<blockquote><font size=1>In reply to:</font><hr>
I was told that gas welding is not as strong as tig since the grains in the metal will be melted when you gas weld. So once your piece has cooled down, it has lost its strength since there are no more grains inside the metal to hold itself together.
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That must be the problem. No more grains.
It sounds like you heard that from someone who may have known what they were talking about but you didn't remember all of what they said.
The grain structure in and around the weld area can change due to the temperature at which the material is heated relative to the critical temperature. There are, many different grain structures that can be present in a given material and it is the grain structure that defines the material properties like strength, ductility, etc. The grains are not lost but rather different molecular bonds are created which result in a different grain structure and thus different mechanical properties.
I was told that gas welding is not as strong as tig since the grains in the metal will be melted when you gas weld. So once your piece has cooled down, it has lost its strength since there are no more grains inside the metal to hold itself together.
<hr></blockquote>
That must be the problem. No more grains.
It sounds like you heard that from someone who may have known what they were talking about but you didn't remember all of what they said.
The grain structure in and around the weld area can change due to the temperature at which the material is heated relative to the critical temperature. There are, many different grain structures that can be present in a given material and it is the grain structure that defines the material properties like strength, ductility, etc. The grains are not lost but rather different molecular bonds are created which result in a different grain structure and thus different mechanical properties.