SU1766976A1 - Quenching medium - Google Patents

Abstract

Use: thermal processing of products from medium carbon steels. The essence of the invention: quenching medium contains incomplete iron salt of polyacrylic acid 0.15-0.30 wt.%: Sodium tetraborate 1.5-2.25 wt.%, Water the rest. 4 tab., 1 Il.

Description

The invention relates to heat treatment, in particular to quenching media, used primarily for cooling parts from medium carbon steels.

The aim of the invention is to improve the quality of quenching,

The quenching medium contains an incomplete iron salt of polyacrylic acid, sodium tetraborate and water in the following ratio of components, wt.%: The incomplete iron salt of polyacrylic acid is 0.15-0.30

Sodium tetraborate 1.5-2.25

WaterEverything

This medium has a working viscosity of 1.2–2.1 and a pH of 7.1–8.0. These physicochemical properties provide high-quality hardening of medium carbon steels. Sodium tetraborate or borax are colorless transparent crystals of

N32B407 UN20.

Borax due to hydrolysis gives a strong alkaline reaction, i.e. performs a role

neutralizer acidic solution of a partial iron salt of polyacrylic acid.

In addition, the introduction of borax reduces the initial viscosity of the solution, which makes it possible not to conduct thermal aging of the medium in order to obtain the desired physicochemical properties. During operation, the composition of the proposed composition is more stable than the known one, in which, due to decomposition of soda ash, due to contact with the heated surface of the parts, the viscosity decreases with increasing operating time.

With the introduction of sodium tetraborate less than 1.5 wt.%, The initial viscosity of the solution does not sufficiently decrease, and the solution has a weakly acidic reaction instead of a neutral one. With the introduction of sodium tetraborate over 2.25 wt.%, The viscosity of the medium approaches the viscosity of water, and the solution has an alkaline reaction. In the first case, the quality of the hardened parts is reduced due to low cooling rates in the pearlite temperature range, which leads to a decrease in hardness. In the second case

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there is a risk of cracking due to low viscosity.

With the introduction of a partial iron salt of polyacrylic acid of less than 0.15 wt.% 5, there is a high probability of thermal cracking due to high cooling rates in the martensitic range. An increase in the concentration of the partial iron salt of polyacrylic acid over 0.4–10 wt.% Impairs the heat transfer and makes cooling in the temperature range of the intermediate transformation slowed down; which leads to the appearance of troscosorbit structures and a decrease in hardness.

The quenching medium is prepared as follows.

For a specific quench tank, the number of components included in the composition is calculated. The tank is then filled with a calculated amount of water, after which the required amount of partial iron salt of polyacrylic acid is added to it, and then this solution is neutralized with sodium tetraborate, which simultaneously lowers the viscosity of the quenching medium to its working value. After mixing, the medium is ready for use.

Example. The proposed medium was studied to determine its hardening properties and cooling ability, affecting the cracking depending on the physicochemical properties of the cooling solution.35

The investigated compositions of the proposed and known media are given in table. one.

Determination of hardness after quenching was carried out on parts of the type of washers of steel 40, s also on more complex shapes such as brackets and levers of steel 45L. The same parts were inspected to establish or no quenching cracks.

The research results are summarized in 45 tables 2-4.

The drawing shows cooling curves for a nickel ball of $ 20 mm in media; curves 1-5 are respectively compositions 1-5, curve 6 is a known composition.

As can be seen from the data table. 2, the best results in terms of hardness and the smallest scatter of the details are obtained after quenching in the medium of the compositions.

The cooling rates in compositions 1-3 are distributed favorably over the entire cooling range. Cooling in medium of composition 5 and known occurs at a slower rate in the temperature range of 800–450 ° C, and in medium of composition 4, cooling is too intense in the martensitic range.

From tab. 4, it can be seen that the viscosity mainly changes during operation. In the medium of the proposed composition, the viscosity is achieved from the moment of the start of operation and during operation remains almost constant. In a medium of known composition, a significant change occurs in the direction of decreasing viscosity during operation.

When using the quenching medium of the proposed composition, the required cooling rates of medium-carbon steels and the stability of the physicochemical properties of the medium are provided, which allows for high quenching quality, eliminating scrap due to reduced hardness and cracks.

Claims (1)

Claims of hardening medium, mainly for medium carbon steels, containing incomplete iron salt of polyacrylic acid, sodium salt and water, characterized in that, in order to improve the quality of quenching, it contains sodium tetraborate as a sodium salt in the following ratio, wt.% : Incomplete ferric salt of polyacrylic acid 0.15-0.30 Sodium tetraborate 1.5-2.25 Water Else. Table 1 table 2 Table 3 Table 4 Ј ft 7cc lot iti toe ten wt g and b t to 12 h Tctr