Standard of the Chromium Alloy Cast Grinding Balls in Building Materials Industry (4)

5.Technical requirements

5.1 The deviate diameter of the casting grinding balls should be accord to the requirements of the Table 1.

5.2 The shape deviation of the cast grinding ball shall be less than or equal to the diameter deviation of the cast grinding ball of the same size

5.3 The chemical composition of the cast grinding ball shall be in accordance with Table 2

   (Table  2 )

Item

Brand Chemical Composition

C

Si Mn Cr Mo Cu V Ti

P

     S

Hi-Cr casting balls

ZQCr17 2. 0-3.2 0.3〜1.0 0- 4~1. 5 (1.6〜2.5) 16 〜19 0~1.0 0〜L2 0-0.3 0 〜0.15 ≤0.10 ≤0. 06
Hi-Cr casting balls ZQCr15 1.8〜3.2 0.3〜1.2 14 〜16 0-1.0 0〜1.2 0〜0.3 0-0.15 ≤0.10 ≤0. 06
Hi-Cr casting balls ZQCr12 1.8-3.2 0, 3〜1.5 11 〜14 0-1.0 0〜1.2 0-0.3 0 〜0.15 ≤0.10 ≤0. 06
Hi-Cr casting balls ZQCr8 2. 1〜3.2 0.5〜2.2 0.5〜1.5 7.0—10 0〜1.0 0-1.2 0〜0.3 0-0.15 ≤0.10 ≤0. 06
 Low-Cr casting balls ZQCr2 2. 0-3- 6 0.3〜1.2 0.5 〜1.5 1.0-3.0 0-1.0 0 〜0.8 0-0.3 0〜0.15 ≤0.10

≤0. 08

5.4 Mechanical Properties of CastingBalls

5.4.1 The surface hardness should be accordance with the table 3

                                 (Table 3)

ITEM

Brand Surface Hardness (HRC)

Quenched (A)

Un-quenched(B)

Hi-Cr casting balls

ZQCrl7 ≥56 ≥48
Hi-Cr casting balls ZQCrl5 ≥56

≥50

Hi-Cr casting balls

ZQCrl2 ≥566 ≥50
Medium-Cr casting balls ZQCr8 ≥52

≥48

Low-Cr casting balls ZQCr2

≥46

5.4.2 The hardness difference of a casting ball along the diameter of the center of the gate on the Cross section from the center of the gate to the center of the ball has specific requirements. For high chrome balls, the difference should be within 2 degrees; for medium and low chrome balls, the difference should be within 3 degrees.

5.4.3 The impact fatigue life of the casting grinding balls: for high chrome balls, the impact value should be equal or over 10 000 times; for medium chrome balls should be equal or over 9 000times; for low chrome balls should be equal or over than 8 000 times.

5.5 The low-power structure of the casting ball is not allowed to have cracks, shrinkage holes, shrinkage porosity, slag inclusion, porosity, segregation and other casting defects that affect the performance.

5.6 The ball breaking rate and ball consumption of the castingball shall be implemented in accordance with appendix A

5.7 The surface quality of the casting balls

5.7.1 Shrinkage holes, casting or heat treatment cracks, severe cold insulation, and wrinkled skin are not allowed

5.7.2 Surface defects allowed for casting balls shall comply with table 4

                                     ( Table 4)

SIZE

The allowable surface defect is not greater than
More meat, less meat at the gate (mm)

Width of sand near gate( mm)

Localized Flash(mm) Holes (not the shrinkage cavity)
Depth

(mm)

Unit area (mm2)

Total area (mm2)

10 ≤SФ≤25

1.0 2.0 0.8 0.5 4 16

30 ≤SФ≤50

1.5 3,0 1.0 1, 0 6

30

      60 ≤SФ≤90                 2.0            4.0             1.0         1. 5             10           45
100≤SФ≤120 2.5 5.0 1.5 2. 0 12

60

NOTE:SФ means the diameter of the balls