RU2411111C2 - Method of anode dynamic hardening of part from current conducting material - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to combined methods of processing involving application of electric field and mechanical surface hardening. Proposed method comprises mechanical and anode processing of part surface by metal granules with application of electric field in weal electrolytes based on non-toxic salts at low DC voltages, the processed part making the anode. Processing is carried out in three stages. At first stage, metal granules are placed on part processed surface. Then, electrolyte is fed along processed surface at the rate allowing granules transfer relative to processed surface, DC current is fed to granules and part to perform anode removal of allowance making the difference between total processing allowance and that for thirst processing stage. At second stage, current and electrolyte feed are interrupted to use the same granules for vibroimpact hardening to required amount of cold-hardening. At second stage, cold-hardened layer is anode-dissolved using current and electrolyte similarly to first stage on adjusting amount of allowance removal till amount of cold-hardening that provides for maximum strength of part material.

EFFECT: guaranteed cold-hardening that allows maximum durability of parts.

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Description

The invention relates to combined processing methods with the application of an electric field and mechanical hardening of the surface layer. It can be used in mechanical engineering when processing the outer and inner surfaces of machine parts.

There is a method of electrochemomechanical processing of the inner surfaces of parts, where the shock effect of the calibrating element is performed to obtain local hardening, accelerating the removal of metal in places of high stock (SU No. 1085734 A, IPC B23P 1/04, B23P 1/10, 04/15/1984).

The disadvantages of the method include the possibility of implementing it when processing only internal surfaces, the inability to use to obtain guaranteed cold work with a large depth and size of the riveted layer after the previous treatment.

A known method of dimensional electrochemical processing, combining sequential effects on the part of the hardening action of the tool to achieve hardening and anodic dissolution during removal of the tool (SU No. 1192917 A, IPC B23H 3/00, 11/23/1985).

The disadvantages of the method include uncontrolled hardening of the processing zone, which does not allow to increase the fatigue strength of the machined parts.

The closest analogue is the processing method, in which the combined surface hardening of the channels is achieved due to the anodic dissolution of the allowance until the hereditary hardening is removed and the allowance for hardening is controlled by the mandrel-shaped tool due to the constant axial displacement of the combined processing-strengthening tool (A S. pp. 663518, IPC B23P 1/04, 05.25.1979).

The disadvantages of the method include the possibility of using it only for axisymmetric channels, restrictions on the use of the method with a depth of hereditary hardening exceeding the allowance for combined processing.

The objective of the invention is to expand the technological capabilities of the combined anodic-dynamic processing on the outer and inner surfaces of the parts with obtaining guaranteed hardening, providing the greatest increase in the fatigue strength of the parts.

The technical result is achieved using the method of anodic-dynamic hardening of a conductive material part, including mechanical and anodic treatment of the conductive material part surface with metal granules with the application of an electric field in a medium of weak electrolytes based on non-toxic salts at low DC voltages, where the part is the anode. The processing is carried out in three stages, at the first stage, metal granules are freely placed on the workpiece part, then electrolyte is fed along the workpiece surface at a speed that allows the granules to move relative to the surface to be treated, a direct current is applied to the granules and the part, anodic removal of the allowance that makes up the difference between the total allowance for processing and the allowance at the third stage of processing, after which at the second stage the current and the supply of electrolyte and the same granule are turned off and produce vibro hardening until reaching the limit value of work hardening, and the third stage produce anodic dissolution of cold-hardened layer by using a current and an electrolyte similar to the first stage and adjusting the magnitude of stock removal to achieve at the workpiece surface hardening value providing the highest fatigue strength of the material items.

By the method of anodic-dynamic hardening, the outer and inner surfaces of the parts are treated. The method is carried out in three stages. At the first stage, metal granules (structural steel, heat-resistant materials), cast irons, etc.) are freely placed on the workpiece part made of any conductive materials, then electrolyte (based on non-toxic salts) is fed along the workpiece surface at a speed that allows the granules to move relative to the surface to be treated, then direct current (at a low voltage of the generator (2-4 V)) is turned on to the granules and the part, anodic removal of the allowance is made, which makes up the difference between with a machining allowance and an allowance at the third processing stage, after which at the second stage the current and the electrolyte supply are turned off and vibrohardening (mechanical processing) is carried out with the same granules until a stable hardening value is achieved. At the third stage, an anodic dissolution of the riveted layer is carried out using current and electrolyte similarly to the first stage and the allowance removal rates are adjusted until the hardening value on the surface of the workpiece is achieved, which provides the greatest fatigue strength of the part material.

In the drawings 1-3, the stages of the method of anodic-dynamic processing are shown: anodic removal of the allowance from the part to obtain an allowance for final processing (Fig. 1), hardening of the surface layer to the maximum depth (Fig. 2), anodic removal of the allowance during final processing ( figure 3).

At least one layer of metal granules 2, which are the cathode during anodic processing, is poured onto a metal part 1, which is the anode during anodic processing, and a screen 3 is installed to hold the granules 2 in the processing zone. When anodic processing, the current comes from the generator 4 with the possibility of regulating the flow of electricity by the regulator 5. The electrolyte 6 is fed between the part and the granules 2. At the first stage of processing, the allowance 7 is removed, at the second a zone of the allowance part 8 with an increased riveting is formed. Tolerance 9 on the geometric dimensions of the workpiece surface and the dynamic impact of vibration hardening 10 are shown in figure 2.

