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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® Round Bar

Microsteel® vs. 4140

(As Quenched Hardness (Rc))

Microsteel® vs. 4140

Available Stock Sizes

Tolerance
Diameters Limits
7/16″ through 4″ +.000 - .002
41/8″ through 6″ +.000 - .003
Diameter
7/16″ through 6″ in 1/16″ increments
Length
0.5 - 25 Ft. (cut to length)

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.ft².°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 .004 .004 .006 .006 .008
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