J. Wadsworth, D.R. Lesuer /Materials Characterization 45(2000) 289-313 Kanehira and the dojigiri by Yasutsuna made over 900 years ago. Photographs of the o-kanehira are shown in Fig.6. 2.7. Medieval damascened knive Piaskowski [24 has reviewed in detail pat sugita komidare welded damascened knives found in Poland dating from the Sth to 12th century. Their real origin is not clear. but Piaskowski believes that some of the knives may be examples of the work of early medieval Polish smiths. The knives all consisted of three regions: a steel cutting edge, adjacent to a complex, central, patterned layered region of carbur ized iron and iron, and a backing layer of iron or itatstrra steel. This is in contrast to other related techniques in which a steel central layer is sandwiched between pattemed layers of iron and steel. Evidence for heat Fig. 5. Types of Hamon(after Sato [23]). treatment to produce martensitic structures, and tempered structures, is described. Techniques invol ving from 3 to 17 initial layers are presented. In all inserted, by one of several methods, inside the high- cases, hammer welding and plastic deformation took carbon jacket steel. In the fourth step, the composite place during manufacture. The carbon contents of the was drawn out to the approximate length of the blade, composition, 0.5%C, is given for one steel in one of layers are poorly evaluated, however, and only one and the fifth step shaped the final blade. The end product is a kawagane steel with the knives excellent mechanical properties because the carbon content is both relatively low(about 0.6-1.0% C) and the carbides are distributed uniformly fine-grained matrix. As discussed later, no visible pattern-welded structure is obtained from this scale of folding, not only because the individual, 0.2-m layers are unresolvable to the naked eye, but also because the carbon content of each layer is iden- cal(carbon atoms diffuse a distance of 1. 4 um in 30 s at 1000C). An observable pattern-welded tructure. however often emerges from the final several folds Thus the method of manufacture and the of the surface patterns on the Japanese sword are quite different from those of Damascus swords Specifically, the principal surface pattem on a Japa nese sword is created as a result of the variou transformation products following heat treatment the blade. There are also surface pattems that consist of a gross texture from the final stages of piling folding, and forging. The earliest reference to sur- face patterns on a Japanese sword, referenced by Smith [161, is to 1065 AD. There are subtleties to these patterns that illustrate several intriguing me- There are an estimated 1 million swords now own to exist; 117 have been designated as Japa- 6.“O- Kanehira” achi by Ka nese national treasures. The most famous and rev- 9.2 cm. Mid-Heian period, approximately 1000 AD ered of the swords are identified with a name o National Museum. Signed Bizen no kuni Kanehira . Tokyo hira of Bizen providence").(After Sato [23]).inserted, by one of several methods, inside the high￾carbon jacket steel. In the fourth step, the composite was drawn out to the approximate length of the blade; and the fifth step shaped the final blade. The end product is a kawagane steel with excellent mechanical properties because the carbon content is both relatively low (about 0.6 ± 1.0% C), and the carbides are distributed uniformly in a fine-grained matrix. As discussed later, no visible pattern-welded structure is obtained from this scale of folding, not only because the individual, 0.2-mm layers are unresolvable to the naked eye, but also because the carbon content of each layer is iden￾tical (carbon atoms diffuse a distance of 1.4 mm in 30 s at 1000°C). An observable pattern-welded structure, however, often emerges from the final several folds. Thus, the method of manufacture and the origins of the surface patterns on the Japanese sword are quite different from those of Damascus swords. Specifically, the principal surface pattern on a Japa￾nese sword is created as a result of the various transformation products following heat treatment of the blade. There are also surface patterns that consist of a gross texture from the final stages of piling, folding, and forging. The earliest reference to sur￾face patterns on a Japanese sword, referenced by Smith [16], is to 1065 AD. There are subtleties to these patterns that illustrate several intriguing me￾tallurgical issues. There are an estimated 1 million swords now known to exist; 117 have been designated as Japa￾nese national treasures. The most famous and rev￾ered of the swords are identified with a name or meito. Two such examples are the o-kanehira by Kanehira and the dojigiri by Yasutsuna made over 900 years ago. Photographs of the o-kanehira are shown in Fig. 6. 2.7. Medieval damascened knives Piaskowski [24] has reviewed in detail pattern￾welded damascened knives found in Poland dating from the 8th to 12th century. Their real origin is not clear, but Piaskowski believes that some of the knives may be examples of the work of early medieval Polish smiths. The knives all consisted of three regions: a steel cutting edge, adjacent to a complex, central, patterned layered region of carbur￾ized iron and iron, and a backing layer of iron or steel. This is in contrast to other related techniques in which a steel central layer is sandwiched between patterned layers of iron and steel. Evidence for heat treatment to produce martensitic structures, and even tempered structures, is described. Techniques invol￾ving from 3 to 17 initial layers are presented. In all cases, hammer welding and plastic deformation took place during manufacture. The carbon contents of the layers are poorly evaluated, however, and only one composition, 0.5% C, is given for one steel in one of the knives. Fig. 5. Types of Hamon (after Sato [23]). Fig. 6. ``O-Kanehira.'' Tachi by Kanehira. Steel. Nagasa 89.2 cm. Mid-Heian period, approximately 1000 AD. Tokyo National Museum. Signed Bizen no kuni Kanehira (``Kane￾hira of Bizen providence''). (After Sato [23]). 296 J. Wadsworth, D.R. Lesuer / Materials Characterization 45 (2000) 289±313