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1、INTERNATIONAL STANDARD IS0 14284 First edition 1996-07-01 Steel and iron - Sampling and preparation of samples for the determination of chemical composition Fontes et aciers - Pr.Gvement et prhparation des Bchantillons pour la d - sample in the form of chips obtained by machining, - sample in the fo
2、rm of fragments obtained by commi- nution, - sample in the form of powder obtained by comminution 3.17 test portion: Part of the sample for analysis, or part of the sample taken from the melt, actually sub- mitted to analysis. In certain cases, the test portion may be selected from the sample produc
3、t itself. NOTES 2 The following special types of test portions in the form of a solid mass obtained from a probe sample are dis- tinguished - test portion in the shape of a small disc, commonly de- scribed as a slug, obtained by punching, - test portion in the form of a small appendage, com- monly d
4、escribed as a lug, - test portion in the form of a small-diameter rod, com- monly described as a pin, obtained by cutting. 3 When the sample for analysis is in the form of chips or powder, or when a sample in the form of a solid mass is analysed by a thermal method, the test portion is obtained by w
5、eighing. In the case of a physical method of analysis, the part actually analysed will constitute only a small mass of the sample for analysis In an optical emission spectro- metric method, the mass of metal consumed in an electri- cal discharge is about 0,5 mg to 1 mg, in an X-ray fluor- escence sp
6、ectrometric method, the characteristic radiation is produced from a very thin surface layer of the sample 3.18 grinding: Method of preparing a sample of metal for a physical method of analysis in which the surface of the sample for analysis is abraded using an abrasive wheel. 3.19 linishing: Method
7、of preparing a sample of metal for a physical method of analysis in which the surface of the sample for analysis is abraded using a flexible rotating disc or continuous belt coated with an abrasive substance. 3.20 milling: Method of preparing sample chips or the surface of a sample for a physical me
8、thod of analysis in which the surface of the sample is ma- chined using a rotating, multi-edged cutting tool. 3.21 consignment: Quantity of metal delivered at one time. 3.22 increment: Quantity of metal obtained by sampling at one time from a consignment. 4 Requirements for sampling and sample prepa
9、ration 4.1 General This clause covers the general requirements for the sample, and for the sampling and sample preparation of iron and steel. Special requirements apply to each category of liquid and solid metal and these are con- sidered in the relevant subclause. The sequence of sampling and sampl
10、e preparation of liquid iron and steel, and cast iron and steel products is shown in figure 1. Special considerations apply to pig irons (see clause 8). 4.2 Sample 4.2.1 Quality Sampling practices shall be designed to provide a sample for analysis that is representative of the mean chemical composit
11、ion of the melt or the sample product. 2 0 IS0 IS0 14284:1996(E) Melt r Sample for analysis (7 a) Liquid iron and steel Preliminary sample Sample for analysis b) Cast Iron and steel products Figure 1 - Sequence of sampling and sample preparation The sample for analysis shall be sufficiently homo- ge
12、neous with respect to chemical composition such that inhomogeneity does not appreciably contribute to the error variability of the method of analysis. How- ever, in the case of a sample taken from a melt, some variability in analysis, both within and between samples for analysis, may be unavoidable;
13、 this varia- bility will form an inherent part of the repeatability and reproducibility of the analysis. The sample for analysis shall be free from surface coatings, and from moisture, dirt or other forms of contamination. As far as possible, the sample for analysis should be free from voids, cracks
14、 and porosity, and from fins, laps or other surface defects. Particular care shall be taken when selecting and pre- paring the sample for analysis, where a sample taken from a melt is expected to be heterogeneous or con- taminated in any way. A sample taken from a melt shall be cooled in such a mann
15、er that the chemical composition and metallurgi- cal structure of the sample is consistent from sample to sample. It is important to recognize that analysis by some physical methods may be influenced by the metal- lurgical structure of the sample, particularly in the case of irons with white and gre
16、y iron structures, and in the case of steels in the as-cast and wrought con- ditions. 3 IS0 14284:1996(E) 4.2.2 Size 0 is0 4.2.5 Arbitration The dimensions of a preliminary sample in the form of a solid mass shall be sufficient to permit additional samples for analysis to be taken for re-analysis, w
17、here necessary using an alternative method of analysis. A sample for analysis, of a sufficient mass to provide for any re-analysis necessary, shall be prepared. Gen- erally, a mass of 100 g will be sufficient for a sample in the form of chips or powder. The dimensional requirements for a sample for
