Deep-sea marine facilities and equipment installation and maintenance, we need the use of underwater welding and underwater cutting. As, the development of marine economy, people growing demand for underwater welding. To meet the needs of our customers and solutions to the relevant circumstances described below: 1, underwater welding
Marine facilities such as offshore drilling platforms and subsea pipeline installation and maintenance, requires better methods of underwater welding and cutting. Requirements process method is safe, high efficiency, good quality of welded joints, equipment reliability and easy as possible.
1.1 "dry" underwater welding
"Dry" also known as the indirect method of underwater welding or soldering diving bell, diving bell apply compressed air to the water discharge, in a certain pressure (with which the water depth equivalent) of gas welding environment.
"Dry" to use more tungsten welding arc welding filler wire, this method can be no more than 300m deep water welding, but productivity is low, it is generally only used for welding the back cover, cover the skin surface electrode manual arc still medication weld. Welding fumes inside the clock must be purified or excluded.
"Dry" the quality of welded joints can be welded on to reach the level of the land, but the adaptive narrow (used for subsea pipeline welding), supporting a long time, high cost, and within minutes the probability of explosion. Therefore, the application subject to certain restrictions.
1.2 "wet" underwater welding
"Wet" welding is divided into general and local drainage Wet Wet. Generally wet welding is characterized by: (1) adaptability, convenient and flexible, low cost; (2) in water and low visibility diving welders poor stability in water, difficult operation; (3) high hydrogen content of weld metal , could easily lead to hydrogen embrittlement, porosity, and cracks; (4) fast cooling rate weldments, welded joints prone to high hardness and microstructure of slag, lack of penetration defects, low ductility and toughness of welded joints.
"Local drainage" wet welding. The joint quality than the average wet Welding Wire has improved significantly. Weld metal and heat affected zone does not exceed the maximum hardness HV350. Joint mechanical properties can be achieved on land, the level of acid electrode of welded joints.
1.3 welding power
Used in underwater welding gas welding arc welding machine on the same power and land. Manual metal arc welding current land should generally be larger than 10 ~ 15%. ≤ 0.42% of the carbon equivalent of carbon steel or low alloy steel, optional features or H08Mn2Si wire electrode 202. Of carbon equivalent> 0.42% or require low-alloy steel weld metal has a higher impact on performance or position of crack resistance, the choice of chrome-nickel stainless steel or nickel-and gold (such as Inconel Ni70Cr20Mo10) welding material. Blowing force, waterproof, anti-porosity and other characteristics.
Local drainage in semi-automatic welding gas drilling platform jacket fixed rod repair and replacement, in the subsea pipeline repair, replacement and add take "three links" pipe welding and other underwater engineering has been applied. Welding work depth of about 38 meters, Stainless Steel Welding pipe working pressure up to 140Kgf/cm2. Joint quality on land to meet the requirements of the corresponding structure of the regulations.
Special 202 welding the welding in the salvage and the reservoir in gate repair and replacement of water pipe, bridge pier construction, welding of steel sheet pile wharf and other aspects of the application.
He asked the process method is safe, high efficiency, in particular that a good quality of welded joints, which, in particular to recommend the company a special purpose welding rod - TECH16080 alloy electrode with water.
Underwater welding TECH16080 it is for all-position welding, vertical down welding can also be of high quality alloy steel electrodes. It has good mechanical properties, which is a high strength, good ductility and toughness. Its outstanding feature is available with water welding, the process performance, easy operation, stable arc, little spatter, weld appearance, easy slag removal, easy arc and the arc, and AC and DC.
It is suitable for high-quality carbon steel, low alloy high strength steel, especially for small pieces of the original plate, short welds, intermittent welds smooth and secure capping.
2, underwater cutting
2.1 underwater electricity - oxygen cutting
Of the normal DC arc welding power source (reverse), to cutting carbon steel, stainless steel, cast iron and non-ferrous metals.
Underwater welding and cutting pliers clamp generally universal, open and close the valve is equipped with a clamp, with the cutting current interruption through and open and close. Clamp electrode head for the folder to eat or cut of the chuck.
Cutting oxygen pressure should be higher than the pressure of the bottom 5 ~ 7Kgf/cm2. Cutting of hollow carbon rods can be used underwater or special cut of from the pipe (outside diameter of 8mm, an inner diameter of 3mm), coated with waterproof leather made from the drug. 2.2 underwater plasma arc cutting
Underwater plasma arc cutting is used, the effective power will be reduced, cutting diminished capacity, arc stability deteriorated, arc more difficult. Therefore, power should increase cutting power, no-load voltage should be increased to 500 ~ 900V. If the cutting depth of 8m thickness 30 ~ 100mm stainless steel work, the current 300 ~ 1000A, operating voltage 180 ~ 450V, Victoria arc current 75 ~ 100A.
Torch should ensure that all parts sealed. Nozzles mounted an outer nozzle, high-speed rotation of the cooling water from the nozzle end of the pore by external spray nozzle out of the formation of umbrella water screen, in order to improve the combustion stability of the plasma arc.
3, underwater welding and cutting safety technology
Underwater welding and cutting the use of DC power supply, as far as possible with low voltage high current. Power placed in the land, the general reverse. Into the water tubes, wires and connectors and solder to, the torch must be waterproof and have good insulation properties. When not working, water circuit should be disconnected.
The operator must comply with underwater welding and cutting of the relevant provisions to ensure safety.
Underwater cutting and welding CUT110 it is slotted iron oxide type coating the electrode, arc blowing force, the use of cutting back and forth on both sides of the slot blowing molten iron, iron slag easy to remove after cutting, the more smooth groove, can be AC and DC.