1. Non-uniform metallurgical transformation during heat treatment.

2. Lowered surface hardness and strength.

3. Reduced fatigue strength of the heat-treated product.

4. Fatal accidents in the case of rail steel.

5. Premature tool failure leading to production losses.

1. Good rolling practice, free form interruptions, normally helps to minimize decarburisation. This is too theoretical and ideal. In practice, due to unexpected breakdowns, some billets remain in the reheating furnace for a longer time. The rolled products corresponding to these billets show higher level of decarburisation. It is very difficult to segregate them.

2. Use of controlled atmospheres like cracked ammonia, exothermic / endothermic gas, nitrogen, liquid hydrocarbon, etc. effectively controls decarburisation. But they cannot be used to the need of additional capital investment, highly skilled operators and safety regulations. Also, frequent entry and exit of rolling stock into and out of the re-heating furnace makes controlled atmosphere ineffective since ingress of air cannot be prevented.

3. Use of a barrier coating which can prevent the basic reactions of decarburisation is the most economical method. Decarburisation and scaling are simultaneous phenomenon; controlling the former leads to a free bonus of controlling the latter without any extra cost.