SU1166943A1 - Method of arc welding with core wire - Google Patents

Abstract

THE METHOD FOR WELDING THE POWDER WIRE, in which additional heating is carried out on the heating section located above the welding current supply section, characterized in that, in order to improve the quality of welding by keeping the core from melting the core and reducing oxidation of the metal components of the wire, 400-800 ° C; wire is used as the flux-cored wire; the core-composition of the core contains gas-forming components with a dissociation temperature of 0.3-0, 7, the heating temperatures are carried out at a speed of 100-300 ° C / s, and in the section of the electrical power supply, protective gas is fed from the outside of the wire with a pressure of 0.3-1.0 MPa. (L

Description

05 О5 00 4

WITH

The invention relates to arc welding and can be used for welding and cladding with cored wire.

The purpose of the invention is to improve the quality of welding by reducing the ingress of air from the core of the wire into the core, reducing the oxidation of the electrode metal when it is heated and reducing the melting of the core from the sheath.

The goal is achieved by the fact that in the heating section inside the shell they create an overpressure of protective gas and in the section of the electrical power supply from the outside of the process joint - a pressure of protective gas equal to 0.3-1.0 MPa, and heating up to 400-800С.

The presence of overpressure of the protective gas inside the shell at the preheating site allows the air between the particles to be expelled through the technological knock into the surrounding space. The core is filled with protective gas. This reduces the oxidation of metal components and prevents air from entering the arc gap.

The protective gas inside the shell is produced by introducing the filler into the composition in the manufacture of the wire with a gas-forming component, dissociating at temperatures of additional heating of the wire, for example organic, metal carbonates, plastics, etc. To create an overpressure, components with a dissociation temperature in the range of 0.3-0.7 preheat temperatures are selected and the heating rate is set equal to IOO-EEP / s. In this case, the volume of liberated gas creates an overpressure of 0.02–0.1 MPa in the sheath, which is sufficient to extract air from the sheath during the movement of the wire through the heating section. With smaller values of the dissociation temperature, premature decomposition of the gas-generating and air suction occurs at the end of the heating section, and with large values, there is not enough pressure to fully expel the air. When choosing a heating rate less than

 the process of ejection of air is delayed in time and the overpressure is not enough to completely remove the air, and more — the overpressure is unevenly distributed throughout the core volume and a portion of the air located in the axial portion of the core is not removed

completely.

The overpressure of the protective gas generated from the outside of the process interface reduces the injection of gas inside

shell, through the joint when moving: the wire along the section of the electrical power supply. The choice of pressure in the range of 0.3i1, 0 MPa allows you to forcefully create in the shell a volume reserve

gas, which compensates for its loss when moving the wire through the area vypet. At lower pressure values, air is introduced into the core, and at large pressures, the loss of protective gas in the device for supplying it to the shell increases.

As a result, protection of 1 metal components against oxidation at all stages of heating and

movement and reduced air flow into the melting zone.

The reduction in the melting of the core from the shell is as follows.

The core of the cored wire is a two-phase dispersed system formed by solid powder particles and gas filling the space

