ASTM A333 Grade 6 is one of one of the most frequently made use of low temperature level steel pipes, its minimal solution temperature level is -70 ℃, generally in normalizing or stabilizing and solidifying problem. ASTM A333-GR6 steel has reduced carbon content, superb reduced temperature level toughness, plasticity and welding efficiency, and also little quenching as well as chilly splitting tendency. The low temperature toughness, namely the capability to prevent weak failure from taking place and also expanding at reduced temperature level, is one of the most crucial aspect affecting its welding efficiency.
Common welding techniques for reduced temperature level steel consist of arc welding, immersed arc welding, argon arc welding and more. MIG welding is one of the most extensively made use of automated or semi-automatic welding technique in low temperature level steel welding. Its welding warmth input is 23-40kJ/ cm. According to the mode of droplet transfer, it can be separated right into brief circuit transition procedure (reduced warm input), jet transition process (high warmth input) and pulse jet shift procedure (the greatest warm input). Short-circuit shift MIG welding may have the defect of not enough melting deepness or bad fusion. In order to make the arc more focused as well as obtain acceptable penetration deepness, CO2 or O2 can be contributed to the pure argon shielding gas. The particular amount of addition must be identified according to the steel grades.
Welding material
Welding products (including electrode, wire and also flux, and so on) will be selected according to the welding approach embraced, joint kind as well as groove form and also demands. For reduced temperature level steel, one of the most crucial thing to focus on is to make the weld steel have enough low temperature sturdiness to match the base steel and also reduce the hydrogen diffused in it. Normally, ER80S-Ni1 argon arc welding cord is used.
Welding process
In welding, I-Shape port is made use of for pipes with diameter much less than 76.2 mm, and also complete argon arc welding is performed. For the V-groove of pipe with diameter greater than 76.2 mm, argon arc support as well as multi-layer filling are taken on, or full argon arc welding That's relies on particular pipeline WLDSTEEL size and also pipeline wall surface density.
( 1) Preheating prior to welding.
When the ambient temperature is lower than 5 ℃, the steel pipeline should be preheated, and also the pre-heating temperature is 100 ~ 150 ℃. The pre-heating array is 100 mm on both sides of the weld; Heated by oxyacetylene flame (neutral fire), the temperature was measured evenly at a range of 50 ~ 100 mm from the weld facility for better temperature control.
( 2) Postweld heat therapy
In order to enhance the notch strength of cryogenic steels, many steel tubes have actually been solidified and also toughened up, to make sure that post-weld warmth treatment is not typically required for cryogenic steels, with the exception of thicker weldments or in serious conditions.
If special parts need to be heat dealt with after welding, according to the home heating price, consistent temperature time as well as cooling price of the heat therapy after welding, the following arrangements have to be strictly implemented:
When the temperature increases above 400 ℃, the home heating price will not go beyond 205 × 25/ δ ℃/ h, as well as will not exceed 330 ℃/ h. Constant temperature level time should be 1 h per 25 mm thickness continuous temperature level, as well as will not be less than 15 min, optimum and minimum temperature level throughout the temperature ought to be lower than 65 ℃. After constant temperature level, the cooling rate will not be more than 65 × 25/ δ ℃/ h, and also shall not be higher than 260 ℃/ h, and all-natural cooling can be done listed below 400 ℃.
Tips for welding ASTM A333 Grade 6 tubes
( 1) Preheat strictly according to the arrangements, control the temperature in between the layers, the temperature between the layers is regulated at 100 ~ 200 ℃.
( 2) Strictly control line energy, small current, low voltage, quick welding.
( 3) complete infiltration process need to be adopted, and also the operation mode of brief arc and no swing.
( 4) The residual elevation of the weld is 0 ~ 2mm, and the size of each side of the weld is less than 2mm.
( 5) Nondestructive testing can be performed at the very least 24 hours after the appearance evaluation of the weld is certified.