Standards：
Standard for malerials and wielding from Chinese classifying society Chinese clasifying society(CCS)
Standard of DNV Det Norske Veritas(DNV)
Standard of Lloyd'S Register of UK(LR) Lloyd'S Register of UK(LR)
Standard of Germanischer Lloyd Germanischer Lloyd(GL)
Standard of American Bureau of Shipping(ABS)American Bureau of Shipping(ABS)
Standard of BUREAU VERITAS(BV)BUREAU VERITAS(BV) 
Standard of RINA Italian classification society(RINA)
Standard of NIPPON KAIJI KYOKAI(NK)NIPPON KAIJI KYOKAI(NK)
GB／T5312 Chinese national standard
Appication：
Seamless steel tubes for manufacturing marine boilers and ovemeaters as we as pressure pipes opf grade I and Ⅱ．
Model N0．of major steel tubesL:
320 ,360, 410，460，490，etc．
Diamensional tolerances:
|
Types of steel tubes
|
Outer diameters
|
wall thickness
|
|
Cold-rolled tubes
|
Rube size(mm)
|
tolerances(mm)
|
Tube sizes (mm)
|
Tolerances(mm)
|
|
＞30～50
|
±0.3
|
≤30
|
±10％
|
|
＞50～219
|
±0.8％
|
|
Hot-rolled tubes
|
＞219
|
±1.0％
|
＞20
|
±10％
|
Mechanical properties：
|
Standard code
|
Models of steel tubes
|
Tensile strength（MPa）
|
Yield strength（MPa）
|
Elongation（％）
|
|
GB/T5312
|
320
|
320～410
|
≥195
|
≥25
|
|
360
|
360～480
|
≥215
|
≥24
|
|
410
|
410～530
|
≥235
|
≥22
|
|
460
|
460～580
|
≥265
|
≥21
|
|
490
|
490～610
|
≥285
|
≥21
|
Chemical compisition:
|
Standard code
|
Models of steel tubes
|
Chemical compisition（％）
|
|
C
|
Si
|
Mn
|
P
|
S
|
|
GB/T5312
|
320
|
≤0.16
|
≤0.35
|
0.40～0.70
|
≤0.035
|
≤0.035
|
|
360
|
≤0.17
|
≤0.35
|
0.40～0.80
|
≤0.035
|
≤0.035
|
|
410
|
≤0.21
|
≤0.35
|
0.40～1.20
|
≤0.035
|
≤0.035
|
|
460
|
≤0.22
|
≤0.35
|
0.80～1.40
|
≤0.035
|
≤0.030
|
|
490
|
≤0.23
|
≤0.35
|
0.80～1.50
|
≤0.035
|
≤0.030
|
Note：residual elements:Cr≤0.25％，Mo≤0.10％，Ni≤0.30％，Cu≤0.30％aggregate≤0.70％
