STK400

STK400 steel pipe is steel grade material according to JIS standard.

Technical Specifications and Extra Services for STK400 Steel Pipe:

The JIS G0320 standard test method for heat analysis;
General technical delivery specifications for steel and steel products by JIS G0404;
Pipes made of steel shall be supplied with plain or bevel end finishing, as needed;
The results of flattening, bending, and hardness tests appear on the original mill certificate;
Surface Protection: Black, Varnishing, Hot-Dip Galvanized, Shop Prime Coating

Why choose tuspipe?

Since 1998, Tianjin United Steel Pipe Co., Ltd (TUSPIPE) has been committed to supplying high-quality line pipes.

With over 500,000 tons annual production capacity, the company serves various fields and industries, such as oil & gas exploitation and transmission, ship & auto-building, water & electricity, environmental protection, mechanical engineering, infrastructure construction and etc.

TUSPIPE places a premium on product quality and rigorous product quality control. In order to maintain good product quality, the company has established a Test & Inspection Center since 2004. With a series of state-of-the-art tests and inspection equipment, the test & inspection center is able to perform the tensile tests, hydro tests, impact tests, DWTT, etc.

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Manufacturing Method of JIS G3444 Grade STK400 Steel Pipe

The following manufacturing procedure shall be used:

Tubes shall be constructed in accordance with a combination of the tube production and finishing methods specified in Table 1. If necessary, the tube may be subjected to a suitable heat treatment.

Tubes may be manufactured using coated steel sheet or coated steel strip at the purchaser’s desire.

Bevel end finishing may be specified by the consumer, in which case the shape will be determined by the maker and the purchaser.

Grade Symbol and Symbol of Manufacturing Method of JISG G3444 STK400

Symbol of Grade	Symbol of Manufacturing Method		Marking of Symbol of Manufacturing Method
Symbol of Grade	Tube manufacturing	Finishing method	Marking of Symbol of Manufacturing Method
STK400	Seamless: S Electric resistance Butt welded: B Automatic arc welded: A	Hot finished: H Cold finished: C As electric resistance welded: G	As given in clause 11 b)

JIS G3444 STK400 Chemical Composition

Symbol of Grade	C	Si	Mn	P	S
STK400	0.25 max.	–	–	0.040 max.	0.040 max.
Notes a) If necessary, alloying elements other than specified in this table may be added. b) For the tube of grade STK540 exceeding 12.5 mm in wall thickness, the chemical composition may be subject to the agreement between the purchaser and the manufacturer.

Mechanical Properties of JIS G3444 STK400

Symbol of Grade	Tensile Strength N/mm²	Yield Point of Proof Stress N/mm²	Tensile Strength in Weld Zone N/mm²	Flattening	Bendability
	Tensile Strength N/mm²	Yield Point of Proof Stress N/mm²	Tensile Strength in Weld Zone N/mm²	Distance between Plates (H)	Bend Angle	Inside Radius
	Applied outside diameter
	All outside diameters	All outside diameters	All outside diameters	All outside diameters	50 mm max.
STK290	290 min.	–	290 min.	2/3 D	90°	6 D
NOTE 1 D of this table is the outside diameter of the tubes. NOTE 2 1 N/mm²—1 MPa Note a) Standard of bend angle shall be the start point of bending.

Tensile Test Piece and the Elongation Request of JIS G3444 STK400

Symbol of grade	Tube Manufacturing Method
	Seamless and butt welded	Electric resistance welded and automatic arc welded		All manufacturing methods
	Applied outside diameter
	All outside diameters	350 mm	Over 350 mm	All outside diameters
	Test Piece and Direction of Test Piece
	No. 11 test piece No. 12 test piece	No. 11 test piece No. 12 test piece	No.5 test piece	No.4 test piece
	Tube axis direction	Tube axis direction	Perpendicular to tube axis direction	Tube axis direction	Perpendicular to tube axis direction
STK400	23	23	18	21	17
For the tubes of outside diameter 40 mm or under, the elongation value in this table shall not be applied. However, the test result for these tubes shall be recorded. Further, the elongation may be specified by agreement between the manufacturer and the purchaser.

Dimensional Tolerances of JIS G3444 STK400

- Outside Diameter Tolerance a)

Classification	Outside Diameter b)	Tolerances on Outside Diameter c)	Applicable Division
Class 1	Under 50mm	± 0.5mm	Applied when there is no specification. Applicable to hot-finished seamless steel tubes.
Class 1	50mm or Over	± 1%
Class 2	Under 50mm	± 0.25mm	Applied when there is a specification. Not applicable to hot-finished seamless steel tubes.
Class 2	50mm or Over	± 0.5%
Notes	a) For the local parts such as repaired parts if the wall thickness can be confirmed to be within the tolerance in the table below, the outside diameter tolerance of this table need not be applied.
	b) The method for measuring the outside diameter of tubes exceeding 350mm in outside diameter may be determined by the circumferential length. The mutual conversion of outside diameter D and the circumferential length l shall be by the following formula: *D = l / π* Where D: outside diameter (mm) l: circumferential length (mm) π：3.1416
	c) The tolerances on the outside diameter of ends of electric resistance welded and automatic arc welded steel tubes exceeding 350mm in outside diameter shall be ±0.5%。

- Wall Thickness Tolerance a)

Classification	For Seamless Steel Tube		For Other than Seamless Steel Tube		Applicable Division
Classification	Wall Thickness	Tolerance of Wall Thickness	Wall Thickness	Tolerance of Wall Thickness	Applicable Division
Class 1	Under 4mm	+0.6mm, -0.5mm	Under 4mm	+0.6mm, -0.5mm	Applied when there is no specification. Applicable to hot-finished seamless steel tubes.
	4mm or Over	+15%, -12.5%	4mm or Over to and excl. 12mm	+15%, -12.5%
	4mm or Over	+15%, -12.5%	12mm or Over	+15%, -1.5mm
Class 2	Under 3mm	±0.3mm	Under 3mm	± 0.3mm	Applied when there is a specification. Not applicable to hot-finished seamless steel tubes.
	3mm or Over	±10%	3mm or Over to and excl. 12mm	±10%
	3mm or Over	±10%	12mm or Over	+10%，-1.2mm
Notes	a) The tolerances on the wall thickness of tubes exceeding 1016.0 mm in outside diameter may be agreed upon between the manufacturer and the purchaser.

Marking of JIS G3444 Steel Grade STK400

Each tube that has passed inspection should bear the following markings. For tubes with a smaller outer diameter or upon the purchaser’s request, marking may be added to a bundle. The sequence in which the markers are arranged is not defined. A portion of the products may be omitted with the purchaser’s agreement.

Grade symbol
Symbol representing the manufacturing process. The following symbol should be used to indicate the production technique. However, a space may be used in place of the dash.
1. As welded steel tube with electric resistance: -E-G
2. Hot finished electric resistance welded steel tube: -E-H
3. Cold finished electric resistance welded steel tube: -E-C
4. Butt welded steel tube: -B
5. Automatic arc welded steel tube: -A

Measurements Outside diameter and wall thickness should be noted for dimensions.
The manufacturer’s name or an abbreviation of the manufacturer’s name
Symbol representing the coating kind (in the case of using coated steel sheet or coated steel strip). The maker and purchaser shall agree on the symbol’s abbreviation.