What can happen when steel gets really hot?
It can’t have escaped anyone’s notice that the weather last week was more than just hot. Lincolnshire saw a record-breaking temperature of 40.2°C on 19th of July which broke the previous record of 2019 by 1.5°C.
Other notable temperatures include: –
- 5,505°C the surface of the sun
- 1,170°C the temperature of the Kilauea volcano lava flow
In the metal fabrication industry, we work with temperatures such as: –
- 1,371°C – 1,540°C the temperature at which steel melts
- 1,650°C the temperature for MIG welding
- 3,325°C the temperature of the tungsten electrode in TIG welding
So, what does happen when steel gets hot?
Heat treating can harden steel, which improves its wear resistance. It can be hardened on just the outside – case hardening or all the way through the steel – through hardening. Exactly how hard the steel becomes depends on the amount of carbon present in the metal. This can make the steel more brittle.
But heating can also weaken steel. Steel can be made more malleable and easy to form by heating the metal to a specific temperature and then cooling it in a slow and controlled way. The resultant, softer metal is also more electrically conductive.
When building bridges, railway lines and other industrial metal work, knowing that as temperatures rise steel expands is very important. For each increase of 38°C steel expands 0.06 – 0.07% in length. This may sound like a tiny increase but a temperature increase of 540°C can cause a 30 meter steel bar to expand by over 24cm.
What this means to us right now
Metal expansion due to extreme heat has been brought sharply to focus recently. Although most of the railway lines can operate when track temperatures heat up to 46°C recently there have been recorded rail temperatures as high as 51°C. This can start to curve the rails, known as ‘buckling’, causing delays and disruption on for commuters and holiday makers alike. You can find more information about network rail here.
We don’t make steel beams, bridges and railway lines – but we still need to be aware of these increases. For example, when we design our rock and roll beds, we need to ensure tolerances are correct so that they will still work perfectly even when the steel expands.
This is why, at Dymond we will always ask a raft of questions about the end use of your products when you work with us, just in case you are going into a volcano or setting up a shop on the sun!