GLASS

A manufacturer of glass street lamp covers occasionally found inclusions in random locations on the pressed glass covers. SEM evaluation using EDS found that the inclusions were iron rich scale that probably dropped into the glass after introduction into the mold. The inclusion was then pressed into the surface during the forming operation. The source was found to be the old, steel structural roof members.

The following examples illustrate some of our contributions to this business sector:

  • Touchstone was contacted by a glass manufacturer regarding a problem concerning cracks in plungers that had been welded to return the wear surface to original dimensions. The problem was found to be caused by failure to properly pre-heat and post-anneal the plungers in the welding operations. This improper practice developed a brittle martensitic layer at the weld interface, which led to crack initiation at this point. Additional recommendations included changing the radius on the inside of the plunger to minimize flexure of the highly stressed nose region during use.
  • A manufacturer of glass mugs asked Touchstone to compare two plungers in terms of metallurgy and chemical composition in order to determine what may be the cause of poor performance. The examination of the microstructure revealed that both plungers were composed primarily of ferritic ductile iron, but one was found to contain significantly more pearlite (12% vs. 3-4%).
  • A manufacturer of glass street lamp covers occasionally found inclusions in random locations on the pressed glass covers. SEM evaluation using EDS found that the inclusions were iron rich scale that probably dropped into the glass after introduction into the mold. The inclusion was then pressed into the surface during the forming operation. The source was found to be the old, steel structural roof members. The problem was solved initially by placing dust covers over the work area.
  • Recommendations were provided to a manufacturer of glass novelties for their color injection nozzles. The zirconium nozzles currently in use appeared to be soluble in the molten glass and deteriorated after only a short service life. The nozzle supplier offered to provide candidate materials with potentially better service life. The project manager also located suppliers for cast iron parts for the forming equipment used in the operation.
  • A manufacturer of thermopane windows was interested in the insulative values of argon versus the nitrogen typically used in double glazed windows. Touchstone adapted an existing apparatus to allow measurements to be performed on windows. In addition, an evaluation of the spacer/frame materials was made. The results helped the manufacturer make decisions on their future window designs.
  • Touchstone was asked to reverse engineer a high pressure sight glass for one manufacturer to determine the type of metal used to form the mounting ring, and to determine the method of sealing the glass to the ring. The ring was formed from 430 stainless, which was etched to produce a layer of chromium oxide on the bore. Molten glass was then poured directly into the ring and the seal was formed when molten glass dissolved and mixed with the chromium oxide. 430 stainless steel is used in this application because it has a coefficient of expansion nearly identical to glass.
  • Finite element analysis was performed on iron plungers used in a glass plant to determine what changes were needed to improve production and service life.

The above examples are only a sample of our work in this area. We would be pleased to provide any additional information you may require. We also invite you to review examples on our website of work that we have performed in support of other business sectors.