EN 10222-5 1.4571 | Type 316Ti Flanges

General Introduction

EN 10222-5 1.4571 flanges generally refer to EN 1092-1 flanges made from Type 316Ti stainless steel forgings, which is a stabilized version of austenitic stainless steel 316. This steel grade corresponds to the steel name X6CrNiMoTi17-12-2. It is equivalent to ASTM A182 F316Ti. Type 316Ti is not a listed material in ASME B16.5 nor ASME B16.47 but it is listed in group 15Eo of EN 1092-1. Moreover, EN 1092-1 flanges may be made from EN 10222-5 1.4571 forgings, EN 10028-7 1.4571 plates, or EN 10272 1.4571 bars. In this article, we only focus on the EN 10222-5 1.4571 forged flanges.

Sensitization Mechanism & Stabilization Methods

When the conventional molybdenum-bearing Type 316 austenitic stainless steel is heated for a period of time in the range of about 425 to 815°C [900 to 1500°F], chromium carbides will precipitate in grain boundaries and the area immediately adjacent is depleted of chromium. This phenomenon is known as sensitization of the stainless steel. The sensitization renders Type 316 susceptible to intergranular corrosion, which is the dissolution of the low-chromium layer or envelope surrounding each grain. Sensitization also lowers resistance to other forms of corrosion, such as pitting, crevice corrosion, and stress-corrosion cracking (SCC).

Several approaches have been taken to minimize or prevent the sensitization of stainless steel 316. If the sensitization is small enough, solution annealing is the only way to correct a sensitized stainless steel. According to the time-temperature-sensitization curves, the modified version of Type 316L with low carbon content can avoid sensitization during relatively brief exposure to sensitizing temperatures, but it will be sensitized by long exposures. Since titanium has higher affinity for carbon and forms carbides readily, Type 316Ti (1.4571) with titanium addition allows the chromium to remain in solution even for extremely long exposures to temperatures in the sensitizing range. In short, the stainless steel is stabilized by titanium against sensitization. The 1.4571 (Type 316Ti) flanges shall be resistant to intergranular corrosion in both delivery condition and sensitized condition when tested in accordance with EN ISO 3651-2.

Chemical Composition Requirements

Element	% by Mass
C	≤0.08
Si	≤1.00
Mn	≤2.00
P	≤0.045
S	≤0.015
Cr	16.5-18.5
Mo	2.00-2.50
Ni	10.5-13.5
Ti	5 x C to 0.70

*Chemical composition requirements for EN 10222-5 1.4571 based on cast analysis.
*If agreed by the buyer, sulfur content can be controlled between 0.015% to 0.030% to improve machinability.

Mechanical Properties at Room Temperature

Item	Requirement
Rp0.2 min. MPa	210
Rp1.0 min. MPa	245
Rm MPa	510-710
A, %, l min.	45
A, %, tr min.	35
KV2 @ 20°C l, min. J	100
KV2 @ 20°C tr, min. J	60

*R_p0.2: 0.2% proof strength; *R_p1.0: 1.0% proof strength; *R_m: tensile strength.
*”A, %, l”: longitudinal elongation after fracture; *”A, %, l”: transverse elongation after fracture.
*”KV2 @ 20°C, l, min. J”: minimum impact energy at 20°C, longitudinally; *”KV2 @ 20°C, tr, min. J”: minimum impact energy at 20°C, transversely.
*The minimum impact energy (transversely) at -196°C is 60 J.

Manufacture & Heat Treatment

EN 10222-5 1.4571 flanges shall be made by a forging process. The raw material/ billet is usually melted by an electric-arc furnace with refining processes, or by a vacuum furnace followed by electrosla-consumable remelting. The heat treatment of solution annealing shall be carried out after forging, in which the steel shall be heated and fully austenitized in the temperature range of 1020 to 1120°C. A water quench shall be performed immediately after the flange leaves the furnace till it cools down to 260°C or below.

p/T Ratings

The p/T ratings for EN 10222-5 1.4571 flanges indicating the maximum allowable pressure (PS, in bar unit) at maximum allowable temperature (TS, in °C unit) for various PN designations are listed in tables below.

