Fig. 1 - Some types of LPG storage tanks use ASTM A537 Cl-2 steel having a minimum tensile strength of 550N/mm2, and LB-62L is one of the most suitable covered electrodes for this steel.

Steady Notch Toughness and Tensile Strength Are Dependable Characteristics of LB-62L

Notch toughness is one of the most important qualities of materials used in low-temperature equipment because it offers resistance against brittle fractures under severe service conditions. Weld notch toughness, however, is commonly affected by variables encountered in welding: heat input, plate thickness, cooling speed, welding position and postweld heat treatment.

LB-62L ensures sufficient notch toughness at low temperatures down to minus 60°C over a wide range of such variables. Figure 2 shows Charpy impact absorbed energies of the weld metal as a function of heat input. The test results show a slight decrease with an increase of heat input. However, the weld metal maintains an adequate level of absorbed energy over the range of heat input.

Figure 3 shows how the strength of the weld metal depends on the cooling speed in welding. Both the tensile strength and 0.2% proof strength are prone to decrease little by little as the cooling speed decreases.

Fig. 2 - Impact absorbed energies of LB-62L weld metal as a function of heat input in welding double-V groove joints in flat, horizontal and vertical-up positions. (As-weld; Power source: AC)

Fig. 3 - Strength of LB-62L weld metal vs. cooling speed (As-weld; Power source: AC)