What's the difference between arc welding and argon arc welding?

The main difference between arc welding and argon arc welding is that the protection forms in the welding process are different. Manual arc welding is to isolate oxygen and nitrogen in the air by covering the smoke produced by covered electrode coating combustion, and cover it on the weld after combustion to prevent the weld from cooling too fast to produce defects, thus achieving the protection effect; Argon arc welding is to form a protective zone around the molten pool by argon in inert gas to isolate the air and form a weld. Welding methods are different. Manual arc welding can be operated by one hand; Argon arc welding must be completed by the cooperation of both hands. Hold a gun in one hand and send welding wire evenly in the other. Applicable workpieces and places are different. Argon arc welding is easier to obtain good shape and quality than arc welding, but the cost of argon arc welding is higher than arc welding.

Arc welding process

Under the thermal action of arc, the coating can produce gas shielded arc on the one hand, and slag can be produced to cover the surface of molten pool on the other hand to prevent the interaction between molten metal and surrounding gas. In addition, the more important role of slag is to produce physical and chemical reaction with molten metal or add alloying elements to improve the properties of weld metal.

Argon arc welding process

Argon gas is used to protect the metal welding material, and the welding material is melted into liquid by high current to form a molten pool on the welding material, so that the welding metal and the welding material can be metallurgically combined. When steel casting manufacturers weld castings by argon arc welding, argon gas will be continuously sent during high-temperature melting welding, so that the welding materials will not contact with oxygen in the air, so that the welding materials can be prevented from being oxidized. Argon arc welding can weld stainless steel and ferrous metals.

Argon arc welding, in some thin parts, small pipes and pressure pipes, the first layer of backing weld can give full play to its advantages and is easy to control and master. And good formability and quality can be obtained. But there is still a gap between power supply and manual arc welding. And argon protection is needed, which increases the welding cost.

Basic operation skills of manual arc welding

(1) scratch method

Scratching is similar to striking a match. Align the end of covered electrode with the weld, twist the wrist, and make the end of covered electrode scrape gently on the surface of the weldment, then level the wrist and lift the covered electrode for 3-4 mm. When the arc is ignited, the arc length will be kept within the range suitable for the diameter of covered electrode. In order to prevent the surface of the weldment from being scratched during arc initiation, the arc initiation must be scratched at the groove at the front end of the weld.

② Direct hitting method

Align the end of covered electrode with the weld, lower the wrist, gently touch the weldment, and then lift the covered electrode for 3-4 mm. After the arc is generated, quickly flatten the wrist to keep the arc length within the range suitable for the diameter of the covered electrode. Although this method is not easy to master, it is an ideal arc striking method. When welding steel with a greater tendency to harden, it is best to use the direct hit method.

Basic strip transportation method

After the arc is ignited, in order to ensure the weld quality and good forming, the covered electrode should move in three basic directions: in order to maintain the required arc length, covered electrode should gradually feed into the weld pool; In order to obtain a certain width of weld, covered electrode must swing laterally; In order to make the molten pool metal form a weld, the covered electrode must move along the welding direction.

In the practice of welding production, according to different weld positions and joint forms, and considering various factors such as covered electrode diameter, welding current and weldment thickness, different swing processes can be selected.

Arc closing

At the end of welding, if the arc is suddenly extinguished, a concave arc pit will be formed at the end of the weld, which will weaken the strength of the welded joint and produce stress concentration, thus leading to arc pit cracks. Therefore, it is necessary to fill the arc pit with an appropriate arc closing method. Commonly used arc closing methods are:

(1) Circular arc extinguishing method When the arc moves to the weld terminal, the end of the coated electrode moves in a circular motion until the arc pit is filled, and then the arc is extinguished. This method is suitable for thick plate welding.

(2) Back welding arc initiation method When the arc moves to the end of the weld, pause for a while, then back weld for a short time, and then break the arc. This method is suitable for alkaline covered electrode.

(3) Repeated arc extinguishing-arc extinguishing method When the arc moves to the end of the weld, perform arc extinguishing and arc starting actions for many times until the arc pit is filled. This method is suitable for high current or thin plate welding.