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Introduction
JIS G 3444 is a Japanese
Industrial Standard that specifies requirements for carbon steel tubes used in
general structural applications. These tubes are widely used in civil
engineering, construction, infrastructure, steel structures and industrial
projects where strength, durability and structural reliability are essential.
JIS G 3444 carbon steel tubes
are available in different grades, each offering specific tensile strength,
yield strength and elongation requirements for various structural applications.
Applicable Standard
JIS G 3444:2025 – Carbon
Steel Tubes for General Structure.
The 2025 edition was
published on 21 April 2025 and replaced the previous JIS G 3444:2021 edition.
Material Type
Carbon Steel (CS)
JIS G 3444 tubes are
manufactured from carbon steel with controlled levels of carbon, manganese,
silicon, phosphorus and sulphur. The material is intended for general
structural purposes and is not classified as stainless steel or alloy steel.
Scope of JIS G 3444
The standard covers carbon
steel tubes used for:
·
Civil
engineering and construction
·
Steel
towers and structural frameworks
·
Scaffolding
and support structures
·
Footing
piles and foundation piles
·
Piles
for landslide suppression
·
General
building and infrastructure projects
The standard generally covers
outside diameters from 21.7 mm to 1,016.0 mm, subject to the applicable product
requirements.
Grades of JIS G 3444
JIS G 3444 includes five
principal grades:
·
STK290
·
STK400
·
STK490
·
STK500
·
STK540
Each grade is selected
according to the required strength, structural design and application.
Chemical Composition
The chemical composition of
JIS G 3444 carbon steel tubes is controlled to achieve the required strength,
ductility and fabrication characteristics. The following table gives the
commonly published grade limits.
|
Grade |
Carbon
(C) % |
Silicon
(Si) % |
Manganese
(Mn) % |
Phosphorus
(P) % |
Sulphur
(S) % |
|
STK290 |
Not
specified |
Not
specified |
Not
specified |
0.050
max. |
0.050
max. |
|
STK400 |
0.25
max. |
Not
specified |
Not
specified |
0.040
max. |
0.040
max. |
|
STK490 |
0.18
max. |
0.55
max. |
1.65
max. |
0.035
max. |
0.035
max. |
|
STK500 |
0.24
max. |
0.35
max. |
0.30–1.30 |
0.040
max. |
0.040
max. |
|
STK540 |
0.23
max. |
0.55
max. |
1.50
max. |
0.040
max. |
0.040
max. |
Notes:
·
A
dash or “not specified” indicates that the standard does not prescribe a
numerical limit for that element in the relevant grade table.
·
Other
alloying elements may be added where necessary, subject to the standard.
·
For
STK540 tubes with wall thickness exceeding 12.5 mm, chemical composition may be
agreed between the purchaser and manufacturer.
·
Product
analysis, where required, is subject to the applicable tolerances.
Mechanical Properties
JIS G 3444 specifies
mechanical requirements covering tensile strength, yield point or proof stress,
elongation, welded-joint tensile strength, flattening resistance and
bendability.
Tensile Strength and Yield Strength
|
Grade |
Tensile
Strength (MPa) Min. |
Yield
Point or Proof Stress (MPa) Min. |
Weld
Tensile Strength (MPa) Min. |
|
STK290 |
290 |
Not
specified |
290 |
|
STK400 |
400 |
235 |
400 |
|
STK490 |
490 |
315 |
490 |
|
STK500 |
500 |
355 |
500 |
|
STK540 |
540 |
390 |
540 |
Manufacturing Process
JIS G 3444 carbon steel tubes
are manufactured using permitted production methods according to the required
grade, dimensions and application.
Manufacturing methods
include:
·
Seamless
manufacturing
·
Electric
resistance welding (ERW)
·
Butt
welding
·
Automatic
arc welding
Finishing methods may include
hot finishing, cold finishing or supply in the as-welded condition, as
applicable to the manufacturing route.
Surface Finish
JIS G 3444 tubes are supplied
with surface finishes suitable for structural applications and the agreed order
requirements.
·
Black
surface finish
·
Plain
mill finish
·
Hot-dip
galvanized finish, where specified
·
Zinc-coated
finish, where specified
·
Other
permitted metallic coatings, subject to the applicable requirements
·
Cut
ends and surface condition as agreed between purchaser and manufacturer
·
Tubes
should be free from defects that adversely affect their intended use
·
Surface
repairs and permissible imperfections are subject to the standard and purchaser
requirements
Delivery Condition
The delivery condition
depends on the manufacturing method, finishing route and purchase
specification.
·
Hot-finished
condition
·
Cold-finished
condition, where applicable
·
As-welded
condition for applicable welded tubes
·
Seamless
or welded supply according to the order
·
Plain
or coated supply, as specified
·
Standard
or agreed fixed lengths
·
Special
lengths according to project requirements
·
Inspection
documentation and test certificates as agreed at the time of ordering
Dimensions and Tolerances
JIS G 3444 tubes are supplied
in specified outside diameters, wall thicknesses and lengths. The standard
provides dimensional requirements and permissible tolerances for the relevant
product categories.
Important dimensional
parameters include:
·
Outside
diameter
·
Wall
thickness
·
Length
·
Unit
mass
·
Straightness
·
Dimensional
tolerances
The standard generally covers
outside diameters from 21.7 mm to 1,016.0 mm. Actual dimensions and tolerances
must be confirmed according to the applicable size range and manufacturing
method.
Forms of Supply
JIS G 3444 carbon steel tubes
can be supplied in different forms according to the selected grade and
manufacturing process.
·
Seamless
carbon steel tubes
·
Electric
resistance welded tubes
·
Butt-welded
tubes
·
Automatic
arc-welded tubes
·
Round
carbon steel tubes
·
Plain-end
tubes
·
Cut-to-length
tubes
·
Galvanized
carbon steel tubes, where specified
Applications of JIS G 3444 Carbon Steel Tubes
JIS G 3444 tubes are used in
a wide range of structural and infrastructure projects, including:
·
Building
and construction frameworks
·
Steel
towers and transmission structures
·
Scaffolding
systems
·
Foundation
and footing piles
·
Civil
engineering structures
·
Structural
supports and columns
·
Road
and infrastructure projects
·
Industrial
and general engineering applications
Key Features
·
Manufactured
according to JIS G 3444 requirements
·
Carbon
steel material for general structural applications
·
Available
in five principal grades
·
Different
tensile and yield strength levels
·
Suitable
for welded and structural fabrication applications
·
Available
through seamless and welded manufacturing routes
·
Multiple
surface and coating options, subject to specification
·
Suitable
for construction, infrastructure and engineering projects
Availability
JIS G 3444 carbon steel tubes
are available on an order basis, subject to grade, dimensions, manufacturing
method and stock availability. Ladhani Metal Corporation supports enquiries for
different grades, sizes, surface finishes and delivery requirements according
to customer specifications.
Conclusion
JIS G 3444 carbon steel tubes
are widely used in construction, civil engineering and structural applications
requiring dependable strength and durability. With five principal grades and
different manufacturing and finishing options, these tubes are suitable for a
broad range of structural requirements. Ladhani Metal Corporation supports the
supply of JIS G 3444 carbon steel tubes according to project specifications and
customer requirements.
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