Our casting grinding steel ball can be divided into three categries including the high chromium type, medium chromium type and the low chromium type.
Casting grinding steel ball is made of the scrap steel, scrap metal and other waste scrap which is melted by the heating of intermediate frequency electric furnace. In the melting process, the amount of precious metal alloy (such as iron, manganese, vanadium etc.) is added into the furnace for chemical composition. Then pour the qualified molten iron into the production line mold of steel ball when temperature of molten iron reaches more than 1550℃and the molten iron meets other technology requirements.
1. The Quality Index of the High chromium Type. The chromium content of the high chromium type product is greater than or equal to 10.0%. And the carbon content is between 1.8% and 3.2%. It is required by the national standard that the hardness of the high chromium type product must be no less than 58HRC, and that the impact value should be greater than or equal to 3.0J/cm2. This type of product must go through the hot quenching and the tempering treatment to come up to th hardness. 2.The Quality Index of the Medium chromium Type. The mediumchromium type casting grinding steel ball is defined as the chromium content ranging from 3.0% to 7.0%, and the carbon content coming between 1.8% and 3.2%. Its impact value should be less than 2.0J/cm2. The national standard requires the hardness of this type of product should be greater than or equal to 47HRC. For ensuring the quality, the medium chromium type of product should be processed with high temperature tempering to eliminate the casting stress.3.The Quality Index of the low chromium Type.Generally,the low chromium type casting grinding steel ball contains the chromium with the content of 0.5% to 2.5%, and the carbon with content ranging from 1.8% and 3.2%. Accordingly,in line with the nation standard, the hardness of the type product should be no less than 45HRC and the impact value should be no less than 1.5J/cm2. The low chromium type product also needs high temperature tempering treatment to guarantee the quality. The treatment can eliminate the casting stress. If the steel ball has dark red surface, it has gone through the high temperature tempering treatment. If the surface still shows the metal color, the steel ball is not treated with high temperature tempering.
Casting steel ball is mainly used in cement plant, chemical plant, power plant, quartz sand factory, silica sand factory and other dry grinding field.
High performance and low cost, wide application range, especially in cement industry as the representative of the dry grinding field
Inspection of raw materials—-Materials ratio—Heating and melting of Intermediate frequency furnace—Pouring into mold— Quenching—-Tempering—-Testing—Package
1.The standard chemical components of casting steel ball.
|Code||Chemical Composition（Mass Fraction），℅|
2.Nominal diameter, allowable deviation, the maximum diameter and the minimum diameter
|Allowable deviation of diameter||+2.0 -1.0||+2.0 -1.0||+3.5 -1.0|
|Difference of the maximum diameter and the minimum diameter||≤1.8||≤2.4||≤3.0||≤3.6||≤4.2||≤4.6|
3.Mechanical Property of casting steel ball
|Code||Surface Hardness||Impact Test||Impact Fatigue Life|
Notes:1. The ball with diameter 100mm is used in impact fatigue test; the test height is 3.5m; the impact times of the ball with other diameter are calculated by this formula, Nx=N*100/D, N is time. 2. The impact toughness and impact fatigue life index is not treated as delivery basis.
Surface Quality1. It is not allowed that crack, obvious porosity, slag inclusion, shrinkage, cold insulation, wrinkled skin and other casting defects exist on the surface.2.Allowed defects on ball surface
|Nominal Diameter||Allowed Surface Defects mm|
|Spare Part on Gate||Sand Dipping Area||Residual Side||Depth||Single Hole Area||Total Area|
Internal qualityIt is not allowed that crack, obvious porosity, slag inclusion, shrinkage, cold insulation, wrinkled skin and other casting defects exist on the section which goes through center of gate and sphere.Test Method and Rules1.Impact test: cutting 10mm×10mm×55mm part through gate in ball as sample2.Rockwell hardness specimen preparation: The surface of the ball takes the test after grinding to platform, and the grinded thickness is 1.5 – 5mm.3. Chemical composition test: when the volume smelting furnace more than 0.5 tons, we should check the chemical composition furnace by furnace; when the volume smelting furnace not more than 0.5 tons, we should check the chemical composition once per shift. Once there is one furnace unqualified, we need to sample double furnace for test. If there is still one not qualified, this branch of balls is unqualified.4. Surface hardness test: sampling from different location of each batch of heating furnace, the number of the ball≥ 5.Once there is one unqualified, we need to sample double balls for test. If there is still a ball not qualified, this branch of balls is unqualified.5. Internal quality detection: we sample 1 largest size casting iron grinding ball in 100 tons the same type cast iron grinding ball of each continuous production. Once there is one unqualified, we need to sample double balls for test. If there is still a ball not qualified, this branch of balls is unqualified.