SU1164290A1 - Method of hardening steel components - Google Patents

Abstract

1. METHOD FOR STRENGTHENING STEEL DETAILS. Advantageously, high-chromium steel, including high-temperature carbonitriding, high tempering, heating for quenching, quenching and low tempering, characterized in that in order to increase the depth of the diffusion layer and G W I & -: ssrew W required distribution of hardness over the cross section, high-temperature nitrocementation is performed by applying an aqueous paste containing carboxymethylcellulose and urea, in the following ratio of components, May.%: Carboxymethylcellulose 12.5-15.0 Urea 2.1-3.0 Water Else and heating for quenching is carried out to a temperature 30-50 s lower than accepted. 2. Method pop.1, distinguished by the fact that, at high temperature, carbonitrization is carried out at 3,760-1050 ° C. (L 3. Method pop, 1, distinguished by the fact that high tempering; carried out at 600-700 s for 1-2 hours. 4. Method according to Claim 1, characterized in that the heating for quenching is carried out salt bath and oven with a protective atmosphere.

Description

one

The invention relates to mechanical engineering, in particular to the hardening of steel parts, mainly die tools from high-chromium steel, for example XI2M.

Known methods of hardening a die tool by quenching and tempering using preliminary chemical thermal treatment: nitriding, cyanidation, carbonitriding ij.

However, the known hardening methods do not provide high performance properties for a die tool of high chromium steel operating under cold deformation conditions.

The closest to the proposed technical essence and the achieved result is a method of hardening steel parts, including high-temperature carbonitriding, at the beginning at 800–900 ° C, and then at 940–960 ° C with subsequent extraction at 630 + 10 ° C, quenching and tempering according to the accepted modes &

After processing steel 12KhNZL hardened layer does not exceed 1.1 m

However, the known method is characterized by the duration of the carbonitriding process and the insufficient depth of the hardened layer. In addition, the application of a known die tool for high-chromium steel does not provide the required hardness distribution.

The purpose of the invention is to enhance the depth of the diffusion layer.

The goal is achieved by the fact that according to the method of hardening steel parts, including high-temperature carbon cementation, high tempering, heating for quenching, quenching and low tempering, high-temperature nitro cementation is performed by applying a water paste with carboxymethyl cellulose and urea, in the following ratio of components, May. %:

Carboxymethylcellulose 12.5-15.0

Urea 2.1-3.0

WaterEverything

at the same time, heating for quenching is carried out to a temperature of 30-50 ° C below that adopted.

High temperature carbonitriding is carried out at 760-1050 °.

1642902

High tempering is performed at 600-700 seconds for 1-2 hours.

Heating, under quenching, is carried out in a salt bath or in a furnace with a protective atmosphere.

The method is carried out as follows.

Paste is lubricated with the workpieces, placed in an airtight container, dried at 250–450 ° C with 0.5–2.0 h depending on the size of the container, then heated and kept in the temperature range 760–1050 s. 5 The discharge time depends on the required depth of the diffusion layer. When heated, the pasta components are decomposed with the release of highly active degradation products and the diffusion of the latter into the surface layer of parts with an average speed of, respectively, 0.175; 0.6; 0.865 and 1.17 mm / h for temperatures of 760, 920, 1000 and 1050 ° C. Thus, the diffusion rate is obviously provided by the high activity of the components separated from the paste, and the secondary upward diffusion of carbon and nitrogen into the metal during further quenching. As shown by comparative studies, carbides and carboxytrides formed in the surface layer increase its microhardness I 140 kgf / mm.

Example. Preparing a paste of the following composition, wt.%: Carb oxyl methylcellulose (CMC) 12.5

Urea2.1

WaterEverything

Specified ingredients carefully

mixed, at room temperature to a uniform mass, and applied to the surface of specimens of steel H12F1 and X12M with a thickness of 2-3 mm. Last 5 are placed in an airtight container and stored for 45 min. The heating options in the G-30 selenite furnace are as follows:

heating temperature 760 ° C, holding for 2 and 4 hours;

heating temperature 920 C, holding time of 1.3 and 4 hours;

heating temperature 1000 C, holding time 1.3 and 4 hours; 5 heating temperature 1050 С, overrun and 3 h.

