cemented carbide solder
According to melting point and brazing temperature, the filler metals of cemented carbide and steel can be divided into three categories: high-temperature filler metals, normal-temperature filler metals and low-temperature filler metals.
Brazing temperature higher than 1000 ° C is called high temperature solder, such as copper and 106 solder;
Medium temperature solder brazing temperature between 850-1000 ℃, such as the H62 and H68 brass filler metal;
Low temperature solder metal refers to the brazing temperature between 650 and 850 ℃, for example - Ag - 1 B and L - Ag - 49 silver filler metal.
The brazing temperature of copper filler metal is high and the weld strength is low, so it is mainly used for vacuum brazing. The pure copper solder is of single-phase structure. Easy to control brazing temperature. It has good wettability, good plasticity and the cheapest price to all kinds of hard alloy.
Copper shear stress of the welded joint is about 150 MPa, can be used under 400 ° C.
The brazing temperature of H68 brass is much lower than that of copper, but it is seldom used because of the low strength of the weld.
H62 brass is a common cemented carbide filler metal because of its low melting point and brazing temperature and its room temperature strength.
Usually used for brazing cemented carbide tools under small or medium load conditions. 105 filler metal shall be used for small welds or welded surfaces requiring high temperature strength. L - Ag - 49 silver due to its low melting point of solder at low temperature (690-710 ℃), good wettability of carbide brazing and low stress and is widely used in foreign countries. When necessary, the copper plate can also be used as a compensation gasket, which can almost completely eliminate the brazing stress and avoid the brazing crack.
It can be used for brazing some crackable cemented carbide or some large brazing surface cemented carbide tools. As the use of the rise of temperature, weld strength drops rapidly, with L - Ag - 49 silver brazing filler metal artifacts of working temperature should be limited to 200 ° C below. Fluorides and chlorides in the flux used with the l-ag-49 silver filler metal are high and require higher cleaning after welding, otherwise the workpiece surface will corrode due to uncleanliness.
B-Ag-1 solder is an ultra - low temperature silver solder. Its melting point is about 600-610 ℃, can further reduce the residual stress of hard alloy joint. It can also be used as a compensation gasket to braze some fragile workpieces.
B-ag-1 solder is also suitable for brazing diamond tools such as diamond saw blades because of its ultra-low melting point and good wettability to tungsten carbide.
However, B - Ag - 1 silver solder is expensive, high temperature strength is low, only apply to the temperature below 150 ° C environment. The content of cadmium in the filler metal is 24%. When the brazing temperature is high, it is easy to evaporate, which is harmful to human health. In addition to controlling brazing temperature, exhaust devices should be installed during brazing operations.
After brazing, cleaning parts should be cleaned to avoid corrosion.