The correct answer is D. All of the above.
Blister steel is a type of steel that is obtained by the cementation process. In this process, wrought iron is heated and then packed in a mixture of charcoal and iron oxide. The iron oxide reacts with the carbon in the charcoal to form cementite, which is a hard and brittle form of iron carbide. The cementite forms blisters on the surface of the wrought iron, which gives blister steel its name.
Blister steel is full of fissures and cavities because of the way it is made. The cementite blisters are not evenly distributed, and they can cause the steel to be weak and brittle. However, blister steel can also be very strong and tough, and it is often used in making tools and machinery.
Blister steel can be easily welded, but it is important to use the correct welding techniques. If the weld is not done properly, it can weaken the steel and make it more likely to crack.
Overall, blister steel is a versatile type of steel that can be used for a variety of purposes. It is important to be aware of its limitations, but it can be a very useful material.