18、analy- sis in the form of a solid mass will depend upon the method selected for analysis. In the case of optical emission and X-ray fluorescence spectrometric methods, the shape and size of the sample will be de- termined by the dimensions of the sample chamber. The dimensions for samples for analys
19、is given in this International Standard should be regarded as indica- tive only. 4.2.3 Identification A sample for analysis shall be assigned a unique identification in order to determine the melt of sample product from which it was taken and, if necessary, the processing conditions of the melt or t
20、he location of the preliminary sample or the sample for analysis in the sample product. A sample for analysis of pig iron shall be assigned a unique identification in order to determine the con- signment or part of a consignment and the increment from which it was taken. Labelling or some equivalent
21、 method of marking shall be used to ensure that the assigned identification remains associated with the sample for analysis. The identification, status and condition of the sample shall be recorded to ensure that confusion cannot arise as to the identity of the item to which analysis and records ref
22、er. 4.2.4 Conservation Adequate storage facilities shall be provided to segre- gate and protect the sample for analysis. During and after preparation, the sample for analysis shall be stored in such a way as to prevent contamination or chemical change. It is permitted to conserve the preliminary sam
23、ple in the form of a solid mass, and a sample for analysis may then be prepared when required. The sample for analysis, or the preliminary sample in the form of a solid mass, shall be kept for a sufficient period of time to protect the integrity of the test lab- oratory. In the case of a sample inte
24、nded for arbitration, the sample for analysis shall be prepared jointly by the supplier and purchaser, or by their representatives. A record shall be kept of the methods used for preparing the sample for analysis. Containers with samples for analysis intended for arbi- tration shall be sealed by bot
25、h parties or by their rep- resentatives. Unless agreed to the contrary, these containers shall be kept by the representatives of each party responsible for the preparation of samples. 4.3 Selection of a sample 4.3.1 Sample from a melt Melts are sampled at various stages in the manufac- turing proces
26、s for the purposes of monitoring and controlling the process. Samples can be taken during the casting of the melt to verify chemical composition in accordance with the specification of the cast prod- uct In the case of liquid metal intended for the pro- duction of a casting, the sample for analysis
27、may be selected from test bars or blocks specially cast from the same metal as that of the casting for purposes of mechanical testing, in accordance with the product standard. Sampling practices for melts shall be designed to provide samples during a particular manufacturing process in accordance wi
28、th requirements for sample quality (see 4.2.1). The sample obtained from a melt is usually in the form of a small ingot, a cylindrical or rec- tangular block, a chillcast disc or a combination of a disc with one or more attached pins; in some cases small lugs are attached to a disc sample NOTE 4 Sam
29、pling probes for use with liquid iron and steel may be obtained from a number of suppliers, the main fea- tures of the different types of probe are distinguished in annexes A and B, which include dimensions for information only 4.3.2 Sample from a product The preliminary sample or the sample for ana
30、lysis can be selected from the sample product at the location indicated in the product specification for the selection of material for mechanical testing, when available. In the case of an iron casting, the sample for analysis can be selected from a bar or block cast onto the casting. In the case of
31、 a forging, the sample for analysis can be selected from the initial starting material from which the forging has been made, or from pro- longations of the forging or from additional forgings. In the absence of requirements given in the product standard, or of a specification when ordering the 4 -,-
32、,- 0 IS0 IS0 14284:1996(E) product, the sample for analysis may, following agreement between the supplier and the purchaser, be selected from the sample for mechanical testing or from the test piece, or directly from the sample product. Chips shall be thoroughly mixed before weighing the test portio
33、n. For most purposes, it is satisfactory to mix the chips by rolling the container on a level sur- face and/or gently tumbling the container. The preliminary sample or the sample for analysis can be obtained from the sample product by machining or by using a cutting torch. Special considerations app
