Comparison_of_existing_ methods_for_the_determination_of_nodularity_ _jk

Transcription

1 ISO/TC 25 N 468 Comparison_of_existing_ methods_for_the_determination_of_nodularity_ _jk Table 1 Definition and description of nodularity in ISO TC 25 Standards ISO 1083 [1] The nodularity of spheroidal graphite cast iron is defined as the percentage of graphite particles that are spheroidal or nodular in shape (form VI and V of ISO 945). The graphite structure shall be mainly of form VI and V in accordance with ISO 945. However, a level of nodularity of 80 % to 85 % or more generally ensures (more than enough for Rp0,2) the minimum tensile properties specified in this International Standard. Most of the 15 % to 20 % of graphite not in form VI and V is then in form IV and possibly in form III. ISO [2] The nodularity of spheroidal graphite cast iron is defined as the percentage of graphite particles that are spheroidal or nodular in shape (forms Vl and V of ISO 945). The graphite structure shall be mainly of form V and Vl in accordance with ISO 945 However, a level of nodularity of 90 %, or more, generally ensures (more than enough for Rp0,2) the minimum tensile properties appearing in this International Standard. Most of the remaining graphite that is not of forms Vl and V is then of form lv. [3] The graphite morphology of compacted (vermicular) graphite cast iron is expressed and defined as the area-percentage of graphite particles that are spheroidal or nodular in shape (form VI and form V according to ISO 945). Compacted (vermicular) graphite cast irons shall have a minimum of 80 % of the graphite particles in the vermicular form (form III in accordance with ISO 945), when viewed on a twodimensional plane of polish. The remaining 20 % of the graphite particles should be of form VI or form V in accordance with ISO 945. Graphite particles larger than 10 µm are classified by roundness-shape factor as either spheroidal (nodular) graphite (form VI according to ISO 945), intermediate forms (form V and form IV according to ISO 945) or compacted (vermicular) graphite (form III according to ISO 945), as shown in Table B.1.. Flake graphite and other undermodified structures are also not considered in the analysis, as they are not permitted in the compacted (vermicular) graphite iron structure (see 7.5). Percent nodularity is calculated on an area basis as follows: Page 1 of 14

2 Table 2 Definition and description of nodularity in CEN TC 190 Standards EN 1563 [4] The nodularity of spheroidal graphite cast irons is defined as the percentage of graphite particles that are spheroidal or nodular in shape (form V and VI of EN ISO 945-1). The graphite structure shall be mainly of form V and VI in accordance with EN ISO However, experience shows that a nodularity of 80 % or more generally ensures the minimum tensile properties specified in this European Standard, as long as the matrix of the chosen variety is adjusted accordingly. Most of the 15 % to 20 % of graphite not being in form V and VI is then in form IV and possibly in form III (and may even be of form II in thick walled castings). EN 1564 [5] The nodularity of spheroidal graphite cast iron is defined as the percentage of graphite particles that are spheroidal or nodular in shape (form V and VI of EN ISO 945-1). The graphite structure shall be mainly of form V and Vl in accordance with EN ISO A more precise definition may be agreed upon by the time of acceptance of the order. However, a level of nodularity of 90 % or more generally ensures (more than enough for Rp0,2) the minimum tensile properties appearing in this standard. Most of the remaining graphite not of forms V and VI is then of form lv. EN [6] The vermicularity of compacted graphite cast irons is defined as the percentage of graphite particles that are of form III according EN ISO Compacted (vermicular) graphite cast irons shall have a minimum of 80 % of the graphite particles in the vermicular form (form III in accordance with EN ISO 945-1), when viewed on a two-dimensional plane of polish. The remaining 20 % of the graphite particles should be of form IV, form V and form VI in accordance with EN ISO Flake (lamellar) graphite (form I and form II according to EN ISO 945-1) is not permitted, except at the rim zone of the casting. Vermicularity is defined by the following equation: Number of graphite particles of form lll Vermicularity = x 100 Total number of graphite particles NOTE Particles < 10 µm should not be counted. Table 3 Definitions of terms related to nodularity in [7] nodule nodularity percent nodularity by area a discrete graphite particle that exceeds both the required minimum size and shape factor as defined by this method degree of roundness, or closeness to a circular periphery, of a graphite particle in ductile iron base upon the shape factor the total area of particles defined as nodules which meet the minimum size requirement devided by the total area of all particles which meet the minimum size requirements, expressed as a percentage. Page 2 of 14

3 Table 4 ISO 945-1/ISO TR 945-2, Roundness of graphite particles that occur in spheroidal and compacted graphite cast irons [8][9] ISO Graphite form Minimum roundness Maximum roundness VI Spheroidal (nodular) V Sligthly irregular spheroidal (nodular) (lv) Temper carbon (Irregular spheroidal) III Compacted (vermicular) (ll) (Crab graphite) I Lamellar (flake) Page 3 of 14

