A pressure vessel manufacturing processes can generally be divided into: raw materials acceptance process, marking processes, cutting operations, blasting operations, machining (including planing, etc.) processes, Rolling processes, group processes, Welding Electrode processes (product welding test plate ), non-destructive testing process, opening crossed process, the total inspection process, heat treatment, pressure testing procedures, anti-corrosion process 2 different welding methods have different welding processes. Welder welding process is mainly based on pieces of material, grade, chemical composition, structure type weldments, welding performance requirements to determine. First, to determine the welding methods, such as arc welding, submerged arc welding, TIG welding, MIG welding gas, etc., many types of welding methods, only according to specific circumstances. Determine the welding method, and then to develop welding process parameters, welding parameters of different types, such as arc welding, including: electrode model (or brand), diameter, current, voltage, welding power source type, polarity connection, welding layers, number of channels, testing methods, and so on.
Deep-sea marine facilities and equipment installation and maintenance, need the use of underwater welding and underwater cutting. With the marine economic development, people's growing demand for underwater welding. We will meet customer needs and solutions related to the situation described below:
1, underwater welding
Marine facilities such as offshore drilling platforms and undersea pipelines installation and maintenance, requires better underwater welding and cutting methods. 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 indirect method diving bell underwater welding or soldering, apply compressed air to discharge the water inside the diving bell, in a certain pressure (and in which the water depth equivalent) of gas welding environment.
"Dry" use more tungsten welding arc welding filler wire, this method can be no more than 300m of water in the depths of welding, but productivity is low, it is generally only used for welding the back cover, cover the skin surface electrode manual arc still medication welding. Welding fumes inside the clock must be purified or eliminated.
"Dry" quality of welded joints can be welded on to the land level, but adaptive narrow (used for submarine 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 and sub-drainage is generally wet and partially wet. Generally wet welding is characterized by: (1) wide adaptability, convenient and flexible, low cost; (2) in water and low visibility diving welder poor stability in water, difficult operation; (3) the 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 plasticity and toughness of welded joints.
"Partial drainage" wet welding. The joint quality than the average wet welding has improved significantly. Weld metal and heat affected zone does not exceed the maximum hardness of HV350. Joint mechanical properties can be achieved on the land electrode of the welded joints acid level.
1.3 Welding Supply
Underwater welding machines used for arc Welding Electrode and gas welding power supply on the same land. Manual arc welding current should be higher than on land generally is 10 to 15%. ≤ 0.42% of the carbon equivalent of carbon steel or low alloy steel, optional or H08Mn2Si special wire electrode 202. Of carbon equivalent> 0.42% of low-alloy steel weld metal or require higher performance or position of the impact of crack resistance, the choice of chrome-nickel stainless steel or nickel-and gold (such as Inconel Ni70Cr20Mo10) soldering materials. 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 additional pick "three links" pipe welding and other underwater engineering has been applied. Welding work depth of about 38 meters, welding pipe working pressure up to 140Kgf/cm2. Joint quality land to meet the requirements of the appropriate structure of rules.
Special welding electrodes 202 of the salvage and the reservoir gate in welding 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, requires 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 can be all-position welding, can also be vertical down welding of high-quality alloy steel welding rod. It has good mechanical properties, that is, high strength, good ductility and toughness. Its outstanding feature is available with water welding, the process performance, easy operation, stable arc, little spatter, bead 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, particularly suitable for small pieces of the original board, short welds, intermittent welds and smooth capping safety.
2, underwater cutting
2.1 Underwater electricity - oxygen cutting
Commonly used in DC arc welding power source (reverse), can cut 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 cuts and interruption of current through the gate. Clamp electrode head for the folder to eat or cut of the chuck.
Cutting oxygen pressure should be higher than the bottom pressure 5 ~ 7Kgf/cm2. Cutting of hollow carbon rods can be used underwater cutting or a dedicated section, the steel tube (diameter 8mm, diameter 3mm), coated with waterproof leather made medicine.
2.2 underwater plasma arc cutting
Plasma arc cutting is used underwater, the effective power will be reduced, cutting diminished capacity, arc stability deteriorated, arc more difficult. So cutting the power supply should be increased no-load voltage should be increased to 500 ~ 900V. If the cutting depth of 8m thickness of 30 ~ 100mm stainless steel work, the current 300 ~ 1000A, Voltage 180 ~ 450V, D arc current of 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 through the outer nozzle spray out to form a water screen, umbrella, in order to improve the stability of the plasma arc burning.
3, underwater welding and cutting safety technology
Underwater welding and cutting the use of DC power, as a low voltage high current. Power to place on land, the general reverse. Into the water pipe, wire and connectors, and weld to, the torch must be waterproof and have good insulation properties. When not working, water circuit should be disconnected.
Underwater cutting and welding CUT110 it is slotted iron oxide type coating of the electrodes, Arc force, the use of cutting back and forth on both sides of the slot blowing hot metal, iron slag easy to remove after the cut, the more smooth groove, can be AC and DC.