The given heat treatment processes are matched to the most suitable outcomes based on how each treatment affects the steel. Let's analyze each heat treatment process in detail:
P (Quenching):
Quenching is the process of rapidly cooling a heated material, usually by immersing it in water or oil. This process hardens the steel by increasing its hardness and strength. The rapid cooling prevents the formation of soft phases in the steel, which results in a hardened steel. Thus, the correct match for \( P \) is 1.
Q (Annealing):
Annealing involves heating steel to a specific temperature and then cooling it slowly. This process is used to relieve internal stresses and soften the material. It is typically used for softening cold-worked steel to improve its ductility. Thus, the correct match for \( Q \) is 2.
R (Tempering):
Tempering is performed after quenching to reduce brittleness. The material is heated to a temperature below its critical point and then cooled in air. This process toughens the steel, increasing its strength and toughness while reducing its brittleness. Thus, the correct match for \( R \) is 3.
S (Carburizing):
Carburizing is a surface-hardening process in which carbon is diffused into the surface of the steel. This is typically done at high temperatures, where the carbon concentration in the surface layer is increased. The result is that the surface of steel becomes hardened, which improves its wear resistance while keeping the core softer. Thus, the correct match for \( S \) is 4.
Final Answer: \text{(C) P-1; Q-2; R-3; S-4}
