Multiarc welding of welded blanks

FIELD: process engineering.

SUBSTANCE: invention relates to multiarc welding of welded blanks for making car body parts by cold forging. First, current and rate of first arc welding are selected proceeding from penetration into the entire depth of blank and fusion isotherm on blank surface on welding side. Selected are the number of arc, current of every next arc and distance there between so make fusion isotherm width for every arc on blank surface at weld side complies with isotherm width on welding side of every previous arc while arc crater diameters in welding bath are smaller than welding bath fusion isotherms on the side of crystallisation front of welding bath fusion isotherm. First arc electrode is set 65-75° to welding direction while electrodes of the next arcs are set at 105-115° to said direction. Blanks are butt welded at water-cooled appliance in atmosphere of protective gases at constant current and with separate supply of the arcs.

EFFECT: invariable weld seam geometry, smaller area of melted zone of weld joint, hoint plastic structure.

9 dwg

 

The invention relates to welding, and in particular to the manufacture of welded sheet blanks (LSS) to obtain from them the methods of cold stamping of body parts, including body parts of the car.

A method of obtaining a guaranteed penetration of edges by automatic argon-arc welding with non-consumable electrode, as the USSR №1426720 from 08.04.86, which set mode settings by measuring geometric dimensions of the weld pool and correction modes based on their deviations from empirical formulas.

The proposed method can improve weld quality by taking into account the influence of the forces acting on the weld pool.

The disadvantages of this method is significant complexity in the choice of mode, requiring the use of high-performance computing and high-speed devices adjustments that significantly limits the use when performing high-speed welding conditions and measurement parameters empirical formula is difficult. Therefore, effective implementation of this method is limited by the lack of ability to precisely specify its parameters.

The known method arc multielectrode welding A.S. USSR №1454602, in which the narrow groove with the location of the electrodes along the axis of the weld and against the sustained fashion by moving the electrodes and welded product to enable welding products of great thickness in one pass svarivaemost the product is placed under an angle of 15-75° to the horizontal plane, the ends of the electrodes are placed on the same level relative to the horizontal plane, and the welding start with the bottom point of cutting.

The proposed process allows to improve quality and productivity by increasing the speed of movement of the molten metal under the arc by the action of gravitational forces.

Disadvantages of the process is the need to create a relatively wide weld pool, which is unacceptable in the manufacture LSS, the complexity of the Assembly of sheets in an inclined position and increasing deviations of the geometry of the weld because of natica metal.

There is a method of arc welding with direct current longitudinal pipe seams by A.S. USSR №1524981 where the welding current flowing through the electrode is divided into two current flowing through the product in the direction opposite to the direction of welding and coincident with him, and separately regulate these currents, characterized in that the welding submerged arc current flowing through the product in the direction coinciding with the direction of welding, chosen depending on the ratio of the current flowing through the electrode, and the diameter of the pipe.

The proposed method provides an increase in welding speed by controlling the deflection of the arc along the junction under the action of the magnetic field welding circuit, leading to separation of the heat is s flows from the arc in two directions and thereby increase the length of the weld pool to output the temperature field outside the force field of the arc to complete the uniform formation of a seam.

The disadvantages of the method are the inability to change the distance between the electrically active spots from passing current through the current leads in front of and behind the weld pool, which limits the effectiveness of management input to ensure an even formation of the weld and limits the performance of welding.

The known method dvuhtokovoe welding by A.S. USSR №1442345, in which the first arc proplast svarivaemost connection to the desired depth, and the second melt the outer layer of the weld, characterized in that use magnetic operation of the second arc. This method improves the performance of the welding process. The disadvantages of this method is the difficulty of welding equipment, welding is a high probability of influence of the quadrupole magnetic field on the process parameters of the first arc, the process is complicated by the lack of regulation regimes of the process. Increasing the distance between the first and second arcs, you can exclude this impact, however, in this case decreases the energy efficiency of the process.

Closest to the claimed method is a method mnogoluchevoi welding by A.S. USSR №1516269, with separate supply of arcs burning in separate baths, characterized in that the supply to the product of the current feeding the first such is the pressure of the welding arc or the first and the following one or more arcs, carry out ahead of the weld pool, and the supply current, the supply of latest and preceding one or more arcs behind the weld pool.

The method also provides for improving the performance of the welding process due to the redistribution of heat flow from the arc.

The disadvantages of the method are its insufficient heat input due to lack of regulation, i.e. the system input heat static and adjustment is provided only by the deviation of the arc due to the efficient electrical power supply.

Objectives of the invention are: to improve performance when welding and increase the stamp of emoti welded joints less.

The tasks are solved by minimizing the deviations of the geometry of the weld from the plane of the sheet, reducing the area of cast weld zone and produce a ductile structure of the weld due to the fact that the way mnogoluchevoi welding sheet welded blanks for subsequent stamping of these body parts, including welding workpieces butt on water cooled fixture nonconsumable electrode shielding gas DC with separate, independent power arcs, with the location of the nonconsumable electrode along the joint and at their simultaneous movement in the welding process, in which the supply to the product of the current feeding the first is upravlenii welding arc, carry out ahead of the weld pool, and the supply of the current to be fed to the subsequent one or more arcs behind the weld pool, wherein the pre-determined current and welding speed, the first arc condition ensure penetration to the entire thickness of the sheet stock and isotherm melting on the surface of the sheets by welding, choose the number of arcs, the current of each subsequent arc and the distance between the arcs of the conditions for melting isotherm from the action of each arc on the surface of the sheet blanks in the place of a joint by welding width consistent with the width of the isotherms on the surface by welding each of the previous arc, and the diameters craters from the force action of the arc in the weld pool were less than the melting isotherm weld pool from the front of crystallization isotherms melting the weld pool, while the first electrode arc set at an angle 65-75° to the direction of welding, and the electrodes subsequent arcs set at an angle 105-115° to the direction of welding.

