S11212-021

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Technical Parameter Table: Carbon Steel Tube S11212-021

Product Name: Carbon Steel Tubes for Machine Structural Purposes
Designation: S11212-021 (JIS G 3445: STB 021)
Standard: JIS G 3445 (Japanese Industrial Standard)
Note: This grade is the Japanese equivalent of ASTM A179 / A214 (Seamless) and covers similar applications.

Parameter Category	Parameter	Value / Description	Notes & Interpretation
Designation Decoding	S11212	Indicates a carbon steel tube.	The “12” typically refers to a specific carbon content range.
	-021	The suffix “-021” specifically denotes the grade “STB 021” under JIS G 3445.	“STB” stands for “Steel Tube Boiler” or “Structural Tubing Carbon”.
Mechanical Properties	Tensile Strength (Rm)	≥ 315 MPa	This is a minimum requirement.
	Yield Strength (Rp0.2)	Not Specified (N/S)	For this grade, yield strength is typically not a controlling factor.
	Elongation (A), min	≥ 30%	Measured on a standard test piece. Indicates good ductility.
	Hardness	Not Specified (N/S)
Chemical Composition (Max %)	Carbon (C)	0.08 – 0.13%	Low carbon content ensures excellent weldability and formability.
	Manganese (Mn)	0.30 – 0.60%
	Phosphorus (P)	≤ 0.040%	Impurity, controlled for weldability and to prevent embrittlement.
	Sulfur (S)	≤ 0.040%	Impurity, controlled to improve hot workability and surface finish.
	Silicon (Si)	Remarks: May be added as a killing agent.	Typically, Silicon is not specified but may be present up to ~0.10%.
Dimensional Standards	Manufacturing Process	Seamless or Welded & Cold-Drawn	The standard covers both, but the final product is typically cold-drawn for precise dimensions.
	Tolerances	Strict dimensional and wall thickness tolerances.	Governed by JIS G 3445. Defines deviations for outer diameter, wall thickness, and length.
Physical Properties	Surface Finish	Smooth, bright finish	Characteristic of cold-drawn tubes.
	Density	7.85 g/cm³	Standard for carbon steel.
Processing & Applications	Weldability	Excellent	Due to its very low carbon content. Can be easily welded by all standard methods.
	Formability	Excellent	Easily bent, flared, and flanged.
	Typical Applications	– Low/Medium-pressure boiler tubes – Heat exchanger tubes – Heat condenser tubes – Air pre-heaters – General mechanical structural parts requiring precise dimensions and good surface finish.	Used in applications where pressure and temperature are relatively low but precise dimensions and reliability are key.