SU1745460A1 - Method of arc welding by electric rivets - Google Patents

Abstract

Use: for electric welding of electric rivets with a non-consumable electrode in the environment of protective gases in various parts of the machine building industry, court of manufacture and automobile industry, mainly for welding non-ferrous metals and alloys of small thickness. SUMMARY OF THE INVENTION: Fix the voltage on the arc and the time from the start of the welding process until the voltage on the arc reaches the voltage equal to the start of the welding process. The arc is sustained at this voltage for a time determined by the formula tn) where t3 is the time from the beginning of the welding process D3 until the initial voltage on the arc is restored; From - the required diameter of the electric rivets, mm: D3 - the diameter of the electric rivets when the arc voltage reaches the initial value, mm. As a result, electric rivets with a weld area of 2-3 times the area of the welded joint, made by a known method, are obtained. 1 tab., 1 Il.

Description

The invention relates to arc welding by electric rivets with a non-consumable electrode in a protective gas environment and can be used in various fields of engineering, shipbuilding and automotive industry mainly for welding non-ferrous metals and thin alloys.

A known method of arc spot welding 1, in which the welding cycle is set in advance, consisting of compressing the elements to be welded and supplying protective gas, initiating and burning the arc, stopping the arc and holding in a compressed state. The whole cycle lasts 1-3 seconds.

The disadvantage of this method is that it is impossible to assess the thermal situation arising in the welded elements. With all the accuracy of the experimentally tested welding modes, obtaining a stable quality joint is extremely difficult, since the limitation of the welding cycle over a predetermined time does not take into account the influence of additional factors (heating of equipment and, consequently, additional heating of the welded elements or intensive heat sink). which are decisive in obtaining a stable joint in structures with a large number of weld points.

g

Ј

ON Oh

The closest technical solution to the present invention is a method of arc welding with electric rivets 2, in which the elements to be welded compress the outside of the formed point, excite the welding arc, and form the electric rivet. This ensures a high stability of the average diameter of the electric rivets, which determines its strength by taking into account the thermal situation in the welding zone by automatically changing the welding time.

The disadvantage of this method is the insufficient strength of the welded electric riveting joints, since the average cross section of the welded point between the sheets is minimal and, therefore, its strength is minimal.

To increase the efficiency of structures, it is necessary to increase the number of welded points, which leads to a decrease in labor productivity. Increasing the welding time by a predetermined amount to increase the diameter of the electric rivet after the arc voltage is restored to its original value leads to instability of the electric rivet. The latter is due to the difference in the thermal situation in the welding zone of the next electrical rivets at the time the voltage on the arc is restored to the original.

The purpose of the invention is to increase the strength of welded electric riveting joints by increasing the point diameter and its stability.

The goal is achieved by the fact that in the method of arc welding with electric rivets, in which the elements to be welded compress outside the edectro-rivets being formed, excite the welding arc and form the electric rivet, during the welding process the voltage on the arc and the time from the start of the welding process until the voltage is reached on the arc equal to the voltage of the beginning of the welding process, and support the arc burning on this voltage for a time

(2 1)

0)

where tft is the time of continuation of the arc after reaching a voltage on the arc equal to the voltage of the beginning of the welding process;

ta is the time from the beginning of the welding process until the restoration of the initial voltage on the arc;

From - the required diameter elektrozaklegt- km, mm;

D3 is the diameter of the electric rivets when the voltage across the arc reaches its initial value, mm.

The proposed method is illustrated in the drawing:

a) a graph of the voltage on the arc Od from the time of welding tee according to a known technical solution;

b) a graph of the voltage on the arc Od versus the welding time ten for the proposed technical solution.

The essence of the proposed welding method is as follows.

It was established experimentally and theoretically that the average diameter of the electrical rivets, which determines the strength of the joint, can be determined by the formula of a linear stationary continuously acting heat source in the plate, described by the formula

No. TW

16at

(2)

where qu is the thermal efficiency power of the heating source, W;

b - thickness of elements to be welded, cm;

DCp is the average diameter of the electric rivets between the welded elements, cm;

EI - integral exponential function;

a is the coefficient of thermal diffusivity of the material being welded,

I - thermal conductivity of the welded material, W cm / deg;

DT is the difference between the melting point of the metal and its temperature in the welding zone before welding, hail;

t is the considered moment of time, s (Stolbov VI, et al. Optimization of the modes of a three-phase compressed arc during aluminum welding with electric rivets / XC welding production. 1989, No. 10, p. 7-9).