TS, °C	PS, bar PN2.5	PS, bar PN 6	PS, bar PN 10
RT	2.5	6.0	10.0
100	2.5	6.0	10.0
150	2.4	5.8	9.8
200	2.3	5.6	9.3
250	2.2	5.3	8.8
300	2.0	5.0	8.3
350	2.0	4.8	8.0
400	1.9	4.6	7.8
450	1.9	4.6	7.6
500	1.8	4.5	7.5
550	1.8	4.4	7.4
560	1.8	4.4	7.4
570	1.8	4.4	7.3
580	1.6	4.0	6.7
590	1.5	3.6	6.0
600	1.3	3.3	5.5

*p/T ratings for 1.4571 flanges of PN 2.5, PN 6, and PN10.

TS, °C	PS, bar PN 16	PS, bar PN 25	PS, bar PN 40
RT	16.0	25.0	40.0
100	16.0	25.0	40.0
150	15.6	24.5	39.2
200	14.9	23.0	37.3
250	14.1	22.1	35.4
300	13.3	20.8	33.3
350	12.8	20.1	32.1
400	12.4	19.5	31.2
450	12.2	19.1	30.6
500	12.0	18.8	30.0
550	11.9	18.6	29.9
560	11.8	18.5	29.6
570	11.7	18.3	29.3
580	10.7	16.7	26.8
590	9.7	15.2	24.3
600	8.8	13.8	22.0

*p/T ratings for 1.4571 flanges of PN 16, PN 25, and PN 40.

TS, °C	PS, bar PN 63	PS, bar PN 100	PS, bar PN 160
RT	63.0	100.0	160.0
100	63.0	100.0	160.0
150	61.8	98.0	156.9
200	58.8	93.3	149.3
250	55.8	88.5	141.7
300	52.5	83.3	133.3
350	50.7	80.4	128.7
400	49.2	78.0	124.9
450	48.3	76.6	122.6
500	47.4	75.2	120.3
550	47.1	74.7	119.6
560	46.6	74.0	118.5
570	46.2	73.3	117.3
580	42.3	67.1	107.4
590	38.4	60.9	97.5
600	34.8	55.2	88.3

*p/T ratings for 1.4571 flanges of PN 63, PN 100, and PN 160.

TS, °C	PS, bar PN 250	PS, bar PN 320	PS, bar PN 400
RT	250.0	320.0	400.0
100	250.0	320.0	400.0
150	245.2	313.9	392.3
200	233.3	298.6	373.3
250	221.4	283.4	354.2
300	208.3	266.6	333.3
350	201.1	257.7	321.9
400	195.2	249.9	312.3
450	191.6	245.3	306.6
500	188.0	240.7	300.9
550	186.9	239.2	299.0
560	185.1	237.0	296.2
570	183.3	234.6	293.3
580	167.8	214.8	268.5
590	152.3	195.0	243.8
600	138.0	176.7	220.9

*p/T ratings for 1.4571 flanges of PN 250, PN 320, and PN 400.

Mechanical Properties at Elevated Temperatures

Temp. °C	Rp0.2 MPa	Rp1.0 MPa	Rm MPa
100	185	218	440
150	177	206	410
200	167	196	390
250	157	186	385
300	145	175	375
350	140	169	375
400	135	164	375
500	129	158	360

*Minimum 0.2% proof strengths, minimum 1.0% proof strengths and minimum tensile strengths of EN 10222-5 1.4571 at elevated temperatures.

Creep Data for Reference

Temp. °C	Creep Rupture Strength, MPa
	104 h	105 h	2x105 h
540	247	194	178
550	233	181	164
560	220	167	151
570	206	154	138
580	193	141	125
590	180	128	113
600	167	116	102
610	155	105	91
620	142	94	81
630	130	84	72
640	119	75	65
650	108	67	58
660	97	60	52
670	87	54	47
680	78	49	43
690	70	44	-
700	63	-	-

*Creep rupture strengths for EN 10222-5 1.4571 (Type 316Ti) flanges at elevated temperatures for 10000 hours, 100000 hours and 200000 hours, respectively.