The experienced drivers have seen the car ruts to rough and hard stones, walls, poles, etc. Paint off is no big deal, what matters is that steel plates are worn.
However, the dump truck pulled hundreds of tons of stones and slammed it out. The cars were running well for years, but the ordinary cars were worn off and rubbed off in one accident. Why?
This will lead to concept of Abrasion Resistant Steel Plate, (wear-resistant steel)? What are the indicators? What are the grades?
what is wear-resistant steel?
Wear-resistant steel is a general term for steel materials with high wear resistance. It is also called abrasion resistant steel, Wear-resistant steel is the largest amount of wear-resistant materials available today.
There are also many methods for classification of wear conditions. If divided according to wear mechanism, it can be divided into abrasive wear, adhesive wear, corrosion wear, erosion wear, contact fatigue wear, impact wear, fretting wear and so on.
Different wear-resistant steels for different use scenarios, such as the body of the dump truck that is resistant to sliding and impact friction, is a kind of wear-resistant shaft and bearing that rotates at high speed for a long time, and of course there are other types of wear-resistant steel. Today we mainly introduce wear-resistant steel for construction machinery used in dump trucks and coal mine scraper conveyors.
Some people may ask, is wear resistance important? As a simple example, for scraper conveyor used in coal mines, the damage caused by the wear of the central trough is 200 billion RMB per year.
Performance Properties of wear-resistant steel
- Hardness Wear-resistant steel for construction machinery, it is required to have high performance characteristics such as high wear resistance, high toughness, impact resistance, easy welding, and easy forming. The main indicator of wear resistance is surface hardness. The higher the hardness, the better the wear resistance. Compared with NM450 and Q345B, the hardness is only increased by 3 times, but under the same working conditions, the average service life is increased by 6-8 times.
- Wear resistance test Compared with the ring block wear test (ASTM G77-05), the wear volume of Q345B is 30 times that of NM400. That is to say, the 30mm thick Q345B steel plate is worn through, and the NM400 is worn away by 1mm. It can be seen that if there is only sliding friction, no impact and other wear, the wear-resistant steel has extremely strong wear resistance.
- Impact resistance Since the impact is mentioned, the NM wear-resistant steel plate has good impact toughness, and the ability to resist dents is significantly better than that of ordinary structural steel when subjected to heavy impact. This property is suitable for the production of dump truck compartments and is suitable for thinning of steel plates. According to the comparison and design of different models, the wear-resistant steel is used as the dumping car body, and the car body is reduced by 30-50%.
What is the concept of 30-50% reduction of the car?
According to the data of a certain ordinary dump truck, the use of wear-resistant steel vehicle has reduced 3.215 tons, and the annual driving cost is 20,000 kilometers. The freight can save 3.2 $/km, and the annual freight cost is nearly 1400 $/car. The reason for pulling and running is that the actual benefits are even higher. According to the statistics of the special car association, it can generate more than 4285$ per vehicle per year.
Moreover, considering the working conditions of the car, the use of wear-resistant steel will be longer, compared with the self-unloading mine car on a coal mine, after 15 months of use, the use of wear-resistant steel body thinning is minimal.
Test of Q345 and NM400 Steel on Dump Truck
According to Steel Mill experiment, a special car factory in China originally used steel plate Q345 to manufacture a wide-body type dump truck with a thickness of 20mm and a thickness of 16mm. The thickness of the bottom plate was reduced to 10mm after the design of NM400 wear-resistant steel. The thickness is 8mm.
When the sample car was put into use on the mine for about 3 months, the thickness of the bottom plate was measured and compared. The bottom plate made of NM400 wear-resistant steel was thinned by 0.3mm, while the Q345B put into use at the same time was thinned by 3mm. 10 times that of ordinary structural steel.
Of course, high strength is also the main performance index of wear-resistant steel. Without high strength, there is no high impact resistance and hardness. However, even if the yield strength of wear-resistant steel exceeds 1000 MPa, the low-temperature impact toughness of -40 °C can still reach more than 20J. This allows construction machinery vehicles to be safely used in a variety of harsh natural environments.
