Which of the following weather phenomena signals the beginning of the mature stage of a thunderstorm?

D2 tool steel is designed to be quenched in

What prevented early man from being able to make steel?

Bonus #1 (2 points)   If a material stretches very much before it breaks, it is said to be ___________________?

Tool steel is

If iron contains more than 2.2 percent carbon, it is no longer called steel. It is called __________________.

Martensite steel is

Bonus #2 (2 points)   If a material stretches very little before it fractures, it is said to be ______________?

________________ steel contains large amount of nickel and small amounts of carbon.  Generally, this steel contains 18-25% nickel.  It can be stretched by 11% of its original size before breaking.  

Which of the following is not a type of hardness testing?