Welding Inspection & Metallurgy API ICP Self Study Notes

Gases, such as hydrogen, which become entrapped in the melt as it solidifies,
can also affect casting integrity. In some cases, these create voids or porosity
in the structure, or can lead to cracking. Weldments are particularly prone to
cracking because of trapped hydrogen gases. This problem can be avoided
by careful cleaning of the weld bevels to remove hydrocarbons and moisture,
the use of low-hydrogen electrodes, correct storage or baking of electrodes
and use of proper purging techniques with high quality welding gases.
For refinery applications, castings are used primarily for components having
complex shapes in order to minimize the amount of machining required.
These include pump components (casings, impellers, and stuffing boxes) and
valve bodies.( 考 试 题 ?)