what the difference welded steel pipe and seamless steel pipe?

Welded steel pipe and seamless steel pipe are two types of steel pipes used in various applications, but they differ in manufacturing processes, appearance, and some characteristics. Here’s a comparison of the two:

Welded Steel Pipe:

Manufacturing process: Welded steel pipes are made by rolling a steel plate or strip into a cylindrical shape and then welding the edges together. The welding process can be either electric resistance welding (ERW), submerged arc welding (SAW), or high-frequency induction welding (HFIW), depending on the application.
Appearance: Welded steel pipes have a visible weld seam along the length of the pipe. This seam may be treated or polished to minimize its visibility, but it will still be present.
Strength: Welded steel pipes are generally strong, but the weld seam can be a weak point, especially in high-pressure applications.
Cost: Welded steel pipes are usually less expensive than seamless steel pipes.
Size range: Welded steel pipes are available in a wide range of sizes, from small-diameter pipes for domestic use to large-diameter pipes for industrial and infrastructure applications.

PRODUCTION PICTURE:
OVERVIEW OF LSAW welded STEEL PIPE:

Product name	Longitudinally Submerged Arc Welding Pipe
Outer diameter	406mm- 1626mm (16″- 64″)
Wall thickness	6.0-44.5mm
Length	3-18m( adjustable according to client’s requirement)
Standard	API,DNV,ISO,DEP,EN,ASTM,DIN,BS,JIS,GB,CSA
Grade	API 5L : Gr.B, X42, X46, X56, X60, X65, X70 ASTM A53: Gr.A, Gr.B, Gr.C EN: S275, S275JR, S355JRH, S355J2H
Surface treatment	Black painting, Varnish painting, bare pipe, Oiled, Hot dip galvanized
End	Beveled end,plain end meet your need
Packing	Bundled/In Bulk, Plastic Caps Plugged, Waterproof Paper Wrapped Usage: Used for Fluids Transmission, Structural Support in Industrial Construction

Tolerance of Outside Diameter and Wall Thickness

Types	Standard
Types	SY/T5040-2000	SY/T5037-2000	SY/T9711.1-1977	ASTM A252	AWWA C200-97	API 5L PSL1
Tube end OD deviation	±0.5%D	±0.5%D	-0.79mm~+2.38mm	<±0.1%T	<±0.1%T	±1.6mm
Wall thickness	±10.0%T	D<508mm, ±12.5%T	-8%T~+19.5%T	<-12.5%T	-8%T~+19.5%T	5.0mm
Wall thickness	±10.0%T	D>508mm, ±10.0%T	-8%T~+19.5%T	<-12.5%T	-8%T~+19.5%T	T≥15.0mm, ±1.5mm

LSAW welded STEEL PIPE MANUFACTURING PROCESS:

welded PRODUCT SIZE:

Out Diameter		Wall Thickness(mm)
Inch	mm	6.4	7.1	7.9	9.53	12.7	14.3	15.9	19.1	22.2	25.4	28.6	31.8	34.9	38.1	41.3	44.5
16	406.4
18	457
20	508
22	559
24	610
26	660
28	711
30	762
32	813
34	864
36	914
38	965
40	1016
42	1067
44	1118
46	1168
48	1219
52	1321
56	1422

Seamless Steel Pipe:

Manufacturing process: Seamless steel pipes are made by extruding or drawing a solid steel billet or ingot into a hollow tube without any seams. The process involves heating the billet and using a piercing mill or extrusion machine to create a hollow tube, followed by further rolling or drawing to achieve the desired dimensions.
Appearance: Seamless steel pipes have a smooth, uniform surface without any visible seams.
Strength: Seamless steel pipes have higher strength than welded steel pipes, as there are no weak points from weld seams. This makes them suitable for high-pressure applications and critical uses where structural integrity is crucial.
Cost: Seamless steel pipes are generally more expensive than welded steel pipes due to the more complex manufacturing process and the higher-quality raw materials involved.
Size range: Seamless steel pipes are available in a wide range of sizes, but they are more limited in diameter and wall thickness than welded steel pipes.

In summary, the main differences between welded and seamless steel pipes are in their manufacturing processes, appearance, strength, cost, and size range. The choice between the two types depends on the specific requirements of the application, such as pressure ratings, mechanical properties, and budget constraints.

