RU2817683C1 - Non-consumable electrode welding method of aluminium and its alloys - Google Patents

Abstract

FIELD: various technological processes.

SUBSTANCE: invention can be used for welding and surfacing structures from aluminium alloys with thickness of 4–10 mm. Argon-arc welding is performed with a non-consumable electrode at a constant speed of the workpiece, wherein ultrasound is applied to arc column at ultrasonic oscillation frequency of 20 kHz and power of 20–60 W. Welding is carried out on alternating current with rectangular shape of pulses with frequency of 20–100 Hz and relative duration of current pulses of reverse polarity making 0.1–0.4 of period time.

EFFECT: method provides high efficiency of welding articles from aluminium alloys without deterioration of quality of welded joints.

1 cl, 9 dwg, 1 tbl

Description

The invention relates to the field of welding and surfacing of metal parts, and can be used in mechanical engineering for welding and surfacing of structures made of aluminum alloys.

There is a known method of electric arc welding or surfacing of plates 6 mm thick from titanium alloy OT4, in which an activating material obtained from a fine powder of an activating flux of the composition CaF ₂ - 30% is supplied to the arc combustion zone; MgF ₂ - 20%; LiF - 35%; CaCl ₂ - 15% calcined and mixed with fluoroplastic-4D powder, having a fraction size of 0.4 microns, in the ratio, wt.% of the mixture: flux powder 40%; polymer powder 60% (patent RU 2226144, IPC B23K35/02, published 03/27/2004). The resulting mixture was dissolved in ethyl alcohol and repeatedly applied to the surface of VT-1 titanium wire with a diameter of 2 mm, sintering each layer at a temperature of 270°C, forming a shell 120 μm thick. The plates to be welded were connected without cutting the edges in the lower position. The arc was ignited from a tungsten electrode with a diameter of 4 mm at a current of 240 A of straight polarity. Then, an activating material consisting of a titanium core coated with a shell of a mixture of polymer and activating flux was introduced into the arc combustion zone.

The disadvantage of this method is that the use of activating fluxes inevitably affects the durability of the electrodes and is practically ineffective at a current strength of more than 275A, due to the fact that the flux turns into a vapor state and is removed from the welding zone, ceasing to influence the arc.

There is a known method of welding aluminum alloys with a non-consumable electrode, which involves mechanical destruction of the oxide film at the welding site with a cutting tool that is moved in front of the weld pool near the melting line, in a zone protected by argon. Increasing the efficiency of the welding process of aluminum alloys is achieved by conducting the process on a current of direct polarity and reducing electrode wear (patent RU 2134628, IPC B23K9/23, published on August 20, 1999).

The disadvantage of this method is the insufficient quality of cathodic cleaning; control of the cutting surface of the tool is required, and disruption of weld formation at critical welding conditions.

There is a known method of arc welding of aluminum and its alloys with a non-consumable electrode, in which the process is carried out using a direct current of direct polarity in inert gases, voltage pulses of reverse polarity are periodically applied to the arc gap, and the pulse voltage is at least 200 V, and their duration is selected from the stated ratio taking into account the pulse frequency (patent RU 2254214, IPC B23K9/23, published on August 20, 1999).

The disadvantages of this method are the cost of electricity from an additional power source (generator), the need to synchronize reverse polarity pulses with welding parameters to ensure arc stability.

There is a known method of welding aluminum alloys with a non-consumable electrode using a combination of arcs, in which the direct arc on the product burns from the non-consumable electrode, and the indirect arc burns between the non-consumable and consumable electrodes. The consumable electrode is fed continuously into the direct arc and provides periodic pulsation of arc currents with the same frequency. The arcs are powered from two identical sources of oppositely polarized rectangular current pulses (patent RU 2728144, IPC B23K9/16 B23K 9/09, 07/28/2020).

The disadvantages of this welding method are the strong interaction of the arcs’ own magnetic fields, leading to instability of the spatial position of the arcs and the transfer of electrode metal into the weld pool, which leads to large spattering of the electrode metal and instability of the dimensions of the weld bead. Two power sources are required and the process also increases power consumption, hence it is not economically viable. The main difficulty of this process is the need to synchronize current pulses.

