Heat treatment method of steel wire torsion spring

Heat treatment method of steel wire torsion spring:
The heat treatment of a flat cross-section cylindrical torsion spring with a length of 50m and an outer diameter of ф60mm is a foreign aid task we accept. In foreign countries, the manufacture of this spring is made by using oil-quenched and tempered steel wire to be wound into shape and then tempered at low temperature. Eliminate the winding stress. In China, there is no professional factory that produces such flat section springs. Therefore, most of the special-shaped section steel wires are rolled or drawn by round steel wires. Then it is quenched and tempered. Obviously, it is very difficult to quench and temper such a long spring. After investigation and analysis and a large number of experiments, we have initially explored the resistance heating quenching process of this long spring and achieved relatively satisfactory results the result of.
   1. Determination of resistance heating process plan and equipment design
According to the longer characteristics and technical requirements of this spring, we compared the following three process options, namely flame quenching, high frequency quenching and resistance heating quenching. After analysis and comparison, it is believed that although the resistance heating quenching program also has certain technical difficulties, but The biggest feature is that it does not require the spring to rotate during heating, and does not spray the professional equipment of the coolant. Therefore, it is determined to use the resistance heating quenching method for the test. We deduced the temperature changing function on the basis of heat and electricity, and in turn deduced the resistance heating In the process, the electric energy is converted into heat energy and the change law of the heat of radiant heat at any time, as a reference basis for determining the parameters of the resistance heating workpiece.
   2. Test equipment and results
   1. Test equipment
The instruments and equipment used in the test are: (1) a ZUDG-253 salt bath furnace transformer; (2) a set of insulation fixing devices for spring heating and quenching; (3) a cooling water tank; (4) WGG2-302 optical pyrometer One IRT-1200 infrared measuring instrument; one stopwatch.
   2. The main content of the test
   Determine the quenching heating time and tempering time, select the quenching medium and observe the metallographic structure.
   3. Test result
(1) The determination of the quenching heating time is based on the resistance heating is the internal heat source heating, and the temperature is a function of time. This test uses a stopwatch, an optical pyrometer and an infrared thermometer to measure the test pieces can reach different temperatures under certain electrical parameters. Continuous heating time to determine the quenching heating time.
  (2) The choice of tempering time is tested with a stopwatch and an infrared thermometer. The results show that the tempering heating time is between 25-30S.