Carbon Steel Tubes For Machine Structural Purpose

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Chinese National Standard CNS 4437 G3103 For Carbon Steel Tubes For Machine Structural Purpose
JIS G3445(Japanese Industrial Standard For Carbon Steel Tubesfor Machine Structural Purposes)

(1) Chemical Composition

Class Symbol Chemical Composition % Nb or V
C Si Mn P S
No.11 A STKM 11A 0.12max 0.35max 0.60max 0.040max 0.040max –
No.12 A STKM 12A 0.20max 0.35max 0.60max 0.040max 0.040max –
B STKM 12B
C STKM 12C
No.13 A STKM 13A 0.25max 0.35max 0.30~0.90 0.040max 0.040max –
B STKM 13B
C STKM 13C
No.14 A STKM 14A 0.30max 0.35max 0.30~1.00 0.040max 0.040max –
B STKM 14B
C STKM 14C
No.15 A STKM 15A 0.25~0.35 0.35max 0.30~1.00 0.040max 0.040max –
C STKM 15C
No.16 A STKM 16A 0.35~0.45 0.40max 0.40~1.00 0.040max 0.040max –
C STKM 16C
No.17 A STKM 17A 0.45~0.55 0.40max 0.40~1.00 0.040max 0.040max –
C STKM 17C
No.18 A STKM 18A 0.18max 0.55max 1.50max 0.040max 0.040max –
B STKM 18B
C STKM 18C
No.19 A STKM 19A 0.25max 0.55max 1.50max 0.040max 0.040max –
C STKM 19C
No.20 A STKM 20A 0.25max 0.55max 1.60max 0.40max 0.40max 0.15max


(2) Mechanical Properties

Class Symbol Tension Test Bend Angle Flattening
T.S N/mm Y.P. N/mm Elongation
No.11.12 Test pc. No.5 Test pc. Bend Angle Inside Radius Distance Between Flattened Plates
No.11 A STKM 11A 290min — 35min 30min 180° 4D 1/2D
No.12 A STKM 12A 340min 175min 35min 30min 90° 6D 2/3D
B STKM 12B 390min 275min 25min 20min 90° 6D 2/3D
C STKM 12C 470min 355min 20min 15min – – –
No.13 A STKM 13A 370min 215min 30min 25min 90° 6D 2/3D
B STKM 13B 440min 305min 20min 15min 90° 6D 3/4D
C STKM 13C 510min 380min 15min 10min – – –
No.14 A STKM 14A 410min 245min 25min 20min 90° 6D 3/4D
B STKM 14B 500min 355min 15min 10min 90° 8D 7/8D
C STKM 14C 550min 410min 15min 10min – – –
No.15 A STKM 15A 470min 275min 22min 17min 90° 6D 3/4D
C STKM 15C 580min 430min 22min 7min – – –
No.16 A STKM 16A 510min 325min 20min 15min 90° 8D 7/8D
C STKM 16C 620min 460min 12min 7min – – –
No.17 A STKM 17A 550min 345min 20min 15min 90° 8D 7/8D
C STKM 17C 650min 480min 10min 5min – – –
No.18 A STKM 18A 440min 275min 25min 20min 90° 6D 7/8D
B STKM 18B 490min 315min 23min 18min 90° 8D 7/8D
C STKM 18C 510min 380min 15min 10min – – –
No.19 A STKM 19A 490min 315min 23min 18min 90° 6D 7/8D
C STKM 19C 550min 410min 15min 10min – –
No.20 A STKM 20A 540min 390min 23min 18min 90° 6D 7/8D

Tension Steel supplies STKM tubes with outsider diameter under 168.3 mm Ø，which is used for precise drawing tubes、cylinder tubes for shock absorber of automotive and motorcycle 、cylinder tubes for hydraulic jacks and tube of heat exchanger for air conditioning etc.