AWS A4.2M pdf free download

AWS A4.2M pdf free download.Standard Procedures for Calibrating Magnetic Instruments to Measure the Delta Ferrite Content of Austenitic and Duplex Ferritic-Austenitic Stainless Steel Weld Metal.
2. Normative References The documents listed below are referenced within this publication and are mandatory to the extent specified herein. For undated references, the latest edition of the referenced standard shall apply. For dated references, subsequent amend- ments to, or revisions of, any of these publications do not apply. ISO 155 10, Stainless steels一Chemical composition. 3. Principle The measurement of the ferrite content of largely austenitic stainless steel weld metal through the attractive force between a weld metal sample and a permanent magnet is based upon the fact that the attractive force between a two- phase (or multiphase) sample containing one ferromagnetic phase and one (or more) non-ferromagnetic phase(s) increases as the content of the ferromagnetic phase increases. In largely austenitic and duplex ferritic-austenitic stainless steel weld metal, ferrite is ferromagnetic, whereas austenite, carbides, sigma phase, and inclusions are non-ferromagnetic. 4. Calibration 4.1 Coating Thickness Standards. The coating thickness standards shall consist of non-magnetic copper applied to an unalloyed steel base of size 30 mm x 30 mm. The thickness of the unalloyed steel base shall be equal to or greater than the experimentaly determined minimum thickness at which a further increase of the thickness does not cause an increase of the attractive force between the standard permanent magnet and the coating thickness standard. The thickness of the non-magnetic copper coating shall be known to an accuracy of +5% or better. The chemical composition of unalloyed steel shall be within the following limits: The copper coating may be covered by a chromium flash. The force required to tear off a given permanent magnet from the copper coating side of such a standard increases as the thickness of the copper coating decreases. NOTE: To ensure adequate reproducibility of the calibration, the coating thickness standards defined above should be used. In particular; coating thickness standards produced by the U.S. National Institute of Standards and Tech- nology (NIST, formerly National Bureau of Standards or NBS) may be used. 4.2 Magnet. The standard magnet shall be a permanent magnet of cylindrical shape, 2 mm in diameter and about 50 mm in length. One end of the magnet shall be hemispherical, with a 1 mm radius and polished. As an example, such a magnet can be made of 36% cobalt magnet steel, 48.45 mm土0.05 mm long, magnetically saturated and then diluted to 85%. The magnetic strength of the magnet shall be such that the force needed to tear off the standard magnet from the different coating thickness standards is within士10% of the relationship shown in Figure 1 (the weight of the magnet excluded). This is equivalent to a relationship between tear-off force and Ferrite Number of 5.0 FN/g土0.5 FN/g.4.3 Instruments. The measurement by this method shall be made by an instrument enabling an increasing tear-off force to be applied to the magnet perpendicularly to the surface of the test specimen. The tear-off force shall be increased until the permanent magnet is detached from the test specimen. The instrument shall accurately measure the tear-off force which is required for detachment. The reading of the instrument may be directly in FN or in grams-force or in other units. If the reading of the instrument is in units other than FN, the relationship between the FN and the instrument read- ing shall be defined by a calibration curve2.AWS A4.2M  pdf download.