There is a known method of welding aluminum alloy 2219 with an electrode powered from a constant current source, with the influence of ultrasonic vibrations of 20 kHz on the workpiece at a distance of 90 mm from the arc. The method provides a penetration depth of 75% at an ultrasonic power of 1000 W (C. Xiaoyu, L. Sanbao, W. Xianneng, Y. Chunli, F. Chenglei Characteristics of Periodic Ultrasonic Assisted TIG Welding for 2219 Aluminum Alloys // Materials. - Harbin Institute of Technology, Harbin, China – 2019).

The disadvantage of this method is the limitation on the size of the workpiece; welding large plates will require more power to achieve the effect, which will affect energy costs.

The objective of the proposed technical solution is to develop a method for non-consumable electrode welding of aluminum and its alloys, increasing the depth of penetration in a wide range of parameters of welding modes and without deteriorating the quality of welds.

The technical result consists in increasing the productivity of welding with a non-consumable electrode without compromising the quality of welded joints for products made of aluminum alloys with a thickness of 4-10 mm.

The technical result is achieved in a method of welding with a non-consumable electrode of aluminum and its alloys, in which argon-arc welding with a non-consumable electrode is carried out using ultrasonic vibrations with a frequency of 20 kHz and a constant speed of movement of the workpiece, while ultrasound with a power of 20-60 W is applied to the area of the arc column, and welding carried out on alternating current with a rectangular pulse shape with a frequency of 20-100 Hz and a relative duration of current pulses of reverse polarity of 0.1-0.4 of the period time.

The essence of the method is that ultrasound acts directly on the welding arc, which makes it possible to increase the penetration depth by 30-40%. The declared relative duration of current pulses of reverse polarity from the time period ensures the necessary quality of cathodic cleaning and durability of the electrode at elevated welding conditions, which allows increasing the productivity of argon arc welding with a non-consumable electrode. Expanding the range of parameters of welding modes allows you to increase the range of welded products made of aluminum alloys without compromising the quality of welds.

Increasing the ultrasonic power to 100 W or more leads to disruption of seam formation at critical welding conditions. The optimal power value of ultrasonic vibrations (UV) is 20-60 W, which ensures the formation of defect-free seams with the greatest penetration depth.

The claimed method ensures the formation of a fine-scaled weld with a smooth transition to the base metal under normal and critical welding conditions.

Examples confirming the influence of ultrasonic vibrations on the penetration depth when welding aluminum alloys with a thickness of 3 to 10 mm are given in the table.

The method is carried out as follows. A non-consumable electrode (for example, brand WL-20) with a diameter of 4 mm is installed at a distance of 3 mm from the surface of the aluminum workpiece. Using alternating current with a frequency of 20-100 Hz with a rectangular pulse shape of reverse polarity of the stated duration, the welding arc for argon arc welding is ignited. An ultrasonic transducer influences the arc with ultrasonic vibrations with a frequency of 20 kHz and an ultrasonic power of 20-60 W. Next, welding is carried out at a constant speed of movement of the workpiece, equal to 22 m/h (welding speed).

Table

Ultrasonic testing parameters Welding mode parameters (per arc) Ultrasound frequency, kHz Ultrasonic testing power (P _{ultrasonic testing} ),
W Welding current strength
(I _St. ), A Welding speed
(V _St. ), m/h AC frequency
current, Hz Duration of current pulses of reverse polarity (τ _arr. ), ms Duration of current pulses of direct polarity (τ _pr. ), ms Relative duration of current pulses of reverse polarity versus period time Gas consumption, l/min Arc length, mm Electrode diameter, mm Penetration area and workpiece thickness - - 150÷160 22 20 7.5 42.5 0.15 12-14 3 4 10-12 mm ² / 3 mm 20 60 150÷160 7.5 42.5 12-14 mm ² / 3 mm - - 150÷160 50 2 18 0.1 14-16 mm ² / 3 mm 20 60 150÷160 2 18 16-18 mm ² / 3 mm - - 150÷160 3 17 0.15 13-15 mm ² / 3 mm 20 60 150÷160 3 17 17-19 mm ² / 3 mm - - 150÷160 5 15 0.25 12-14 mm ² / 3 mm 20 60 150÷160 5 15 16-18 mm ² / 3 mm

