DAIKOWT 9CrMo

GTAW
  • CREEP RESISTING STEELS
9CrMo

Description

Rod with 9% Cr-1% Mo for high-temperature service
Rod formulated for 9% Cr and 1% Mo alloy steels, ideal for applications in pressurized hydrogen in oil refineries subjected to prolonged service and high temperatures up to around 650 °C. Developed to ensure high toughness and improved corrosion resistance in the presence of superheated steam, hot hydrogen gas, and crude oil with a high sulfur content, surpassing the performance offered by 5% chromium and 0.5% molybdenum steels.
Specifications
EN ISO 21952-A
W CrMo 9 Si
AWS A5.28
ER80S-B8
Shielding
I1
Positions
PA, PB, PC, PD, PE, PF
Current
DC-
Packaging Type
5kg carton tube
Asme qualifications
F-No (QW432)
6
A-No (QW442)
5
Chem. Comp. %
DEFAULT
C
0.07
Mn
0.6
Ni
0.1
Cr
9
P
0.015
S
0.01
Mo
1
Si
0.5
Cu
0.1
Mechanical Properties
min
variant
Tensile strength Rm MPa
550
710
Yield strength Rp0.2 MPa
470
590
Elongation A (L0=5d0) %
17
23
Impact Charpy ISO-V
-
40J @ -20°C
Impact Charpy ISO-V
-
-
Welding Parameters
1.6 mm
2.4 mm
Ampere
95A - 135A
145A - 205A
Voltage
-
-
Packaging
Ø 1,2÷3,2mm
Ø 1,2÷3,2mm
Packaging Type
5kg carton tube
5kg carton tube
Description

Application

Designed for high-temperature applications, 9CrMo offers a reasonable degree of corrosion resistance in superheated steam, hot hydrogen gas, and high-sulfur crude oil, surpassing the performance of 5% Cr-0.5% Mo steels. It is particularly suitable for welding heat-treatable steels, quenched and subsequently tempered. Ideal for piping and components resistant to caustic embrittlement, it maintains its effectiveness up to service temperatures of 600 °C. It is primarily used for
boiler superheater piping, heat exchangers, pipelines and
pressure vessels in oil refineries and power plants.

Alloy Type

9%Cr-1%Mo martensitic alloy for elevated temperature service.

Microstructure

In the PWHT condition the microstructure consists of tempered bainite.

Materials

  • EN W.Nr.: X12CrMo 9 1 (1.7386), X7CrMo 9 1 (1.7388), GS-12CrMo 10 1 (1.7389)
  • ASTM: A387 gr. 9, A335 gr. 9, A234 gr. WP9 (fittings), A199 gr. T9, A213 gr. T9, A182 gr. F9, A336 gr. F9, A217 gr. C12

Welding & PWHT

Given the hardness of the material in its deposited state (up to 450 HV) and the poor fracture resistance of the martensitic microstructure, preheating and a minimum interpass temperature of 200 °C are required to prevent hydrogen-induced cracking. By using well-controlled electrodes, the weld metal can maintain hydrogen levels below 5 ml/100 g. For TIG welds and particularly for root TIG passes, preheating below 150 °C may be acceptable. During the welding process, transformation might not complete between 200-350 °C; hence, partial cooling to about 150 °C is recommended before direct transfer to post weld heat treatment (PWHT), followed by non-destructive examinations (NDE). If PWHT is performed after full cooling and NDE, the preheat temperature must be adequately maintained according to thickness, to facilitate hydrogen dispersion. This precaution is less critical for solid wire TIG and MAG processes. PWHT for weld tempering is usually performed between 705-780 °C (as indicated, for example, by ASME B31.3 between 705-760 °C). The minimum recommended holding time is two hours. For castings, the minimum recommended PWHT temperature is slightly lower, with the possibility of dropping to 670 °C.

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