RU1791466C - Method for removal glass-enamel coatings of metal articles - Google Patents

Abstract

SUMMARY OF THE INVENTION: the method includes local heating of an article of predominantly cast-iron baths from the side of the coating by exposure to pulses of a focused light beam from an xenon arc lamp at a pulse current of 450-500 A, pulse durations of 0.5-1.5 s and a pulse repetition rate of 0.15-0 , 5 followed by removal of enamel chips. 1 tab.

Description

The invention relates to a technology for re-enameling cast-iron bathtubs and can be used both in the production of enamelled bathtubs and for their repair.

A known method for removing glass enamel from the surface of metal products by chemical etching.

The disadvantages of this method include the low cleaning rate, the complexity and high cost of this method.

There is also a known method for removing enamel from large cast iron products with a shot blasting apparatus at a pressure of 3-5 atmospheres.

The disadvantages of this method are the low productivity of cleaning from enamel coating, the complexity associated with the need to disperse fractions and waste enamel

Closest to the invention is a method of removing from the surface of metal products by thermal shock using induction heating by high-frequency currents of a metal substrate while simultaneously cooling the SES with running water.

The disadvantages of the invention include the possibility of damage to the cast iron substrate (cracking), because with this method, thermal shock occurs when cast iron is heated, not enamel; the difficulty in using this method to remove the SES from the surface of cast-iron baths due to their complex configuration, large dimensions and different thicknesses of the product (side, bottom, side walls); the complexity of the method due to the need to cool the surface of the enamel layer with water, which is not always possible.

ck about

The aim of the invention is to increase the performance of cleaning the surface of cast iron baths from EPP.

The goal is achieved in that in the implementation of a method based on heating the product and removing enamel chips, heating is carried out locally from the side of the coating by exposure to pulses of a focused light beam, for example, an xenon arc lamp, with a pulse current of 450-500 A, pulse duration 0.5-1.5 s, pulse repetition rate 0.15-0.5 ..

Pulsed local heating in a predetermined mode is carried out using an optical-beam installation containing a pulsed power source (radiant energy generator, T-13021 type welding semiautomatic device column, product, swivel cart.

The ability to operate the xenon lamp in pulsed mode is achieved using a pulsed power supply. The power supply comprises: a three-phase transformer, a rectifier, an ignition unit, a radiant energy generator. In order to operate the DKSSh-10000 xenon arc lamp, the control input of the thyristor control unit is connected to the master oscillator, and the output is connected to a three-phase transformer, the output of which is connected to the rectifier input. The radiant energy generator is connected to the rectifier and the ignition unit by its outputs.

The frequency and duration of the pulses, the magnitude of the pulse current is set by the thyristor control unit using the master oscillator G5-60. Depending on the mode specified by the generator, the modulated power is supplied through the rectifier to the radiation generator. The xenon lamp is ignited by a high voltage ignition device.

The proposed method for cleaning the BOT is implemented with the achievement of a high quality result when exposed to pulses of an arc xenon lamp DKSSh-10000-1 with the following parameters: pulse current (s) 450-500 Ar pulse duration (gi) 0.5-1.5 s, pulse repetition rate (v 0.15-0.5.

The limiting values of v are determined by the technical capabilities of the switching power supply control device. The lower limit of the electrical parameters of a pulsed xenon arc lamp is set by evaluating the shear efficiency of enamel. With a value of less than 400 A, enamel cleaving does not occur, but goes

SES reflow. The upper limit of the pulse current is determined by the working life of the arc lamp and is equal to 600 A.

The experimental values of pulsed light processing are confirmed and

calculations: the relative elongation during heating of the upper enamel layer is determined from the linear expansion formula

e Д1 / 10 аДТ (1) value of relative increase

temperature from the Bouguer-Lamberg equation

(l-R) 1/2

lt

(2)

where d is the density of the incident stream: R is the reflection coefficient; I - thermal conductivity coefficient; a-coefficient of thermal diffusivity;

v - pulse repetition rate, Hz, lengthening of the upper layer creates stresses, which from Hooke's law

a-e-e (3) substituted (1,2) in (3), we obtain the formula for the dependence of the stresses developed in the glass enamel under optical irradiation

o-.a.E-- -Qjlll (av)

1/2

(4)

Kv

Wed-p

) / 2 (5)

since p,

then a 2 a E q0 (1 - R) (

where Cp is the specific heat;

p-density of enamel.

Formula (5) made it possible to estimate the pulse repetition rate v to create ultimate stresses in the enamel when exposed to a source with a given q0. For enamel

TK-17 v 2-6 Hz, depending on the preheating temperature (continuous emission).

A specific example of this method is the removal of SEL from

walls, bottom and sides of the cast-iron bath.

An enameled cast-iron bath is mounted on a swivel trolley so that the surface being cleaned is perpendicular to the direction of light

ray. The light beam was focused on the surface in the form of a focal spot with a diameter of 40 mm and pulses were generated with a duration of 0.5-1.5 s, with a repetition rate of 0.15-0.5. The value of the pulse current varied within 400-600 A. The quality of surface cleaning from the SES, as well as the absence of cracking of the cast-iron substrate, was evaluated visually, the shearing performance was determined by the shearing value of the enamel (S) for 1 min. The results are shown in the table. As can be seen from the table, enamel cleavage is most effectively achieved by exposure to pulses of a light beam with a duration of 0.5-1.5 s. with a pulse repetition rate of 0.15-0.5, the pulse current value of 450-500.A.

The average productivity of the cleaning methods of the proposed and protop can be calculated as follows:

Bath cleaning time

tB t6 + tc + tfl

where te is the cleaning time of the sides, min; tc is the wall cleaning time, min; 1d - bottom cleaning time, min.

The cleaning time for the sides, walls, bottom is determined by the formula

t-s

where S is the enamel area, cm;

V is the cleaning rate, cm2 / min. For the proposed method

te

5500

290

18.9 minutes

tc J | i ° A 39.0 min.

tA

320

4500

32.1 min

140, 9 + 39.0 + 32, min.

For the prototype (according to the act of testing cleaning with an inductor)

t6

0

tc

V

5500

160

12500

80

4500

100

34.4 minutes

156.3 minutes

45.0 min

- ,, 4 + 156.3 + 45., 7 min. Thus, productivity

cleaning baths according to the proposed method is more than 2.5 times higher than the prototype. In addition, the average power consumption of a xenon arc lamp source (within 2.9-4.0 kW is easy to calculate from

description tables) 10-30 times lower than the power consumption of the inductor power generator. An advantage of the invention is also the simplification of a process that does not require water

Claims (1)

cooling the coating, ensuring that the cast iron bathtubs are cleaned from the EPB without damaging the cast iron mercury substrate (cracking) due to its intended heating. The claims A method for removing glass-enamel coatings from metal products, mainly cast-iron baths, including heating the product and removing enamel chips, and so on, with the aim of increasing the productivity of the process, the product from the side of the coating locally heated focused pulses light beam xenon arc lamp with a pulse current of 450-500 A, a pulse duration of 0.5-1.5 s and a pulse repetition rate of 0.15-0.5. Table continuation