ASTM A322 (4140)

ASTM A322 Specification 4140 Alloy Steel (4130 here)

Steel Bars. 0.95 Cr, 0.20 Mo. – (Average Alloying Elements)

ASTM A322 is a standard spec from ASTM International. ASTM governs hot-wrought alloy steel bar production, including 4140 steel, which is one of the most widely used Cr-Mo alloy steels for forging, heat treatment, and machining amongst others..

4140 steel under ASTM A322 is a chromium-molybdenum alloy steel that offers a strong balance of strength, toughness, fatigue resistance, and hardenability, making it suitable for a wide range of high-stress mechanical and structural applications.

Typical Chemical Composition of 4140:

• Carbon: 0.38–0.43%
  Chromium (Cr): 0.80–1.10%
  Molybdenum (Mo): 0.15–0.25%
  Manganese (Mn): 0.75–1.00%
  Silicon (Si): 0.15–0.35%

4140 Alloy Steel in ASTM A322 Specification per ASTM International:

“This specification covers hot-wrought alloy steel bars. Bar applications include forging, heat treating, cold drawing, machining and many structural components.

This specification covers hot-wrought alloy steel bars. The steel shall be made by one or more of the following primary processes: open-hearth, basic-oxygen, or electric-furnace. The primary melting may incorporate separate degassing or refining and may be followed by secondary melting using electro-slag remelting or vacuum arc remelting. Where secondary remelting is employed, the heat shall be defined as all of the cast product remelted from a single primary heat. The steel shall be furnished as strand cast or ingot cast.

Immediately after hot forming, the bars shall be allowed to cool to a temperature below the critical range under suitable conditions to prevent imperfections caused by too rapid cooling. The bars shall be free of pipe, cracks, and flakes. Within the limits of good manufacturing and inspection practices, the bars shall be free of injurious seams, laps, segregation, or other imperfections which, due to their nature, degree, or extent, will interfere with the use of the material in machining or fabrication of suitable parts.”

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