ASTM A333 Grade 6 is one of the most generally used low temperature steel pipes, its minimal service temperature level is -70 ℃, typically in stabilizing or normalizing and also tempering problem. ASTM A333-GR6 steel has low carbon content, outstanding reduced temperature level durability, plasticity and also welding efficiency, and also tiny quenching as well as chilly cracking tendency. The low temperature level toughness, namely the ability to prevent breakable failure from happening and also increasing at low temperature, is one of the most crucial element influencing its welding efficiency.

Regular welding methods for low temperature level steel include arc welding, submerged arc welding, argon arc welding and more. MIG welding is the most commonly used automatic or semi-automatic welding method in reduced temperature level steel welding. Its welding warm input is 23-40kJ/ centimeters. According to the mode of bead transfer, it can be separated right into brief circuit change process (reduced warmth input), jet shift process (high warmth input) as well as pulse jet transition process (the greatest heat input). Short-circuit shift MIG welding might have the defect of insufficient melting deepness or poor combination. In order to make the arc much more focused and also acquire sufficient penetration deepness, CO2 or O2 can be contributed to the pure argon securing gas. The specific amount of enhancement ought to be established according to the steel grades.

Welding product

Welding products (including electrode, wire and also flux, etc.) will be chosen according to the welding approach taken on, joint kind as well as groove form and needs. For reduced temperature level steel, the most essential point to take notice of is to make the weld steel have enough low temperature level durability to match the base metal as well as lessen the hydrogen diffused in it. Typically, ER80S-Ni1 argon arc welding wire is utilized.

Welding procedure

In welding, I-Shape port is made use of for pipelines with size much less than 76.2 mm, and full argon arc welding is performed. For the V-groove of pipe with diameter above 76.2 mm, argon arc backing and multi-layer filling are embraced, or full argon arc welding That's depends on certain pipe diameter as well as pipeline wall density.

( 1) Preheating before welding.

When the ambient temperature level is lower than 5 ℃, the steel pipeline need to be preheated, as well as the pre-heating temperature is 100 ~ 150 ℃. The pre-heating variety is 100 mm on both sides of the weld; Heated by oxyacetylene fire (neutral fire), the temperature was gauged uniformly at a distance of 50 ~ 100 mm from the weld center for better temperature level control.

( 2) Postweld warm treatment

In order to improve the notch toughness of cryogenic steels, many steel tubes have been toughened up and tempered, to ensure that post-weld heat therapy is not typically needed for cryogenic steels, besides thicker weldments or in extreme problems.

If special parts need to be warm dealt with after welding, according to the heating rate, consistent temperature level time and also cooling rate of the heat therapy after welding, the following arrangements have to be purely applied:

When the temperature increases over 400 ℃, the home heating rate shall not surpass 205 × 25/ δ ℃/ h, and WLDSTEEL will not go beyond 330 ℃/ h. Constant temperature time should be 1 h per 25 mm density constant temperature, and will not be much less than 15 min, optimum and also minimum temperature level throughout the temperature level ought to be lower than 65 ℃. After continuous temperature level, the cooling price will not be above 65 × 25/ δ ℃/ h, as well as shall not be above 260 ℃/ h, as well as all-natural cooling can be done listed below 400 ℃.

Tips for welding ASTM A333 Grade 6 tubing

( 1) Preheat strictly according to the provisions, control the temperature level between the layers, the temperature between the layers is regulated at 100 ~ 200 ℃.

( 2) Strictly control line energy, tiny present, low voltage, quick welding.

( 3) complete infiltration procedure should be taken on, and the operation mode of brief arc as well as 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 hrs after the look assessment of the weld is certified.