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1、International Standard 5940 0 * 4 4 , ? . f ., : . v,E;.,:* !, ;I Y).$.- ,., _ /a* ; ( j ,-i .!. ;:p; 3f r err L .c ,-j S;Q $ I. Carbonaceous materials for the production of aluminium - Pitch for electrodes - Determination of softening point by the ring-and-ball method Produits carbon - internal dia
2、meter at bottom : 15,9 ?I 0,l mm; - internal diameter at top : 17,5 + 0,l mm; - external diameter above shoulder : 20,6 f 0,l mm; - external diameter below shoulder : 18,5 + 0,5 mm. 5.1.2 Steel balls, of diameter 9,53 mm, each weighing 3.50 * 0,05 g. 5.1.3 Ball centring guides. A suitable form of gu
3、ide is shown in figure 3. 5.1.4 Bath; a heat-resistant glass squat form beaker of capacity 800 ml. 5.1.5 Ring support, having the shape and dimensions shown in figures 1 and 4. The support consists essentially of two parallel brass plates, one above the other, and 25 Y!I 0,5 mm apart. The upper plat
4、e is designed to support the two rings (5.1. I) and its thickness is equal to the distance between the lower surface of one ring and its shoulder. The two plates are supported by a circular or rectangular holder which rests on the top of the bath and which has a central hole intended for the thermom
5、eter (5.1.6). 5.1.6 Thermometer, solid-stem, mercury-in-glass type, having : a) a range from 0 to 120 “C for pitches which have soften- ing points between 30 and 120 OC; b) a range from 50 to 210 “C for pitches which have softening points greater than 120 X. Details of suitable thermometers are give
6、n in annex A, but other thermometers of similar characteristics may also be used. 1 -,-,- Is0 5940-1981 (El 5.1.7 Tripod and open mesh wire gauze, supporting the bath (5.1.4). 6.3 Determination Place the Bunsen burner (5.1.8) midway between the axis and the edge of the beaker and on a diameter at ri
7、ght-angles to that which includes the rings and the thermometer as indicated in figures la) and lb). 5.1.8 Bunsen burner, fitted with a governor if the gas supply is liable to fluctuate. Heat so that the temperature is raised by 5 “C each minute. Ex- cept for the first 3 min, it is essential to main
8、tain this heating rate to within + 0,5 OC over each 1 min period. It is essential that this rate should not be merely the average over the period of the test. Reject any results in which the heating rate does not conform to these requirements. 5.1.9 Moulding plate, having the dimensions shown in fig
9、ure 5. 5.2 Draught screen, of suitable design to protect the assembled apparatus from draughts. NOTE - It is also possible to use an automatic ring-and-ball apparatus in place of the manual apparatus, provided that it has the same dimen- sions and that the same results are obtained. Record the tempe
10、rature at which the pitch surrounding each ball first touches the lower plate of the support. If, for the two balls, this temperature differs by more than 1 OC, reject the results and repeat the test. If the test is repeated for any reason, carry out the whole procedure using a new test portion. 6 P
11、rocedure NOTE - At about 85 OC, slightly higher results are obtained when using glycerol than when using water. 6.1 Preparation of test piece Using the method specified in annex B, melt a test portion of approximately 50 g of the laboratory sample (see IS0 6257, sub-clause 3.10) and heat the rings (
12、5.1.1). 7 Expression of r b) the reference of the method used, stating whether glycerol or water was used as the heating medium; Place the ball centring guides (5.1.3) above each ring and place two of the balls (5.1.2) in the bath, but not on the pitch con- tained in the rings. Place the beaker on t
13、he tripod (5.1.7) so that the ring supporting holder is horizontal. c) the results and the method of expression used; d) any unusual features noted during the determination; Allow the assembled apparatus to stand for 15 min without allowing the temperature of the bath to rise, and then, using tongs,
14、 place the balls in their guides on the surface of the discs of pitch. e) any operations not included in this International Stan- dard, or in the International Standard to which reference is made, or regarded as optional. 2 IS0 5940-1981 (E) Annex A Details of thermometers I oto 120 oc I 50 to 210 T
15、 IG raduation I 0,5 T I 0,5 Yz I 100 mm 100 mm Lonaer lines at each ) 1 and 5 “C 1 and 5 OC I Fully figured at each I 10 YZ I 10 oc I Maximum overall length I 430 mm I 430 mm I Minimum length of main scale I 240 mm I 240 mm Maximum error + 0,6 “ 2 I f 0,8 -2 1) The lines corresponding to each 5 OC s
16、hall be slightly longer than those corresponding to each 1 C. B.0 Introduction Annex B Melting of pitch samples Prior to determining the softening point of pitch, it is necessary to melt the sample. The precision of the determination, and particularly its reproducibility, is considerably influenced
17、by the homogeneity of the molten sample and its freedom from air bubbles. The procedure specified in this annex is designed to minimize variations in test results by standardizing the temperature and heating time. B.l Apparatus B.l.l Dish, 55 mm diameter, 35 mm deep. Dishes sold for use with penetro
18、meters are suitable. B.1.2 Oven, capable of being maintained at 50 OC above the expected softening point of the sample. B.2 Procedure Weigh approximately 50 g of the laboratory sample, powdered if its softening point permits, into the dish (B.l .I) and place it in the oven (8.1.2) set at a temperatu
19、re of 50 OC above the ex- pected softening point of the pitch. Also place the rings (5.1 .I 1 in the oven. Maintain the pitch and the rings at this temperature for 2 h and then use the heated rings and the molten pitch to prepare the test piece as described in 6.1. NOTE - After heating, the surface
20、of the molten pitch should be smooth, shiny and free of skin. If the surface of the molten pitch is covered with froth, suggesting the presence of water, discard it and prepare another melt using a further 50 g of the laboratory sample, powdered if its softening point permits, which has been dried b
21、y allowing it to stand in an evacuated desiccator in the presence of a suitable desiccant. 3 IS0 5940-1981 (El Dimensions in millimetres Central hole J, a) Front view Lower plate /- ;:d”t h” ;y b) Side view Figure 1 - Assembled apparatus NOTE Ball centring guides have been omitted for clarity. 4 -,-
22、,- IS0 5940-1981 (E) Dimensions in millimetres Figure 2 - Tapered ring Guide fits on top of ring (rigidly) to position the ball in centre of sample -q I q7, 5J& q-l- 15,3 17,7 17.7 15,3 i _5,1 I -I- Y- I 76,2 Figure 4 - Support for rings L 21 J k- 21 j _ -f Figure 3 - Recommended form of ball centring guide Figure 5 - Plate for moulding 5 -,-,-