Estimation of temperature in the lubricant film during cold forging of stainless steel based on studies of phase transformation in the film

Thomas Steenberg, J.S. Olsen, Erik Christensen, Niels Bjerrum

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

Changes in friction during backward can extrusion of stainless steel war observed for four different lubricant systems. The observed changes in friction are believed to be caused by phase transitions in the lubricant. The lubricant systems consisted of two different carrier coatings (crystalline Zn-3(PO4)(2). 4H(2)O and amorphous Zn1.5Ca1.5(PO4)(2)) lubricated with soap or MoS2. The temperature in the lubricant film during the process was estimated from changes in friction in correlation with observed phase transitions in the lubricant. Phase transitions in the carrier coatings as a function of pressure and temperature were investigated. Several previously unknown phase transitions were discovered. Four different crystal structures of Zn-3(PO4). xH(2)O were observed as a function of temperature. At 700-900 degrees C Zn-3(PO4)(2) becomes amorphous (depending on the pressure). Amorphous Zn1.5Ca1.5(PO4)(2) crystallises at 200-300 degrees C and a second phase transition is observed at 400-700 degrees C (depending on the pressure). It is estimated on the basis of the results from the backward can extrusion and analysis of the structure as a function of temperature that the temperature may reach in the excess of 450 degrees C at a height/diameter ratio of two. (C) 1999 Elsevier Science S.A. All rights reserved.
Original languageEnglish
JournalWear
Volume232
Issue number2
Pages (from-to)140-144
ISSN0043-1648
DOIs
Publication statusPublished - 1999

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