T4 T12004 S18-1-2-5 1.3255 SKH3 High Speed Tool Steel

AISI T4 tool steel is one of tungsten type high speed tool steel, which belongs to ASTM A600 specification, the standard for high speed tool steel materials.

ASTM T4 tool steel is similar to T1 Tool Steel materials, but with 4.25~5.75% cobalt added to increase heat resistance. The red hardness of T4 steel and the high temperature hardness is a little higher than T1 tool steel. AISI T4 tool steel is a deep hardening alloy capable of Rockwell C 64 hardness.

Applications of ASTM/AISI T4 Tool Steel

AISI T4 high speed tool steels are widely used as cutting tools, broaches and cold extrusion punches, turning, planing and milling cutters for roughing work.

Typical applications are:

Drills,

Milling Cutters,

Thread Cutting Tools,

Knurling Tools,

Cold extrusion punches

Broaches etc.

Relevant Steel Specifications of AISI T4 High Speed Tool Steels

Country	USA	German	Japan
Standard	ASTM A600	DIN EN ISO 4957	JIS G4403
Grades	T4/T12004	S 18-1-2-5/1.3255	SKH3

AISI T4 Tool Steel and Equivalents’ Chemical Composition

ASTM A600	C		Mn		P	S	Si		Cr		V		W		Mo		Co
T4	0.70	0.80	0.10	0.40	0.03	0.03	0.20	0.40	3.75	4.50	0.80	1.20	17.50	19.00	0.40	1.00	4.25	5.75
DIN ISO 4957	C		Mn		P	S	Si		Cr		V		W		Mo		Co
S 18-1-2-5/1.3255	0.75	0.83	…	0.40	0.03	0.03	…	0.45	3.80	4.50	0.80	1.20	17.50	18.50	0.50	0.80	4.50	5.50
JIS G4403	C		Mn		P	S	Si		Cr		V		W		Mo		Co
SKH3	0.73	0.83	…	0.40	0.03	0.03	…	0.45	3.80	4.50	0.80	1.20	17.00	19.00	…	…	4.50	5.50

Mechanical Properties of T-4 Steel

Properties	Metric	Imperial
Modulus of elasticity	190-210 GPa	27557-30458 ksi
Poisson’s ratio	0.27-0.30	0.27-0.30

Thermal Properties of T4 Tool Steels

Properties	Metric	Imperial
Thermal expansion co-efficient	11.9 µm/m°C	6.6 µin/in°F

Forging of ASTM T4 Tool Steel Materials

Forging of T4 steel can be carried out from 850 to 1120°C (1775 to 2100°F).

Preheat T4 steel material uniformly and slowly to 860-880°C.

Increase the forging temperature up to 1050-1120°C.

T4 hss tool steel should be cooled very slowly after forging.

AISI/ASTM T4 Tool Steel Heat Treatment and Properties

Hardening:

Harden T4 high speed tool steel from a temperature of 1260-1290oC followed by oil, air quenching or warm bath at 550oC. Hardness after quenching is 63-66 HRC.

Annealing:

T4 steel should be annealed after hot working. Increase the temperature of T4 high speed steel to 860°C(Max220°C per hour). Hold at the temperature and then cool slowly with the furnace. The annealed hardness achieved should be below HB255.

Tempering:

Tempering temperature: 2x 560-580oC. Hardness after tempering is 64-65 HRC.