subject: Making The Best Decision For Retreatment [print this page] In order to make the best decision when you are deciding on retreatment. You should take a few things into consideration before making your final decision.
After the special coating is applied, the casting finish is much more effective because the crevices have been filled by producing a smoother finish and appearance to the castings. The threads, cracks and tool marks are then all smoothed and the die surface can now produce castings with a finish as fine as 8 R.M.S. when required.
Heat Checks are greatly reduced following the special coating treatment but is not removed completely. However, it is noticeable that the usual rapid progress of the heat checking is virtually stopped for a period following the coating. After the treatment, heat checks still may be visible on the castings and may not be completely eliminated. Later, when checking does progress, it is at much reduced rate.
Before additional retreatment's, the die impressions always should be stoned and/or polished, especially in the areas of severe checks. This action may seem foolish since the existing chromium coating cannot be completely stoned off the die surface. However, the edges of heat check cracks will be smoothed to give a more even surface, or at least one that is smoother than it was before the die is to be retreated. This practice will be helpful in ensuring a good coating retreatment time after time.
In many cases, material flow will be enhanced after the coating has been applied. The 72 Rc surface resists sticking and material build up making for a cleaner die environment. Please keep this in mind when you consider. In addition, this 72 Rc hardness will enhance the parting line edges, helping to reduce or eliminate flashing. Since the coating will not peel, crack, or chip, the surface integrity of the coating on the die surface is absolute.
When recoating is called for it is absolutely important that you prepare, clean, weld and repair the die steel to its best condition to ensure that coating will deliver its many advantages.
Needless to say, profits can be increased by reducing the cost of salvaging castings and increasing die life. It should be considered that when heat checked castings are produced, they require more and separate handling. The cost of the treatment is very reasonable and is an excellent option for all die casters to consider in reducing these operations.
by: Matthew McKernan
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