1、 FORD LABORATORY TEST METHOD EU-BA 054-01 Date Action Revisions 200 0 08 30 Revised Editorial no technical change A. Cockman 2000 05 22 Editorial no technical change A. Cockman 1994 02 28 Printed copies are uncontrolled Page 1 of 4 Copyright 2000, Ford Global Technologies, Inc. METAL FOIL METHOD FOR
2、 DETERMINATION OF C- AND N-POTENTIAL OF CARBURIZING AND CARBONITRIDING FURNACE ATMOSPHERES Application The metal foil method is used to check the C and N potential of carburizing and carbonitriding furnace atmospheres. Materials and Apparatus Required 1. Foil Balance Torsion precision balance The ba
3、lance shall be positioned in such a way that neither vibration nor temperature will influence functioning and accuracy of balance. Weighing Range 0 - 10 mg Preload 100 mg Accuracy of Reading .01 mg minimum Standard Weight For the balance Foil Supporting Bar Bar with supporting spiral is used to inse
4、rt foil into the furnace. Control-Metal-Foil Foil Thickness, approx. 3 mm Weight 01 mg +/ - 1 mg Carbon Cont ent, approx. % The accurate carbon content must be indicated on the package of each shipment. Source: Messrs. Aichelin Industrieofenbau 7014 Kornwestheim Forceps Desiccator To hold prepared o
5、r gas treated foils. FORD LABORATORY TEST METHOD EU-BA 054-01 Page 2 of 4 Copyright 2000, Ford Global Technologies, Inc. Cleaning Materials (optional) Ca rbon Tetrachloride Acetone 2. Muffle - Furnace Adjustable to a temperature of 580 C with an accuracy of +/ - 10 deg. Device For denitrifying of ca
6、rbonitrided foils (see sketch). Boat For foils Inert Gas Composition: H 2 20 % N 2 80 % 3. Flowmeter 10 - 140 L at 20 C and 4.9 kN/m 2 4. Hot Air Blower Conditioning and Test Conditions All test values indicated herein are based on material conditioned in a controlled atmosphere of 23 +/ - 2 C and 5
7、0 +/ - 5 % relative humidity for not less than 24 h prior to testing and tested under the same conditions unless otherwise specified. Procedure 1. Preparation of Foil Clean foil which must be free from rust using one of the cleaning materials and form into a small tube. Dry foil under hot air blower
8、 holding it with forceps (do not touch foil with fingers). Weigh foil on torsion precision balance (G 0 ). 2. Gas Treatment of Foil Using the forceps, place foil into the spiral on the bar and insert into the hardening furnace. To prevent foil from dropping out bend the wire slightly at the end of s
9、piral. After a holding time in the hardening furnace of approx 10 minutes, remove the bar with the spiral and inserted foil from the furnace. Allow to cool in a inert atmosphere (e.g. in the hole for the foil support ing bar in the wall of the hardening furnace). Reweigh foil and note weight (G 1 )
10、Discard foils, which are discolored by oxidation. FORD LABORATORY TEST METHOD EU-BA 054-01 Page 3 of 4 Copyright 2000, Ford Global Technologies, Inc. 3. Denitrifying Foils which have been exposed to a carbonitriding furnace atmosphere must be denitrified after having be en reweighed to determine the
11、 N - potential. Denitrifying is carried out in a muffle furnace using inert gas at 580 +/ - 10 C for a minimum of 2 hours. Flow rate of inert gas approx 50 1/h under normal conditions. Allow the annealed foils to slowly cool do wn to 23 +/ - 2 C within the inert gas. Reweigh the denitrified foils (G
12、 2 ). Evaluation (a) Symbols C F = C - content in foil material (indicated on the package) % G 0 = Weight of foil in its original condition in mg G 1 = Weight of the carbonitrided foil in mg G 2 = Weight of the denitrided foil in mg (b) Determination of N-potential N - potential (%) = G 1 - G 2 (c)
13、Determination of C-potential 1. Foil Weight (G 2 ) G 0 C - potential (%) = C F + (G 2 - G 0 ) 2. Foil weight (G 2 ) G 0 ) C - potential (%) = C F - (G 0 - G 2 ) Storage of Foils Foils which, for any reason, are not immediately used after preparation or gas treatment or denitrifying shall be held in
14、a desiccator. General Recommendation The accuracy of the balance should be checked daily using a standard weig ht. Chemicals, materials, parts, and equipment referenced in this document must be used and handled properly. Each party is responsible for determining proper use and handling in its facilities. FORD LABORATORY TEST METHOD EU-BA 054-01 Page 4 of 4 Copyright 2000, Ford Global Technologies, Inc. RECOMMENDED DEVICE FOR DENITRIFYING OF CARBONITRIDED FILMS
