IS 4432:1988 20Mn5Cr5 Steel: Specifications & Listings
IS 4432:1988 20Mn5Cr5: 20Mn5Cr5 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. The printed Tables 4 and 5 read 20MnCr5; Amendment 1 (April 1994) corrects the name to 20Mn5Cr5.
Matched by chemical composition and mechanical properties, not a formal equivalence claim. Always verify against the applicable standard before substitution.
Order as 20Mn5Cr5-S: sulphur 0.020 to 0.035, phosphorus 0.035 max
Sulphur and phosphorus range can also be ordered under clause 5.1, Limit 2.
Source: IS 4432:1988 with Amendment 1 (April 1994), Table 1 note 1, clause 5.1, Table 2 note 1
Other composition limitsfrom the clauses and notes
Deoxidation
Fully killed, unless otherwise agreed
Elements not specified for this grade, if present, maximum
Ni 0.30, Cu 0.25, V 0.05, Mo 0.05 percent
Copper plus 10 times tin, 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 temperatures4 values
Hot working temperature range
1150 to 850 °C
Normalising temperature
840 to 870 °C
Full annealing (A) temperature
860 to 900 °C
Sub-critical anneal for softening, after normalising
650 to 700 °C
Recommended temperatures, for guidance only, for controlling hardness, machinability and shearability.
Source: IS 4432:1988 with Amendment 1 (April 1994), Table 3
Case hardening treatment7 values
Jominy end quench test, quenching temperature
870 ± 5 °C
Carburising temperature
890 to 940 °C
Direct and single hardening temperature
810 to 840 °C
Double hardening, core hardening temperature
860 to 880 °C
Double hardening, case hardening temperature
790 to 830 °C
Quenching medium
Oil / thermal bath / poly quench
Tempering temperature
170 to 200 °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 diameter3 sections
Tensile strength (MPa)
Yield strength, min (MPa)
Elongation, min (%)
Reduction of area, min (%)
Test bar diameter (mm)
1000 to 1300
750
7
25
16
1000 to 1300
700
8
30
30
800 to 1100
550
10
35
63
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
249 HB
Annealed to maximum hardness (A), maximum
217 HB
Treated for improved machinability (M)
160 to 210 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
Hardenability, end quench testHardness band
Hardness band (HRC, minimum to maximum) by distance from the quenched end (mm)
1.5
5
20
30
40
Distance from quenched end (mm)
1.5
5
20
30
40
Maximum, HRC
49
48
37
34
30
Minimum, HRC
41
36
23
20
-
Recommended values. Jominy test as per IS 3848. Minor variation in ladle analysis from Table 1 is permitted for steel with guaranteed hardenability.
Source: IS 4432:1988 with Amendment 1 (April 1994), Table 7
Blank hardened hardnesscore strength guarantee
Blank hardened hardness, HRC
35
Blank hardening treatment
870 ± 10 °C, 45 minutes soak, followed by oil quenching
Blank hardening is done on a 30 mm diameter turned specimen from the same location of the billet as the tensile specimen; hardness is taken at the centre. Recommended value, applies when agreed.
Source: IS 4432:1988 with Amendment 1 (April 1994), Table 7 notes 1 and 2, clause 14.1 (d)
Active IS 4432:1988 20Mn5Cr5 Listings on M-EX (For Sale)