SU1627587A1 - Composition for borating of steel parts - Google Patents

Abstract

The invention relates to metallurgy, in particular to the chemical and heat treatment of metals and alloys, and can be applied to improve the wear resistance of the surface layers of iron-based alloys in mechanical engineering, machine-tool construction and other industries. The goal is to improve the quality of products by reducing the porosity and increasing the frequency of use of the composition. The composition for boronization of steel products contains the following components, wt%: boron carbide 40-50; sodium fluoride 3-7; iron dross 30-50; graphite 2-5, calcium carbonate 5-10. 3 tab.

Description

The invention relates to metallurgy, in particular to chemical heat treatment, and can be applied to improve the wear resistance of the surface layers of iron-based alloys in mechanical engineering, machine-tool construction, in the construction industry and in other industries.

The purpose of the invention is to improve the quality of products by reducing the porosity of the surface and increasing the multiplicity of use of the composition.

The composition for boring steel products, containing boron carbide, sodium fluoride and iron oxide, additionally contains graphite and calcium carbonate (CaCO3) in the following ratio, wt.%:

Carbide boron 40-50

Sodium Fluoride 3-7

Iron dross 30-50

Graphite 2-5

Calcium carbonate 5-10

The proposed powdery boroning composition, in contrast to the known one, has a longer service life and eliminates the formation of pores in the hardened layer due to graphite and calcium carbonate introduced into the mixture.

The introduction of graphite helps to protect the saturating mixture from oxidation due to its interaction with atmospheric oxygen. In addition, its presence in the mixture increases the saturability due to the reduction of boron from boron oxide.

The addition of calcium carbonate to the mixture prevents sintering of the components of the proposed composition and eliminates the need to grind the mixture before re-using it.

When the content of graphite in the mixture is less than 2%, the lifetime of the mixture is reduced due to its premature oxidation and loss of saturability after 3 times use.

The introduction of graphite into a saturating mixture in an amount of more than 5% leads to the formation of small pores in the hardened layer, which ultimately reduces the wear resistance of the product.

The optimum content of calcium carbonate in the mixture, as established empirically, is 5-10%. When its content is less than 5.0%, sintering of the mixture is observed, which requires additional costs for its grinding before reuse. The introduction of the named component into the mixture in an amount of more than 10% reduces the saturability and the lifetime of the mixture.

Example. Conductor diffusion saturation of plates СМ 816А 04-283Б and СМ 816А 04-286Б from steel 20 with dimensions 290x155x9 and 155x132x9 mm. The compositions are prepared by mixing powdered components: boron carbide (GOST 5744-76), sodium fluoride (GOST 4463-76), iron oxide, graphite (GOST 6912-74) and calcium carbonate (GOST 4539-76). Iron scale is a waste in the process of heat treatment of forging billets. The average composition in the recipe used scale, wt.%: Fe 78; SI 0.15; Mn 0.40; S 0.05; P 0.02.

Plates are placed in a container, covered with a mixture and covered with a lid. The container with the plates is placed in an electric furnace with a temperature of 930 ° C. The duration of diffusion saturation is 4 hours. Then the container is discharged into the air and cooled. Next, the mixture is poured out of the container, remove the hardened plates from it. Install a new batch of plates into the container and repeat the operations mentioned above. In this way, the mixture is used 5-6 times (Table 1). The exhaustion of the mixture is judged by reducing the surface hardness and reducing the depth of the hardened layer. By reducing the surface hardness to HVs 1000, the mixture is regenerated by introducing 3-4% of sodium fluoride activator into it.

When processing plates of steel 20 in the mixture of the proposed composition, the presence of pores in the hardened layer was not detected.

In tab. 2 shows the results of studies of the properties of the hardened layer after boroning steel 20 in a mixture containing May. %:

Boron carbide 45 Boric anhydride 10

Sodium fluoride 5

Iron Dross 40

Samples of sizes 40x40x9 mm were saturated at 930–10 ° C for 4 h. The results of the studies showed that the mixture of known composition quite rapidly loses its saturability, as evidenced by the sharp decrease in the hardness of the hardened surface. Moreover, the surface hardness below 1000 HVs is observed in the case of using the known composition already 3 times. In the case of saturation of steel 20 in the proposed composition, the activity of the saturating mixture is maintained for 5 times its use.

The results of processing plates of steel 20 in the proposed and known compositions are given in table. 3

Thus, the mixture of the proposed composition can be used 5-7 times, and the mixture of known composition - 2 times.

Claims (1)

Invention Formula The composition for boring steel products, including boron carbide, fluoride sodium and iron oxide, is characterized in that, in order to improve the quality of products by reducing the porosity of the surface and increasing the multiplicity of use of the composition, it additionally contains graphite and carbonate calcium in the following ratio, wt.%; Carbide boron 40-50 Sodium fluoride 3-7 Iron oxide 30-50 Graphite2-5 Calcium carbonate 5-10 Surface properties of steel plates 20 after boronation in the mixture of the proposed composition Table 1 Table 2 The properties of the hardened layer of steel 20 after boriding in known composition The effect of the composition of the mixture on the shortness of its use and the quality of the reinforcement of a little layer on strikes 20 Table 3