The diamond segment is a kind of artificial diamond tool commonly used in stone cutting. It has a hard texture and strong grinding performance. These segments are sintered from very fine metal powder and diamond powder. So what is sintering? How to sinter? This article will explain in detail for you.
The diamond segment turns the powder into the diamond block shape that we finally see through two processing processes of cold pressing and hot pressing(sintering). The powder is initially pressed and formed by cold pressing, the sintering process is to finally sinter the cold-pressed sheet-like structure into a more tightly bonded diamond segment.
In the sintering process, the main sintering methods are solid-phase sintering and liquid-phase sintering. Solid-phase sintering is the main combination method. Through high temperature and high pressure, the atoms between metals interact with each other, making the structure more compact. In a high-pressure environment, an alloy-shaped metal block is formed, so the formation of the diamond segment is not a process of melting all the original materials of the segment, and then cooling and combining it together, but using a solid-phase sintering method. Metal powder and diamond better form a bond with firm structure, high strength, suitable rigidity and hardness. Since the bond mainly plays the role of fixing the diamond and protects the diamond like the metal bond, the sintering process is also called the matrix bond.
However, it has been found that there will inevitably be some voids in pure solid-phase sintering, which will lead to an increase in the porosity of the segment, and the structure of such a segment will be unstable. Some metals with lower melting points, such as Zn, Sn, and even P, during the sintering process, these elements begin to melt and fill the voids of solid-phase sintering, and this method of sintering through metal liquefaction is also called liquid phase sintering. It is worth noting that if there are too many liquefied elements in liquid phase sintering, there will be overflow in the high temperature and high pressure environment, which is often referred to as "flowing material". In order to avoid this situation, the sintering formula, The proportion of these low melting point metals should not be higher than 5% of the total formula metal species.
After knowing the principle of segment sintering, there is a question that how is the diamond segment sintered through graphite? It is divided into several steps:
1. Customized graphite mold: The customization of the mold is the first thing to do. According to the size of the segment, typesetting is performed on the graphite mold of the specified size. Generally speaking, if the size of the segment is relatively large (about 24mm in length), the layout when fabricating use the upper, middle and lower rows for arrangement. If the segment of small and medium size (about 40mm in length) is arranged, the upper and lower layers are arranged in the way of arrangement, and other sizes will be arranged according to the actual size.
2. Molding: diamond segment are put into the graphite mold, which are the working layer (edge material), groove, working layer (middle material).... groove, working layer (edge material). After placing them in the diamond segment mold, the bolts can be tightened. Then they start to be sintered.
3. Sintering: The graphite mold is quickly energized. Due to the strong resistance of graphite, the graphite heats up rapidly under the working state of high current. When the temperature rises to a certain level, the increase of the current is controlled to maintain a constant temperature. Usually the process is called the heating and holding stage of the sintering of the segment, and this stage lasts for about 8 minutes.
4.After eight minutes:take the graphite mold out of the sintering machine and cool it at room temperature. This process is called the cooling stage. Due to the good heat preservation effect of graphite, the segment can continue to shrink during the cooling process. The segment and the mold can be peeled off better.
Graphite is mainly used for mold sintering segments, which mainly play several roles, such as shaping, preventing material flow, rapid heating, and constant heat preservation. Therefore, at present, diamond segments are sintered with graphite molds.
