Gas-shield electric arc welding process with use of non-consumable electrode

FIELD: machine engineering, possibly gas-shield electric arc welding by means of non-consumable electrode.

SUBSTANCE: method comprises steps of alternatively feeding several gases or their mixtures by pulses; at each next pulse feed using gases (gas mixtures) having ionization potentials different in comparison with those of gases or gas mixtures of previous pulse feed; periodically changing electric arc gap simultaneously with gas feed pulses; setting basic voltage of electric arc equal to optimal voltage in medium of gas or gas mixture with minimum ionization potential; setting difference between maximum and minimum voltage values of arc at periods of previous and next pulse feed of gases or gas mixtures in range 1 - 7 V.

EFFECT: enhanced quality of welded joints, possibility for adjusting fusion depth.

1 tbl, 1 ex

 

The invention relates to mechanical engineering and can be used in arc welding in shielding gases non-consumable electrode.

There is a method of arc welding in shielding gases, in which several gases or their mixtures are served alternately pulses, with each pulse using gases or their mixtures, differing ionization potentials by at least 20% of the ionization potential of a gas or a mixture of the previous pulse (RF patent No. 15586 04, CL 23 To 9/16). However, this method does not always ensure getting high quality especially long welds due to the irregular spacing of the burner from the welded product around the perimeter of the welded connection.

There is a method of arc welding in shielding gases, in which several gases or their mixtures are served alternately pulses, with each pulse, use gas or mixture of gases with ionization potential than the ionization potential of the gas or mixture of the previous pulse, characterized in that the carry out periodic change of the arc gap, synchronous with the pulses of the feed gases or mixtures (RF patent No. 2130370, CL 23 To 9/16). This method adopted by the authors as a prototype.

The method improves the quality of welds by increasing the gas-dynamic impact n the crystallization of the weld pool. However, this method does not always ensure stable quality due to the lack of recommendations on the choice of parameters changes in the magnitude of the arc gap.

The objective of the proposed technical solution is to improve the quality of welded joints and regulating the depth of penetration.

This problem is solved due to the fact that in arc welding in shielding gases, in which two or more gases or their mixtures are served alternately pulses and each pulse using gases or a mixture of different potentials of ionization potential ionization of a gas by the previous pulse and the simultaneous change of the arc gap. This set of basic arc voltage is equal to the optimal voltage in the gas environment with minimal ionization potential, and the difference between the maximum and minimum value of the arc voltage in the periods preceding and following pulses of gas supply installed within 1÷7th Century

The essence of the method consists in the following.

Welding carry out constant arc in inert gases or mixtures thereof, which serves in turn the burner and which differ from each other by the ionization potential. Synchronously with the change of gas composition change the length of the arc gap, pre-setting the reference value of napryajeniya arc equal to the optimum arc voltage, burning the gas with minimum ionization potential, ensuring the difference between the maximum and minimum arc voltage in the periods preceding and following pulses within 1÷7 C. the Magnitude of the arc gap is directly dependent on the voltage of the welding arc, so the change in the voltage leads to a change in the value of the arc gap. The increase in the arc voltage at the time of filing a protective gas with a higher ionization potential decreases the length of the arc gap, which increases electrogasdynamics pressure on the weld pool and, consequently, increases preplasma ability of the arc when reducing the width of the weld. Such an effect of the arc on the weld pool allows a wide range to control the formation of the seam. Changing the length of the arc in certain limits, reach wide regulation of the gas pressure provided by the arc on the weld pool when changing the potential of the shielding gas.

When establishing the base value of the arc gap equal to the optimal value of the arc gap at the arc in a gas with a minimum value of the ionization potential of providing the difference between the maximum and minimum value of tension is placed on the arc in the periods preceding and following pulses within 1÷ 7, this is an opportunity to further improve the quality of welded joints and getting the joints with a uniform formation of fusion and amplification.

It also allows to increase the depth of penetration without increasing heat input of the arc, which is especially effective when welding materials that are sensitive to the welding thermal cycle.

Example 1. Performed welding samples of steel VNS-2 with a thickness of 3.0 mm, the welding is carried out nonconsumable tungsten electrode in argon and helium, which was filed in the welding torch alternately pulses using a special device. As a power source arc used SVU-315. The welding current was 75 And the speed of 5.4 m/h, argon flow rate of 3.5 l/min, the flow rate of helium - 3.5 l/min, frequency shifts of argon and helium are the same and amounts to 70 times per minute. The installation distance of the electrode from the welded plates were 1.5 mm and was optimal. This distance corresponds to an optimal basic arc voltage in argon to a value of 10 Century shielding gas argon has the lowest ionization potential of these applied shielding gas: Ar and No, the ionization potentials are respectively: UiAr=15,m; UiHe=24,5 eV.

Other parameters of welding conditions and the results obtained are presented in table 1.

As can be seen from the obtained Raza is tatou, way, in addition to improve the formation of the joints, helps to stabilize the strength and ductility of welded joints, as well as to exclude the formation of undercuts and poor penetration.

Method of arc welding with tungsten electrode shielding gas, in which several gases or their mixtures are served alternately pulses, with each pulse using gases or mixtures, which are potentials of ionization potentials of ionization of gases or mixtures of the preceding pulse, and carry out periodic change of the arc gap, synchronous with the pulses of the feed gases or mixtures, characterized in that establish the basic arc voltage equal to the optimal voltage in the environment of the gas or mixture with minimum ionization potential, and the difference between the maximum and minimum value of the arc voltage in the periods preceding and following pulses feed gases or mixtures set within 1÷7th Century



 

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