To avoid quench cracks, a metal is first cooled to just above Ms and held until the temperature equalizes in the steel. Quenching after the initial cooling allows all of the steel to transform to martensite at about the same time. This heat treatment is called .
a. center quenching
b. marquenching
c. surface quenching
d. slow quenching

b. marquenching

Explanation:

It is also known as martempering, it is a system of heat treatment for steel, it involves austenitisation and then quenching, the quenching is done at a fast rate so as to avoid the steel from forming ferrite, perlite or bainite to a temperature a little more than the temperature at which martensite begins. The major reason for marquenching is to cause a delay in the time required for cooling.

it would be kevlar ^^

find the surface area of the sphere to the nearest square unit. use a calculator.

a. 254 in.2

b. 64 in.2

c. 127 in.2

d. 1,018 in.2