EN 1092-1 Type 11 WNRF | EN10222-4 P355QH1

Generally, EN 1092-1 Type 11 (WN) flanges made from EN 10222-4 P355QH1 shall be manufactured by a open die forging process. P355QH1 is a weldable fine grain steel with high proof strength. It has the steel number of 1.0571 and shall meet all general requirements for open die forgings as specified in EN 10222-1. Especially, P355QH1 steel has a minimum requirement for the addition of aluminum. Aluminum is widely used as a deoxidizer in molten steel and for controlling/refining grain size. When added to steel in controlled amounts, it produces a fine grain size.

Chemical Composition Requirements

Element	Composition, %
C	≤0.18
Si	≤0.40
Mn	0.90-1.50
P	≤0.025
S	≤0.010
Al	≥0.020
N	≤0.015
Cr	≤0.30
Cu	≤0.30
Mo	≤0.25
Nb	≤0.05
Ni	≤0.50
V	≤0.10
Nb+V	≤0.12
CE	≤0.47

*Generally, aluminum shall be ≤ 0.050%. If only aluminum is used for nitrogen binding, a ration Al/N ≥ 2 shall apply.
*CE(carbon equivalent) = C + Mn/6 + (Cr+Mo+V)/5 + (Ni+Cu)/15.
*All values are based on cast analysis.

Heat Treatment & Mechanical Properties

The P355QH1 steel of EN 10222-4 shall be furnished in quenched and tempered condition. The steel flanges shall be soaked at a temperature between 860°C and 940°C till full austenization and then rapidly cooled in cold water or oil (as shown in the picture). Subsequent tempering treatment shall be performed at a temperature between 600°C and 700°C.

Tensile Tests	Requirements
ReH(70＜T≤100)	≥315
ReH(100＜T≤250)	≥295
ReH(250＜T≤400)	≥275
Rm	470~630
A(longitudinal)	≥21
A(transverse)	≥19

*R_eH: yield strength at room temperature, MPa; R_m: tensile strength at room temperature, MPa; A: elongation after fracture, %; T: thickness of the ruling section of the flange.

Specimens	Temp. °C	KV2 J
Longitudinal	+20	≥63
Longitudinal	0	≥55
Longitudinal	-20	≥47
Longitudinal	-40	≥34
Transverse	+20	≥40
Transverse	0	≥34
Transverse	-20	≥27

*The impact energy KV₂ at a test temperature for P355QH1 flanges.

Temp. °C	Rp0.2 min. MPa 70＜T≤100	Rp0.2 min. MPa 100＜T≤250	Rp0.2 min. MPa 250＜T≤400
50	305	285	266
100	287	268	250
150	265	249	232
200	244	228	213
250	224	209	195
300	206	192	179
350	190	178	166
400	179	167	156

*Minimum 0.2% proof strength at elevated temperatures for P355QH1 flanges.

Tests to Be Carries Out

EN 1092-1 flanges made from EN 10222-4 P355QH1 shall take mandatory tests including cast analysis, tensile test at room temperature, impact test, dimensional inspection, and visual testing. Some optional tests can also be done upon request such as tensile test at elevated temperatures, magnetic particle testing, ultrasonic testing for verification of internal soundness, test for resistance to intergranular corrosion, hydrostatic test. If the flange is to be used in corrosive H2S containing environments (usually referred to as “sour service”), a HIC test to evaluate the resistance to hydrogen induced cracking shall be performed in accordance with EN 10229.