Arc Welding of Specific Steels and Cast Irons

Arc Welding of Heat-Resistant Low-Alloy Steel
In addition to the conventional steels discussed above, Enhanced 2.25Cr-1Mo,
2.25Cr-1Mo-0.25V, and 3Cr-1Mo-0.25V-Ti-B steels have been developed. These advanced steels
have higher strength than those of the conventional steels, as shown in Table 1.2. The higher
strength is derived from lower tempering temperatures for Enhanced 2.25Cr-1Mo steel and
small amounts of alloying elements for the other two types. The higher strength facilitates the
use of higher allowable stresses over a range of metal temperatures, as shown in Fig. 1.3, as
compared with conventional 2.25Cr-1Mo steel. These advanced steels, therefore, can be used
in higher temperature services and facilitate the use of decreased thickness of stress
sustaining components. The typical applications are pressure vessels subjected to hydrogen
service at elevated temperatures and high pressures in petroleum refineries and
petrochemical plants.
Table 1.2 — Chemical and mechanical requirements for advanced steels in comparison with
conventional 2.25Cr-1Mo steel
Chemical elements
and mechanical properties
Carbon (%)
Manganese
Phosphorus
Sulfur
Silicon
Chromium
Molybdenum
Copper
Nickel
Vanadium
Titanium
Boron
Columbium
Calcium
Tensile strength (ksi)
0.2% yield strength (ksi)
Elongation (%)
Conventional
2.25Cr-1Mo steel
(A387 Gr.22)
0.15 max
0.30-0.60
0.035 max
0.035 max
0.50 max
2.00-2.50
0.90-1.10
—
—
—
—
—
75-100
45 min
18 min
Enhanced
2.25Cr-1Mo steel
(A542 Type B Cl.4)
0.11-0.15
0.30-0.60
0.015 max
0.015 max
0.50 max
2.00-2.50
0.90-1.10
0.25 max
0.25 max
0.02 max
—
—
85-110
55 min
20 min
2.25Cr-1Mo-
0.25V steel
(A542 Type D Cl.4a)
0.11-0.15
0.30-0.60
0.015 max
0.010 max
0.10 max
2.00-2.50
0.90-1.10
0.20 max
0.25 max
0.25-0.35
0.030 max
0.0020 max
0.07 max
0.015 max
85-110
60 min
18 min
3Cr-1Mo-0.25V-
Ti-B steel
(A542 Type C Cl.4a)
0.10-0.15
0.30-0.60
0.025 max
0.025 max
0.13 max
2.75-3.25
0.90-1.10
0.25 max
0.25 max
0.20-0.30
0.015-0.035
0.001-0.003
—
—
85-110
60 min
18 min
Metal temperature (Deg. F)
700 750 800 850 900
Allowable stress value (kgf/mm 2 )
15
10
2.25Cr-1Mo-0.25V
(for ASME Sec. VIII, Div. 1
per Code Case 2098-2)
Conventional
2.25Cr-1Mo
20
15
Allowable stress value (ksi)
Fig. 1.3 — A comparison between
advanced 2.25Cr-1Mo-V steel and
conventional 2.25Cr-1Mo steel on
maximum allowable stress as a
function of metal temperature
400 450 500
Metal temperature (Deg. C)
2-5