Example 2. Preparing a paste of the following composition, May. %: Carboxymethylcellulose14 Urea.2.5 Water Else Process Operations And heating options are carried out in the same way as Example K Example 3. Preparing a paste of the following composition, wt.%: Carboxymethylcellulose15 Urea 3.0 Water Else Process procedures and options for heating are similar after the samples after surface saturation, they were cooled in air together with the container, after which they were temporarily vacated at 650 + 10 0 for 1.5 h and then polished from one end to a depth of 3 mm. In order to obtain high values of toughness and tensile strength, heating for quenching was carried out in a salt bath at temperatures: steel H12F1 1000 + 10 ° С steel X12M 960 + 10 ° С, which is 30-50 ° С below optimum 1x, with a holding 15 -30 per 1 mm of cross-section. Pre-heating was carried out up to 860 C. The parts were cooled in oil. The tempering temperature is 190 + 10 ° С, the tempering time is 1.5 hours. Heating for quenching can be done in electric furnaces using protective atmospheres. The results of the study of the samples are given in Tables 1 and 2. After heat treatment, the matrix hardness of the parts was HRC 5557, in the surface layers the microhardness was 1140 kgf / mm and gradually decreased to the matrix microhardness equal to HJQ 6 1 3-644 kgf / that -conditions a strong bond between the hardened surface layer and the matrix. After grinding with a clearance of 5.4–0.5 mm, the microhardness on the ground surface did not significantly decrease to 890,940 kgf / mm and with increasing depth it gradually changed to 613. 644 kgf / mm, which allows reat high wear resistance, toughness and strength. The proposed method allows uve. Remove the depth of the hardened layer to 2.5 mm and at the same time increase the plasticity of the matrix. The latter is achieved due to the reduction of the quenching temperature by 30–50 ° C. It is known that die steels become quenched to a grain of 10–11 steel points, which corresponds to the maximum hardness of the matrix layers. Lowering the quenching temperature to 30 ° C does not significantly affect the grain size, which corresponds to 11 points. Hardness after tempering is HRC 56-57. A further decrease in temperature by 30–50 ° C makes it possible to obtain a grain of 12–14 points, and the hardness is HRC 53–56 (after tempering at 200 ° C). A decrease in the quenching temperature by more than 50 ° C significantly reduces the hardness of the matrix layers (HRC 52 and below), which drastically reduces the resistance to plastic deformations. The limiting concentrations of CMC and urea in the paste are justified from the point of view of technology and economics. The content of CMC in which is lower than 12.5%, is impossible due to its instantaneous evaporation during heating, requires prolonged drying, which makes it difficult to seal the muffle. The concentration of CMC in the paste over 15% has little effect on the hardness and depth of uzionnogo layer. The addition of urea within 2.13, 0% ensures the diffusion of nitrogen into the metal along with carbon, lowers the temperature range of austenite, and significantly affects the acceleration of carbon diffusion. A further increase in the concentration of urea in the paste leads to the fact that during the saturation process, fragile carbonitride phases are formed in the surface layers, which degrades the pulping. Example 4, Preparing a paste of the following composition, wt%: Carboxylmethylcellulose12 Urea3 WaterOther Process operations are carried out as in Example 1. Insufficient sealing was detected. It is characteristic that with an increase in the ejection time, the decarburization of the surface layers of the samples occurs.

PRI me R 5. Prepare a paste of the following composition, May, 7,

Carboxylmethylcellulose20

Urea 3

Technological operations are carried out analogously to example 1.

Example 6. Preparing a paste of the following composition, mAs .:

Carboxymethylcell

ш оза оза 20 20

Urea4

WaterEverything

The results of the sample study are shown in Table 2.

Thus, the proposed method provides high surface hardness to a depth of 2.5 mm with a gradual reduction to the core, which ensures high operational stability.

The economic effect per unit of output from the use of a punch to cut down the stator and rotor sheets of an electric motor will be up to 40% due to an increase in wear resistance under operating conditions.

Table 1

The value of microhardness is indicated at a distance of 20-30 µm from the surface.

The microhardness value is indicated at a distance of 15-25 µm from the surface. A non-etched carbonitride layer 10-15 microns thick was found.

The decarburization of the surface to a depth of 0.3-0.4 mm appears.

Table 2

Claims (4)

1. METHOD FOR STRENGTHENING STEEL PARTS mainly of high-chromium steel, including high-temperature nitrocarburizing, high tempering, quenching, quenching and low tempering, characterized in that in order to increase the depth of the diffusion layer and the required distribution of hardness over the cross section, high-temperature nitrocarburizing is carried out by application of an aqueous paste containing carboxymethyl cellulose and a blowing ratio Carboxymethyl cellulose Urea Water and heating under quenching to a temperature of 30 minutes. urea, with selecomponents, May.%: 12.5-15.0 2.1-3.0 The rest is carried out 50 ° C lower at 2. The method according to claim 1, characterized. and with the fact that high-temperature nitrocarburizing is carried out at 76О-1О5О ° С. 3. The method of pop. 1, characterized in that the high vacation · carried out at 600 ~ 700 ° C for 1-2 hours 4. The method of pop. 1, characterized in that the hardening is carried out in a salt bath and in a furnace with a protective atmosphere. 1,164,290 A