Hot vs Cold: What’s the Difference in Carbon Bars?

A105 Carbon Steel Round Bars

What are Hot and Cold Carbon Bars?

All cold-finished goods are hot-rolled, but not all hot-rolled goods are cold-finished in the debate between hot-rolled and cold-finished goods. It all depends on how the bars are handled, though.

Hot rolled items are considered first-stage metal with little finishing and processing because of the tolerances being broader and the finishing not being aesthetically pleasing. Hot rolling brings things to their finished size.

This hot-rolled item then becomes cold finished if it undergoes a number of extra procedures. 

In pressure systems, A105 Carbon Steel Round Bars are used for ambient- and higher-temperature usage. It is a low-carbon steel having silicon, manganese, and less amount of manganese than AISI 1330.

Difference between Hot and Cold Carbon Bars:

The main difference lies in manufacturing. While turning and polishing remove surface flaws and produce a finer, brighter, smoother finish, cold drawing gives a hot-rolled bar a bright, clean, uniform surface that increases tensile and yield strength. Grinding processes the bar to the tightest tolerance while also giving it a high degree of straightness and a superior finish.

The bar is initially cooled at room temperature. Then, it is subjected to the annealing or temper rolling process, which offers advantages such as enhancing the physical characteristics and surface appeal, straightening it, and improving the dimensional tolerances.

Manufacturing of Carbon Bars:

Here are some techniques for producing cold carbon bars to make them more beneficial as compared to hot carbon bars:

1. Cold sketching

This describes the operation of passing a hot-rolled bar through a smaller die. A hot-rolled bar with a cold-drawn surface has a brighter, cleaner, more uniform surface, which boosts tensile strength and yield strength.

Additionally, cold drawing improves machinability significantly and boosts torsional strength, surface hardness, wear resistance, and efficiency. Cold-drawn bars may occasionally even undergo procedures like grinding and polishing.

2. Using the turn and polish

This involves cutting the bar to the proper size using a lathe or turning machine, then polishing it by rotating it over rolls made of hardened steel. Turning will eliminate any surface flaws from the bar’s surface. In comparison to cold drawing, polishing results in a finer, brighter, smoother finish.

3. Grinding

Some bars will go through this process where they are kept very straight throughout the operation and ground to tight tolerance in centerless grinders. They are then burnished to a beautiful, bright sheen after being saw-cut on both ends to provide a square, true cut. As a result, the finished bars have a superior polish, a very high degree of straightness, and an exceedingly narrow size tolerance.

Conclusion: 

The distinctions between hot and cold items aren’t as obvious as the rolling temperature. Everything depends on how that bar is handled, along with the toughness, normalization, and specific numbers regarding the application. 

Hot vs Cold: What’s the Difference in Carbon Bars?

by PIYUSH STEEL time to read: 2 min
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