Cast Iron Railway Brake Block Sand Casting
There're two types of cast iron brake block, normal type and high phosphorous cast iron brake shoe. The difference lies in the content of the phosphorus. The P content in normal type is 0.7-1.0%, while in high phosphorous cast iron brake block, the P content is above 10%.
The wear resistance of high phosphorus cast iron brake is 1 times bigger than normal type. Practice shows that the life span of high-phosphorus brake block is 2.5 times of the normal type.
High phosphorus brake block is also characterized by little spark.
The friction coefficient increases with the increasing of phosphorus content, so the friction coefficient of high phosphorus brake brake is greater than the normal type.
However, the high phosphorus content will increase the brittleness, so when the phosphorus content is above 1%, there may be crack, so it requires a backing plate for high phosphorous brake block.
Cast iron brake block has been in use on railway vehicles for more than a century in history. The main advantages of cast iron brake block are:
1. a small friction coefficient affected by the environment and more stable, so it is "all-weather" operational;
2. good thermal conductivity, low thermal damage to the wheels;
3. The coarsening of the wheel surface can obtain more adhesion, which can reduce the mechanical abrasion of the wheel;
4. Durable, low prices.
But the friction coefficient of ordinary gray cast iron brake shoe is small, and with the increase of friction velocity, friction coefficient decreased rapidly especially when it is in high-speed running.
So ordinary cast iron brake shoes are generally used for low-speed operation of passenger trains.
For cast iron brake used in high speed train, we can improve the performance by increase the content of phosphorus or add some alloy element.
In fact, it is the high phosphorus cast iron brake block that is widely used now, to avoid the crack, a backing plate is used to reinforce.
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