The method is as follows: apply one or more layers of granules 2 to the surface of part 1, include (Figs. 1 and 3) a low concentration electrolyte 6 from the pump (not shown), and increase the pressure of electrolyte 6 until the granules 2 begin to move along details 1 and from it by the magnitude of the rebound (δ ₁ ). The granules 2 reach the screen 3 and are reflected by them until they return to the surface of the part 1. The electrolyte 6 is drained through the screen 3 and reused. Current (Figs. 1 and 3) is supplied from the generator 4 to part 1 (anode) and granules 2 (cathode). The allowance 7 at the first stage of processing (figure 1), removed by anodic dissolution, is calculated by the formula:

- for an external surface

where L ₁ is the thickness of the workpiece, mm;

L ₂ - the thickness of the part, mm;

Z ₂ - allowance 7 to achieve the maximum hardening of the surface layer of the part during vibration hardening, mm.

- for an internal surface

The processing at the first stage is controlled by time τ ₁ , which is:

where Z ₁ - find by (1) and (2) depending on the type of surface being treated, microns;

α is the electrochemical equivalent of the material of the part (reference material), kg / (A × min);

γ is the density of the material of the part (reference material), kg / m ³ ;

η - current output (reference material), depends on the selected electrolyte;

χ is the conductivity of the electrolyte (reference material), depends on the composition and temperature of the electrolyte, cm / m;

- средняя величина отскока гранул, мм. Регулируется скоростью потока в диапазоне 2-4 мм;

- the average value of the rebound of the granules, mm It is regulated by a flow rate in the range of 2-4 mm;

U - generator voltage, V. Adjustable in the range of 2-4 V;

ΔU - voltage loss (reference material), depends on the composition of the electrolyte, the magnitude of the rebound of the granules, the processed material, V.

At the second stage, the time of dynamic vibration hardening 10 is selected or found experimentally by the value of obtaining a stable value of hardening on the part of the allowance 8, counted from the tolerance 9 on the part.

At the third stage, the guaranteed optimum hardening is obtained due to the anode removal of part of the allowance 8 and movement of the allowance removal margin to the middle of tolerance 9. Here, it is necessary to ensure the exact volume of material removal, therefore, the anode removal is carried out by monitoring the end of the process with regulator 5 (such as an electricity meter) the calculated value of the amount of electricity (Q):

where Z ₂ - the maximum depth of the zone of increased hardening of the allowance part 8, microns;

- средняя величина поля допуска 9 на деталь, мм.

- the average value of the tolerance field 9 per part, mm

The processing modes in the third stage can be selected similar to the process of anodic dissolution in the first stage.

An example implementation of the method. A compressor blade made of conductive heat-resistant material EI437A was subjected to the method of anodic dynamic hardening, the ultimate hardening of which after hardening reaches 37% (Sulima AM, Evstigneev MI The quality of the surface layer and the fatigue strength of parts made of heat-resistant and titanium alloys. - M .: Engineering, 1974, p. 97, table 3.7). According to our research, the optimal hardening should be 5% ± 1% with a depth of residual stresses of up to 0.1 mm. Pellets for dynamic hardening were balls with a diameter of 4-5 mm made of SCh 20 cast iron. The time of dynamic hardening was 15 minutes with an amplitude of rebound of granules of 4 mm (Smolentsev V.P. Technology of electrochemical processing of internal surfaces. - M .: Mashinostroenie, 1978 , p. 117, table 35). A 5% sodium chloride solution at a temperature of 290 K was selected as the electrolyte for the anode treatment. The operating voltage was 4 V. The total allowance for processing was 0.4 mm. At the first stage, an anode dissolution of 0.3 mm was removed (formula (1)), which took about 2 minutes of machine time (formula (3)). Dynamic vibrohardening in the second stage was 15 minutes. The anodic dissolution in the third stage was monitored by using 1.36 ampere hours of electricity (processing time of about 1.3 minutes). Measurement of residual stresses by the Davidenkov method of the used parts on a PION-3 device showed that the degree of hardening was 4.1-5.5%. This met the requirements for optimal fatigue strength (σ _-1 = 470 MPa) of the heat-resistant material EI437A.

Claims (1)

The method of anodic-dynamic hardening of a part from a conductive material, including mechanical and anodic treatment of the surface of a part from a conductive material with metal granules with an electric field in a medium of weak electrolytes based on non-toxic salts at low DC voltages, where the anode is a part, characterized in that the processing carried out in three stages, at the first stage, metal granules are freely placed on the workpiece part, then the electrolyte is fed along the surface of the part at a speed that allows the movement of the granules relative to the surface to be treated, they include a direct current to the granules and the part, anode removal of the allowance is made, which is the difference between the total allowance for processing and the allowance in the third stage of processing, after which the current and the electrolyte flow are switched off in the second stage and the same granules produce shockproof hardening until the limit value of hardening is reached, and at the third stage anodic dissolution of the hardened layer is carried out using m current and electrolyte similar to the first stage and adjusting the magnitude of stock removal to achieve at the workpiece surface hardening value providing the highest fatigue strength of the material items.

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