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How to weld ASTM A333-GR6 reduced temperature steel pipe

ASTM A333 Grade 6 is among the most typically made use of low temperature steel pipelines, its minimum service temperature is -70 ℃, generally in normalizing or normalizing as well as toughening up problem. ASTM A333-GR6 steel has reduced carbon content, excellent low temperature level strength, plasticity as well as welding performance, and also little quenching as well as chilly fracturing propensity. The low temperature level toughness, particularly the ability to stop fragile failing from taking place and also increasing at reduced temperature level, is the most crucial element affecting its welding efficiency.

Normal welding approaches for reduced temperature steel include arc welding, submerged arc welding, argon arc welding and so on. MIG welding is the most extensively utilized automatic or semi-automatic welding technique in reduced temperature steel welding. Its welding heat input is 23-40kJ/ cm. According to the setting of droplet transfer, it can be divided into short circuit transition process (reduced warm input), jet shift process (high warm input) and also pulse jet transition process (the highest heat input). Short-circuit change MIG welding might have the issue of insufficient melting depth or poor blend. In order to make the arc extra focused and obtain satisfying penetration deepness, CO2 or O2 can be contributed to the pure argon shielding gas. The particular quantity of addition should be established according to the steel grades.

Welding product

Welding products (consisting of electrode, cable and also change, and so on) shall be chosen according to the welding approach taken on, joint type and groove form as well as needs. For low temperature steel, the most crucial thing to pay attention to is to make the weld metal have sufficient low temperature level sturdiness to match the base metal as well as lessen the hydrogen diffused in it. Generally, ER80S-Ni1 argon arc welding wire is utilized.

Welding procedure

In welding, I-Shape port is used for pipelines with size much less than 76.2 mm, and full argon arc welding is carried out. For the V-groove of pipe with diameter greater than 76.2 mm, argon arc support as well as multi-layer dental filling are taken on, or complete argon arc welding That's depends on specific pipe size and pipeline wall surface density.

( 1) Preheating before welding.

When the ambient temperature is lower than 5 ℃, the steel pipeline must be preheated, and also the pre-heating temperature level is 100 ~ 150 ℃. The pre-heating range is 100 mm on both sides of the weld; Heated by oxyacetylene flame (neutral flame), the temperature was determined equally at a range of 50 ~ 100 mm from the weld center for much better temperature level control.

( 2) Postweld warm treatment

In order to improve the notch sturdiness of cryogenic steels, the majority of steel tubes have been tempered and solidified, to make sure that post-weld warm treatment is not generally needed for cryogenic steels, besides thicker weldments or in serious problems.

If unique parts need to be warmth dealt with after welding, according to the heating price, continuous temperature time as well as air conditioning price of the heat treatment after welding, the list below arrangements must be purely executed:

When the temperature increases above 400 ℃, the home heating rate will not surpass 205 × 25/ δ ℃/ h, and also shall not go beyond 330 ℃/ h. Constant temperature level time need to be 1 h per 25 mm thickness constant temperature, and also will not be less than 15 minutes, maximum as well as minimum temperature during the temperature level must be lower than 65 ℃. After continuous temperature, the cooling rate will not be above 65 × 25/ δ ℃/ h, as well as will not be greater than 260 ℃/ h, and natural cooling can be done listed below 400 ℃.

Tips for welding ASTM A333 Grade 6 tubing

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

( 2) Strictly control line power, small present, low voltage, fast welding.

( 3) full infiltration procedure have to be adopted, and also the operation setting of short arc and no swing.

( 4) The residual elevation of the weld is 0 ~ 2mm, and the width of each side of the weld is less than 2mm.

( 5) Nondestructive testing can be executed at least 24 hours after the appearance inspection of the weld is qualified.

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