The method mnogoluchevoi welding welded sheet blanks is illustrated in the following graphics. Figure 1. 2 shows a diagram of the welding process, in which an electrical arc 1, burning with the welding electrode 2, which is installed at an angle α to the direction of welding and nourish the current I1from the source of the DC-3, the current leads 4 and 5 which connect the circuit polarity to the electrode 2 and welded blanks 6 and 7 before the welding bath of molten metal 8, limited isotherm T=TPL. Arc 1 problemset sheets 6 and 7 on their entire thickness, as shown by the isotherm T=TPLunder the arc 1. At a distance of L1from arc 1 arc set 9, burning with the welding electrode 10, which is installed at an angle β to the direction of welding and nourish current L from power source 11, the leads 12 and 13 which connect the circuit polarity to the electrode 10 and welded blanks 6 and 7 for welding bath of molten metal 8. At a distance of L2from arc 9 arc set 14, the burning from the welding electrode 15, which is installed at an angle γ to the direction of welding and nourish the current I3from the power source 16, which leads 17 and 18 connected according to the scheme of direct polarity to electrode 15 and welded blanks 6 and 7 for welding bath of molten metal 8. All arcs move simultaneously with velocity VStin one direction near VSt. Figure 2 shows the scheme of the formation of a seam 19 by welding, which shows the spot of force 20 arc 1, the spot of force 21 arc 9, spot of force 22 arc 14 acting on the weld pool 8, limited from what Ermou T=T PLat the intersection of front crystallization isotherms with a spot of force arc weld metal begins to crystallize in the crater 23 formed by the pressure of the arc in the liquid metal bath 8, resulting in formation of defects in the form of undercuts 26 and 27, and also proportional to their excess bulges 28 and 29 (figure 3), which is determined from the condition of constancy of the volume of the metal. Subsequent exposure of the arc 9 the depth and width of the undercuts 26 and 27 and exceeding the bumps 28 and 29 are reduced (figure 4), due to the decrease in spot of force arc 9 while maintaining the width of the isotherms T=TPLdue to the summation of thermal energy previously nested arc 1 and added after arc 9, which is shown as the intersection of crater 24 isotherm T=TPL. A similar process occurs when successive welding arc 14 behind the arc 9, the result is the exclusion of scores and the minimality of excess bulges 28 and 29 (figure 5) due to the exclusion of intersection of the crater 25 from the arc pressure and the crystallization front weld pool 8.

Install the electrode 2 at an angle of inclination α in the range of 65-75° with the direction of the labour movement during welding from the plane of the sheet, while delivering deep, narrow penetration (6) with a smaller amount of heat input by increasing the intensity of the displacement liquid R is fused metal from under the arc due to the change of the force vector arc pressure compared with welding under normal location (figure 3), and the electrodes subsequent arcs 10 and 15 set with an inclination to the direction of welding angles β and γ in the range of 105-115°, thus providing a shallow penetration and uniform surface formation of the weld width, the width of arc seam 1 (Fig.7, 8).

To increase stanoevska of weld metal number of arcs, their power, in the previously determined range of values of current and voltage of each arc, the distances L1, L2 and so on (figure 1), choose provides the lowest cooling rate of the weld metal. When welding only arc 1 perform heating to a predetermined temperature, 30 (Fig.9) with subsequent cooling curve 31, when this reaches a critical cooling rate of the metal, which leads to the formation of solid deformable and less-plastical patterns, and when mnogoluchevoi welding by heating multiple arcs to the desired temperature 32 and 33 slow the cooling rate along the curve 34 (Fig.9).

By choosing the number of arcs, independent regulation of their power and the distance between them, the method eliminates the intersection of the crystallization front weld pool crater from the arc pressure, to reduce the cooling rate of the weld metal, resulting in an increase in the quality of the geometry of the weld, reducing the amount of solid cast zone of the weld and heat-affected zone, the reduction number is the number of solid hardening structures in metal casting zone of the weld.

The way mnogoluchevoi welding sheet welded blanks for subsequent stamping of these body parts, including welding workpieces butt on water cooled fixture nonconsumable electrodes in inert gases at a constant current with a separate independent power arcs, nonconsumable electrodes lie along the joint and the welding process at the same time move the supply to the product of current to be fed first in the direction of the welding arc, carry out ahead of the weld pool, and an inlet for product supply, the supply of latest and preceding one or more arcs behind the weld pool, wherein the pre-determined current and welding speed, the first arc condition ensure penetration on the entire thickness of the sheet stock and isotherm melting on the surface of the sheets by welding, choose the number of arcs, the current of each subsequent arc and the distance between the arcs of the conditions for melting isotherm from the action of each arc on the surface of the sheet blanks in the place of a joint by welding width consistent with the width of the isotherms on the surface by welding each of the previous arc, and the diameters of the craters from the force action of the arc in the weld pool were less than the melting isotherm weld pool from the front of crystallization isotherms of fusion welding VA the us, while the first arc electrode set at an angle 65-75° to the direction of welding, and the electrodes subsequent arcs set at an angle 105-115° to the direction of welding.



 

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