Some welding methods of thermocouple and thermal resistance

1. Arc welding Arc welding can be divided into branch welding and AC welding. During DC welding, connect the thermocouple to the positive pole of the power supply, and connect the carbon rod (spectral) to the negative pole of the power supply. Use the carbon rod to instantly contact the top of the hot electrode to start the arc, and leave the carbon rod quickly after the measuring end is melted into a spherical shape. This welding method is simple, easy to operate, and the measuring end is not easy to be stained. It is used for the welding of precious metal thermocouples. 1. Arc welding 　　 　　 arc welding can be divided into two types: branch welding and AC welding. When 　　 　　 DC welding, the thermocouple is connected to the positive pole of the power supply, and the carbon rod (spectral) is connected to the negative pole of the power supply. The carbon rod is instantaneously contacted with the top of the thermoelectrode to start an arc. After the measuring end is melted into a spherical shape, quickly leave the carbon rod. This welding method is simple, easy to operate, and the measuring end is not easy to be stained. It is used for the welding of precious metal thermocouples.　　 　　 AC welding is suitable for welding low-cost metal thermocouples. Before welding, carefully remove the oxides in the 25-30mm section of the measuring end, and then tie the tops of the two electrodes together and twist them into a twist. When welding, dip the flux on the top of the hot electrode, melt it in an arc flame for 3-5S, and quickly take it out after it becomes a ball, so that the residue on the solder joint can be cleared. This method is simple in equipment and easy to operate, but the thermocouple welding point and nearby electrodes are carburized and contaminated.　　 　　2, argon arc welding 　　 　　 argon arc welding device consists of 5 parts: DC welding power supply, high frequency oscillator, welding torch, butt welding power supply, tooling and fixture. During welding, the cerium-tungsten wire extending from the nozzle of the welding gun is used as the negative electrode, and the welded thermocouple is fixed on the fixture as the positive electrode. When the two poles pass through the high frequency and high pressure, the arc will be ignited. SCR is used to adjust the voltage to control the arc intensity. Under the protection of argon gas, the arc discharge is generated between the cerium-tungsten and the welded thermocouple, which is generated by the arc. The high temperature melts the end surface of the thermocouple wire into a ball. In order to facilitate the alignment of the thermocouple and the electrode, the working fixture and the welding torch can be moved horizontally and vertically in space. The welding gun is equipped with 1mm and 1.5mm diameter cerium-tungsten electrodes for welding thermocouples of different diameters. 3. When gas welding is used for gas welding, the top of the hot electrode should be heated and dipped in flux (for example, the flux of nickel-chromium-nickel silicon couple is a mixture of sodium tetraborate and quartz sand), and then the hot electrode should be placed in acetylene or In the hydrogen-oxygen flame, quickly take it out after melting into a spherical shape, and immediately put it in hot water to wash away the residue on the soldering point. This method is simple to operate and has a wide range of applications. Suitable for welding low-cost metal thermocouples.　　 　　4. Carbon powder welding 　　 　　 The carbon powder welding device is similar to arc welding, except that one pole of the power source is not connected to a carbon rod, but to a graphite crucible containing carbon powder, and the other pole is connected to a thermocouple to be welded. When welding, insert the hot electrode into the graphite powder, and the welding can be completed after a few seconds. This welding method is more convenient than arc welding, but it is easy to cause brittle fracture of the hot electrode. This method is suitable for welding low-cost metal thermocouples.　　 　　 5. Salt water welding 　　 　　 Put sodium chloride solution in a beaker, put platinum wire in the aqueous solution as one electrode, and the hot electrode as the other electrode. When welding, slightly touch the top of the thermocouple with the solution, turn on the power, and quickly turn off the power after the arc starts. This welding method is suitable for welding thermocouples with a thinner diameter of 0.03mm-0.3mm. If you don’t understand the problem, please call our official website at 0517-86987700