Welding in the core of the welding of alloy elements on
1) Carbon (C) Carbon is the main alloying elements in steel, when the carbon content increases, the steel {strength and hardness significantly increased, while the plasticity decreases. In the welding process, carbon deoxidation play a role in the arc under high temperature combined with the role of oxygen to produce carbon monoxide and carbon dioxide gas, the arc around the air exclusion zone and the weld pool to prevent the air of oxygen, nitrogen and harmful gases adverse impact on the pool to reduce the weld metal oxygen and nitrogen content. If the carbon content is too high, reduction of severe, will cause a larger splash and stomata. Taking into account the hardening of carbon steel and its increasing impact on the crack sensitivity,  core general cluster 0.1 percent.
2) Manganese (Mn) of manganese in welding alloys  is a good agent, the manganese content was increased, the strength and toughness will be increased. In the welding process, the manganese is also a good oxygen scavenger, to reduce the oxygen content in the weld. Together with the formation of manganese sulfide MnS float in the slag, thus reducing the tendency of weld hot cracking. It is generally the core of carbon structural welding electrode material manganese content is 0.30% ~ 0.55%, some special-purpose wire welding, the manganese content of up to 1. 70% of a 2.10%.
3) Silicon (Si) alloy of silicon is also a good agent, adding an appropriate amount of silicon steel can improve the yield strength, flexibility, and the acid resistance; if content is too high, reduce the plasticity and toughness. In the welding process, silicon also has good oxygen capacity, with oxygen to form silicon dioxide, but it will increase the slag viscosity, easy for non-metallic inclusions generated.
4) Chromium (Cr) chromium can increase the hardness, wear resistance and corrosion resistance. For low carbon steel, the chromium is a kind of accidental impurities. The main metallurgical characteristics of chromium is easy to rapidly oxidized to form a refractory oxide of 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) Nickel (Ni nickel on the toughness of steel have more significant effects, generally require a higher temperature impact value, the proper incorporation of a number of nickel.
6) Sulfur (S) Sulfur is a harmful impurity, with the increase in sulfur content, will increase the weld hot cracking tendency, so the content of sulfur in the core welding shall not exceed 0.04%. Important structure in the welding and sulfur content of no greater than 0.03%.
7) Phosphorus

All cellulose-based welder down Welding Wire of the main requirements are:
(1) has a steep drop external characteristics;
(2) The thrust of current work outside the trailer when its value should be large enough;
(3) an appropriate increase in drag outside the static characteristic curve inflection point, in order to achieve a small droplet.

At present, the number of regional long-distance pipeline network construction and some areas of water, automatic, semi-automatic welding electrode material and equipment due to environmental constraints, not easily accessible areas of the long-distance pipeline construction project and more use of this technology, such as Zhenhai Refining & Chemical - Hangzhou Cambridge pipeline project.

All cellulose-based downward welding process parameters in Table 1. The process is the key to backing weld forming side welding when required; Yang welding position to prevent the droplets appear on the back of the gravity sag and adhesion of hot metal rod. Next to the welding of both early-type cellulose.

Keywords: mig welding wires