Calculating cooling time t8/5

Don't worry. We're not going to bog you down here with a long treatise on technical and scientific basics; we'll just cover the key points of the subject. After all, the heading is "Practical knowledge", not "Research and technology".

t8/5 is the time it takes for the weld seam and adjacent heat-affected zone to cool from 800 °C to 500 °C. This is the interval in which the most important structural changes occur in the steel.

• If the period is very short, ferritic, perlitic, bainitic and martensitic structures can form. There is also the risk of coarse grain formation, and this has negative effects on the mechanical properties of the steel.
• If the period is very long, only ferrite and perlite can form from the austenite, and this reduces the hardness.

Steps you can take:

• Avoid high peak temperatures during welding. You can, for example, use a fast-regulating, microprocessor-controlled power source, in combination with low-heat welding processes such as coldArc, rootArc or forceArc where appropriate.
• Use our cooling time calculator to determine the correct preheating and cooling times for a perfect welding result.

With its simple and self-explanatory menu navigation, the EWM calculator is a powerful partner when it comes to calculating the required cooling time, and ensuring the desired welding result.

All values are, of course, purely theoretical and may vary considerably under practical conditions.

Our tip:
Always make a test weld under real conditions using the calculated values.