The core and the drug electrode by the welding of two parts the skin. Metal welding electrode is external to the core coating (drug skin) evenly to carefully applied pressure on the core welding. Different types of welding rod, welding core is different. Welding electrode metal core that is the core, in order to ensure the quality and performance of the weld, butt in the core content of the metal elements, there are stringent requirements, especially for harmful impurities (eg sulfur, phosphorus, etc.) content, there should be strict limitations, better than the base metal. Welding core components directly affect the weld metal composition and performance, so the welding core of the harmful elements to as little as possible.

Welded carbon steel and low alloy steel welding core, low-carbon steel is generally used as a welding core, and fill up the manganese, silicon, chromium, nickel and other ingredients (see the national standard GB1300 an 77 wire). The reason one is low carbon low carbon steel wire plastic, wire drawing easier, on the other hand reducing gas to reduce CO content to reduce spatter or porosity, and increased the temperature of the weld metal solidification, beneficial to the overhead position welding. Other major alloying elements added to ensure the weld mechanical properties, while the welding performance and to remove impurities, also have a role.

High-alloy steel and aluminum, copper, iron and other metal materials, its core components in addition to welding and welded metal similar requirements, but also have control of impurities, according to process requirements often adding certain alloying elements.

Electrode is coated with a drug for skin melt welding electrodes used in arc welding, it is a drug and the skin-core solder composed of two parts. Drug in the skin are the front electrode of about 45 ° chamfer, which is to facilitate the arc. In the rear there is a bare core welding, welding rod length of about 1 / 16, to facilitate the welding clamp holding and help conduct electricity. Electrode diameter Chung actually refers to welding core diameter) is usually 2,2. 5,3 2 or 4, 5 or 6mm and other types of specifications, used a small 3.2 small 4 small 5 three species, its length "L" is generally between 250 ^ -450 mm.

1. Welding core

Electrode was covered medicine bag welding the metal core as the core. Welding core is generally a certain length and diameter of the wire. Welding, welding core has two effects: first, conduction welding current, arc to convert electrical energy into heat energy, the second is filled with weld metal core itself is melted as the liquid base material with the formation of the weld metal fusion.

Welding electrodes, welding metal core part of the total weld metal. So the chemical composition of welding core {a direct impact on the quality of the weld. Therefore, as the electrode core wire is a single potential with the provisions of its independence and composition grades. If used for submerged arc welding, electroslag welding, gas welding, gas welding method for welding filler metal, then known as the wire. (1) welding in the core of the impact of alloying elements on the welding

1) carbon (C) Carbon is the main alloying elements in steel, when the carbon content increases, the steel {strength, hardness markedly improved, and the plastic lower. In the welding process, the carbon oxygen play a role in the arc under high temperature and oxygen compounds, generating carbon monoxide and carbon dioxide gas, the air around the arc and weld pool exclusion zone to prevent the oxygen in the air, nitrogen gases adverse impact on the pool, reducing the weld metal oxygen and nitrogen. If the carbon content is too high, to restore the role of severe, will cause a larger splash and pores. Taking into account the carbon steel hardened to the crack and its increased sensitivity to the effects of low-carbon steel welding core of the general cluster 0.1%.

2) Manganese (Mn) of manganese in steel is a good alloying agent, as the manganese content increases, the strength and toughness will be increased. In the Welding Electrodes, the manganese is also a good dose of oxygen, can reduce the oxygen content in the weld. Together to form manganese sulfide and manganese sulfide float in the slag, thus reducing the tendency to weld hot cracking. Therefore, carbon structural steel welding core general's manganese content is 0.30% ~ 0.55%, some special-purpose wire welding, the manganese content of up to 1.70% a 2.10%.

3) Silicon (Si) silicon is a good alloying agent in steel by adding an appropriate amount of silicon can increase the steel yield strength, flexibility and acid resistance; if the content is too high, reduce the plasticity and toughness. In the welding process, silicon also has good oxygen capacity and oxygen to form silicon dioxide, but it will increase the slag viscosity, easy to promote non-metallic inclusions generated.

4) Chromium (Cr) chromium steel to improve hardness, wear resistance and corrosion resistance. For low carbon steel, the chromium is a kind of accidental impurities. The main features of chrome is easy to rapid oxidation of metallurgy, the formation of refractory oxide chromium oxide (Cr203), which increases the likelihood of weld metal inclusions. Transition to the chromium oxide slag, the slag viscosity can improve, lower liquidity.

5) Ni (NO nickel on the toughness of the steel has a relatively significant effect, the general low-temperature impact values ​​are higher, the appropriate incorporation of some of the nickel.

6) Sulfur (S) Sulfur is a harmful impurity, with the sulfur content increases, the tendency to increase weld hot cracking, so the welding core sulfur content of no greater than 0.04%. Important in the welded structure, the sulfur content not more than 0.03%.

7) P

(2) the classification of welding core

Welding core is based on national standards, "welding wire" (GB 1300-77) of the classification provided for the welding of steel wire can be divided into carbon steel, alloy steel, stainless steel three categories.

2 drug skin

Pressure applied to the welding surface of the core is called drug-coated skin. Drug skin electrodes in the welding process plays an extremely important role. The use of a drug-free light skin electrode welding, the welding process, oxygen and nitrogen in the air will be a substantial intrusion of molten metal, the metal iron and beneficial elements carbon, silicon, manganese oxide and nitride formation of various oxides and nitride, and left in the weld, causing the weld slag or cracks. And melt into the pool of gas may produce large amounts of weld porosity, these factors can make the weld mechanical properties (strength, impact value, etc.) greatly reduced, while the weld brittle. In addition, the use of optical Carbon Steel Welding Rod arc is very unstable, serious splash, poor weld.

People in practice found that out in the light electrode coated with a layer formed from a variety of minerals and other skin medicines, can make the arc combustion stability, improved weld quality, this electrode is called coated electrodes. With the continuous development of industrial technology, it created a now widely used high-quality thick coated electrodes.