IS 4432:1988 15C8 Steel: Specifications & Listings
IS 4432:1988 15C8: 15C8 is a case hardening steel in IS 4432:1988 (Specification for case hardening steels), which covers wrought low carbon unalloyed and alloy steel bars, billets, rods and finished forgings for case hardening.
Matched by chemical composition and mechanical properties, not a formal equivalence claim. Always verify against the applicable standard before substitution.
Chemical Composition (%)
C
Si
Mn
S
P
0.10-0.20
0.15-0.35
0.60-0.90
<=0.035
<=0.035
Mechanical Properties
Core Tensile Strength
600-850 MPa (16 mm) / 550-800 MPa (30 mm)
Core Yield Strength
>=400 MPa (16 mm) / >=330 MPa (30 mm)
Core Elongation
>=12% (16 mm) / >=14% (30 mm)
Core Reduction of Area
>=35% (16 mm) / >=40% (30 mm)
Hardness, annealed (A)
<=150 HB
More data from IS 4432:1988
From the standard
Other composition limitsfrom the clauses and notes
Deoxidation
Fully killed, unless otherwise agreed
Elements not specified for this grade, if present, maximum
Cr 0.30, Ni 0.30, Cu 0.25, V 0.05, Mo 0.05 percent
Copper plus 10 times tin, maximum
0.50 percent
Ni + Cr + Mo added together, maximum
0.50 percent
Micro-alloying elements
Titanium, niobium, vanadium or boron may be added by agreement, singly or together
Elements not specified in Table 1 are not added except by agreement or to finish the heat. Reasonable precautions are taken against unwanted elements from scrap.
Source: IS 4432:1988 with Amendment 1 (April 1994), Table 1 notes, clauses 3, 3.1 and 5.3
Heat treatment temperatures5 values
Hot working temperature range
1100 to 850 °C
Normalising temperature
880 to 910 °C
Full annealing (A) temperature
900 to 930 °C
Sub-critical anneal for softening, after normalising
650 to 700 °C
Isothermally transformed condition
To a ferrite and pearlite structure without bainite, as per the transformation diagrams
Recommended temperatures, for guidance only, for controlling hardness, machinability and shearability.
Source: IS 4432:1988 with Amendment 1 (April 1994), Table 3
Case hardening treatment6 values
Carburising temperature
900 to 940 °C
Direct and single hardening temperature
830 to 860 °C
Double hardening, core hardening temperature
870 to 890 °C
Double hardening, case hardening temperature
780 to 820 °C
Quenching medium
Water / thermal bath at 140 to 220 °C
Tempering temperature
150 to 180 °C
Recommended conditions for reaching the core properties below, for guidance only. Time for austenitising about 45 minutes for a 25 mm section; tempering at least 1 hour, preferably 90 minutes. For direct and single quenching use fully aluminium killed fine grained steel. If direct hardened, a carburising temperature of 940 °C is generally not exceeded. Thermal bath includes suitable salt baths.
Source: IS 4432:1988 with Amendment 1 (April 1994), Table 5
Core properties after case hardening, by test bar diameter2 sections
Tensile strength (MPa)
Yield strength, min (MPa)
Elongation, min (%)
Reduction of area, min (%)
Test bar diameter (mm)
600 to 850
400
12
35
16
550 to 800
330
14
40
30
Core properties of simulated case-hardened test bars, treated as in the case hardening treatment above. Values apply to test bars taken from rounds in the direction of rolling. Applies when the steel is ordered on this basis.
Source: IS 4432:1988 with Amendment 1 (April 1994), Table 4
Hardness by delivery condition3 conditions
As rolled (R), maximum
180 HB
Annealed to maximum hardness (A), maximum
150 HB
Treated for improved machinability (M)
105 to 170 HB
Brinell hardness. A different as-rolled maximum for cold shearability, or a different range for improved machinability, may be agreed at the time of order.
Source: IS 4432:1988 with Amendment 1 (April 1994), Table 6, clause 7.2
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