Carbon Steel Square Seamless Pipe | Structural & Mechanical Seamless Square Tube

🟧 Product Overview

Carbon Steel Square Seamless Pipe is manufactured through hot rolling or cold drawing to achieve excellent mechanical strength, uniform wall thickness, and precise dimensions. Its seamless structure provides superior load‑bearing performance and reliability, making it ideal for structural engineering, machinery manufacturing, and industrial frameworks.

Compared with welded square tubes, seamless square pipes offer higher pressure resistance, better mechanical properties, and improved durability.

🟧 Standards

Available Standards (depending on customer requirements):

• ASTM A106
• ASTM A53
• EN 10210 / S355
• GB/T 8162
• GB/T 8163
• GB/T 3087

🟧 Product Specifications & Available Sizes

Specification	Details
Size (Square)	10×10 – 400×400 mm
Wall Thickness	1–40 mm
Length	5.8 m / 6 m / 12 m / custom
Manufacturing Process	Hot Rolled / Cold Drawn
Surface	Black / Oiled / Varnished
Ends	Plain End / Beveled End
Tolerance	As per applicable standard

Dimensions mm	Dimensions mm
20*20*1.0	80*80*3.5
25*25*1.8	80*80*7.75
25*25*2	100*100*11.75
25*25*2.5	100*100*2.75
25*25*2.75	100*100*3.75
250*250*9.5	100*100*4.75
30*30*0.7	100*100*7.75
30*30*1.5	120*120*2.75
30*30*1.8	120*120*4.75
30*30*2	150*150*11.75
30*30*2.5	150*150*3.75
30*30*2.75	150*150*5.75
40*40*1.5	180*180*8
40*40*2.5	200*200*4.75
50*50*2.5	200*200*7.5
50*50*2.5	200*200*7.75
50*50*3.0	300*300*11.75
50*50*3.5	300*300*12
50*50*3.5	300*300*9.75
60*60*2.5	400*400*11.5
60*60*3.0	400*400*11.75
80*80*2.5	500*500*11.75
The above are the general items, for the special types, we can also meet your needs.

🟧 Chemical Composition (Typical for Carbon Steel)

Element	Range (%)
C	0.06–0.30
Mn	0.25–1.20
Si	≤ 0.35
P	≤ 0.035
S	≤ 0.035

（The specific composition may vary slightly depending on the standard）

🟧 Mechanical Properties

Property	Typical Value
Tensile Strength	350–600 MPa
Yield Strength	200–450 MPa
Elongation	≥ 20%
Hardness	≤ 187 HB

🟧 Primary Industry Usage

• Structural engineering
• Steel frameworks
• Machinery manufacturing
• Automotive and equipment fabrication
• Mechanical support structures
• Construction and industrial projects

🟧 Why Use Carbon Steel Square Seamless Pipe

• Seamless structure ensures superior strength
• Excellent weldability and machinability
• High load‑bearing capacity
• Suitable for both structural and mechanical applications
• Available in a wide range of sizes and thicknesses

🟧 Why Choose WelSteels

• High‑precision seamless square tubes
• Hot rolled and cold drawn options available
• SGS / BV inspection services
• Custom cutting, beveling, and processing
• Export‑grade seaworthy packaging
• Fast delivery from stock and mill production

