What are Stainless Steel U-Bends?

Stainless steel U-bends (also called return bends or U-tubes) are straight tubes bent into a “U” shape for use in shell-and-tube heat exchangers, boilers, condensers, and superheaters. The tight radius and precise ovality/thinning control ensure maximum heat transfer efficiency and structural integrity under high pressure and temperature.

Key Advantages

Precise Bending Control – Minimum wall thinning & ovality per ASME SA-688
Solution Annealed & Pickled – Full restoration of corrosion resistance after bending
High Temperature & Pressure Resistance – Suitable up to 550°C+ (grade dependent)
100% Hydrostatic / Eddy Current Tested – Guaranteed leak-free performance

Technical Specifications

Parameter	Details
Standards	ASTM A213, A269, A688, A803, ASME SA688, EN 10216-5
Outside Diameter	12.7 mm – 50.8 mm (½″ – 2″)
Wall Thickness	0.7 mm – 5.16 mm (SWG/BWG)
Bend Radius (R)	1.5 × OD up to 1500 mm (custom tighter radii available)
Leg Length	Up to 12 meters (developed length)
Straight Length (L)	Min 1.0 m per leg (customizable)
Heat Treatment	Solution annealed + pickled (bright annealing optional)
Surface Finish	Pickled, polished, or as per customer requirement
Testing	Hydrostatic, Eddy Current, PMI, Dimensional inspection

Stainless steel return U bend Standard Specifications

Chemical Composition of Stainless Hollow Sections (Grades 304, 304L, 316, 316L per ASTM A554/A312)
Grade	C (% max)	Mn (% max)	Si (% max)	P (% max)	S (% max)	Cr (%)	Ni (%)	Mo (%)	N (% max)
304	0.08	2.00	1.00	0.045	0.030	18.0-20.0	8.0-11.0	-	0.10
304L	0.03	2.00	1.00	0.045	0.030	18.0-20.0	8.0-12.0	-	0.10
316	0.08	2.00	1.00	0.045	0.030	16.0-18.0	10.0-14.0	2.0-3.0	0.10
316L	0.03	2.00	1.00	0.045	0.030	16.0-18.0	10.0-14.0	2.0-3.0	0.10

The low carbon content in 304L and 316L enhances weldability, while molybdenum in 316 and 316L improves resistance to pitting and crevice corrosion, making Stainless steel return U bend ideal for harsh environments.

Mechanical Properties of Stainless Hollow Sections (Grades 304, 304L, 316, 316L per ASTM A554/A312)
Grade	Tensile Strength (min, MPa)	Yield Strength (min, MPa)	Elongation (min, %)	Hardness (max, HB)	Hardness (max, HRB)
304	515	205	40	201	92
304L	485	170	40	201	92
316	515	205	40	217	95
316L	485	170	40	217	95

These mechanical properties make Stainless steel return U bend suitable for applications requiring high strength and corrosion resistance, such as architectural structures, marine environments, and chemical processing.

Comparison table of stainless steel brands of various countries

In order to solve the cumbersome and difficult to remember stainless steel grades, improve the practicability of the brand representation, and the contrast with the international standard grades, China has formulated the "Universal Code System for Steel and Alloy Grades", such as 06Cr19Ni10, corresponding to 304. Different grades of stainless steel have different ingredients, but they all have a national standard. The standards of each country are also different.

