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ASTM A 250-89a / ASME SA 250 

ELECTRIC RESISTANCE WELDED CARBON 

MOLYBDENUM ALLOY STEEL BOILER AND 
SUPERGEATER TUBES

This standard is issued under the fixed designation A 250/A 250M; the number immediately following the designation indicates the year of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A superscript epsilon ( ε) indicates an editorial change since the last revision or reapproval.

1.Scope

1.1 This specification covers several grades, designated T1, T1a, T2, T11, T12, and T2, of minimum-wall-thickness, electric-resistance-welded, carbon-molybdenum and chromium-molybdenum alloy-steel, boiler and superheater.


1.2 The tubing sizes and thicknesses usually furnished to this specification are 1/2 to 5 in. [12.7 to 127 mm] in outside diameter and 0.035 to 0.320 in. [0.9 to 8.1 mm], inclusive, in minimum wall thickness. Tubing having other dimensions may be furnished, provided such tubes comply with al other requirements of this specification.


1.3 Mechanical property requirements do not apply to tubing smalle than 1/8 in. [3.2 mm] in inside diameter or 0.015 in. [0/4 mm] in thickness.


1.4 The values stated in either inch-pound units or SI units are to be regarded separately as the standard. Within the text, the SI units are shown in brackets. The values stated in each system are not exact equivalents; therefore, each system must be used independently of the other. Combining values from the two systems may result in nonconformance with the specification. 

The inch-pound units shall apply unless the "M" designation of this specification is specified in the order.

Chemical composition

Grade Mfg. Process Chemical composition(%)
C Si Mn P S Ni Cr Mo Others
T1 E 0.10~0.20 0.10~0.50 0.30~0.80 0.045Max 0.045Max - - 0.44~0.65 -
T1a E 0.15`0.25 0.10~0.50 0.30~0.80 0.045Max 0.045Max - - 0.44~0.65 -
T1b E 0.14Max 0.10~0.50 0.30~0.80 0.045Max 0.045Max - - 0.44~0.65 -
T2 E 0.10~0.20 0.10~0.50 0.30~0.81 0.030Max 0.020Max - 0.50~0.81 0.44~0.65 -
T11 E 0.05~0.15 0.10~0.50 0.30~0.60 0.030Max 0.020Max - 0.80~1.25 0.44~0.65 -
T12 E 0.05~1.15 0.50Max 0.30~0.61 0.030Max 0.020Max - 0.80~1.25 0.44~0.65 -
T22 E 0.15Max 0.50Max 0.30~0.60 0.030Max 0.020Max - 1.90~2.60 0.87~1.13 -



Mechanical Properties 


Grade Tensile Test MPa or N/mm2 Remaks (Similar to JIS) Possibility Temperature
Min Yield point Tensile Strength
T1 205 380Min (STBA12)
T1a 220 415Min (STBA13)
T1b 195 365Min -
T2 205 415Min -
T11 205 415Min -
T12 205 415Min -
T22 205 415Min -

 

Chemical Composition

The steel shall conform to the requirements as to chemical composition prescribed in Table 


TABLE 1 Chemical Requirements 


Element Composition, %
Grade
T1
Grade
T1a
Grade
T1b
Grade
T2
Grade
T11
Grade
T12
Grade
T22
Carbon 0.10-0.20 0.15-0.25 0.14 0.10-0.20 0.05-0.15 0.05-0.15 0.15
Manganese 0.30-0.80 0.60-0.80 0.30-0.80 0.30-0.61 0.30-0.60 0.30-0.61 0.30-0.60
Phosphorus,max 0.025 0.025 0.025 0.025 0.025 0.030 0.025
Sulfu,max 0.025 0.025 0.025 0.020 0.020 0.020 0.020
Silicon 0.10-0.50 0.10-0.50 0.10-0.50 0.10-0.30 0.50-1.00 0.50 0.50
Molybdenum 0.44-0.65 0.44-0.65 0.44-0.65 0.44-0.65 0.44-0.65 0.44-0.65 0.87-1.13
Chromium       0.50-0.81 1.00-1.50 0.80-1.25 1.90-2.60



TABLE 2 Number of Tubes in a Lot Heat Treated by the Continuous Process


Size of Tube Size of Lot
2 in.[50.8 mm]and over in outside diameter and 0.22 in. [5.1mm]and over in wall thickness not more than 50 tubes
Less than 2 in. [50.8 mm] but over 1 in. [25.4 mm] in outside diameter or over 1 in. [25.4 mm] in outside diameter and under 0.200 in. [5.1 mm]in wall thickness not more than 75 tubes
1 in. [25.4 mm] or less in outside diameter not more than 125 tubes

TABLE 3 Tensile Requirements

Grade T1 T1a T1b T2 T11 T12 T22
Tensile strength, min, ksi[MPa] 55 [380] 60 [415] 53 [365] 60 [415] 30 [415] 60 [415] 60 [415]
Yleld strength, min, ksi [MPa] 30 [205] 32 [220] 28 [195] 30 [205] 32 [220] 32 [220] 30 [205]
Elongation in 2 in. or 50 mm, min, % 30 30 30 30 30 30 30
For longitudinal strip tests a deduction shall be made 
for each 1/32-in. [0.8-mm] decrease in wall thickness 
belw 5/16 in. [8 mm] from the basic minimum elongation 
of the following percentage points
1.50 A 1.50 A 1.50 A 1.50 A 1.50 A 1.50 A 1.50 A



A The following table gives the computed minimum values:Wall Thicknessin.

Wall Thickness Elongation in 2 in. or 50 mm, min, % B
in. mm Grades T1,T1a, T2, T11, T12, and T22
5/16 8 30
9/32 7.2 29
1/4 6.4 27
7/32 5.6 26
3/16 4.8 24
5/32 4 22
1/8 3.2 21
3/32 2.4 20
1/16 1.6 18



NOTE-The above table gives the computed minimum elongation values for each 1/32-in. [0.8 mm] 
decrease n wall thickness. Wall thickness. Where the wall thicness lies between two values shown
above, the minimum elongation value shall be determined by the following equation:

E= 48t + 15.00 [E=1.87t + 15.00] 


where: E =elongation in 2 in. or 50 mm in %, and 
t = actual thickness of specimen, in. [mm].
B Calculated elongation requirements shall be rounded to the nearest whole number.


TABLE 4 Hardness Requirements

Grade Brinell hardness Number
(Tubes 0.200 in. [5.08 mm]
and over in wall thickness
Rockwell Hardness 
Number (Tubes less than 0.200 in. [5.08 mm] in wall thickness
T1 146 B80
T1a 153 B81
T1b 137 B77
T2 163 B85
T11 163 B85
T12 163 B85
T22 163 B85

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