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The underwater welding overview and requirements Rod
- Special
Equipment installation and maintenance of marine facilities and deep-sea underwater welding and underwater cutting, along with the development of the marine economy, expanding demand for underwater welding. Relevant solutions to meet customer demand, as follows:
1 underwater welding
Marine facilities, such as the installation and maintenance of offshore drilling and production platforms and subsea pipelines, require the better underwater welding and cutting. Security requirements process for the production of high efficiency, good quality of welded joints, and equipment and as much as possible simple.
1.1 "dry underwater welding
"Dry law" also known as indirect underwater welding or diving bell method welding, for compressed gas discharged water inside the diving bell, welding gas environment with some pressure (in which the water depth equivalent).
Use of "dry" Welding WireTIG tungsten fill, this approach can not more than 300m of the depths of the welding, but low productivity, it is generally used only for the back cover welding, manual arc cover surface is still covered electrodes medication welding. The flue gas welding clock must be decontaminated or excluded.
"Dry" the quality of welded joints can reach the level of welding on land, but the adaptive narrow (used for subsea pipeline welding), auxiliary long time, high cost, and the probability of explosion bell. Therefore, the application is subject to certain restrictions.
1.2 "Wet underwater welding
The "wet" welding was divided into general the Wet and local drainage wet. The generally wet welding characteristics: 1) wide adaptability, convenient and flexible, and low cost; 2) water visibility is low, diving welders stability in water, difficult operation; 3) high hydrogen content of the weld metal, and could easily lead to hydrogen embrittlement, pores and cracks; 4) weldment cooling rate faster, welded joints prone to high hardness microstructure and slag, incomplete penetration defects, low ductility and toughness of welded joints.
"The local drainage" wet welding. A significant improvement in the quality of their joints than the average wet welding. The weld metal and heat affected zone does not exceed the maximum hardness HV350. The joint mechanical performance can be achieved the acid electrode of welded joints in the land level.
1.3 welding power source
The gas welding underwater welding arc welding machine power and land on the same. Manual arc welding current should generally be more than the land is 10 to 15%. ≤ 0.42% of the carbon equivalent of carbon or low alloy steel, optional a special 202 the electrode or H08Mn2Si wire. Of carbon equivalent of 0.42% of the low-alloy steel weld metal has a higher status impact performance or crack performance, choice of chrome-nickel stainless steel or nickel-and gold (as a result Inconel Ni70Cr20Mo10), the welding material. And
Blowing force, waterproof, strong anti-stomatal characteristics.
1.4 Applications
The local drainage gas protection semiautomatic welding rod repair and replacement of fixed drilling platform jacket, subsea pipeline repair, replacement and then the "three direct links" pipe welding and other underwater engineering has been applied. Welding work approximately 38 meters water depth, welded pipe working pressure up to 140Kgf/cm 2. Joint quality land to meet the regulations require the corresponding structure.
Special 202 welding electrodes in welding the salvage and Reservoir Gate river tube repair and replacement, has been applied to the bridge pier construction, pier welding of steel sheet pile.
He asked the process safe, high production efficiency, and in particular the requirements of quality of welded joints, In this regard, the company is particularly recommended to you a special purpose welding rod - TECH16080 alloy steel with a water electrode.
Underwater welding electrodes TECH16080 it can be all-position welding can also be vertical down welding of high-quality alloy steel electrodes. It has good mechanical properties, that is, with high strength, good ductility and toughness. Prominent feature with water welding process performance, easy to operate, stable arc, little spatter, weld bead appearance, easy slag, the arc and arc easily, but AC and DC.
It is suitable for high-quality carbon steel, high strength low alloy steel, especially suitable for the original board small pieces, short welds, intermittent welds and smooth capping.
2 underwater cutting
The 2.1 underwater electric - oxygen cutting
The general DC arc welding power supply (reverse), cutting carbon steel, stainless steel, cast iron and non-ferrous metal.
The underwater welding pliers and cutting pliers generally generic, the clamp is equipped with opening and closing the valve, with the cutting current through and interrupt the opening and closing. The clamp head clip eat electrode or cut Article chuck.
Cutting oxygen pressure should be higher than the bottom pressure 5 ~ 7Kgf/cm 2. Cut the strips can be used hollow carbon rods or dedicated underwater cutting strips, made by steel tube (outside diameter of 8mm, inner diameter of 3 mm), coated with waterproof drug skin.
