STK400

STK400

STK400 steel pipe is steel grade material according to JIS standard. STK400 pipes are mainly used for the following purposes.

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.

PRODUCT FEATURES

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

Tube manufacturing

Finishing 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

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.

STK400

400 min.

235 min.

400 min.

 2/3 D

90°

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 the 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 the tube axis direction

Tube axis direction

Perpendicular to the 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.

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.
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