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JIS G3444 STK500,STK540 Carbon Steel Tubes

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JIS G3444 is a Japanese Industrial Standard that specifies the requirements for carbon steel tubes used in general structural applications, such as construction, machinery, and other engineering purposes. The standard covers seamless and welded tubes made from carbon steel, with specified mechanical properties and dimensional tolerances. Below is a detailed description of STK 500 and STK 540 under this standard:

Material Grades: STK500 And STK540
The standard includes several grades, among which STK500 and STK540 are common. These grades denote the minimum tensile strength of the steel tubes:

STK500: Minimum tensile strength of 500 MPa

STK540: Minimum tensile strength of 540 MPa

Both grades are widely used in structural applications where moderate strength and good weldability are required.

Chemical Composition (Typical Values)
The chemical composition of STK500 and STK540 generally follows:

Element	STK500	STK540
Carbon (C)	≤ 0.24%	≤ 0.23%
Silicon (Si)	≤ 0.35%	≤ 0.55%
Manganese (Mn)	0.30% ~ 1.50%	≤ 1.50%
Phosphorus (P)	≤ 0.040%	≤ 0.040%
Sulfur (S)	≤ 0.040%	≤ 0.040%

Exact composition may vary slightly depending on the manufacturer and production method.

Mechanical Properties

Property	STK500	STK540
Tensile Strength (min)	500 MPa	540 MPa
Yield Strength (min)	355 MPa	390 MPa
Elongation (min, %)	15%	20%
Weld Tensile Strength (min)	500 MPa	540 MPa
Flattening Resistance	7/8D (where D is the outside diameter)	7/8D (where D is the outside diameter)
Bendability	90° bend with an inside radius of 8D	90° bend with an inside radius of 6D

These properties ensure that the tubes can withstand structural loads while maintaining ductility.

● Flattening Test: This test checks for flaws or cracks in the pipe by flattening a specimen between two parallel plates. For STK 500 and STK 540, the distance between the plates is 7/8 of the outside diameter (D). The specimen must not show any cracks after the test.
● Bendability Test: Pipes with an outside diameter of 50 mm or less can be tested for bendability. The pipe must be bent to a 90° angle around a mandrel with a specified radius (8D for STK 500 and 6D for STK 540) without cracking.

Manufacturing Process
The manufacturing methods for these pipes include seamless (S), electric resistance welding (E), butt welding (B), and automatic arc welding (A).

The finishing methods can be hot finished (H) or cold finished (C).

Applications
STK 500 and STK 540 pipes are suitable for applications requiring higher strength and reliability. They are commonly used in:

● Structural frameworks for buildings and bridges
● Piling and foundation works
● Automotive components and trailers
● General industrial applications where high load-bearing capacity is needed
These grades offer a balance of strength and ductility, making them versatile for various engineering and construction projects.

Conclusion
JIS G3444 STK500 and STK540 are medium-strength carbon steel tubes suitable for structural applications where good strength, weldability, and formability are required. They are widely used in Japan and internationally in construction and mechanical engineering.

JIS G3444 STK500,STK540 Carbon Steel Tubes

JIS G3444 STK500,STK540 Carbon Steel Tubes Grade: STK500,STK540 Standard: JIS G3444 Manufacturing Methods:SMLS, ERW, LSAW... Specification: OD: 20MM - 660MM(ERW), 245MM - 1420MM(LSAW) WT: 1.3MM - 16MM(ERW), 10MM - 50MM(LSAW) Length: Commonly used 5.8M、6M、12M,or as your requirement. Surface Treatments: Powder coating, Hot-dip galvanized, Primer painted. Application: Civil engineering, Architecture, Construction, Machinery, Automotive & Industrial Equipment.

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