Reference Meterial
    JIS G3445
    JIS G3472
  Range of Products
 
 
 
Reference Meterial
JIS G3445 Carbon Steel Tubes for Machine Structural Purposes

 
Table 1 Chemical Composition
Grade
Designation
Chemical composition %
C
Si
Mn
P
S
Nb or V
Grade 11
A
STKM 11A
0.12
0.35
0.60
0.040
0.040
-
Grade 12
A
STKM 12A
0.20
0.35
0.60
0.040
0.040
-
B
STKM 12B
C
STKM 12C
Grade 13
A
STKM 13A
0.25
0.35
0.30
~ 0.90
0.040
0.040
-
B
STKM 13B
C
STKM 13C
Grade 14
A
STKM 14A
0.30
0.35
0.30
~ 1.00
0.040
0.040
-
B
STKM 14B
C
STKM 14C
Grade 15
A
STKM 15A
0.25
~ 0.35
0.35
0.30
~ 1.00
0.040
0.040
-
C
STKM 15B
Grade 18
A
STKM 18A
0.18
0.55
1.50
0.040
0.040
-
B
STKM 18B
C
STKM 18C
Grade 19
A
STKM 19A
0.25
0.55
1.50
0.040
0.040
-
C
STKM 19C
Grade 20
A
STKM 20A
0.25
0.55
1.60
0.040
0.040
1.50
 
 
Table 2 Mechanical Property
Grade
Designation
Chemical composition %
Flattening test
Bending test
Tensile Strength kgf/mm2 (N/mm2)
Yield point or proof stress kgf/mm2 (N/mm2)
Elongation (%)
Distance between flat parts (D:Outside diameter)
Bend angle
Inside radius (D:Outside diameter)
No.11 specimen
Grade 11
A
STKM 11A
30
   (294)
—
35
1/2 D
180°
4 D
Grade 12
A
STKM 12A
35
   (343)
18
   (177)
35
2/3 D
90°
6 D
B
STKM 12B
40
   (392)
28
   (275)
25
2/3 D
90°
6 D
C
STKM 12C
48
   (471)
36
   (353)
20
—
—
—
Grade 13
A
STKM 13A
38
   (373)
22
   (216)
30
2/3 D
90°
6 D
B
STKM 13B
45
   (441)
31
   (304)
20
3/4 D
90°
6 D
C
STKM 13C
52
   (510)
39
   (382)
15
—
—
—
Grade 14
A
STKM 14A
42
   (412)
25
   (245)
25
3/4 D
90°
6 D
B
STKM 14B
51
   (500)
36
   (353)
15
7/8 D
90°
8 D
C
STKM 14C
56
   (549)
42
   (412)
15
—
—
—
Grade 15
A
STKM 15A
48
   (471)
28
   (275)
22
3/4 D
90°
6 D
C
STKM 15B
59
   (579)
44
   (431)
12
—
—
—
Grade 18
A
STKM 18A
45
   (441)
28
   (275)
25
7/8 D
90°
6 D
B
STKM 18B
50
   (490)
32
   (314)
23
7/8 D
90?
8 D
C
STKM 18C
52
   (510)
39
   (382)
15
—
—
—
Grade 19
A
STKM 19A
50
   (490)
32
   (314)
23
7/8 D
90°
6 D
C
STKM 19C
56
   (549)
42
   (412)
15
—
—
—
Grade 20
A
STKM 20A
55
   (539)
40
   (392)
23
7/8 D
90°
6 D
 
 
Table 3 Tolerances on outside diameter   Table 4 Tolerances on Wall Thickness
 
Division
Tolerances on outside diameter
No. 1
Under 50 mm
 ?0.5 mm
50 mm
 ±1%
No. 2
Under 50 mm
 ±0.25 mm
50 mm
 ±0.5%
No. 3
Under 25 mm
 ±0.12 mm
25 mmD<40 mm
 ±0.15%
40 mmD<50 mm
 ±0.18%
 
Division
Tolerances on outside diameter
No. 1
Under 4 mm
 +0.6 mm
-0.5 mm
4 mm
 +15%
-12.5%
No. 2
Under 3 mm
 ±0.3 mm
3 mm
 ±10%
No. 3
Under 2 mm
 ±0.15 mm
2 mm
 ±8%
 
 
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