AISI 4145H

It is a high-strength, chromium-molybdenum (chromoly) alloy steel specifically designed for applications requiring exceptional hardenability, toughness, and fatigue resistance.

Descriptions

1. Chemical Composition

AISI 4145H features a higher carbon content compared to AISI 4140, enhancing its strength and hardenability. Chromium and molybdenum improve wear resistance and high-temperature stability.

Element	Composition (% by Weight)	Role
Carbon (C)	0.43-0.48	Enhances hardness and tensile strength.
Manganese (Mn)	0.75-1.00	Improves hardenability and toughness.
Silicon (Si)	0.15-0.35	Strengthens ferrite and deoxidizes molten steel.
Chromium (Cr)	0.80-1.10	Boosts hardenability, wear, and corrosion resistance
Molybdenum (Mo)	0.15-0.25	Enhances high-temperature strength and creep resistance.
Phosphorus (P)	0.035 max	Controlled impurity (minimizes brittleness).
Sulfur (S)	0.040 max	Controlled impurity (improves machinability in small amounts).
Iron (Fe)	Balance	Base metal.

2. Mechanical Properties

AISI 4145H forgings achieve superior mechanical performance through heat treatment (e.g., quenching and tempering). Hardenability bands (H-code) ensure uniformity in large cross-sections.

Property	As-Forged	Quenched &Tempered	Normalized	Test Standard
Tensile Strength	700-900 MPa	1000-1200 MPa	750-900 MPa	ASTME8
Yield Strength (0.2% offset)	500-700MPa	850-1050 MPa	550-700 MPa	ASTME8
Elongation (%in 50 mm)	12-18%	10-15%	15-20%	ASTME8
Reduction of Area	40-50%	35-45%	45-55%	ASTME8
Hardness (Brinell)	220-270HB	302-375HB	200-250 HB	ASTME10
Impact Toughness (Charpy V)	30-50 J(room temp)	20-40J	40-60J	ASTME23