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Introduction
JIS G 3128 specifies high
yield strength steel plates for welded structures that require high mechanical
strength, reliable weldability and structural performance. These hot-rolled
steel plates are designed for demanding applications such as bridges, pressure
vessels, high-pressure equipment and other heavy-duty structures.
JIS G 3128 steel is generally
classified as high-tensile, low-alloy structural steel, rather than stainless
steel or conventional mild steel. Its controlled chemical composition and
manufacturing process help achieve high strength while maintaining suitable
weldability.
The latest edition is JIS G
3128:2025, titled High Yield Strength Steel Plates for Welded Structure.
Applicable Standard
·
Standard:
JIS G 3128:2025
·
Standard
title: High Yield Strength Steel Plates for Welded Structure
·
Product
form: Hot-rolled steel plates
·
Material
classification: High-tensile, low-alloy structural steel
·
Strength
level: Approximately 685 MPa proof stress and 780 MPa tensile strength for the
specified grade and thickness range
·
Main
requirements: Chemical composition, mechanical properties, heat treatment,
weldability, dimensions, tolerances and appearance
The applicable edition and
purchase specification should be confirmed when ordering, as requirements may
vary by grade, thickness and delivery condition.
Material Type
JIS G 3128 plates are
high-strength structural steel plates designed for welded fabrication.
·
SS
(Stainless Steel): No. JIS G 3128 is not a stainless steel standard.
·
MS
(Mild Steel): No. It is not conventional mild steel; it provides significantly
higher strength.
·
CS
(Carbon Steel): It contains carbon, but it is more appropriately described as
high-tensile, low-alloy structural steel.
·
Alloy
Steel: It is commonly classified commercially as alloy or low-alloy structural
steel because controlled alloying elements contribute to its strength and
performance.
Scope of JIS G 3128
The standard covers
hot-rolled steel plates with high proof stress, high tensile strength and
excellent weldability. These plates are intended for structures where strength,
toughness and fabrication performance are important.
Typical applications include:
·
Bridges
and bridge girders
·
Pressure
vessels and high-pressure equipment
·
Heavy
welded structures
·
Industrial
plant structures
·
Load-bearing
components
·
Engineering
and infrastructure projects
Steel Grades Covered
The commonly referenced grade
designations associated with JIS G 3128 include the following. The exact grade
availability and applicable requirements should be verified against the current
edition and purchase specification.
|
Grade |
Description |
Typical
application |
|
SHY 685 |
High yield strength steel plate |
Bridges, heavy welded structures and
pressure equipment |
|
SHY 685N |
High yield strength steel plate with
specified alloying and toughness requirements |
Welded structures requiring specified
impact performance |
|
SHY 685NS |
High yield strength steel plate with
specified alloying and enhanced toughness requirements |
Structures requiring performance at lower
temperatures |
Chemical Composition
The following table provides
commonly published maximum chemical composition limits for SHY 685 under the
2021 edition of JIS G 3128. Since JIS G 3128:2025 is the latest edition, these
values should be verified against the current standard before being used as
contractual acceptance limits.
|
Element |
Maximum content (%) |
|
Carbon (C) |
0.18 |
|
Silicon (Si) |
0.55 |
|
Manganese (Mn) |
1.50 |
|
Phosphorus (P) |
0.030 |
|
Sulfur (S) |
0.025 |
|
Chromium (Cr) |
1.20 |
|
Copper (Cu) |
0.50 |
|
Molybdenum (Mo) |
0.60 |
|
Vanadium (V) |
0.10 |
|
Boron (B) |
0.005 |
Other alloying elements may
be added where permitted by the applicable specification. Chemical composition
is determined through the prescribed analysis method, and the requirements for
the ordered grade and edition take precedence.
Mechanical Properties
The following values are
commonly published for SHY 685 under the 2021 edition. Mechanical properties
depend on plate thickness and the applicable delivery condition.
|
Property |
Thickness
6 mm to 50 mm |
Thickness
over 50 mm to 100 mm |
|
Tensile strength |
780–930
MPa |
760–910
MPa |
|
Minimum proof stress / yield strength |
685
MPa |
665
MPa |
|
Charpy impact energy at −20°C |
Average
of 47 J for the specified test condition |
Subject
to applicable test requirements |
Elongation requirements
depend on specimen type, thickness and sampling direction. The values above are
reference data from the 2021 edition and should not replace verification
against JIS G 3128:2025 or the ordered material specification.
Manufacturing Process
JIS G 3128 steel plates are
produced through controlled steelmaking and hot rolling to achieve the required
strength, toughness and weldability.
