Product introduction

AISI 4140 Alloy Steel is a common chromium-molybdenum steel that usually used after quenched and tempered, with high intensity, high hardenability. The alloy 4140 plate also has high fatigue strength and good low-temperature impact toughness.

has great advantage on 4140 steel plate:

• 1500+ tons daily stock of 4140 alloy plate or flat bar.
• Hot rolled / annealed / Q+T (PH prehardened) condition available. 
• Thickness 4-300mm available for 1-3 days shipment.
• Thickness 1-10mm cold rolled sheet for 30 days lead time.
• Cut to width & cut to length service available.
• Machined to tolerance & roughness pieces service available.

Technical data

4140 Grade Designation

When discussing AISI 4140, it is important to understand what the grade number means:

How is 4140 Steel Made?

AISI 4140 is made by placing iron, carbon, and other alloying elements into an electric furnace or oxygen furnace. The major alloying elements added to AISI 4140 are:

• Chromium
• Manganese
• Molybdenum

Once the iron, carbon, and other alloying elements have been mixed together in liquid form, it is allowed to cool. The steel may then be annealed; possibly several times.

After the annealing is complete, the steel is heated to a molten phase again so that it can be poured into the desired form and can either be hot worked or cold worked through rollers or other tools to reach the desired thickness. Of course, there are other special operations that can be added to this to reduce mill scale or improve mechanical properties.

Mechanical Properties of 4140 Steel

AISI 4140 is a low alloy steel. Low alloy steels rely on elements other than just iron and carbon to enhance their mechanical properties. In AISI 4140, additions of chromium, molybdenum, and manganese are used to increase the strength and hardenability of the steel. The additions of chromium and molybdenum are why AISI 4140 is considered a “chromoly” steel.

There are several important mechanical properties of AISI 4140, including:

• Tensile Strength: AISI 4140 steel typically has a target ultimate tensile strength of around 95,000 psi.
• Toughness
• Ductility
• Hardenability

Chemical Properties

The table below highlights the chemical composition of AISI 4140:

The addition of chromium and molybdenum promotes corrosion resistance. The molybdenum can be particularly useful when trying to resist corrosion due to chlorides. The manganese in AISI 4140 is used to increase hardenability and as a deoxidizer. In alloy steels, manganese can also combine with sulfur to improve machinability and make the carburizing process more effective.