Common problems of abrasion resistant steel

In recent years, abrasion resistant steel has been widely used in industry and construction. The most famous wear plate in the world is hardox 400 plates, hardox 500 from Sweden.In China more frequently used is the domestic production of NM450 NM500 NM550.Wear resistant plate is characterized by wear resistant, hard and durable. Different grades of wear resistant steel plate have different hardness coefficients, and you need to choose the grade according to the actual application. Compared with ordinary steel plates, wear resistant steel not only has a longer service life, but also more environmentally friendly, which is the trend of the development of the steel industry. In this article I will introduce wear resistant steel and common problems of it.

Types of abrasion resistant steel

High manganese steel

High manganese steel refers to alloy steel with manganese content above 10%. Typical steel grades are Mn13, Mn12, Mn17, etc. The steel is generally treated with solid solution water toughness to improve the toughness and wear resistance of the material. Suitable for high impact wear conditions.

Low alloy wear-resistant steel

Low alloy wear-resistant steel refers to alloy structural steel based on the development of multiple alloying smelting, with the post quenching, low temperature tempering and other means to obtain low-cost wear resistance.

Typical steel grades are hardox400,hardox450,hardox450tuf,hardox500,hardox500tuf,hardox550,hardox600,hardox600extra produced by SSAB of Sweden.

XAR400,XAR450,XAR500,XAR550,XAR600 produced by Germany dillinger hutte.

NM360,NM400,NM450,NM500,NM550,NM600 produced by China Wusteel.

Bulletproof steel apro500,apro550,apro600,arm produced by Liansteel in China.

Surfacing wear-resistant steel

Due to the limitations of the two materials on the surface hardness is difficult to break through 700HRB, in order to cope with the extremely harsh wear environment such as cement plants, glass factories, scrap mills and other needs, manufacturers used in the ordinary steel welding wear-resistant weldments on the method made of surfacing materials are generally based on high chromium content, the finished product surface hardness of up to 700HRB.

Steel Grade Analysis: (8+6) HB700 The thickness of the base plate is 8MM, the thickness of the wear-resistant welding material is 6MM, and the hardness is 700HRB.

Manufacturer of abrasion resistant steel

Wear-resistant steel manufacturers are divided into domestic and foreign, each with different characteristics.

Chinese abrasion resistant steel

Northern steel mills to Wusteel, Ansteel, Baosteel and other enterprises, common grades are NM360, NM400 and so on. Among them, Ansteel strong technical force, participated in the construction of Baosteel and technical assistance, with VD vacuum refining and other technologies to enhance the quality of billet, but also imports of rolling mills and heat treatment equipment, and constantly improve the quality of wear-resistant plate for different customers have a variety of composition and heat treatment process programme, in the tempered steel plate thin specifications plate shape control and thick specifications of the supply of outstanding performance.

The southern steel mill, mainly Shenglong, has an annual output of 16 million tonnes of steel production capacity. Located in the port area of Fangchenggang City, it facilitates the import of raw materials and export of products at competitive prices. It has invested in recycling companies and terminals to promote industrial development and is a high-profile company in south-west China.

Foreign abrasion resistant steel

There are Swedish Oklund (HARDOX series), Japanese steel giants (JFE series, etc.), Germany’s ThyssenKnauber (XAR series), and so on. At present, the highest level of foreign wear-resistant plate is HARDOX Extreme of Swedish Oklund, with an average Brinell hardness of 700HB, advanced technology, and products in the leading position in the industry.

Price

China has rich mineral resources and a perfect iron and steel industry chain, in the production process of wear-resistant plate, the cost of raw material procurement and production and processing costs are relatively low, which makes China’s wear-resistant plate in the price has a strong competitive edge. Compared with similar foreign products, the price of Chinese wear-resistant plate is often more advantageous in the case of comparable performance, which can reduce the procurement cost for users.

Performance

China’s wear-resistant plate manufacturers continue to increase investment in technology research and development, product performance is constantly improved. At present, the wear resistance, strength, toughness and other key indicators of domestic wear plates have reached or are close to the international advanced level, and some of them are even better in specific working conditions, which can provide users with high-performance products at a more reasonable price, and have a higher cost-effective.

Response speed

Chinese wear-resistant plate manufacturers are closer to the domestic market and can respond quickly to the individual needs of customers. For the special specifications and performance requirements put forward by customers, domestic enterprises can organize R&D and production more quickly, shorten the product delivery cycle and meet the urgent needs of customers.

Product customization capability

After years of development, Chinese enterprises have accumulated rich production experience and technical strength, and are able to provide customers with customized wear-resistant plate products according to the needs of different industries and working conditions. For example, for the special abrasion environments of mining, cement, electric power and other industries, we have developed wear-resistant plates with specific abrasion resistance, corrosion resistance or impact resistance, so as to better satisfy the actual use requirements of customers.

Innovation to meet market demand

China’s wear-resistant plate manufacturers closely combine the characteristics and needs of the domestic market to carry out targeted technological innovation. For example, in response to the demand for large-scale mining and transportation in the domestic coal and mining industries, they have developed high wear-resistant and impact-resistant wear-resistant plate products suitable for harsh working conditions, which have strong adaptability and competitiveness in the domestic market, and have also won a good reputation for Chinese wear-resistant plates in the international market.