ASTM Standard for seamless steel pipe

Executive Standard	Grade / Material	Product Name
ASTM A53	A, B	Black and Hot-Dipped Zinc-Coated Steel Pipes Welded and Seamless
ASTM A106	A, B	Seamless Carbon Steel for High Temperature Service
ASTM A179	Low Carbon Steel	Seamless Cold-Drawn Low-Carbon Steel Heat Exchanger and Condenser Tubes
ASTM A192	Low Carbon Steel	Seamless Carbon Steel Boiler Tubes for High Pressure
ASTM A210	A1, C	Seamless Medium-Carbon and Alloy Steel Boiler and Super heater Tubes
ASTM A213	T5, T11, T12, T22 TP 347H	Seamless Ferritic and Austenitic Alloy Steel Boiler, Superheater and Heat- Exchanger Tubes
ASTM A312	TP304/304L, TP316/316L	Seamless Steel Pipe for Stainless Materials
ASTM A333	Gr.6	Seamless and Welded Steel Pipe for Low-Temperature Service
ASTM A335	P9, P11, P22	Seamless Ferritic Alloy Steel Pipe for High-Temperature Service
ASTM A519	4130,4140	Seamless Carbon and Alloy Steel for Mechanical Tubing
ASTM A789		Seamless Ferritic/Austenitic Stainless Steel Tubing for General Service

API Standard for seamless steel pipe

Executive Standard	Grade / Material	Product Name
API Spec 5CT	J55, K55, N80, L80,C90, C95, T95, P110, M65	Specification for Casing and Tubing
API Spec 5L PSL1 / PSL2	A,B X42, X46, X52, X56, X60, X65,. X70	Specification for Line Pipe

EN/DIN Standard for seamless steel pipe

Executive Standard	Grade / Material	Product Name
DN 17175/EN10216-2	ST35, ST45, ST52, 13CrMo44	Seamless Steel Tube for Elevated Temperature
DIN 2391/EN10305-1	St35, St45, St52	Cold Drawn Seamless Precision Pipe
DIN 1629/EN10216-1	St37, St45, St52	Seamless Circular unalloyed Steel Tubes Subject to Special Requirements

Product	Seamless Steel Pipe For Exploration & Production
OD	13.72 mm – 914.4 mm
WT	1.65 mm – 22 mm
Length	0.5 m – 20 m
Standard	API 5L PSL1 /PSL2
Material	GR.B/X42/46/X52/56/X60/65/X70/80
Usage	Chilled Water Pipe, Drinking water Pipe, W aste Water Pipe, Structural Tube, Fluid Pipe, Boiler Pipe, Oil and Gas Transportation Pipe, Mechanical Structure Pipe

Chemical composition and mechanical properties:

API 5L PSL1
Standard	Grade	Chemical Components				Tensile STrength(min)	Yield Strength(min)
		C	Mn	P	S	Mpa	Mpa
API 5L	A	0.22	0.90	0.030	0.030	331	207
PSL1	B	0.28	1.20	0.030	0.030	414	241
	X42	0.28	1.30	0.030	0.030	414	290
	X46	0.28	1.40	0.030	0.030	434	317
	X52	0.28	1.40	0.030	0.030	455	359
	X56	0.28	1.40	0.030	0.030	490	386
	X60	0.28	1.40	0.030	0.030	517	414
	X65	0.28	1.40	0.030	0.030	531	448
	X70	0.28	1.40	0.030	0.030	565	483

API 5L PSL2
Standard	Grade	Chemical Components				Tensile STrength(min)	Yield Strength(min)
		C	Mn	P	S	Mpa	Mpa
API 5L	B	0.24	1.20	0.025	0.015	414	241
PSL2	X42	0.24	1.30	0.025	0.015	414	290
	X46	0.24	1.40	0.025	0.015	434	317
	X52	0.24	1.40	0.025	0.015	455	359
	X56	0.24	1.40	0.025	0.015	490	386
	X60	0.24	1.40	0.025	0.015	517	414
	X65	0.24	1.40	0.025	0.015	531	448
	X70	0.24	1.40	0.025	0.015	565	483
	X80	0.24	1.40	0.025	0.015	621	552