The best quality of high carbon steel is T10, the carbon content was 1.03%, and the element contains a small amount of chromium, molybdenum, vanadium, after heat treatment can reach HRc 58-60 hardness. Toughness is very good, but it is not resistant to rust. It is applied to traditional european-style hunting knife, large cutting knife and military dao.
Differential Hardening
A differential hardened blade will usually be coated with an insulating layer. The insulation layer is quite often a mixture of clay, ashes, polishing stone powder, and salts, which protects the back of the blade from cooling very quickly when quenched. The clay is often applied by painting it on, coating the blade very thickly around the center and spine, but leaving the edge exposed. This allows the edge to cool very quickly, turning it into a very hard microstructure called martensite, but causes the rest of the blade to cool slowly, turning it into a soft microstructure called pearlite. This produces an edge that is exceptionally hard and brittle, but is backed-up by softer, tougher metal. The edge, however, will usually be too hard, so after quenching the entire blade is usually tempered to around 400 °F (204 °C) for a short time, to bring the hardness of the edge down to around HRc60 on the Rockwell hardness scale. The exact composition of the clay mixture, the thickness of the coating, and even the temperature of the water were often closely guarded secrets of the various bladesmithing schools. With the clay mixture, the main goal was to find a mixture that would withstand high temperatures and adhere to the blade without shrinking, cracking, or peeling as it dried. Sometimes the back of the blade was coated with clay, leaving the edge exposed. Other times the entire blade was coated and then the clay was cut away from the edge. Another method was to apply the clay thickly at the back but thinly at the edge, providing a lesser amount of insulation. By controlling the thickness of the edge-coating along with the temperature of the water, the cooling rate of each part of the blade can be controlled to produce the proper hardness upon quenching without the need for further tempering.Quench
After the blade has been shaped, the sword would be quenched.Today we quench our swords in either water or oil.Quenching a sword in water is more difficult to control, but yields better results. The defect rate is about five times higher than oil quenching, which is much more stable and easier to control.Blades quenched in oil are still considerably hardened and do have superior flexibility compared to a water quenched blade. The more rapidly a blade cools down, the harder it becomes. Thus, when a hot blade enters the water, the water also gains heat and the blade will cool more gradually. Therefore, the first part of the blade that enters the water will be the hardest.
Therefore, the technique of quenching was also very important.Katana swords would simply enter the water edge and tip first, leaving the spine or back and lower section of the blade softer. This was also done for practical reasons, as the ‘softer’ sections were better for absorbing shock and impact and employed for defensive measures.
HOW TO APPRECIATE BLADE QUALITYPaymentDelivery detailsContact usAttentionHOW TO APPRECIATE BLADE QUALITY Generally, we appreciate blades with the three elements. At first shape, then steel, and then hamon. 1) Shape You must take an over-all look at the blade first. Seeing the shape completely is very important to appreciate blades. It should be well-ordered from the bottom of tang to the top of kissaki. All the elements of the blade are condensed to its shape. So understanding the distinction between good shape and poor shape is necessary to know its quality. For the good shape, every line must be smooth and sharp, every surface even, and full meat is kept on the cutting surface. And the harmony of the whole shape is most important. A good shape will come from good steel and good tempering. It illustrates a sense of the smith. But it is difficult to explain the "shape" by words or images. "Good shape" doesn't mean some design of blade. It is general word used for every kind of style of blades. 2) Steel Steel is a base of blade quality. A good steel is necessary for good shape and for good tempering effect. It is not a meaning of layer pattern. 3) Hamon Various types of Hamon patterns are attractive for beginners eye, but to see the quality of hamon is far more important. Utsuri (shadow of hamon) also can be seen by this way. Real colours come up. Hamon pattern is not a matter for blade quality. Difference of hamon pattern means just a difference of pattern, never mean difference of quality. Hamon is the most visible appearance of the sword. Looking at it is very interesting. Hamon is a big factor of the character of a blade. Its pattern is very attractive for beginners eye. But, the pattern does not mean the quality. An aesthetic hamon pattern doesn't mean a good hamon. It is just a matter of liking. The brightness and the fineness of the hamon, not only the hamon line but also the hamon area, is a bigger criterion of the quality. HOW TO TREAT THE BLADE? Japanese blade is made from the pure steel, and is completely polished. So, suitable treatment is necessary. Because the surface is delicate and the cutting edge is very sharp. The blade should be always coated with good oil. And we never touch the blade with naked finger. Please do not put the blade on a carpet. Please put it on a clean table cloth and use some soft cloth or paper as a pillow for the blade. Careless treatment makes scratches onto the blade surface. Payment All payments are expected within 7 days after the last winning auction is closed. All items from unpaid auctions will be forfeited and an Unpaid Item claim will be filed against your account on eBay. Delivery details We only ship to the confirmed address provided by Ebay. Before you pay, please make sure your address in Ebay matches the address you would like us to ship to. Buyers' Information: We strive our best to provide you the most reliable, affordable way of shipping service. However, sometimes international delivery is highly depended on the courier company and local customs/duties. If you do not receive your item on time, please contact us immediately for further assistance. Please note that we do not ship on weekends, or national holidays. If you make a payment by eCheck, it may take longer since it has to clear your bank first before the order is processed. We recommend our buyer to combine shipping. Contact us If there is any problem, just contact us. Please contact with us before you leave feedback. We will try our best to solve the problem for you, thank you. Customer satisfaction is always the most important for us.Sometimes,you may not get our reply immediately due to the time difference among each country. However, please be assured that we’ll strive to reply you as soon as possible once we got your messages. Wish you have a very pleasant buying experience with us. Attention International Buyers – Please Note: a) Import duties, taxes and charges are not included in the item price or shipping charges. These charges are the buyer’s responsibility. b) Please check with your country’s customs office to determine what these additional costs will be prior to bidding/buying.