RU1793005C - Method of article surface preparation for working by cutting - Google Patents

Abstract

SUMMARY OF THE INVENTION: the method includes nitriding and softening treatment in a cyanide-cyanate melt containing, wt%: sodium cyanide 42-44; potassium cyanite 44-46; ferrocyanide 0.3-0.6 and sodium carbonate the rest at a temperature of 580 ± 10 ° C for 55-65 minutes. 1 tab.

Description

The invention relates to methods for preparing (softening the surface layer of parts) mainly from stainless steels, and can be used in mechanical engineering for machining parts by cutting.

There is a method of increasing tool resistance in the processing of parts made of stainless steel grade 12X18H9T, which has ductility and viscosity, which consists in reducing the viscosity of the material and increasing its hardness by pretreating the parts in liquid nitrogen at low temperature (-283 ° C) for 45- 50 minutes, and then holding in a metal container until the parts are restored to normal temperature (+ 20 ° C) for 2. ,, 3h.

However, the known method has the following disadvantages: uneven nitriding of the surface layer, difficulty in adjusting the depth of the hardened layer, and insufficient efficiency for viscous, alloy steels and alloys.

Closest to the technical nature of the proposed is a method

preparing the surface of stainless and heat-resistant steels for cutting, including copper-plating of the material and: the next exposure to its surface layer of a moist and chemically active medium (water vapor and ammonia) to soften the latter to form porosity (corrosion pits) with a depth less than the depth of cut .

The disadvantages of this method are the length of the preparation process due to the presence of preliminary galvanic copper plating of the parts, followed by nitrogen saturation of the surface layer and its softening in an environment that does not provide a high degree of saturation of the surface layer, as well as insufficient intensity of the softening process. As a result, the surface layer removed during cutting is viscous, while the chip being removed is poorly crushed into separate elements, and when it comes in contact with the front surface of the cutter, significant heat generation occurs, as a result of which the cutter resistance and cutting force productivity are low.

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The purpose of the method is to reduce the complexity of manufacturing parts from stainless steels by intensifying the process of preparing the surface layer.

This goal is achieved by the fact that in the method of preparing the surface of the parts for cutting, mainly from stainless steels, nitriding is used as a preliminary treatment, and treatment in a cyanide-cyanate melt containing, wt.%: Cyanide is used as a softening treatment sodium 42-44; potassium cyanide 44-46; ferrocyanide 0.3-0.6 and sodium carbonate the rest at a temperature of 580 ± 10 ° C for 55-65 minutes,

The method is carried out as follows.

Stainless steel parts are pre-nitrided, for example, in a bath with molten cyanide salts. After saturation of the surface layer with nitrogen, the parts are loaded into the bath for softening; in the melt of cyanide salts with an increased (0.3-0.6 wt.%) content of complex compounds of iron-ferrocyanides.

Complex salts are used for surfacing the baths; 40-45 wt.% NaCH, 42-48 wt.% KCNO, 10-15 wt.% No.COs. An increase in the melt temperature to 580 ± 10 ° С and the presence of a high concentration of potassium cyanite contribute to an increase in the chemical activity of the melt,., Its oxidizing ability. As a result of the chemical interaction of the melt with the surface of the parts, iron complexes Na4Fe (CN) 6 - ferrocyanides are formed. The accumulation of ferrocyanides in the melt in the range of 0.3-0.6 wt.% Promotes the formation in the carbonitride (outer) zone of the surface layer - porosity, softening it, to the formation of corrosive pits. At the same time, the diffusion zone lying beneath the carbonitride zone is more fully saturated with nitrogen.

The melt temperature is controlled by an XA thermocouple and maintained at a given value of 580 ± 10 ° C. The concentration of ferrocyanides is determined by sample analysis after 1.0-1.5 hours.

After finishing softening, the parts are removed from the baths, cooled with ammonia,

the hardness of the surface layer is washed, measured (for control), the nature of the softening of the surface layer is evaluated by the value of the corrosion pits and transferred to cutting.

The results of the experiments are shown in the table.

The table shows the selectivity of the softening process by the degree of crushing removed during processing by cutting

shavings and tool life in accordance with the dependence of the nature of the softening of the surface layer on the impact of a melt of a certain temperature and concentration of the melt, as well as the duration of the process.

As can be seen from the above examples, the proposed method allows to intensify the process of preparation (softening) of the surface layer of parts from

stainless steels to their processing by cutting, as well as to increase the degree of crushing of the chips into individual elements and to increase the tool life by reducing heat release when the contact is crushed

(brittle) chips with the front surface of the cutter.

Thus, when performing the method of preparing the surface layer of stainless steel parts by softening

neither in the melt of cyanide salts with a high content of ferrocyenides

softening process intensity

increases (increases), and the complexity

the manufacture of stainless steel parts is reduced.

Claims (1)

The claims A method of preparing the surface of parts for machining, mainly from stainless steels, including pretreatment and subsequent softening treatment to form porosity, and that, in order to reduce the complexity of manufacturing due to the intensification of the process preparation, nitriding is used as a preliminary treatment, and processing in a cyanide-cyanate melt containing 42-44 wt.% sodium cyanide, 44-46 wt.% potassium cyanite, 0.3-0.6 wt. .% ferrocyanide and the rest is sodium carbonate at a temperature of 580 ± 10 ° C for 55-65 minutes,