# An Investigation on Base Metal Block Shear Strength of Ferritic Stainless Steel Welded Connection
## 2 Overview of Previous Experimental Studies  
A total of seven specimens of ferritic stainless steel (STS430) welded connections with base metal fracture were tested by [PERSON] [21] and this chapter summarizes the test results. Table 1 includes the names of the specimens and the test results according to the combination of the weld length (\(L\)) in the loading direction and the weld length (\(T\)) perpendicular to the loading direction. The test specimens were composed of three parts (test part, coupling part, and clamping part). Test and clamping parts were chosen with 3.0 mm thick plane plates and coupling part was machined with 6.0 mm thick plane plate. Two plates of test part and clamping part were joined to Arc weld with 3.0 mm weld size (\(S_{u}\)) on both sides of coupling part (refer to the Figure 4a of the reference [21]). In order to evaluate the difference of structural behaviors according to the weld length and welding direction of the STS 430 welded connection, the specimens were produced by combining the weld lengths in the loading direction and perpendicular to the applied load as the main variables. Post weld heat treatment (PWHT) for Arc welded specimens after arc welding was not performed additionally and they were air cooled. Electrode for Arc welding of ferritic stainless steel (STS430) plates was chosen as E430-16 (minimum specified strength of \(Fxx\) = 480 MPa) with the diameter of 3.2 mm specified in KS D 7014 (corresponds to E430-16 in AWS A5.4). Three tensile coupons were tested to determine material properties of nominal 3.0 mm thick ferritic stainless steel (STS430) plate in accordance with KS B 0802 (Method of tensile test for metallic materials, corresponds to ISO 6892). The average plate thickness (\(te\)) is 2.93 mm, elastic modulus (\(E\)) was 179.50 GPa, the yield stress (\(\sigma_{y}\)) was 259.93 MPa, the tensile strength (\(\sigma_{u}\)) was 412.87 MPa, the yield ratio (\(\sigma_{y}/\sigma_{u}\)) was 62.93%, the ultimate strain at tensile stress was 0.36 mm/mm, and the elongation (\(EL\)) at failure was 42.28% [21]. Material test for the heat affected zone (HAZ) of welded connection with 3.0 mm thick ferritic stainless steel plate was not conducted in the previous study. Based on the previous test results, the fracture modes and the load-displacement curves of the representative specimens at the end of the experiment are shown in Figures 1 and 2, respectively. As shown in Figure 1, the block shear fracture, which is a combination of a tensile fracture in the perpendicular direction to the load and a shear fracture in the loading direction, occurred in the base metal near the toe of the weld metal, rather than in the weld metal. As shown in the load-displacement curves of Figure 2, it was found that stress was concentrated on the welding end point of shear plane and shear yielding or shear crack started at the point. As a result, temporary strength drop on the curves of the specimens were observed due to the shear yielding or shear fracture of both ends (welding end point) in the loading direction. However, the shear yielding or shear fracture did not contribute to the determination of ultimate strength. Finally, tensile fractures in the direction perpendicular to the load occurred as the enforced displacement increased, and determined the ultimate strength. In the existing experimental study of ferritic stainless steel (STS430), welded connections with base metal block shear fracture [21] and block shear strengths were investigated according to weld lengths and welding methods and were compared with those calculated by current design equations.