JISG3444 STK490 carbon steel tubes are utilized in civil engineering and architectural structures such as steel towers, footing piles, foundation piles, landslide suppression piles, and many others.

Standards: JIS G3444

Grade: STK490

Outer Dimensions: 6mm ~ 350mm.

Wall Thickness: 2mm ~ 22 mm.

Packing: wooden protection/Beveled/black painting/ plastic caps/ in bundles/ steel strips.
Surface treatment: Varnish, Passivation, Phosphating, Shot Blasting, Oil-dip.
Mark: As customer’s request.

Delivery Condition: Annealed, Normalized, Normalized, and Tempered.


Manufacturing Method of JIS G3444 Grade STK490 Steel Pipe

The manufacturing method shall be as follows:

Tubes should be constructed in accordance with a combination of the tube production and finishing methods specified in the JIS standard. 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 form will be determined by the maker and the purchaser.

Grade Symbol and Symbol of Manufacturing Method of JIS G3444 STK490

Symbol of Grade

Symbol of Manufacturing Method

Marking of Symbol of Manufacturing Method

Tube Manufacturing

Finishing Method


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 STK 490 Chemical Composition

Symbol of Grade







0.18 max.

0.55 max.

1.65 max.

0.035 max.

0.035 max.


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.

JIS G3444 Grade STK 490 Mechanical Properties

Symbol of Grade

Tensile Strength



Yield Point of Proof Stress



Tensile Strength in Weld Zone





Distance between Plates


Bend Angle

Inside Radius

Applied outside diameter

All outside diameters

All outside diameters

All outside diameters

All outside diameters

50 mm max.


490 min.

315 min.

490 min.

 7/8 D


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.

JIS G3444 Grade STK490 Tensile Test Piece and the Minimum Value of Elongation

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







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 STK490

Each tube having passed the inspection shall be marked with the following items on each STK490 tube. For tubes of smaller outside diameter or when there is a special request by the purchaser, marking may be applied on a bundle. The order of arrangement of the markings is not specified. When approved by the purchaser, part of the items may be omitted.

  • 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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