- - 150÷160 22 50 8 12 0.4 12-14 3 4 9-11 mm ² / 3 mm 20 60 150÷160 8 12 12-14 mm ² / 3 mm - - 150÷160 100 1.5 8.5 0.15 17-19 mm ² / 3 mm 20 60 150÷160 1.5 8.5 20-22 mm ² / 3 mm - - 200÷210 50 5 15 0.25 14-16 14-16 mm ² / 4 mm 20 60 200÷210 5 15 22-24 mm ² / 4 mm - - 250÷260 3 17 0.15 16-18 18-22 mm ² / 6 mm 20 60 250÷260 3 17 26-30 mm ² / 6 mm - - 300÷310 3 17 18-20 Defects (undercuts, bumps, etc.) /10 mm 20 20 300÷310 3 17 38-42 mm ² / 10 mm 60 300÷310 3 17 40-44 mm ² / 10 mm 100 300÷310 3 17 Defects (bumps, undercuts) / 10 mm

In fig. Figure 1 shows the formation of a seam at critical welding conditions (material AMg-6, plate thickness - 10 mm, _Ist. =300 A, _Vst. =22 m/h) without ultrasound, Fig. Figure 2 shows the formation of a seam at critical welding conditions (material AMg-6, plate thickness - 10 mm, _Ist. =300 A, _Vst. =22 m/h) with ultrasound, Fig. Figure 3 shows a macrosection (AMts material, plate thickness - 4 mm) of a weld obtained without ultrasonic testing; Fig. Fig. 4 shows a macrosection (AMts material, plate thickness - 4 mm) at P _UT = 20 W, in Fig. Figure 5 shows a macrosection (AMts material, plate thickness - 4 mm) at P _UT = 60 W, in Fig. Fig. 6 shows a macrosection (AMts material, plate thickness - 4 mm) at P _UT = 100 W, in Fig. Figure 7 shows the depth of penetration without ultrasonic testing (material AMg-6, δ=10 mm, _Ist. =250 A; _Vst. =22 m/h), in Fig. Figure 8 shows the depth of penetration at ultrasonic testing power P _{ultrasonic testing} = 60 W (material AMg-6, δ = 10 mm, I _St. = 250 A; V _St. = 22 m/h), in Fig. Figure 9 shows the penetration depth at ultrasonic testing power P _{ultrasonic testing} = 100 W (material AMg-6, δ = 10 mm, I _St. = 250 A; V _St. = 22 m/h).

The method provides an increase in the penetration depth by 30-40% and significantly improves the formation of the weld at critical welding conditions (I _St. = 300 A, V _St. = 22 m/h).

Thus, the method of argon arc welding with a non-consumable electrode of aluminum and its alloys using ultrasonic vibrations with a frequency of 20 kHz influencing the area of the arc column with ultrasound power of 20-60 W, in which welding is carried out at a constant speed of movement of the workpiece, on alternating current with a rectangular pulse shape with a frequency of 20 -100 Hz and the relative duration of current pulses of reverse polarity 0.1-0.4 from the time period, allows you to increase the productivity of welding with a non-consumable electrode without deteriorating the quality of welded joints for products made of aluminum alloys with a thickness of 4-10 mm.

Claims (1)

A method of welding with a non-consumable electrode of aluminum and its alloys, in which argon-arc welding with a non-consumable electrode is carried out using ultrasonic vibrations with a frequency of 20 kHz and a constant speed of movement of the workpiece, characterized in that ultrasound with a power of 20-60 W is applied to the area of the arc column, welding is carried out at alternating current with a rectangular pulse shape with a frequency of 20-100 Hz and a relative duration of current pulses of reverse polarity of 0.1-0.4 from the time of the period.