welding rod

Introduction

The covered electrode is a uniform and centripetal coating of the coating (coating) on ​​the core outside the metal core. The core of the welding rod is the metal core of the welding rod. In order to ensure the quality and performance of the welding seam, the content of each metal element in the welding core is strictly regulated, especially for the content of harmful impurities (such as sulfur, phosphorus, etc.). The limit is better than the base metal. The electrode consists of two parts: the core and the coating. The types are different and the cores are different. The composition of the core directly affects the composition and properties of the weld metal, so the harmful elements in the core should be as small as possible.

Welded carbon steel and low alloy steel cores are generally selected from low carbon steel as the core and added with manganese, silicon, chromium, nickel and other components (see National Standard GB1300-77 for details). The reason for using low carbon is that the steel wire has good plasticity when the carbon content is low, and the wire drawing is relatively easy. On the other hand, the CO content of the reducing gas can be reduced, the splash or pores can be reduced, and the temperature at which the weld metal is solidified can be increased. It is good for overhead welding. The addition of other alloying elements is mainly to ensure the comprehensive mechanical properties of the weld, and also has a certain effect on the welding process performance and the removal of impurities.

High-alloy steel and other metal materials such as aluminum, copper, cast iron, etc., in addition to the requirements of the metal core of the weld metal, also control the content of impurities, and often add certain alloying elements according to the process requirements.

The welding rod is a molten electrode for coating electrode arc welding, which is composed of two parts: a coating and a welding core. The chamfer at the front end of the electrode has a chamfer of about 45°, which is for the purpose of arc ignition. There is a section of bare core at the end, which accounts for about 1/16 of the total length of the electrode, which facilitates the clamping of the welding tongs and facilitates electrical conduction. The diameter of the electrode actually refers to the diameter of the core. It is usually 2, 2.5, 3.2 or 3, 4, 5 or 6 mm. The most commonly used are small 3.2, small 4 and small 5, and the length is "L". "Generally between 200 and 550 mm.

Claim

(1) It is easy to lead the arc to ensure the stability of the arc and the splash is small during the welding process.

(2) The melting speed of the coating should be slower than the melting speed of the core to form a flared sleeve (the length of the sleeve should be smaller than the diameter of the core), which is conducive to the droplet transfer and the protective atmosphere;

(3) The specific gravity of the slag should be less than the specific gravity of the molten metal, and the solidification temperature should also be slightly lower than the solidification temperature of the metal, and the slag shell should be easily removed;

(4) having alloying and metallurgical treatment;

(5) Adapt to welding at various locations.

classification

According to different situations, there are three classification methods for welding electrodes: classification according to the purpose of welding rods, classification according to the main chemical components of the coatings, and classification according to the characteristics of the molten slag after melting of the coatings.

According to the use of the welding rod, there are two forms of expression. One is compiled by the former Ministry of Machinery Industry. The welding electrode can be divided into: structural steel welding rod, heat-resistant steel welding rod, stainless steel welding rod, surfacing welding rod, low-temperature steel welding rod, cast iron welding rod. , nickel and nickel alloy electrodes, copper and copper alloy electrodes, aluminum and aluminum alloy electrodes and special purpose electrodes. The second is the national standard, which is carbon steel electrode, low alloy electrode, stainless steel electrode, surfacing electrode, cast iron electrode, copper and copper alloy electrode, aluminum and aluminum alloy electrode. There is no principle difference between the two. The former is indicated by a commercial grade and the latter by a model.

If classified according to the main chemical composition of the electrode strip, the electrode can be divided into: titanium oxide electrode, titanium oxide calcium electrode, ilmenite electrode, iron oxide electrode, cellulose electrode, low hydrogen electrode , graphite type electrode and salt-based electrode.

If the characteristics of the slag are classified according to the characteristics of the slag after melting, the electrode can be divided into an acid electrode and a basic electrode. The main component of the acid electrode coating is an acidic oxide such as silica, titania, or ferric oxide. The main component of the alkaline electrode coating is an alkaline oxide such as marble or fluorite.

There are many classification methods for welding electrodes, and the welding electrodes can be classified according to the application, the alkalinity of the slag, the main components of the electrode coating, and the performance characteristics of the welding rod. Classified by purpose

China's current welding rod classification method is mainly based on the national standard of welding rods and the "welding material samples" compiled by the former Ministry of Machinery Industry. The welding rod models are divided into 8 categories according to national standards, and the welding rod grades are divided into 10 categories according to their purposes.