Microsteel® CHROME-NICKEL-MOLY ALLOY STEEL

MICROSTEEL®

Microsteel® is a tough, shock and fatigue resisting Chrome-Nickel- Moly alloy steel provided in the turned-ground and polished condition. In the delivered quenched and tempered condition, it has the highest combination of tensile strength and ductility while maintaining comparable high machinability.

Bars are delivered in turned-ground and polished condition, with a hardness range of 269-341 BHN. For most applications, Microsteel is both hard and tough enough to be used without additional hardening. Microsteel is quenched and tempered, stress relieved and machine straightened prior to shipment. This process insures proper grain structure alignment, removal of longitudinal stress factors and confines hardness range to within 2% variance in any bar or plate section. Most aircooled alloy products, except tool steel, cannot meet these qualifications. A slight reduction in hardness from surface to core is more desirable than “air hardened steel” since this process provides much higher ductility and resistance to shock.

Advantages

Superior Fatigue Strength
Deep Hardened
High Tensile & Yield Strength
High Shear Strength
Uniform Fine Grain Structure
Easily Machinable
Fully Stress Relieved
Machine Straightened
Demagnetized

Microsteel® vs. 4140

(As Quenched Hardness (Rc))

Available Stock Sizes

Tolerance
Diameters	Limits
7/16″ through 4″	+.000 - .002
41/8″ through 6″	+.000 - .003

Length
0.5 - 25 Ft. (cut to length)

Diameter
7/16″ through 6″ in 1/16″ increments

Chemistry(%)

C	Mn	P	S	Si	Ni	Cr	Mo
.37-.43	.60-.85	.035*	.04*	.15-.30	1.65-2.00	.70-.90	.20-.30

*max %

Physical Constants:

Density	0.283 lb/in³
Melting point	2600 °F
Thermal conductivity (typical steel)	309 BTU in/hr.ft^².°F
Coefficient thermal expansion	68°F, specimen oil hardened, 1110°F temper …....…..6.83 μin/in°F
Electric resistivity(68°F )	2.48x10-⁵Ohm*cm
Electric resistivity(212°F )	2.98x10-⁵Ohm*cm
Elastic modulus	27557-30458 ksi

Typical Properties

	Annealed	Normalized	Drawn
Tensile Strength, psi	120000	180000	142000
Yield Strength, psi	80000	145000	110000
Elongation, % in 2"	18	8	20
Reduction of Area, %	35	22	38
Brinell Hardness	250	370	260

Low Temp. Charpy Impact

Ft. Lbs. (V-Notch)

	Temperature of Test
Normalized Hardened	+68° F	+14° F	-10° F	-94° F
Normalized 40Rc	12.4	7.4	6.4	4.8
Hardened 35Rc	81.8	82.3	87.1	77.3
Hardened 28Rc	93.6	78.0	74.8	36.0

FABRICATION

We recommend the use of St. Lawrence’s comprehensive fabrication services to eliminate processing and fabrication errors.

Cutting Keyways

Use a four or six fluted high-speed end mill; with widths up to 1/2″, use up to 60 RPM; over 1/2″ wide, reduce RPM to the 25 – 40 range. Take the full depth of keyways up to 5/8″ deep in one pass. Use two passes for depths greater than 5/8″. Use coolant to keep the cutter and steel cool. A special word about keyways – the majority of fatigue failures in shafting made from any steel can be traced back to sharp corners and notches like those found at the base of a squared corner keyway. To greatly increase your shafting life, put a small radius at the corners of the key- ways and place a corresponding radius on the matching corners of the key.

Machining

Microsteel has a fine grain microstructure (8-9) with closely controlled carbide particles which provide improved machinability. The oil quench and temper process of Microsteel, followed by controlled stress relieving, insures against distortion and run-out commonly found in air-hardened alloys. Turning, boring and facing is more easily accomplished using mated tungsten-carbide inserts with chip-breaker. Always refer to your equipment user manual for recommended setting.

WELDING

Microsteel has good welding characteristics. It can be readily gas or arc welded. Welding electrodes of close to the same composition are recommended. Be sure to use a dry mated rod when arc welding. This process will retard excess grain growth. Preheating to 250° F is suggested. Since Microsteel has air hardening properties, stress relieving or normalizing following the welding process is recommended. Post-heating to 300- 350° F is also acceptable.

Turning

High Speed Steel Tool
Cut Depth	Speed fpm	Feed ipr
.150	50	.010
.025	65	.005

Drilling

Using HSS Tool Material

	Feed - Inches Per Revolution Normal Hole Diameter - Inches
Speed fpm	1/8	.003	.004	.004	.006	.006	.008
35	.002	.003	.003	.004	.006	.006	.008