The 2.2 underwater Plasma arc cutting
Plasma arc cutting is used underwater, and the effective power will be reduced, cutting diminished capacity, poor arc stability, arc more difficult. Cutting Power should increase the no-load voltage should be increased to 500 ~ 900V. 8m water depth cut 30 ~ 100mm thick stainless steel work, the operating current of 300 to 1000A, operating voltage 180 ~ 450V, dimensional arc current 75 ~ 100A.
The torch should ensure a good seal of the various components. Nozzles mounted an outer nozzle, the cooling water from the high-speed rotation of the nozzle end portion is injected through the outer nozzle channel, to form a mushroom water screen, to enhance the plasma arc combustion stability.
3 underwater welding and cutting safety technology
Underwater welding and cutting using DC power as much as possible with low voltage and high current. The power is placed in the land, and generally use reverse.
Tube into the water line connector and welding the torch must have good waterproofing and insulation properties. Underwater circuit should be disconnected when not working.
The operator must comply with the relevant provisions of underwater welding and cutting, in order to ensure safety.
Underwater cutting and slotted electrode CUT110 the iron oxide type coating electrodes, Arc force move before and after the use of cutting strips of hot metal on both sides of the blowing notch, easy to remove after cutting iron slag, trough than smooth can AC and DC.
joint form
SMAW basic joint form butt, lap, fillet and T-. The select joint form, mainly based on the structure of the product, and considering the stress conditions, processing costs and other factors. Butt and lap force uniform save metal, it is most widely used. Butt joints compare the sizes of materials and assembly requirements
Strict.
groove forms
Processed into a certain geometrical shape, the area to be welded in the welding member according to the design or process needs, and the groove by the groove after assembly constituted called. The use of mechanical (cutting, planing or turning), flame or arc (carbon arc gouging), chamfering process called open groove. The open groove the arc to look deep into the bottom of the groove, to ensure that the underlying penetration, ease of cleaning residue, and good weld formation, but also to adjust the proportion of the base metal and filler metal in the weld metal.
Arc beveling form should be based on the structure of the weldment, the thickness and technical requirements optional common groove form: I-shaped, V-shaped, X-shaped, Y-shaped, double-Y shape, a U-shaped groove with a blunt edge, etc. . General butt joint thickness 1-6mm, with I-shaped groove weld on one side or both sides welded to ensure penetration; plate thickness ≥ 3mm, in order to ensure the effective thickness of weld penetration, improve weld forming processed into a Y-shaped, X-shaped, U-shaped and other shapes of groove.
In the plate thickness with the same double-sided groove than the single-sided groove, a U-shaped groove is consumed than the V-shaped groove electrode small, small welding deformation, these advantages become more prominent as the thickness increases. U-shaped groove processing more difficult, groove processing fees, generally used for more important structures.
When different thickness steel plate butt groove side of the thick steel plate thinning treatment, should be the requirements of the relevant standards and technical documents.
The form and dimensions of the groove are generally vary with the thickness and the Shihai welding method, welding position, the amount of heat input. Groove processing methods and the workpiece material. See the national standard of the form and size of the groove GB/T985-1988 "gas welding, arc welding and gas shielded weld groove of the basic form and size."
weld pad
When requirements weld full penetration and only from the connector side welding, in addition to forming side welding welding operation technology, but also can be used to back seam plus Garmnent. The purpose of using theWelding Wire pad is to provide the conditions of the first layer, the metal is deposited over the pad, thereby eliminating the layer of molten metal to leak through the bottom from the joint.
The used pad has four forms: the lining of the backing weld copper liner and non-metallic liner.
1) lining the strip of metal strips on the connector on the back. The first weld combination of both sides of the joint in - starting with the lining of the phase. If the lining of not impede the use of the joint characteristics, can be retained in the original position; otherwise, furring shall be removed out. The lining of the required material to match with the base metal and Welding Rodused in metallurgy.
2) copper gasket copper liner is sometimes used to support the joint underlying weld pool, it applies to straight butt weld. The higher the thermal conductivity of copper, help to prevent the weld metal and the liner fusion.
3) non-metallic liner refractory liner is a scalable Molding jig or pressure-sensitive tape snapping the back of the joint, it is suitable for space curved butt weld. The SMAW method sometimes use this pad. Should be used to follow the specifications recommended by the liner manufacturer.
4) the backing weld backing weld-sided groove weld joints in one or more channel the back of the weld. Weld before the first welds deposited in front of the groove in the connector on the back of Deposited after the bottoming weld is completed, all the rest of the weld groove from the front.
