JPH02235576A - Shielding gas for gas shielded consumable electrode arc welding - Google Patents

Abstract

PURPOSE:To improve the decarbonizing performance and to improve the welding strength at a weld zone by making shielding gas to mixed gas of Ar, He, CO2 and O2 whose mixing ratio is specified. CONSTITUTION:The shielding gas used for gas shielded consumable electrode arc welding is made to the mixed gas set, by vol. ratio, to 71-75% Ar, 18-22% He, 5-10% CO2 and 1.2-1.8% O2. If necessary, 0.1-5.0% Kr is added to facilitate generation of an arc. In addition, in place of the above-mentioned composition, the mixed gas is set to 71-75% Ar, 168-22% He, 5-10% CO2 and 0.1-1.8% N2O to stabilize the arc and contribute to decarbonization and nitriding of the metal surface. If necessary, 0.1-1.8% O2 is further added to control the quantity of nitrogen. By this method. the shielding gas excellent in welding workability is furnished at a low cost.

Description

DETAILED DESCRIPTION OF THE INVENTION <<Industrial Application Field>> The present invention relates to a MAG-based shielding gas used in gas-shielded consumable electrode type arc welding.

《Prior art》 Conventionally, as a mixed gas for shielding of this type, Japanese Patent Application Laid-Open No. 1986-
One having the component ratio shown in Japanese Patent No. 72679 is known. This shielding gas is Ar, He, co,, O!
A mixed gas composed of four components: He: 2 5
~60 vol%, co. :2.5~8.5vol%
,O, :Q. The mixing ratio is 1 to 0.8 vol%, and the balance is Ar.

[Problem to be solved] Conventional shielding gas for MAG welding has a high mixing ratio of expensive He, which not only increases costs but also
Since the mixing ratio of He, which is difficult to ionize compared to r, is high, there was a problem in that a stable arc could not be obtained unless a high voltage was applied. In addition, since the mixing ratio of o is low, there is a problem that the decarburization effect is low and easily causes cracks.

The present invention has been made with attention to such points, and an object of the present invention is to provide a shielding gas that is inexpensive and has good welding workability.

<Means for Solving the Problems> In the first invention, the shielding mixed gas used in gas shield consumable electrode type 7-k welding is Ar, He, CO, 0.
, and the mixing ratio of these gases in volume ratio is Ar
:71-75%, He:18-22%, CO, :5-1
It is characterized in that it is set to 0%, O,: 1.2 to 1.8%.

In addition, in the second invention, the shielding gas used in the gas shield consumable electrode type arc welding is Ar, He, CO, N.
, O, and the mixing ratio of these gases is expressed as a volume ratio, A
r: 7 1-7 5%, He: 18-22%, Co,:
It is characterized in that it is set at 5 to 10%, N, O: Q, i-1.8%.

<<Function>> In the first invention, the shielding mixed gas is Ar, He, CO.
,, O, and the mixing ratio of these gases in volume ratio is Ar: 7 1 to 7 5%, He: 18 to 22%, c
O: 5 to 10% and Ot: 1.2 to 1.8%, so the blending ratio of the expensive He gas is lower than in the shielding gas mixture of the conventional configuration described above. Because of this, it is possible to provide a shielding gas mixture with good welding performance at a low cost.In addition, since the blending ratio of 0. This will increase the welding strength. Also, some of He is K
It may be replaced with r, in which case, Kr
Since it is easier to ionize than He or Ar, it becomes easier to generate an arc, so the applied voltage can be lowered.

Further, in the second invention, the shielding gas used in the gas shield consumable electrode type arc welding is A (He, CO, NO.
Ar:
71-75%, He: 18-22%, CO2: 5-10
%, Neo: Since it is set to 0.1 to 1.8%, N
, N due to the strong oxidation properties of O molecules and discharge energy
, O, which are generated during decomposition, further stabilize the arc, contribute to decarburization, and nitridize the metal surface. In this case, since the amount of nitrogen increases, oxygen may be added alone to control the amount of nitrogen.