4 Table 5 Graphite particle classification by roundness value or shape factor ISO Graphite form ISO 1083 EN ISO TR GB 9441 [10] JIS G 5505 [11] Roundness Roundness Roundness Roundness Roundness Roundness Shape factor Roundness Shape factor VI (1,00-0,81) 1) 1,00-0,625 (1,00-0,81) 1,00-0,81 1,0 1,00 0,86 1,0 1,00-0,60 V (0,80-0,61) (0,80-0,61) 0,80-0,61 0,8 0,85 0,56 0,9 0,624-0,525 Vl (0,60-0,46) (0,60-0,46) 0,60-0,41 0,6 0,55 0,31 0,4 III (0,45-0,16) < 0,525 (0,45-0,16) (0,45-0,16) 0,40-0,21 0,3 0,30 0,21 0,2 ll 0,20 0,11 0,05 (< 0,15) (< 0,15) (< 0,15) < 0,20 0 I < 0, µm Minimum particle size to be considered 2) 10 µm 10 µm or 25 µm 2 10 µm 20 µm 10 µm 1) Values between brackets are not specified in standard but are estimated, see Table 4. 2) Maximum Féret diameter. Page 4 of 14

5 Table 6 Formula for the calculation of nodularity Standard Formula ISO 1083 Nodularity = (N Vl + N V ) / (N all ) x 100% Nodularity = (A Vl + 0,5 x (A V + A lv )) / (A all ) x 100% EN Vermicularity = (N lll ) / (N all ) x 100% Nodularity = (A Vl + A V ) / (A all ) x 100% {Nodularity = (N Vl + N V ) / (N all ) x 100%} GB 9441 Nodularity = (1 x N Vl + 0,8 x N V + 0,6 x N lv + 0,3 x N lll + 0 x N ll-l ) / (N all ) x 100% JIS G 5505 Nodularity = (1 x N Vl + 0,9 x N V + 0,4 x N lv + 0,2 x N lll x N ll + 0 x N l ) / (N all ) x 100% Where: N Vl = number of graphite particles of form Vl and meeting the minimum size requirement N all = total number of graphite particles which meet the minimum particle size requirement A Vl = area of all graphite particles of form lv which meet the minimum size requirement A all = area of all graphite particles which meet the minimum size requirement Page 5 of 14

6 Table 7 Comparison of methods for the determination of nodularity, spheroidal graphite cast iron N Vl 80 ISO ,1 N V 40 N lv 10 90,1 N lll 2 N ll 0 N All 132 GB ,8 JIS G ,2 N Vl 40 ISO ,1 N V 80 N lv 10 90,1 N lll 2 N ll 0 N All 132 GB ,8 JIS G ,2 N Vl 20 ISO ,8 N V 80 N lv 20 75,8 N lll 12 N ll 0 N All 132 GB JIS G N Vl 20 ISO N V 50 N lv N lll 22 N ll 0 N All 132 GB JIS G Page 6 of 14

7 Table 8 Comparison of methods for the determination of nodularity, compacted (vermicular) graphite cast iron N Vl 10 N V 10 N lv 0 N lll 200 N ll 0 N All 220 6,8 9,1 GB ,5 JIS G ,8 EN (Vermicularity) 90,9 N Vl 5 N V 5 N lv 10 N lll 200 N ll 0 N All ,5 GB ,1 JIS G ,3 EN (Vermicularity) 90,9 N Vl 10 N V 10 N lv 40 N lll 150 N ll 10 N All ,9 9,1 GB ,5 JIS G ,8 EN (Vermicularity) 68,2 Page 7 of 14

8 Tables 9, 10, 11 and 12 Comparison of methods for the determination of nodularity, examples of JIS G 5505 Annex B Table 9 Example 1 N Vl 0 N V 41 N lv 194 N lll 187 N ll 159 N l 24 N All 605 JIS G GB EN (Vermicularity) 31 Page 8 of 14

9 Table 10 Example 2 N Vl 2 N V 70 N lv 142 N lll 82 N ll 49 N l 3 N All 348 JIS G GB EN (Vermicularity) 24 Page 9 of 14

10 Table 11 Example 3 N Vl 8 N V 70 N lv 55 N lll 26 N ll 16 N l 4 N All 179 JIS G GB EN (Vermicularity) 15 Page 10 of 14

11 Table 12 Example 4 N Vl 19 N V 110 N lv 68 N lll 9 N ll 3 N All 209 JIS G GB EN (Vermicularity) 4 Page 11 of 14

12 Table 13 and 14 Comparison of methods for the determination of nodularity, examples of CETEM [12] Table 13 Sample 2 N Vl 267 N V 959 N lv 264 N lll 163 N ll 24 N All 1677 JIS G GB ISO Page 12 of 14

13 Table 14 Sample 3 N Vl 1777 N V 789 N lv 47 N lll 85 N ll 6 N All 2704 JIS G GB ISO Page 13 of 14

14 Biblography [1] ISO 1083, Spheroidal graphite cast irons -ASTM Classification [2] ISO 17804, Founding - Ausferritic spheroidal graphite cast irons - Classification [3], Compacted (vermicular) graphite cast irons - Classification [4] EN 1563, Founding - Spheroidal graphite cast irons [5] EN 1564, Founding - Ausferritic spheroidal graphite cast irons [6] EN 16079, Founding - Compacted (vermicular) graphite cast irons [7], Standard test method for determining nodularity and nodule count in ductile iron using image analysis [8] ISO 945-1, Microstructure of cast irons Part 1:Graphite classification by visual analysis [9] ISO/TR 945-2, Microstructure of cast irons Part 2:Graphite classification by image analysis [10] GB 9441, Metallographic test for evaluation of spheroidal graphite cast iron [11] JIS G5505, Compacted (vermicular) graphite cast irons [12] Gomez, O.F.M. and Paciornik, S. Automatic classification of graphite in cast iron. Microscopy and Microanalysis 11 (4): , 2005 Page 14 of 14