Arc Welding of Specific Steels and Cast Irons

Arc Welding of High-Strength Steel
3. Welding processes and procedures
In order to get a satisfactory result in welding high-strength steels, suitable welding
consumables should be selected and appropriate welding processes and procedures should be
used. As shown in Table 3.1, applicable welding processes for 50 to 80 kgf/mm 2 -class
high-strength steels are shielded metal arc welding, submerged arc welding, gas metal arc
welding, and gas tungsten arc welding.
Table 3.1 — Welding processes for high-strength steels
Welding process
Type of high-strength steel
HT50 HT60 HT70 HT80 HT100
Shielded metal arc welding ◎ ◎ ◎ ◎ ○
Submerged arc welding ◎ ◎ ◎ ◎ ○
Gas metal arc welding ◎ ◎ ◎ ◎ ◎
Gas tungsten arc welding ○ ○ ○ ○ ◎
Electroslag welding ○ △ — — —
Electrogas welding ○ △ — — —
Note: ◎: Widely used; ○: Used; △: Occasionally used; —: Not used.
3.1 Shielded metal arc welding
3.1.1 Types and features of covered electrodes
Covered electrodes for welding high-strength steels should satisfy the following general
requirements:
a) The weld metal satisfies the mechanical properties (tensile strength,
ductility, notch toughness) required by the relevant standards and specifications.
b) Crack resistance of the weld metal is sufficient.
c) Usability is good enough to make sound welds
d) Welding efficiency is sufficiently high.
Various types of covered electrodes are available for welding high-strength steels, as shown
in Tables 3.2 and 3.3 referring to the Japanese Industrial Standard (JIS) and the American
Welding Society (AWS) Standard, respectively.
Among low-hydrogen type covered electrodes, advanced electrodes offer specific
characteristics of moisture-resistance, extra-low hydrogen, ultra-low hydrogen, and less-fume.
The moisture-resistant electrodes offer better resistance to moisture absorption as discussed
above referring to Figs. 2.7 and 2.8. This type of electrode allows a longer hour use without
redrying because of slower moisture pickup in the atmosphere. The amount of diffusible
hydrogen (by glycerol method) with usual low-hydrogen electrodes is about 3-5 ml per 100g of
weld metal. Extra-low-hydrogen electrodes offer lower diffusible hydrogen of approximately
1.5-3 ml/100g. Ultra-low-hydrogen electrodes are characterized by far lower diffusible
hydrogen of about 0.5-1.5 ml/100g. The lower the diffusible hydrogen, the lower the crack
susceptibility. The cold cracking test results, as shown in Table 3.4, reveal that with ultra-low
hydrogen electrodes the preheating temperature can be lower than with extra-low hydrogen
electrodes. Less-fume electrodes emit lower amounts of fumes during welding by 25-40%
compared with conventional electrodes. This is less hazardous to the welding workers.
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