HFW steel pipe defects in production

HFW welded steel pipes are widely preferred in Oil, Natural Gas, Water and other liquids transportation and distribution lines, heating, cooling, ventilation piping and steel structures for construction and other general purposes by means of precise production tolerances and high capacity manufacturing method.

Finishing Operations: Plain-End, Square Cut or bevelled.

Surface Condition

Black self-colored / uncoated
Mill protective coating (varnish) on outside surface
Three Layer Extruded Polyethylene – Polypropylene coating (plus rough coating)
Fusion Bond Epoxy Single – Dual Layer coating
Liquid Epoxy coating

HFW steel pipe defects in production

Technical requirements	For oil and gas transport	For low pressure fluid conveying
Material	Gr.b	Gr.b
Pipe body diameter	D＜508mm, ±0.75%; D≥508mm, ±0.75%	D≤168.3, ±1.0%; 168.3＜D≤508,±0.75%;
Wall thickness	D＜508mm,+15.0%，－12.5%; D≥508mm, +17.5%，－10%	±12.5%
Bending	≤0.2%	≤0.2%
Ovality	D≥508mm，≤±1%	≤±0.75%
Bevel	≤1.59mm	≤5mm
Hydrostatic testing	100%	100%
Nondestructive testing	100% non-destructive weld inspection	Ultrasonic flaw detection is 100%

Yield strength of the N80 is higher than the J55 up to 173 ~ 206 MPa.
On the same area of the sample, the elongation of N80 is higher than J55.
Under the same size, the same sample orientation, the same minimum sample size, J55 grade couplings, coupling stock, coupling material, semi-finished and coupling attachment material can absorb lower than N80 steel grade.
The nondestructive testing methods of seamless pipe,coupling stock, welded tube with J55 and N80 is differeent.
J55 and N80 steel grade is not the same color: length greater than or equal 1.8m, J55 painted a bright green, N80 painted a red;
J55 chosen by the manufacturer, or organize according to the order specified length normalized (N), normalizing and tempering (N & T) or quenching and tempering (Q & T). N80 is a whole, full-length heat treatment is mandatory. By the manufacturer selected for normalizing (N) or normalizing and tempering (N & T) + quenching (Q).