If high pressure chrome steel pipe is to be built, then sections have to be heated up to 300 degrees C before welding can safely commence. Pre-heating is also a fact of life when looking to weld pipes fabricated from other materials - such as low temperature steels and those with low hydrogen requirements. If such welds are to be of high integrity, then pipe interiors need to be purged with argon to eliminate oxygen down to levels below 0.1 per cent.
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