Common problems of abrasion resistant steel

Process

Oxyfuel cutting

Wear-resistant steels usually have a high carbon content or contain a variety of alloying elements, which reduces the toughness and increases the brittleness of the material at low temperatures. When gas cutting, the cutting area is subjected to high thermal stresses due to rapid heating and cooling. At temperatures below 5 degrees, this thermal stress is more likely to cause cracks in the material. A preheating treatment of 80-200 degrees will increase the material temperature uniformly, reduce the effect of thermal stresses, and improve the toughness of the material so that it can better withstand thermal influences during gas cutting and prevent cracks from occurring in the cut. Slowing down the cutting speed also allows the heat to be transferred more evenly and reduces the concentration of thermal stress.

When cutting small components for a long time, due to the small heat capacity of small components, the heat in the gas cutting process is easy to make the overall temperature of the components rise, and the heat is not easy to disseminate. Wear-resistant steel undergoes organisational transformation at high temperatures, which can lead to a reduction in hardness when the temperature exceeds a certain range and lasts for a long time.

Drilling

Wear-resistant steel has high hardness and strength, ordinary drill bits are easy to wear, and it is difficult to ensure the accuracy and efficiency of drilling. Carbide drill bit with high hardness and good wear resistance can effectively cut on wear-resistant steel and maintain better drilling accuracy and surface quality; HSS drill bit has good toughness and certain wear resistance, is not easy to break in the drilling process, and can withstand certain impact load.

If the working speed is too fast, the cutting force between the drill bit and the wear-resistant steel will increase, generating a large amount of heat, which not only accelerates the wear of the drill bit, but also may make the local temperature of the wear-resistant steel too high, resulting in changes in the material properties, such as reduction of hardness and thermal deformation. In addition, too fast a working speed may also cause the drill bit to be subjected to too much torque, increasing the risk of the drill bit breaking.

Bending

Although wear-resistant steel is hard, it still has a certain degree of plasticity. When sufficient external force is applied, wear-resistant steel can be plastically deformed to achieve bending. However, wear-resistant steels require a greater bending force to overcome their higher yield strength than ordinary steels.

When bending, the inner side of the steel plate is subjected to compressive stress and the outer side is subjected to tensile stress. If the bending radius is too small, that is, the degree of bending is too large, the stress on the inner and outer sides of the steel plate will be too large, more than the material’s ability to withstand, which will easily lead to cracks, fractures and other defects in the bending of the steel plate. For wear-resistant steel such as high hardness, toughness is relatively low material, in order to ensure the quality of bending, to avoid defects, you need a larger bending radius to disperse the stress, so the provisions of the bending radius R to be greater than 5 times the thickness.

Welding

Welding material selection

Different types of wear-resistant steel need to choose a specific welding material. NM450 wear-resistant steel, recommended to use more than 50KG level of electrodes, such as J507; NM500, NM600 need to use 60 – 80KG level of electrodes, also can be used to choose the A102 austenitic electrodes.

Welding process parameters

Gas-shielded welding welding current of 200 – 280A, welding voltage of 25 – 30V, welding speed of 18 – 24m / h. Manual arc welding, submerged arc welding, automatic submerged arc welding, carbon dioxide gas-shielded welding and other welding methods. Manual electric arc welding, submerged arc automatic welding, etc. There are also corresponding preheating temperature and heat input parameters.

Welding operation points

Hand welding, swing not more than 10MM, using multi-layer multi-channel short-pass welding method, so that the weld is repeated within a short period of time to ensure the quality of welding.

Factors affecting welding performance

Chemical composition: the carbon element has the greatest influence on the cold cracking and welding performance of wear-resistant plate, followed by the Mn element, Cr – Mo – V and other elements also have an impact. National standard wear plate copper content shall not exceed 0.3%, boron element can improve the hardenability, but the welding performance has a significant impact on the mainstream steel mills generally avoid adding or a small amount of additive. Welding performance can be assessed through the carbon equivalent formula.

Processing technology: cutting or welding process may be delayed cracks and post-weld cracks, common methods to avoid domestic and foreign pre-cutting and pre-weld preheating, cutting and post-weld cooling, for more than 40mm tempered steel plate and hardness of more than 450HB, 30mm steel plate should be.

Wear-resistant steel manufacturers are divided into domestic and foreign, each with different characteristics. Domestic manufacturers, represented by Wusteel, Ansteel, etc., produce a variety of wear-resistant steel products to meet different needs through their own technological and equipment advantages; foreign manufacturers, such as the Swedish Oklund Company, the Japanese steel giants, etc., with advanced technology, produce high-level wear-resistant plates, which occupy an important position in the global market.

Application

Insufficient wear resistance

Although the wear-resistant steel has high wear resistance, but in some extremely harsh wear conditions, such as high stress impact wear, strong corrosive wear and other environments, the wear resistance of the wear-resistant steel may not be able to meet the use of the requirements, resulting in premature wear and the need for frequent replacement of parts, which increases the maintenance costs and downtime.

Insufficient toughness leading to fracture

Some wear-resistant steel in order to pursue high hardness and wear resistance, may sacrifice a certain amount of toughness. In actual use, when subjected to large impact load or alternating load, wear-resistant steel parts are prone to brittle fracture, resulting in equipment failure and safety accidents.

Corrosion resistance problem

In some working environments containing corrosive media, such as humid mines, chemical production and other places, wear-resistant steel may be corroded, resulting in surface rust, spalling, which not only reduces the wear resistance of wear-resistant steel, but also affects its mechanical properties and service life.

Conclusion

In the future, more wear-resistant steels will be produced for different applications. Wear-resistant steels will become more specialized, and this article will be updated continuously.