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ISO 3887-2017 pdf free download
ISO 3887-2017 pdf free download.Steels Determination of the depth of decarburization
Aciers — Determination de Ia profondeur de décarbu ration.
5.2.2 Selection and preparation of the sample
The metallographic polishing, carried out by applying the usual methods, shall not round the edges.
In order to achieve this, the sample may be mounted or held in a clamp, and the surface of the product
may, if necessary, be protected by a metallic deposit obtained by electroless or electrolytic plating.
Automatic/semi-automatic preparation techniques should be used, where possible.
Etching in a solution of 1,5 % to 4 % nitric acid in ethanol (nital) or 2 % to 5 % picric acid in ethanol(picral) will reveal the structure of the steel.
As a rule, the reduction in the carbon content can be determined for the following:
a) ferrite and pearlite: from the decrease in the amount of pearlite;
b) pearlite and hypereutectoidally developed carbides: from the decrease in the amount of hypereutectoidally developed carbides and/or of pearlite;
c) ferrite matrix with dispersed carbides: from the decrease in the amount of carbides in the ferrite matrix.
This method can also be applied for assessing changes in the microstructure if the carbon content leads to clear changes in the microstructure, e.g. for hardened or quenched and tempered microstructures, but only if a distinct boundary which is decisive for the depth of decarburization exists within the characteristic structure. Examples of typical decarburization microstructure are given in Annex A.
The distance from the surface to the point at which the structure does not differ from that of the core shall be measured (total decarburization). The measurement shall be conducted using suitably calibrated equipment.
The choice of magnification depends on the depth of decarburization and shall be chosen by the assessor unless otherwise agreed between the parties concerned. The maximum magnification that allows the full extent of decarburization to be viewed should be adopted. A magnification of x 100 is recommended as a useful magnification for the majority of instances.
A preliminary examination of the whole surface at low magnification ensures that any great variation in the depth of decarburization along the periphery will be observed for further evaluation.
The deepest uniform decarburization zone is selected from the preliminary examination of the surface of the section. One of two methods of measurement should be used. The choice of the measurement method shall be in accordance with the agreement between the parties concerned.
— The worst field method is the simplest method and is adequate for many purposes. One measurement of the depth of decarburization is conducted and reported at the deepest uniform decarburization zone.
— The average method is the alternative method. Beginning at the deepest uniform decarburization zone, the first measurement point, the surface is divided into parts of equal size, at the ends of which the depth of decarburization is also measured. Unless otherwise agreed, four individual measured values are determined. The depth of total decarburization of the sample is defined as the average of these measurements. Measuring points that are affected by surface defects are not taken into account when determining the average.
The various bands of decarburization are shown schematically in Figure 1. The boundaries separating the various types of decarburization are shown as hatched bands with the width of the band illustrating the practical variability in measurements due to the uncertainty of interpretation.
lithe product has undergone a process involving carburization, the definition of the “core” shall form the subject of an agreement between the parties concerned.
The permissible depth of decarburization shall be specified in the appropriate standard covering the product or shall be the subject of an agreement between the parties concerned.ISO 3887-2017 pdf free download.
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