| 摘要 |
The invention relates to a process for coating manufactured highheavy-strength duty steel plate products containing steel made of various alloying constituentscomponents, especially Mn, Al, Si and/or Cr, with a protective metal layer, whereby the steel plate product is first treated with heat and then coated in a smelting bath of at least 85% zinc and/or aluminum with the protective metal layer while in at its warmed elevated up statetemperature. As per the invention, the heat treatment includes the following processing steps: a) the steel plate product is heated to a temperature of > 750 ‹C to 850 ‹C up in a reduced atmosphere with an H2 content of at least 2% to 8% to a temperature of > 750 ‹C to 850 ‹C. b) The steel plate product is treated with heat for 1 to 10 seconds, whereby the surface, primarily made of pure iron, is converted into an iron oxide coating at a temperature of > 750‹C to 850‹C in a reaction chamber integrated into a continuous furnace with an oxidizing atmosphere that has an O2-content of 0.01 % to 1 %. Cc) The steel plate product is then annealed in a reduced atmosphere with an H2-content of 2 % to 8 % by heating it up to a maximum of 900 ‹C over a period of time that is longer than the duration of the thermal treatment needed to generate the iron oxide coating (process step b) thus reducing the pure iron in the surface of the previously generated iron oxide layer. Dd) The steel plate product is then cooled to smelting bath temperature. ® KIPO & WIPO 2009 |