between them. Due to the small contact area of the solid when the particles are packed into the core, the heat transfer properties of the latter are mainly determined by the conditions of convective heat transfer by the gas phase. In turn, these conditions are directly dependent on the pressure and temperature of the gas. With an overpressure and an increase in the heating temperature to 400,800 ° C, the thermal conductivity of gases increases dramatically, which is caused by an increase in the number and spatial mobility of elementary heat carriers — gas molecules. The gas, heated in the layer adjacent to the shell, diffuses rapidly. deep into the core and micropores of the clock. This reduces the temperature unevenness over the cross section of the core and decreases the lag of the core melting from the shell. When heated to temperatures less than the average, the gas temperature rises slightly due to the heat inertia of the process for heating the core and a small fraction of the radiant heat. Therefore, the heat transfer to the axial portion of the core is hardly improved. When heated, heat losses from the surface of the wire to radiation increase more, and the shell stiffness decreases, which deteriorates the performance of the welding process. The drawing shows a general scheme for performing the method. Arc welding is carried out from the power source 1 connected to the product 2 and the current lead of the welding current 3. Powder wire A containing a sheath with a process joint 6 and a core 7 is used as an electrode wire. The core is introduced into the core with the dissociation temperature 0, 3-0.7 heating temperature in the amount of 2-30% of the core volume. Additional heating of the wire is carried out at the LO heating section, located above the current-carrying current and welding current 3, in one of the well-known ways: by the electrocontact method, high-frequency current, by a laser beam, by a flame. In the case of electrocontact heating, a separate power source 9, for example, a transformer, is connected to the current supply of the welding current 3 and the current supply to the heating 8. On the section of the electrical power supply LT from the outside of the process joint 6, an external pressure P of the protective gas (carbon dioxide, argon, helium, etc.) is created, the value of which is set in the range of 0.3-1.0 MPa. Practically this is done, for example, by groove 10, located in the current lead concentrically to the shell 5, into which gas is fed gas through the tube 11. Turn on the supply of wiring with speed control unit. The heating temperature is maintained in the OO-SOO range by adjusting the heating current (power). The heating rate is set equal to 100-300 C / s inversely proportional regulation of the length of the heating section L When heated, the gas-forming components decompose in the wire and create an overpressure Pj inside the casing, protecting the metal from oxidation and billowing air 12 into the surrounding space. Next, the wire enters the section of the electrical power supply L, where the pressure prevents gas from escaping through the joint and fills its volume with additional portions of gas p sufficient to protect the components from oxidation as it moves along the departure area Lg. PRI me R. Conducted arc surfacing with cored carbonate-fluorite type cored wire with a diameter of 3 mm, made of metal tape and containing a technological joint in the shell. In the process of welding, the shell was heated in a section located above the current supply of the welding current from a separate 2.5 kVA transformer with thyristor control of the heating power. The heating temperature was varied within 350–900 ° C, and the heating rate was 50 AOO C / s. Powder wires containing one of the gas-forming components with different dissociation temperatures in the core were made: aluminum carbonate (tg 125 C), starch (tg 200-250 ° C), soda ash (tg -400-500 C) and marble (tg. 600- 700 O in the amount of 8% of the core volume. In the current tip, a bore was drilled concentrically to the guide hole, into which carbon dioxide was supplied under a pressure of 0.25-1.1 MPa. The overpressure was determined by sealing the heating section and measuring the pressure gaseous fuses. or mild steel plate at 180-220A current, voltage 22-24 V. was monitored overpressure shielding gas, heating the area Pj, gas pressure in the current leads of welding current P preheating temperature i, heating rate di lei-t

51

The quality of welding was evaluated by the content of oxygen and nitrogen in the weld metal, the protruding portion of the core lf, the loss coefficient V. Dp comparisons were also carried out surfacing in accordance with the method of the prototype.

The data are given in the table. As follows from the test results, when welding in accordance

tg / c

Welding method

Famous 1

669436

with the proposed method, by reducing the oxidation of metal components, eliminating the ingress of air from the core, reducing 5 lags of core melting from the shell, the welding quality indicators are improved; gas saturation of the weld metal is reduced by 20-35%, the loss of the electrode metal is 1.310 1.6 times.

 G piT

PI,

cJ-tH / c

with

MPa "C /

Known I 0,030-0,040 0,040-0,055 3,0-3,5

12.70

Claims (1)

METHOD OF ARC WELDING WITH POWDER WIRE, in which additional heating of the wire is performed in the heating section located above the welding current supply section, characterized in that, in order to improve the quality of welding by defending the core melting from the sheath and reduce the oxidation of the metal components of the wire, heating is carried out to 400 -800 ° C, a wire is used as a flux-cored wire, gas-forming components with a dissociation temperature of 0.3-0.7 temp are introduced into the core perature heating, heating is performed at a speed of 100-300 ° C / s, and the area of the current lead wire on the outside is supplied with protective gas pressure 0.3-1.0 MPa. -SU „„ 1166943 1166943 2