Grinding balls produced of steel round billets (according to DSTU 3499-97, DSTU 8538: 2015 or GOST 7524-2015 and TU U 27.1-26524137-1376: 2008).
Received billet in the workshop must comply with the requirements to GOST 2590-2006 and regulatory documentation and it should comply to DSTU 3499-97 in terms of the carbon mass fraction and the carbon equivalent value (Table. 1).
Table. 1.
| Ø | Hardness group | Carbon, % | Equivalent, % |
| 15-55 | 1,2 | 0,40 | 0,50 |
| 3 | 0,60 | 0,70 | |
| 4,5 | 0,75 | ||
| 60-70 | 1,2 | 0,50 | 0,70 |
| 3,4 | 0,60 | 0,75 | |
| 5 | 0,80 | ||
| 80-120 | 1,2 | 0,50 | 0,70 |
| 3,4 | 0,60 | 0,75 | |
| 5 | 0,85 |
The 20mm, 25mm and 120mm grinding balls rolled by billet with a length from 3200 to 4000 mm on a ball rolling mill SHPK 20-120. The 30mm, 40mm, 50mm, 60mm, 70mm, 80mm, 90mm and 100 mm grinding balls rolled by billet with a length from 4000 to 6000 mm on the ball rolling mill SHPK 20-120.
Limit deviations by billet diameter and length must not exceed the values indicated in Table. 2
Table. 2.
| Nominal billet diameter, mm | Limit deviations of the billet diameter, mm | Limit deviations of the billet length, mm | Weight 1m of the billet length, kg |
| 30 | + 0,3
– 0,7 |
+50 | 5,55 |
| 32 | + 0,4
– 0,7 |
+50 | 6,31 |
| 33 | +50 | 6,71 | |
| 40 | +50 | 9,86 | |
| 50 | + 0,4
– 1,0 |
+50 | 15,42 |
| 60 | + 0,5
– 1,1 |
+50 | 22,19 |
| 70 | + 0,5
– 1,1 |
+50 | 30,21 |
| 80 | + 0,5
– 1,3 |
+50 | 39,46 |
| 90 | + 0,5
– 1,3 |
+50 | 49,94 |
| 100 | + 0,6
– 1,7 |
+50 | 61,65 |
| 120 | + 0,8
– 2,0 |
+50 | 88,78 |
| Note. Weight 1m of the billet length calculated according to nominal dimensions. It is a reference value In calculating the steel density is assumed equal to 7.85 g / cm3. | |||
Billet diameter allowed ovality not exceeding the tolerances sum for the diameter.
The billet curvature should not exceed 0.4% of its length. The curvature of 90mm, 100mm, 120mm billets should not exceed 0.5% of them length. The cracks, sunsets, bubbles and slag inclusions not allowed in the billet surface. The remains of the shrink shell and the bundles not allowed at the billet ends. Separate small captivity, shells, dents and ripples should not exceed:
- 1 mm (inclusive) – for 30 mm and 40 mm billets;
- 2 mm (inclusive) – for 50 mm – 80 mm billets;
- 3 mm (inclusive) – for 90 mm – 120 mm billets.
The rolled steel macrostructure during tests on etched templates or in a break, should not have: shrinkage shell, looseness, bubbles, cracks, delaminations, slag inclusions and flock. Point heterogeneity, central porosity, segregation square should not exceed a score – 2 (GOST 10243-75).
Billets deliver by rail transport or road transport in packages weighing no more than 6 tons. Packages should be tied in two places by wire rope. In addition, two wire rod loading-unloading rings (clamps) must be on each package, in accordance with the requirements of the standard instruction agreed with the state supervisory authority.
A label with the heat number (melting number), the steel grade, the billet numbers, the weight, the brigade mark and the stamp of the OTK should be on each package.
Each wagon or car should accompanied by a shipping certificate with a certificate indicating the heat number, steel grade and steel chemical composition, billet number, billet diameter, billet length, billet weight and the date of shipment (DSTU 3058; GOST 7566).
Received billets unloaded in billet warehouse. Billet packages in the warehouse cells with a division by their diameter.
Billet delivery carried out by “heat number” way. It allows composite heat number. The composite heat number includes billets the same steel brand of different heat number. The carbon mass fraction difference in the composite heat number should not exceed 0.05% of heat number analysis, manganese mass fraction difference – not exceed 0.15%, alloying elements mass fraction difference – not exceed 0.20% for ladle analysis.
Billets entrance control made by laboratory assistants of the testing laboratory. Billets entrance control performed in the 100% volume of incoming billet batch by such technical characteristics: length, diameter, curvature, surface defects. Three samples are taken from each incoming billets batch for the billet steel chemical analysis, as well as for macro-structure research. The results of the billet entrance control formalized in the conclusion.
The billet entrance control is a very important operation of technological scheme the grinding balls production, because it identifies defects and allows use just high-quality billet for further production and, as a result, receive high-quality products.