Welding puts pressure on the joints you fuse together. Metal under stress becomes brittle. Post-weld heat treatment is the answer to relieving that stress.
Post Weld Heat Treatment (PWHT) is about more than just controlling the heat on your joints. If you don’t perform PWHT after crucial welds, you lose both tensile strength and structural integrity. Lose too much of either of these, and your welding will weaken the overall structure rather than add strength to it. These other 6 benefits of Post Weld Heat Treatment should help explain why it’s a non-negotiable in metalworking.
The 6 Benefits of PWHT
We consulted with the experts to find out what the benefits of PWHT are. This is what they had to say.
1 – Makes the Metal Less Brittle
AxiomHT post weld heat treatment services say, the main reason for post weld heat treatment is to reduce the brittleness of the fractured join. The process of heating, wetting, and cooling back down the joints takes some of that brittleness out. It does this by redistributing the heat and, therefore, the pressure that the weld is under.
2 – Reduces Stress on the Joints
Making the metal less brittle and taking the pressure off the joint are the same thing, both fixed by PWHT. When you start to heat up a weld, the metal molecules vibrate extremely quickly. This volatility can lead to breaks immediately after the weld is complete. PWHT reduces the pressure the joint is under immediately after the weld.
3 – Regulates the Temperature
When you weld metals together, you heat them to elevated temperatures. Obviously, heating metal to high temperatures is dangerous, and you cannot leave it hot. By using a post weld heat treatment, you improve the hardness by making it less brittle while you are also stabilizing the temperature.
4 – Stops Hydrogen Induced Cracks Appearing
Occasionally hydrogen becomes trapped in the spaces between the metal molecules. This trapped hydrogen must escape and will eventually cause cracks in the joints. Instead of waiting for hydrogen-induced cracking to cause your metal to become brittle and crack, a post weld heat treatment reduces the risk by giving the hydrogen a safer way out.
5 – PSHT Tempers the Metal
We all know that tempered metal is far stronger than standard, non-treated metal. We create tempered metal by heat treating it. The metal is heated to the critical point, and before it melts, it is left to cool off naturally. PSHT is the faster version of this, where the weld is heated to a critical point and cooled down safely.
6 – It Reduces the Hardness
When we talk about tempering improving the hardness of a metal, we mean it is reducing. The harder the metal is, the likelier it will be, brittle and crack. We want the metal to be slightly softer so that the weld stabilizes. A metal that has a little softness bends easier. If you are building a structure in high winds or in an earthquake zone, brittle metals can be dangerous.
PWHT is Better for Welded Metals
If you have welded metals on your site, post weld heat treatments will make your structure safer for longer.
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