 80 80 81 81 55 0.60 0.60 0.60 0.60 0.60 0.60 0.60 0.60 0.60 0.60 0.60 81 81 * 82 82 81 * ' 82 ** 81 *** 82 82 81 * 82 * 55 0.60 0.60 0.60 0.60 0.60 0.60 0.60 0.63 0.60 0.60 0.60 82 82 83 81 ** 82 82 83 * 81 82 81 82 55 0.55 0.55 0.60 0.55 0.60 0.60 0.55 0.60 0.55 0.60 2x55 in* 83 81 82 ** 80 81 83 * 81 81 80 ** 82 55 0.55 0.55 2x55 0.55 0.55 0.55 0.55 0.60 0.55 0.55 0.55 82 80 * 80 OT * 80 vg * 81 ” 80 80 81 ** 83 * 82 XX X - 83 XXX- 82 J.A__ 83 0.60 0.60 0.60 0.60 80 80 * 81 ** 81 ** 0.60 0.60 0.60 0.60 81 ** 81 * 82 ** 82 * 0.60 0.60 0.60 0.60 82 * 80 82 82 0.60 0.60 0.60 0.55 83 * 80 80 81 '* ’ 0.55 0.55 0.55 0.55 80 82 81 83