Stainless Steel Grade Equivalents Across Standards
No	China (GB)		Japan (JIS)	American		Korea (KS)	EU (BS EN)	India (IS)	Australia (AS)	Taiwan (CNS)
No	Old	New (07.10)	SUS	ASTM	UNS	STS	EN	IS	AS	CNS
Austenitic Stainless Steel
1	1Cr17Mn6Ni5N	12Cr17Mn6Ni5N	SUS201	201	S20100	STS201	1.4372	10Cr17Mn6Ni4N20	201-2	201
2	1Cr18Mn8Ni5N	12Cr18Mn9Ni5N	SUS202	202	S20200	STS202	1.4373	—	—	202
3	1Cr17Ni7	12Cr17Ni7	SUS301	301	S30100	STS301	1.4319	10Cr17Ni7	301	301
4	0Cr18Ni9	06Cr19Ni10	SUS304	304	S30400	STS304	1.4301	07Cr18Ni9	304	304
5	00Cr19Ni10	022Cr19Ni10	SUS304L	304L	S30403	STS304L	1.4306	02Cr18Ni11	304L	304L
6	0Cr19Ni9N	06Cr19Ni10N	SUS304N1	304N	S30451	STS304N1	1.4315	—	304N1	304N1
7	0Cr19Ni10NbN	06Cr19Ni9NbN	SUS304N2	XM21	S30452	STS304N2	—	—	304N2	304N2
8	00Cr18Ni10N	022Cr19Ni10N	SUS304LN	304LN	S30453	STS304LN	—	—	304LN	304LN
9	1Cr18Ni12	10Cr18Ni12	SUS305	305	S30500	STS305	1.4303	—	305	305
10	0Cr23Ni13	06Cr23Ni13	SUS309S	309S	S30908	STS309S	1.4833	—	309S	309S
11	0Cr25Ni20	06Cr25Ni20	SUS310S	310S	S31008	STS310S	1.4845	—	310S	310S
12	0Cr17Ni12Mo2	06Cr17Ni12Mo2	SUS316	316	S31600	STS316	1.4401	04Cr17Ni12Mo2	316	316
13	0Cr18Ni12Mo3Ti	06Cr17Ni12Mo2Ti	SUS316Ti	316Ti	S31635	—	1.4571	04Cr17Ni12MoTi20	316Ti	316Ti
14	00Cr17Ni14Mo2	022Cr17Ni12Mo2	SUS316L	316L	S31603	STS316L	1.4404	02Cr17Ni12Mo2	316L	316L
15	0Cr17Ni12Mo2N	06Cr17Ni12Mo2N	SUS316N	316N	S31651	STS316N	—	—	316N	316N
16	00Cr17Ni13Mo2N	022Cr17Ni13Mo2N	SUS316LN	316LN	S31653	STS316LN	1.4429	—	316LN	316LN
17	0Cr18Ni12Mo2Cu2	06Cr18Ni12Mo2Cu2	SUS316J1	—	—	STS316J1	—	—	316J1	316J1
18	00Cr18Ni14Mo2Cu2	022Cr18Ni14Mo2Cu2	SUS316J1L	—	—	STS316J1L	—	—	—	316J1L
19	0Cr19Ni13Mo3	06Cr19Ni13Mo3	SUS317	317	S31700	STS317	—	—	317	317
20	00Cr19Ni13Mo3	022Cr19Ni13Mo3	SUS317L	317L	S31703	STS317L	1.4438	—	317L	317L
21	0Cr18Ni10Ti	06Cr18Ni11Ti	SUS321	321	S32100	STS321	1.4541	04Cr18Ni10Ti20	321	321
22	0Cr18Ni11Nb	06Cr18Ni11Nb	SUS347	347	S34700	STS347	1.4550	04Cr18Ni10Nb40	347	347
Austenitic-Ferritic Stainless Steel (Duplex)
23	0Cr26Ni5Mo2	—	SUS329J1	329	S32900	STS329J1	1.4477	—	329J1	329J1
24	00Cr18Ni5Mo3Si2	022Cr19Ni5Mo3Si2N	SUS329J3L	—	S31803	STS329J3L	1.4462	—	329J3L	329J3L
Ferritic Stainless Steel
25	0Cr13Al	06Cr13Al	SUS405	405	S40500	STS405	1.4002	04Cr13	405	405
26	—	022Cr11Ti	SUH409	409	S40900	STS409	1.4512	—	409L	409L
27	00Cr12	022Cr12	SUS410L	—	—	STS410L	—	—	410L	410L
28	1Cr17	10Cr17	SUS430	430	S43000	STS430	1.4016	05Cr17	430	430
29	1Cr17Mo	10Cr17Mo	SUS434	434	S43400	STS434	1.4113	—	434	434
30	—	022Cr18NbTi	—	—	S43940	—	1.4509	—	439	439
31	00Cr18Mo2	019Cr19Mo2NbTi	SUS444	444	S44400	STS444	1.4521	—	444	444
Martensitic Stainless Steel
32	1Cr12	12Cr12	SUS403	403	S40300	STS403	—	—	403	403
33	1Cr13	12Cr13	SUS410	410	S41000	STS410	1.4006	12Cr13	410	410
34	2Cr13	20Cr13	SUS420J1	420	S42000	STS420J1	1.4021	20Cr13	420	420J1
35	3Cr13	30Cr13	SUS420J2	—	—	STS420J2	1.4028	30Cr13	420J2	420J2
36	7Cr17	68Cr17	SUS440A	440A	S44002	STS440A	—	—	440A	440A