■ Chemical Constituents
Material Science
|
Chemical Constituents (wt%)
|
|
C
|
Si
|
Mn
|
P
|
S
|
Cr
|
v
|
Ti
|
Cu
|
| B2 |
|
0.70-1.20 |
0.80-1.00 |
≤0.030 |
≤0.035 |
0.20-0.50 |
≤0.1 |
≤0.1 |
≤0.1 |
| B3 |
0.45-0.70 |
0.30-1.20 |
0.40-1.00 |
≤0.030 |
≤0.035 |
0.20-0.50 |
-- |
-- |
|
| B4 |
0.075-1.05 |
0.12-0.32 |
1.05-1.15 |
≤0.025 |
≤0.025 |
0.5-0.6 |
- |
- |
|
■ Size And Allowable Deviation
Permissible Diameter/mm
|
≤50
|
60-95
|
100-120
|
≤50
|
|
Allowable Deviation /mm
|
+2
-3
|
+2
-3
|
+3
-4
|
+2
-3
|
|
Roundness/%
|
≤2
|
≤3
|
≤4
|
≤2
|
■ Technical Requirements
The mechanical properties of grinding balls should meet the requirements of Table 3.
Table 3 Mechanical properties of grinding balls.
Code Name
|
Fatigue Life of Falling Ball Impact
|
Rockwell Hardness (HRC)
|
Impact Toughness Ak(J)
|
Surface Hardness/HRC
|
Core Hardness/HRC
|
|
|
H40
|
≥8000 times
|
61-63
|
≥60
|
≧12
|
|
H50
|
≥8000 times
|
61-63
|
≥60
|
≧12
|
|
H60
|
≥10000 times
|
60-63
|
≥60
|
≧12
|
|
H65
|
≥13000 times
|
60-63
|
≥59
|
≧12
|
|
H70
|
≥13000 times
|
60-63
|
≥59
|
≧12
|
|
H75
|
≥13000 times
|
60-63
|
≥59
|
≧12
|
|
H80
|
≥20000 times
|
60-63
|
≥59
|
≧12
|
|
H85
|
≥20000 times
|
60-62
|
≥59
|
≧12
|
|
H90
|
≥20000 times
|
60-62
|
≥59
|
≧12
|
|
H95
|
≥20000 times
|
60-63
|
≥59
|
≧12
|
|
H100
|
≥20000 times
|
60-63
|
≥58
|
≧12
|
|
H120
|
≥20000 times
|
59-62 |
≥58 |
≧12 |
■ Broken Ball Rate
The crushing rate should be less than 1%.
■ Surface Quality Of Grinding Ball
◆ No cracks and serious folding or lack of meat are allowed on the surface of grinding balls.
◆Scar, pitting, depression and abrasion on the surface of grinding ball should not be larger than the diameter tolerance specified in Table 1.
■ Test Methods
◆ The numerical modification method is carried out according to G B/T 8170.
◆ The surface defects of steel balls are not allowed to be observed and inspected by naked eyes.
The hardness test of 6.5 hardness (HRC) was carried out according to GB/T 230.1. When the sample is prepared by WEDM or EDM, the surface of the ball should be ground into a platform for inspection. The thickness of the ball should be 0.2mm-0.5mm.
◆ Shock impact fatigue life test is carried out according to the method specified in Appendix C of this standard.
◆ The impact test was carried out with 10 mm xl0 mm x55 mm non-notched sample on the product body according to GB/T 229.
■ Inspection Rules
◆ Hardness testing is carried out according to GB/T 230.1. Specific sampling and testing methods are as follows: 6 steel balls are sampled in each batch. The core-pulling strip method was used to cut into 10.2 mm *10.2 mm strips and grind them flat to 10 mm *10 mm. A plane was drawn for core, 3/4R, 1/2R, 1/4R and edge HRC hardness test. The hardness values were measured three times at each point and recorded. After inspection, one forged ball is not qualified, and the deviation is less than 95% of the minimum value. Double steel balls should be allowed for re-inspection. If there is still one unqualified steel ball, and the average hardness value still meets the requirements of Table 3, it should be judged as qualified, otherwise the batch is unqualified.
◆ For the determination of chemical composition of grinding spheroidization, the steel balls should be sampled in batches. If the samples are not qualified, the samples should be double sampled and re-examined. If there are still unqualified samples, the batches will be unqualified.
◆ The allowable deviation of diameter, roundness and surface defects of grinding balls are sampled according to GB/T 2828.1.
◆ The quality of products shall be inspected by the company's quality control department or a third-party inspection institution.
■ Packaging, Marking, Transportation, Storage and Quality Certificate
◆ Grinding balls can be packed in woven bags.
◆ When long-distance transportation is carried in bulk, the type and specifications of balls shall be marked with signs in the carriage. When packing and transporting, it should be marked on the surface of the package:
a) The name, address and arrival of the demander;
b) Types and specifications of steel balls;
c) packing number;
d) Gross and net quality;
e) Name and address of the supplier.
◆ Each batch of ex-factory products shall be accompanied by a certificate of quality indicating:
a) marks;
b) Types and specifications;
c) Batch number and batch size;
d) Test results;
e) Number of this batch.
Appendix B
(Information Appendix)
Metallographic grade, allowable diameter deviation and mechanical properties of forged ball.
