Wholly Sintered, Silver Brazed and Laser Welded Diamond Saw Blades
Perhaps the most commonly sighted diamond circular saw blades are the sintered metal-bonded ones, on which diamonds are mixed and sintered with metal bond materials to form the blades’ cutting edge — diamond segment. Normally, these blades are made via 3 methods: wholly sintering, silver brazing and laser welding. The diamond blades made via these 3 methods are different and have their respective features and applications.
1. Wholly Sintered Diamond Saw Blades
Wholly sintered diamond blades are made by putting the steel cores along with diamonds and metal bond materials into molds, and then sintering them in sintering machines. Blades of this type are often referred to just as sintered diamond blades. Normally, their diameter is no bigger than 400 mm. One of the reasons maybe is for the limitation of the size of the sintering machines.
Generally, the main steps in making sintered diamond blades are: First, put the steel cores, diamonds and metal bond materials into high-strength steel molds. Second, put the molds into a press machine to press them to form the blanks without heating. Third, take out the blanks from the steel molds and examine the blanks. Fourth, put the blanks into graphite or stainless-steel molds. Fifth, put the molds into a sintering machine and sinter them to produce the diamond blades.
In the above fifth step, there are many types of sintering machines which can be chosen. Some sintering machines can exert pressure on the blanks during the sintering process. This can make the diamond segments of the blade be well alloyed, and the segments’ density is high. The produced blades are normally called hot-pressed diamond blades. These blades have a longer service life. However, some sintering machines cannot exert pressure on the blanks when sintering. The produced blades are normally called cold-pressed diamond blades. These blades’ diamond segments’ density is low and porosity is high. This can improve the cooling condition when the blades are being used, but will also lead to a shorter service life.
Sintered diamond blades can be used to cut granite, marble, concrete, asphalt, ceramics and many other building materials. Some of them can only be used in wet cutting (e.g. continuous rim diamond blades), while some of them can be used in both wet and dry cutting (e.g. segmented diamond blades, turbo diamond blades and turbo wave diamond blades).
In making sintered diamond blades, the steel cores are also put into molds and sintered. So the diamond blades can be produced in bulk, and the production output is high. But also for this reason, the steel cores cannot be quenched, so their hardness and toughness are not high, and so the steel cores may deform in high-load and high-intensity cutting processes. Therefore, in some cases sinter diamond blades’ cutting efficiency cannot be very high.
2. Silver Brazed and Laser Welded Diamond Saw Blades
When silver brazed or laser welded diamond blades are made, the diamond segments on the blades need to be firstly produced. Normally, the method for making these diamond segments is hot pressing, and is similar to the method used to make the sintered diamond blades, while there is no the steel core’s participating. When the diamond segments are available, they are silver brazed or laser welded onto the steel cores to form silver brazed diamond blades or laser welded diamond blades.
Silver brazed diamond blades’ diamond segments do not necessarily need a transition layer. They are brazed to the steel cores via silver-based brazing films which normally contain 40% – 50% silver. The connection between the diamond segment and the steel core depends on the melted and penetrated silver solder, so the connection strength is not very high (normally, its bending strength is 350 – 600 MPa). Silver brazed diamond blades can only be used in wet cutting, because if they are used in dry cutting, the high temperature generated in the dry cutting can cause the silver solder to be melted, and the diamond segments may fall off the blade and fly out and may hurt the operator.
Laser welded diamond blades, however, have many advantages. Laser welding is a kind of fusion welding. It causes the junction of the diamond segment and the steel core to be melted and then form a metallurgical connection. The depth-width ratio of the weld is high, which can reach 5:1 or even 10:1. So the connection strength is high and the bending strength can reach 1800 MPa. Therefore laser welded diamond blades can be used to cut some relatively softer materials (e.g., many kinds of stone) without the water cooling (dry cutting). But please note, when cutting very hard or abrasive materials, for example, concrete containing reinforcing rebar, the laser welded diamond blade should still be used with adequate water. Otherwise, the diamond segment itself may break or the steel core below the segment may wear off and break, and then cause serious security issues. Laser welded diamond concrete saw blades are usually made for wet cutting applications.
The diamond segments used on laser welded diamond blades have a transition layer. This layer has no diamonds and is normally 1.5 – 2 mm thick. Its function is to connect the working layer (containing diamonds) of the segment to the steel core.
Like sintered diamond blades, silver brazed and laser welded diamond blades can also be used to cut many building materials, such as granite, marble, concrete, asphalt and ceramics. Because these blades’ diamond segments are welded onto the steel cores, these blades have to be produced piece by piece, so their production output is lower than sintered diamond blades’. However, because the steel cores do not participate in the sintering, the steel cores can be quenched and processed with other heat treatments, so their hardness and toughness can be high, therefore the diamond blades can be used in high-load and high-intensity cutting processes without deformation and high cutting efficiency can be gained.
Also because silver brazed and laser welded diamond blades’ steel cores can be treated separately, the blades’ diameter can be large, which can reach several meters. Also, the steel cores can have many designs to meet various requirements. For example, the steel core can be designed as a sandwich type which has two layers of steel cores outside and one layer of damping material in the middle. This design can reduce the noise generated in the cutting significantly, and this blade is a kind of silent diamond blade.
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