From formula (2) it follows that

  / - Dip

 E, (16at

(3)

For a given difference in the temperature of the DTydethermal metal effective power qu and the thermophysical characteristics of the metals a and i, the right part of formula (3) should be a constant value, i.e.

16at

const - k

(four)

moreover, condition (4) is satisfied in each

time point for a given thermal situation.

Using the formula (4), by the known time t3 from the beginning of the welding process until the initial voltage on the arc is restored (the hole collapses time) and the average diameter of the electric rivets at this point D3, the value of the coefficient k can be determined when welding this point tuatsii in a zone of welding. It is known that when the thermal situation changes, only the time t, s changes. and the diameter D3 does not depend on the thermal situation, since it is determined by the specific mechanism of the formation of electrical rivets

LP 16at3

Further, it is possible to determine the arc burning time tr. for which the required point diameter DT is reached

V

B 16ak

(b)

By comparing (5) and (6), you can make a proportion30

tr D s Di

From here

 h-to, Dl

The time during which the arc should burn after the voltage on the arc is restored to its original value (after the hole collapses) is determined from the formula 45

5 10 15

20

25

thirty

35

40

45

It is fixed by means of a special device following the arc voltage. The same device shuts off the arc when the time l is reached after the voltage on the arc is restored to its original value.

The proposed welding process makes it possible to obtain electrical rivets by means of a welded joint, 2-3 times larger than the area of the joint, made by a known method.

Heat is introduced into the parts after the formation of a joint, which increases the heat input to the bottom sheet and evens out the cross section of the electrical rivets through the thickness of the sheets. This ensures a high stability of the diameter of the electric rivets when the thermal situation in the weld zone changes. A change in the heat situation can be caused by heating the metal from previous points, a change in the effective arc power, a change in the heat sink conditions in the tooling, and other reasons.

An increase in the area of electrical overlap leads to a proportional increase in their strength and reduces the number of welded points on the structure. This leads to an increase in labor productivity by a factor of 1.5 due to a reduction in auxiliary time.

Example. A batch of parts made of AMts alloy with a thickness of 1 mm each was welded at a plate temperature of 290 K. We tried to get an electric rivet with an average diameter of mm. Pre-empirically determined the average diameter of the electrical rivets during welding by a known method and the welding time ta. With the welding current A, plasma-argon consumption l / min, the length and diameter of the plasma nozzle channel mm, the initial length of the open arc section mm, MM s were obtained.

The value of the coefficient k is calculated by the formula (5), i.e.

cЈ

tA-tr-ta-tsCg-1).

In formula (9), the average diameter DT must be obtained during welding, the average diameter Da (at which the voltage on the arc is restored to the original) known before welding is stable and does not depend on the thermal situation in the welding zone. It can be determined experimentally by welding by a known method. Time ta from the start of welding to the time the voltage on the du

 0.62

16-0.5-3

 15-10

- 3

At the same temperature

AM alloy was assumed equal to 5 cm2 / s. Then, the time tT was calculated, for which at the given part temperature the required diameter of the electric rivet will be reached, 8 cm.

.Y

about - vi, - 3, about C.

about

0.6

The time during which the arc should burn after the voltage on the arc is restored to its original value will be equal to

m .. ,, 3 p.

Then, using an electronic controller of the welding cycle, which was previously adjusted to the diameters DT and D3, were welded in the same mode using the proposed method of a plate with an initial temperature K, Tn-390 K and K. The results of welding the samples are shown in the table.

The table shows how great the influence of heating of the parts to be welded can be in a certain mode. The proposed method allows the use of heated parts from pre-welded parts and accessories, to maximize the rate of welded electric rivets with high stability of the rivet section, their strength and reduced auxiliary time. So, in the above example, the cross section of the electric rivet on the proposed method was increased (8/6) 1.77 times, respectively, increased

0

five

0

five

Claims (1)

joint strength, which reduces the number of points to be welded. Claims The method of arc welding by electric rivets, in which the elements to be welded are squeezed outside the formed electric rivets, excite the welding arc and form an electric rivet, characterized in that, in order to increase the strength of the welded electric rivets, the welding voltage is fixed at the arc and the time from the process start welding until the voltage on the arc is equal to the voltage of the start of the welding process, and the arc is sustained at that voltage for a time d-and (C-1) where ta is the time from the beginning of the welding process until the restoration of the initial voltage on the arc; DT is the required diameter of electric rivets, mm; D3 is the diameter of the electric rivets when the voltage across the arc reaches the initial value, mm. willow Utl w { / tr-tj