Alloying effects in steels — role of chromium When chromium (Cr) is added to carbon steel in conventional alloying amounts, what is the general effect on the tensile strength of the steel?

Introduction / Context:
Chromium is a widely used alloying element in steels for structural, tool, and stainless applications. Understanding its broad influence on mechanical properties, especially tensile strength, helps with material selection and performance prediction after heat treatment.

Given Data / Assumptions:

• Cr is added in moderate amounts typical of low-alloy and stainless steels.
• Carbon content and heat treatment are within practical ranges.
• Question asks for the general trend, not a specific grade curve.

Concept / Approach:
Chromium increases hardenability, refines pearlite, and promotes formation and stability of carbides (e.g., Cr carbides) in appropriate conditions. These effects tend to raise strength levels after standard heat treatments. In stainless steels, high Cr also aids corrosion resistance via passive films; mechanical effects still include higher strength relative to plain-carbon steels at similar processing histories.

Step-by-Step Solution:
Note metallurgical action: improved hardenability → deeper martensite/tempered martensite after quench and temper.Carbide strengthening and grain refinement add to tensile strength.Therefore, chromium broadly increases tensile strength for comparable conditions.Select the option reflecting this general increase.

Verification / Alternative check:
Property charts for Cr-Mo or Cr steels show higher ultimate tensile strength versus plain-carbon analogs after similar heat treatments.

Why Other Options Are Wrong:
“Does not effect” is incorrect; “decreases” contradicts data; the remaining distractors are exaggerated or non-general behaviors.

Common Pitfalls:
Confusing effect of excessive carbide formation on toughness with tensile strength trends; strength can rise while toughness may require careful tempering.

Final Answer:
increases