<<Example>> Ar: 7.1 vol%, He: 20 vol%, Go
, : 7.5 vol%, O*: 1.5 vol%, and a conventionally known four-component shielding gas, namely Ar: 66 vol%, He: 26 vol%, C.
Welding current was 400 using shielding gas mixed at a ratio of O2: 7.5 vol% and Ot: 0.5 vol%.
The results of welding in A are shown in the table below.

Chemical composition of the welding wire used in the first example (wt%) Chemical composition of the weld metal (wt%) Welding efficiency Chemical composition of the welding wire used in the second example (wt%) Chemical composition of the weld metal (wt%) As is clear from the results of welding efficiency, the shielding gas having the above composition was able to obtain welding results comparable to conventional ones.

Note that Kr may be substituted for a part of He, which is expensive. When Kr is used, since Kr has a larger atomic radius and is easier to ionize than He, a stable arc can be obtained even if the applied voltage is lowered.

Furthermore, laughing gas (Nto) may be used instead of oxygen in the mixed gas as a shielding gas for consumable electrode type arc welding.

In this case, N. N. due to the strong oxidation properties of O molecules and discharge energy. The active nitrogen and active oxygen generated during O decomposition further stabilize the arc and contribute to decarburization and nitridation of the metal surface. Note that when laughing gas is mixed, an increase in the amount of nitrogen is observed, so oxygen alone may be added at the same time.

<<Effect>> In the first invention, the shielding gas mixture is Ar, He, and CO.
, 0, and the mixing ratio of these gases in terms of volume ratio is Ar: 71-75%, He: 18-22%, Co. :
5-10%, ot:t. Since it is set at 2 to 1.8%, the blending ratio of expensive He gas is lower than in conventional shielding mixture gases, so it can be used for shielding with the same welding performance as conventional shielding gases. In addition to being able to provide a mixed gas at a low cost, it also has an increased blending ratio of O compared to conventional products, which improves decarburization performance and increases welding strength at welded parts. . Also, He
In the case where a part of Kr is replaced with Kr, the rare gas Kr is easier to ionize than r{e and Ar, so arc generation becomes easier, so the applied voltage can be lowered.

Further, in the second invention, the shielding gas used in gas shielded consumable electrode type arc welding is ArSHe, CO, N,
Ar
:71-75%, He:18-22%, Co. :5～
10%, NtO: 0.1 to 1.8%, so N. The active nitrogen and active oxygen generated during N and O decomposition due to the strong oxidizing properties of O molecules and discharge energy further stabilize the arc and contribute to decarburization and nitridation of the metal surface. Therefore, the metal structure at the welded part is improved, and a good welded part can be obtained. Note that when N and O are used, the amount of nitrogen may increase too much, so the amount of nitrogen is controlled by adding oxygen alone, and the adverse effects of the increase in the amount of nitrogen can be prevented.

Patent applicant: Iwatani Sangyo Co., Ltd. Procedure Shin City Seisho

Claims (1)

[Claims] 1. A mixed gas composed of Ar, He, CO_2, and O_2, the mixing ratio being Ar: 71 to 75% by volume;
He: 18-22%, CO_2: 5-10%, O_2:
Shielding gas 2 for gas shield consumable electrode type arc welding, characterized in that it is set to 1.2 to 1.8%, and a mixed gas composed of Ar, He, CO_2, and O_2 with a volume ratio of 0.1 to 5. The shielding gas 3 for gas shield consumable electrode type arc welding according to claim 1, which contains 0% Kr, is a mixed gas composed of Ar, He, CO_2, and N_2O, the mixing ratio being Ar by volume, :71~75%
, He: 18-22%, CO_2: 5-10%, N_2
Shield gas 4 for gas shield consumable electrode type arc welding characterized by setting O: 0.1 to 1.8%, a mixed gas composed of Ar, He, CO_2, and N_2O with a volume ratio of 0.1 to 1.8%. The shielding gas for gas shield consumable electrode type arc welding according to claim 3, wherein 1.8% O_2 is added.