34、ly in the case of sampling for the determination of cer- tain elements. 4.4 Preparation of a sample 4.4.1 Preliminary preparation If any part of the sample is liable to be non- representative in chemical composition, for example due to oxidation, it may be agreed, following an inves- tigation to est
35、ablish the nature and extent of any change in composition, to remove from the sample those parts that have changed. Following this oper- ation, the sample shall then be protected from any change in composition. If necessary, the surface of the metal shall be laid completely bare at the point of mach
36、ining, by any suitable means, to remove any coating that has been applied during manufacture If necessary, the surface of the metal shall be degreased by means of a suit- able solvent, taken care to ensure that the manner of degreasing does not affect the correctness of analysis. 4.4.2 Sample for an
37、alysis in the form of chips The sample for analysis shall consist of chips of a regular size and shape. These may be obtained by methods such as drilling, milling, turning or punching. The chips shall not be taken from a part of the sample that has been affected by the heat of a cutting torch. The t
38、ools, machines and containers used during preparation of the sample shall be cleaned beforehand to prevent any contamination of the sample for analy- sis. Machining shall be carried out in such a way that the chips are not subject to overheating, as indicated by a change in the colour (blueing or bl
39、ackening) of the chips. Unavoidable coloration of chips obtained from some types of alloy steels, for example manganese and austenitic steels, can be minimized by selection of appropriate tools and cutting speeds. Heat treatment may be required to soften the sample for machining The use of coolants
40、during machining is only permit- ted in exceptional cases; after which the chips shall be cleaned by means of a suitable solvent which does not leave any deposit. 4.4.3 Sample for analysis in the form of a powder or fragments Where drilling of the sample to obtain chips is imprac- ticable, it shall
41、be cut or broken into pieces. These pieces shall then be crushed using a percussion mor- tar or a vibratory grinding mill, also known as a disc mill or ring mill, to obtain a sample for analysis in the form of a powder, the whole of which passes through a sieve of a specified aperture size. In some
42、applications for the determination of carbon using a thermal method of analysis, the sample is crushed in a percussion mortar to obtain a sample for analysis in the form of fragments with a particle size range of approximately 1 mm to 2 mm. Equipment used for comminution shall be constructed from ma
43、terial which does not alter the sample com- position. Suitable tests may be necessary to show that the use of such equipment does not affect the composition of the sample for analysis in any way. Comminution shall not be used for the preparation of samples of graphite-bearing irons. The sieving oper
44、ation shall be performed taking all precautions necessary to avoid contamination or loss of material. When sieving hard materials, care shall be taken to avoid damaging the fabric of the sieve. The sample for analysis shall be homogenized before weighing the test portion. Powders can be homogen- ize
45、d by stirring. CAUTION - Finely-divided metals of particle size less than approximately 150 urn can present a fire risk. Ensure that there is adequate ventilation during comminution. 4.4.4 Sample for analysis in the form of a solid mass 4.4.4.1 Selection of the sample for analysis The sample for ana
46、lysis shall be obtained by cutting, from the sample product or preliminary sample, a piece of size and shape suitable for the method of analysis. Samples shall be cut by sawing, abrasive cutting, shearing or punching. In the absence of any indication in the product stan- dard, analysis by a physical
47、 method shall be carried out on that part of the sample corresponding to a transverse section of the product, provided that the material has sufficient thickness. 5 IS0 14284:1996(E) 0 IS0 4.4.4.2 Surface preparation of the sample for analysis The sample for analysis shall be prepared to expose a su
48、rface suitable for the method of analysis. Prep- aration of a surface for analysis shall not be carried out on any part of a sample that has been affected by the heat of a cutting torch. The equipment used for sample preparation shall be designed to minimize overheating the sample and, where appropr
49、iate, shall incorporate systems of cooling. Four main types of equipment used for surface prep- aration may be distinguished. a) A milling machine capable of removing a pre- selected depth of metal in a reproducible manner, for use with samples that are within a hardness range suitable for milling. The equipment should be able to be used, if required, with a sample taken from a melt where the sample is still hot. b) A grinding machine with a fixed, rotating or oscil- lating head capable of removing a preselected depth of metal in a reproducible man
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