Typical manufacturing stages
include:
·
Steelmaking
and chemical composition control
·
Casting
of slabs
·
Reheating
and hot rolling to the specified plate thickness
·
Controlled
cooling and heat treatment, as required
·
Surface
inspection and dimensional checks
·
Mechanical
testing and preparation of inspection documentation
Manufacturing Conditions
Manufacturing conditions are
selected according to the grade, plate thickness and specified mechanical
properties.
Important production controls
include:
·
Control
of carbon and alloying elements
·
Rolling
and cooling control
·
Heat-treatment
control
·
Verification
of strength and toughness
·
Dimensional
and surface-quality inspection
These controls help provide
consistent performance in structural and welded applications.
Heat Treatment
Quenching and tempering are
commonly associated with high-strength SHY 685 plates to achieve the specified
strength and toughness.
The required treatment must
be confirmed against the current standard and purchase order. Any additional
treatment requested by the purchaser should be agreed with the manufacturer.
Surface Finish
JIS G 3128 plates are
generally supplied with a hot-rolled surface. Depending on the order and intended
application, plates may be supplied with surface preparation or other finishing
operations by agreement.
The plate surface should be
suitable for the intended fabrication and inspection requirements.
Delivery Condition
The delivery condition
depends on the applicable grade and purchase specification. Plates are supplied
in the condition required to achieve the specified mechanical properties.
The order should identify the
required grade, thickness, dimensions, delivery condition and inspection
documentation.
Dimensions and Tolerances
Plate dimensions and
permissible variations are subject to the applicable JIS requirements and
purchase agreement.
Specifications normally
identify:
·
Thickness
·
Width
and length
·
Dimensional
and shape tolerances
·
Quantity
and plate identification
·
Special
cutting or processing requirements
Custom dimensions and
cut-to-size plates may be available subject to stock and manufacturing
arrangements.
Product Characteristics
JIS G 3128 high yield
strength steel plates offer several useful characteristics for demanding
structural applications:
·
High
yield strength and tensile strength
·
Good
weldability when processed using suitable procedures
·
Potential
for reduced structural weight through the use of high-strength material
·
Suitability
for heavy welded structures
·
Performance
appropriate for bridges and specified pressure equipment
·
Compatibility
with engineered fabrication procedures
Welding consumables,
preheating and other fabrication parameters should be selected based on plate
thickness, joint design and the approved welding procedure.
Forms of Supply
JIS G 3128 steel is primarily
supplied as hot-rolled plates. Depending on availability and order
requirements, supply may include:
·
Standard-size
steel plates
·
Cut-to-size
plates
·
Plates
for welded structural fabrication
·
Plates
supplied with inspection and material test documentation
Availability of specific
thicknesses and grades should be confirmed at the time of enquiry.
Applications
JIS G 3128 high yield
strength steel plates are used in applications where strength and welded
structural integrity are important.
Common applications include:
·
Bridge
construction and bridge girders
·
Pressure
vessels and high-pressure equipment
·
Heavy
engineering structures
·
Industrial
fabrication
·
Load-bearing
welded assemblies
·
Infrastructure
and specialised structural projects
Material selection should
consider design loads, temperature, thickness, welding requirements and the
applicable engineering code.
Key Features
·
High-tensile,
low-alloy structural steel classification
·
High
yield strength for demanding load-bearing applications
·
Good
weldability with suitable fabrication procedures
·
Available
in hot-rolled plate form
·
Suitable
for bridges, pressure equipment and heavy structures
·
Chemical
and mechanical requirements defined by the applicable JIS edition
Availability
Ladhani Metal Corporation
supplies steel products for industrial, structural and engineering
applications. JIS G 3128 high yield strength steel plates can be enquired about
by specifying the required grade, thickness, width, length, quantity, delivery
condition and inspection documentation.
Availability is subject to
stock, sourcing and order requirements.
Conclusion
JIS G 3128 high yield
strength steel plates are high-tensile, low-alloy structural steel plates
intended for demanding welded applications. They are distinct from stainless
steel and conventional mild steel, offering higher strength for bridges,
pressure equipment and heavy structural fabrication.
Ladhani Metal Corporation can
assist with enquiries for JIS G 3128 steel plates based on the required grade,
dimensions and project specifications. For procurement, the latest JIS G
3128:2025 requirements and the applicable material test certificate should be
confirmed to ensure compliance with the intended application.
FOR REQUIREMENT OF THIS GRADE OR FOR DETAIL CONTACT US AT :-
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