IMM 5/99

How do you verify the quality of the tool steel being used to build a mold for you? Are there portable testers, analyzers, or certain certifications you can use when visiting a tool vendor?

The quality of steel in a mold should never be compromised no matter how small or large the project. The cost for brand name steel vs. a piece from a steel broker is next to nothing for small projects. The labor associated with a large project is too expensive to risk on a piece of steel from someone who will not replace the labor if it is flawed.

Without chemical analysis, you could not verify the steel on a shop visit. You can carry a portable Rc tester, but its finding could be subject to rebuttal. I recommend you start at the quoting stage. Request the following: the brand of steel to be used, a copy of the purchase invoice, and most importantly, heating charts from the heat treating process. The hardness of the steel is only part of the story. It in no way indicates the stresses that can be left after improper heating, and stresses cause steels to break. Also request a sliver of steel from the insert; if there is a problem, it will be needed for evaluation. It can also be used as welding material for high-appearance parts if damaged in production. This is the only way color matching can be achieved. We generally drill a hole in the ejection housing parallel with a .25-inch pipe plug and fill it with this material, so it never gets lost.

A quality moldbuilder will normally use only one steel manufacturer. His technical support is better by doing this. For example, we buy only Uddeholm; we know where every piece of steel in our house came from. So the best way to ensure you are getting quality steel in your mold is simply to inquire up front. Trust plays an important role in moldbuilding. Finally, don't be afraid to get information from the steel mills directly. Most of them have metallurgists at your disposal.
-B. Desilets, VW Tooling Systems Inc., Louisville, KY, (502) 935-2806.

Generally speaking, it is very difficult to judge a mold steel by performing a quick hardness check, visual examination, or a review of the material certification. In fact, mill certs will normally state only the chemical composition and annealed hardness level of the tool steel. Therefore, often one does not realize there is a problem with the mold steel until the machining or polishing operation takes place.

The best way to ensure that your molds are being made from a quality material is to specify the actual steel supplier to your mold builder. Many producers of mold steels have developed specific grades with improved properties. Steels with high cleanliness levels for superior polishability or unique chemistries that provide excellent corrosion resistance are available. These improvements can extend mold life and also ensure that you are using the best possible material for your tooling
-I. Kaszynski, Bohler, Arlington Heights, IL, (800) 638-2520.