Firstly the different material of hot rolled steel ball(by skew rolling mill) and casting steel ball：
Hot rolled steel ball——low alloy high carbon steel, The finished round steel is produced by formal special steel factory, Its compression ratio is above 10. that means, The finished round steel is through billet hot extrusion using its 10 times volume. for example, if you want to get 100mm finished round steel, you have to use at least 1000mm billet as material to hot roll into the finished steel bar.
Casting steel ball——Waste steel scrap with some proportion alloying element.
There are four different properties of hot rolled steel ball(by skew rolling mill) and casting steel ball because of their different material
1．The principle of forming steel ball hardness is different
A hot rolled steel ball(by skew rolling mill) is making the steel cooling rapidly by its quenching process. Prompted the type of metal organization body into a fairly abrasive hardness martensite structure, So It gets the hardness by quenching.
Casting steel ball get the hardness and abrasive resistance by adding some alloy elements of chromium, The abrasive resistance of casting steel ball is according to the Cr content, The higher abrasive resistance, the higher Cr content, but the cost of casting ball will be higher, Some casting steel ball Cr content can achieve 18%, Its hardness is 60～62HRC, Abrasive resistance is very good, but its price is very high.
2．Density different
Because the material which is used for skew rolling hot rolled steel ball is hot extruded from square steel, and the hot rolled steel ball is also skew rolled from the round steel billet. So the density of the hot rolled steel ball is above 7.85 ton/M3.
Casting steel ball is adopted traditional sand casting process, it is hard to avoid to produce blowhole and sand inclusion inside the casting steel ball, and existing casting slitter edge, So its density is about 7.45ton/M.
3．The different uniformity of quality
Because the hot rolled steel ball adopt finished round steel, Quality unified, The process of hot rolled steel ball is Heating–skew rolling mill–quenching–tempering–Cooling–packing, This process achieve mechanized assembly line work mode, At the same time, Temperature, speed, the, etc technological parameter is follow-up controlled by computer, To ensure the stability of the production quality.
The material of the casting steel ball is waste metal scrap, It’s uneven material, and ingredient proportion, and casting rate of every furnace is affected by the human factor, It is difficult to stabilize the product quality.
4．impact toughness and crush resistance different
Because of the high density of hot rolled steel ball by skew rolling machine, Impact toughness≥12（J/cm2），6m high falling ball test, its fatigue life≥10000 times, So its breakage rate is very low.
Because of the porosity and sand inclusion of casting steel ball, Its impact toughness ≤4(J/cm2), falling ball test can’t be carried out, So its breakage rate is high.
In conclusion, Hot rolled steel balls by skew rolling machine and casting steel balls are two different concepts of steel balls. the performance of hot rolled steel ball by skew rolling machine is better and environmental protection and energy-saving during producing. At last, it will replace the traditional process of casting the ball.
Youtube about skew rolling mill: https://www.youtube.com/user/skewrollingmachine
