4140 Steel Plate
General Information 
4140 alloy steel is a low alloy steel that contains chromium, molybdenum, and manganese. Because it contains chromium and molybdenum it is sometimes referred to as chromoly steel. 4140 also has high fatigue strength, excellent strength to weight ratio, abrasion and impact resistance, and torsional strength.
4140 steel plate can be plasma or flame cut to shape, then annealed onsite in our furnace. As a result, annealing greatly improves results from grinding and increases machinability. A thorough annealing is also required before quench and tempered hardening processes.
Purchased as-rolled, pre-hardened (PH) or in the annealed condition, 4140 steel plate possesses a full range of hardening and wear resistance properties. Due to it’s good hardness penetration and uniformity, flame hardening, induction hardening, or oil hardening can increase the wear resistance of 4140 steel. 4140 PH has the same industry standard chemistry as 4140 HR plate but with an industry standard Rockwell C hardness rating of 28 – 32.
Common Uses of 4140 Steel Plate
4140 steel can be used for a wide variety of applications where better wear resistance and toughness is needed over normal carbon steels.
Common uses of 4140 steel plate: tooling, machine plates, gears, shafts, sprockets, special machine parts, molds, metal stamping, tool & die, shredders, couplings, reamer bodies, screws, flywheel components, axles, shafts, bolts, sprockets, piston rods and rams.
Work Qualities
4140 steel has good machinability when annealed. 4140 steel is not easily welded and post weld treatment should be performed. This steel can be formed using conventional techniques when annealed. However, more pressure is required when forming because it is tougher than plain carbon steels.
Chemical Composition
4140 steel chemical composition table
% Carbon (C) 0.380 – 0.430
% Chromium (Cr) 0.800 – 1.10
% Iron (Fe) 96.785 – 97.77
% Phosphorus (P) 0.035
% Silicon (Si) 0.150 – 0.300
% Sulfur (S) 0.040
Physical Properties
4140 steel physical properties table
Steel Type Alloy
ASTM Designation ASTM 4140
Common PGI Inventory 0.375″-4.00″ inquire for thicker plate
Minimum Yield Stress (ksi) 60.2
Average Tensile Strength (ksi) 95
Elongation at Breakage 25.7%
Brinell Hardness 197
Knoop Hardness 219
Approximate Hardness (Rb) 92
Approximate Hardness (Rc) 13
Vickers Hardness 207
Machinability 0.65