International Standards

China	America	Germany	Japan	France	Britain	International
GB3077	AlSI	DIN	JIS	NE	BS	ISO
20Mn2	13201221	20Mn5	SMn21	20M5	150M19	–
30Mn2	1330	30Mn5	SMn24	32M5	150M28	–
35Mn2	1335	36Mn5	SMnl	35M5	150M36	–
40Mn2	13401341	–	SMn2	40M5	–	–
45Mn2	1345	46Mn7	SMn3	45M5	–	–
50Mn2	1052	50Mn7	–	55M5	–	–
20MnV	–	20MnV6	–		–	–
30Mn2MoW	–	—	–		–	–
27SiMn	–	27MnSi5	–		–	–
35SiMn	–	37MnSi5	–	38MS5	–	–
42SiMn	–	38MnSi446MnSi4	–	38MS5	–	–
20SiMn2MoV	–	–	–	–	–	–
25SiMn2MoV	–	–	–	–	–	–
37SiMn2MoV	–	–	–	–	–	–
40B	14B35	35B2	–	–	–	–
45B	50B46H	45B2	–	–	–	–
50B	14B50	–	–	–	–	–
4OM∏B	15B41	–	–	–	–	–
45MnB	15B4850B44	–	–	–	–	–
20Mn2B	–	–	–	–	–	–
20MnMoB	80B20	–	–	–	–	–
15MnVB	–	–	–	–	–	–
–	–	–	–	–	–	–
–	–	–	–	–	–	–
20MnVB	–	–	–	–	–	–
40MnVB	–	–	–	–	–	–
20MnTiB	–	–	–	–	–	–
25MnTiBRE	–	–	–	–	–	–
2OSiMnVB	–	–	–	–	–	–
15Cr	50155115	15Cr3	SCr21	12C3	523A14523M15	–
15CrA	–	–	–	–	–	–
20Cr	5120	20Cr4	SCr22	18C318C4	527A19527M20	683/1120Cr420CrS4
30Cr	5130	28Cr4	SCr2	28C432C4	530A30530A32	–
35Cr	5135	34Cr437Cr4	SCr3	38C4	530A36	683/83、 3a、 3b
40Cr	5140	38Cr441Cr4	SCr4	42C4	530A40530M40	683/14、 4a^ 4b
45Cr	5145	42Cr4	SCR5	45C4	–	–
50Cr	51505152	–	–	50C4	En48	–
38CrSi	–	–	–	–	–	–
12CrMo	4119	13CrMo44	–	12CD415CD2	–	–
15CrMo	ASTMA-387Gr. B	15CrMo516CrMo44	SCM21	15CD4. 05	BS1653	–
20CrMo	4118	20CrMo522CrMo4	SCM22	18CD420CD4	CDS 12CDSllO	–
30CrMo	4130	25CrMo4	SCM2	30CD4	CDS 13	–
30CrMoA	–	32CrMol23ICRMo12	–	–	–	–
35CrMo	41354137	34CrMo435CrMo4	SCM3	35CD4	78A37	683/1C35eaC35eb
42CrMo	41404142	41CrMo442CrMo4	SCM4	40CD442CD4	708M40708A42709M40	683/13
12CrMoV	–	–	–	–	–	–
35CrMoV	–	35CrMoV5	–	–	–	–
12CrlMoV	–	13CrMoV4.2	–	–	–	–
25Cr2MoVA	–	24CrMoV5.5	–	–	–	–
25Cr2MolVA	–	–	–	–	–	–
20CR3MoWVA	–	21CrVMoW12	–	–	–	–
38CrMoΛl	6370 (ΛMS)	34CrAlMo541CrAlMo7	SACM645	40CAD6.12	905M39	683/1041CrAlMo74
20CrV	6120	22CrV4	–	22CrV4	–	–
40CrV	6140	42CrV	–	42CrV4	–	–
50CrVA	6150	50CrV4	SUPlO	50CV4	735A50	–
15CrMn	–	16MnCr5	–	16MC5	–	–
20CrMn	5120	20MnCr5	SMC21	20MC5	–	–
40CrMn	5140	–	SMC3	–	–	–
20CrMnSi	–	–		–	–	–
25CrMnSi	–	–	SMKl	–	–	–
30CrMnSi	–	–	–	–	–	–
30CrMnSiA	–	–	–	–	–	–
35CrMnSiA	–	–	SMK2	–	–	–
20CrMnMo	4119	20CrMo5	SCM23	–	–	–
40CrMnMo	4140	–	–	–	–	–
20CrMnTi	–	–	SMK22	–	–	–
30CrMnTi	–	30MnCrTi4	–	–	–	–
20CrNi	3120	20NiCr6	–	20NC6	637A16637M17	–
40CrNi	3140	46NiCr6	SNCl	35NC6	640A35640M40	–
45CrNi	3145	45NiCr6	–	–	–	–
50CrNi	3150	–	–	–	–	–
12CrNi2	3115	14NiCrlO	SNC21	IONCll14NC11	–	–
12CrNi3	3310	13NiCrl2	SNC22	10NC1214NC12	655A12655M13	–
20CrNi3	–	22NiCrl4	–	20NC11	–	–
30CrNi3	–	28NiCrlO31NiCrl4	SNC2	30NC1130NC12	–	–
37CrNi3	–	35NiCrl8	SNC3	35NC15	–	–
12Cr2Ni4	E3310	14NiCrl8	–	12NC15	–	–
20Cr2Ni4	E3316	22NiCrl4	–	20NC14	659A15659M15	–
20CrNiMo	8620    8720	20NiCrMo221NiCrMo2	–	20NCD2	805A20805M20	–
40CrNiMoA	4340     9840	36NiCrMo440NiCrMo6	SNCM8	35NCD540NCD3	817M40816M40	–
45CrNiMoVA	4437	–	SNCM9	–	–	–
18Cr2Ni4WA
25Cr2Ni4WA