Ion nitriding china-africa nitriding surface shielding protection method

Ion nitriding china-africa 2019 - nitriding surface shielding protection method 07 - 30 xiu-lan Yang ( Qinghai hua ding gearbox co. , LTD. ) Ion nitriding method is in 0. 1～10Torr（ 1Torr=133. 3Pa） Nitrogen atmosphere, furnace body as anode, processed workpiece as the cathode, the electrode of Yin and Yang of hundreds of volts dc voltage, because the glow discharge phenomenon will produce like the neon light cover in the processing of the workpiece surface. At this point, the ionized gas composition are accelerated electric field, the impact is processed workpiece surface and the heating, at the same time rely on nitriding processing such as sputtering and ionization effect. As a kind of brand-new nitride method, has been widely used in automobiles, machine tools, aerospace, plastics machinery, textile machinery, precision instrument, mould, toughening and many other areas, and its application range is still growing. At present, our country in ion nitriding has certain theory and technology is a world leading level. Compared with the gas nitriding, ion nitriding has many advantages, mainly displays in: carbonitriding layer is easy to control, brittle small; After nitriding distortion small; Energy saving, provincial gas; Non-toxic and pollution-free. The effect of ion nitriding, mainly depends on the material and the preliminary heat treatment in advance, blank normalizing and tempering treatment and aging treatment, heat treatment process is used to eliminate machining to produce stress, reduce the workpiece deformation when the nitride. Second, ion nitriding artifacts before cleaning process is critical, clean degree directly affect the length of arc, such as cleaning is not comprehensive, will eventually after nitriding surface was damage, burning-out, soft point defects such as local. When cleaning should pay attention to the workpiece holes, blind holes, narrow gap of oil, iron filings, burr, etc. , and cleaning after the workpiece must be dry. Small hole on the workpiece, deep blind holes, grooves and, in areas such as the narrow gap may cause a arc and local temperature is too high, must be shielded processing ( Unless the product requirements for nitriding processing) 。 In the ion nitriding, the workpiece of nitride is very strict protection, on the surface of the workpiece on the threaded hole, pin hole must for shielding protection. Past our shielding measures commonly used asbestos cord plugged hole or with yellow cement plugging holes, in the process of ion nitriding, asbestos rope and yellow cement loose, easily weather-shack gap formation, resulting in killing arc phenomenon, make the normal operation of the equipment, the more serious will be wounded artifacts, its shielding effect is not very ideal. Can be used in gas nitriding, besmear prevent nitride coating to prevent nitriding parts for protection, but in ion nitriding, nitriding furnace nitride coatings for oil pollution prevention, playing in the process of the arc to be aborted, easy appear killed arc phenomenon, the normal operation of the equipment. Therefore cannot be used in ion nitriding nitride coatings for protection. Groped after a long time of study, found that the design of shield equipment such as cylindrical pin or cases for screen protection effect is very good. Made shielding tooling, its geometry shape, in accordance with the requirements of nitrogen chemical parts. Cylindrical pin or gaps between cases and workpiece size directly affect the protective effect of good or bad. Figure 1 to ion nitriding artifacts. The part of the graphic data with a dotted line for protection. To this end, we design the shielding tooling is a cylindrical pin and a protective sleeve, as shown in figure 2. The cylindrical pin and cases into artifacts required to protect parts, as shown in figure 3. Recruitment for shielding protection of ion nitriding, must pay attention to is: ( 1) Cylindrical pin or protective gap between workpiece and guarantee in 0. 10 to 0. 30mm。 （ 2) Of the key parts of the cylindrical pin or cases are not allowed to have chamfer, which ensures that there will not be killed in ion nitriding arc phenomenon. Shielding protection on the surface of a workpiece of nitride, the improvement methods during the ion nitriding to ensure the normal operation of the nitriding furnace, ensure the workpiece after ion nitriding surface without damage, without sintering, local soft point defects such as, to ensure the normal order after machining, improve the production efficiency. Abandoned material of the horn side be make full use of to prevent the nitrogen chemical loading, and tooling can be repeated use, has a certain economic benefits. Source: the metal processing ( Hot working) Magazine,