H39WM | Paralloy Group | Paralloy Group

25/35 Cr/Ni 0.4%C

Microalloy Steam Reformer & Cracker

Application

Long-Established 25/35 Alloy

H39WM is the reference alloy, developed in 1990s for the “heavy-duty” passes of Pyrolysis Cracker Coils where high carburisation resistance is required, and “peak” temperatures can exceed 1125°C, the alloy is widely used today. The very high creep rupture strength also makes it ideal for steam reformer furnaces where high tube temperatures or thinner tube walls are required. Because of the combination of exceptional creep strength and carburisation resistance, microalloyed H39WM boasts a proven track record of success within the petrochemical industry over many years.

H39WM (HP Nb mod) is a weldable chromium nickel heat resistant steel which is the microalloyed version of H39W (HP Nb Mod). In addition to the controlled niobium content, further creep strengthening is introduced by making microalloy additions. The important elements interact by the process of “synergism” to increase the high temperature strength.

Nominal Composition

6
C Carbon

0.4
14
Si Silicon

1.5
25
Mn Maganese

1
24
Cr Chromium

25
28
Ni Nickel

35
43
Nb Niobium

1.2

Physical Properties

Coefficient of Thermal Expansion (mm/mm°C)	Thermal Conductivity (W/m°K)	Density (kg/m³)	Young Modulus (N/mm2 x 103)	Specific Heat (J/KgK)
20 – 100°C – 15.5 x 10⁻⁶	100°C – 13	7.97 x 10³	20°C – 158.5	455
20 – 800°C – 18.9 x 10⁻⁶	750°C – 24.3		800°C – 108.2
20 – 1000°C – 19.4 x 10⁻⁶	1000°C – 27.7		1000°C – 95.1
20 – 1100°C – 19.7 x 10⁻⁶	1000°C – 29.7

Mechanical Properties

Download specifications

UTS (N/mm²) 450
Proof Stress 0.2% (N/mm²) 250
Elongation (%) 8 (tube) / 6 (static)

Temp (°C)	10,000 Hour Life		50,000 Hour Life		100,000 Hour Life
	Minimum	Mean	Minimum	Mean	Minimum	Mean
900	35.28	40.2	28.99	33.04	26.48	30.18
925	30.06	34.26	24.2	27.58	21.9	24.96
950	25.28	28.81	19.92	22.7	17.86	20.36
975	20.99	23.91	16.18	18.43	14.36	16.37
1000	17.19	19.59	12.95	14.76	11.39	12.98
1025	13.9	15.84	10.23	11.66	8.9	10.14
1050	11.1	12.64	7.97	9.08	6.86	7.82
1075	8.74	9.96	6.13	6.98	5.22	5.94
1100	6.79	7.74	4.64	5.29	3.91	4.45
1125	5.21	5.94	3.47	3.95	2.89	3.29
1150	3.95	4.5	2.56	2.92	2.1	2.4

Download specifications

UTS (N/mm²)	450
Proof Stress 0.2% (N/mm²)	250
Elongation (%)	8 (tube) / 6 (static)

Temperature (°C)	UTS (N/mm²)	0.2% (N/mm²)	Elongation (%)
800°C	265	136	31
900°C	172	94	38
1000	117	66	43
1100	82	50	45

Temp (°C)	10,000 Hour Life		50,000 Hour Life		100,000 Hour Life
	Minimum	Mean	Minimum	Mean	Minimum	Mean
900	35.28	40.2	28.99	33.04	26.48	30.18
925	30.06	34.26	24.2	27.58	21.9	24.96
950	25.28	28.81	19.92	22.7	17.86	20.36
975	20.99	23.91	16.18	18.43	14.36	16.37
1000	17.19	19.59	12.95	14.76	11.39	12.98
1025	13.9	15.84	10.23	11.66	8.9	10.14
1050	11.1	12.64	7.97	9.08	6.86	7.82
1075	8.74	9.96	6.13	6.98	5.22	5.94
1100	6.79	7.74	4.64	5.29	3.91	4.45
1125	5.21	5.94	3.47	3.95	2.89	3.29
1150	3.95	4.5	2.56	2.92	2.1	2.4