Effect of Fold-Forging Techniques for Sword Making Process on Mechanical Properties of Medium Carbon Steel
The most important procedure for making a traditional Samurai sword consists of metal forming at high temperature and subsequent quenching. Hereby, two specific techniques are additionally included, namely, fold-forging and mixing of different steel grades. In this work, both particular processes were applied to the steel grade AISI 1055, a conventional low carbon steel and the Nam-Phee steel, which has been commonly used to produce the well-known Nam-Phee sword for a long time in Thailand. Afterwards, mechanical properties of produced samples were investigated and compared. Four combinations between the examined steels and both techniques were taken into account. It was found that Nam-Phee steel samples subjected to the fold-forging obviously showed more homogenous and finer microstructure. Their resulting tensile strength, flexural strength and impact energy were significantly increased. The improved mechanical properties of the Nam-Phee specimens were close to those of the Tamahagane steel used for making Samurai sword. Moreover, AISI 1055 steel specimens mixed with the low carbon ductile steel as core exhibited much higher flexural strength and impact energy.