High temperature flexural strength of magnesia carbon brick

There are many factors that affect the high-temperature flexural strength of magnesia carbon brick, the most important of which is the purity of raw material, carbon content, binder, matrix composition and organizational structure of magnesia carbon brick. The purity of raw material is relatively simple, the purity of magnesia is high, the crystal scale is large, the low melting point phase content distributed in the periclase grain boundary is low, the direct bonding degree is high, the high-temperature flexural strength is better; the purity of graphite The research on matrix composition, microstructure and other aspects is relatively complex, and it is also the most concentrated research field to improve the high-temperature flexural strength of magnesia carbon brick, which is roughly divided into the following three directions.

1、Add metal powder

In the aspect of improving the flexural strength at high temperature, the metal powders mainly include A1, Si, etc

① Al4C3 and SiC are formed by the reaction of metal Al and Si with graphite and resin carbon in magnesia carbon brick, strengthening the combination of carbon and carbon, and improving the strength;

② whiskers and fibers are formed in MgO-C brick by metal Al and Si, which strengthen the material matrix;

③ The formation of magnesia alumina spinel and the improvement of ceramic bonding

2、In situ formation of carbide, nitride and other whiskers

The improvement of high temperature flexural strength of MgO-C brick is usually achieved by in-situ formation of carbide and nitride whiskers.

Whiskers are generally one-dimensional crystalline materials of nanometer or submicron scale, with few internal defects, and the strength and modulus are close to the theoretical value of crystal materials. At the same time, the net distribution of whiskers in the brick or the pinning and locking effect in the microstructure of MgO-C brick also endow the material with a better mechanical properties Good strength. For example, yijingguang et al. Found that with the increase of heat treatment temperature, the high-temperature flexural strength and residual flexural strength of MgO-C brick added with metal Si powder and Al powder increased, while the flexural strength of the sample after heat treatment at 1400 ℃ was larger.

Through the analysis of microstructure, it was found that there was not only needle like AlN formation in the brick, but also inlaid on the surface of magnesia particles at 1400 ℃, At the same time, there are a large number of SiC whiskers and acicular β – Sin whiskers. In such a microstructure, when the material is subjected to external force, the stress can be transferred from the matrix to the whisker through the interface layer, and the whisker disperses the stress on the matrix and reduces the damage effect.

When the crack size of the sample under the action of thermal stress is small, the whisker plays a bridging role, When the crack increases, the whisker at the crack tip will be further destroyed, and the whisker will be pulled out of the matrix to consume energy. At this time, the pull-out effect will give the magnesia carbon brick high temperature mechanical properties

3、Generation or addition of nano carbon in magnesia carbon brick

Carbon nanotubes are new materials which appear in recent years, and their mechanical properties are very outstanding. Therefore, in the aspect of improving the high-temperature flexural strength and microstructure of MgO-C brick, some scholars have formed carbon nanotubes in the material by introducing catalysts and other ways, and achieved good results.

For example, we ì and other scholars modified phenolic resin and prepared low-carbon MgO-C brick by introducing Fe nano sheets. It is found that doping 0 A large number of carbon nanotubes with a diameter of 50-100nm and a length of micrometer are produced by the MgO-C brick with a mass fraction of. 5%. Compared with the sample without doping Fe nano sheet, the high-temperature flexural strength increases from 8.29mpa to 10.29mpa with a amplitude of about 24%, reaching the highest value. The presence of a large number of carbon nanotubes firmly locks the MgO particles.

When the stress is applied to the blank sample, the For the 0.5% doped sample, when the crack passes through the MgO particles, the carbon nanotubes can absorb and release the stress at the crack tip through the bridging and crack deflection mechanism due to its high strength and toughness.

In addition to the formation of carbon nanotubes in MgO-C brick, nano carbon is also introduced to improve the microstructure of MgO-C brick and improve the high-temperature flexural strength of materials. For example, on the basis of 3% mass fraction of graphite, by introducing different proportions of nano carbon and graphite, the high-temperature flexural strength (hMOR) increases with the increase of nano carbon content, and its value increases from 2.5MPa When it reaches 4.5MPa (0.9% mass fraction) and keeps constant when the nano carbon is further increased, as shown in Figure 21. Further analysis shows that with the increase of the content of nano carbon, the filling and compaction effect is better. At the same time, the nano carbon has very high reactivity and can form carbides at a higher rate when contacting with the gold additive, with stronger binding force and higher strength.

LMM GROUP

Service life and flaw detection standard of cold-rolled work rolls and cold-rolled intermediate rolls

The main links in the manufacturing process of cold-rolled work rolls and cold-rolled intermediate rolls are smelting, forging, heat treatment, processing and inspection.

Cold-rolled work rolls and cold-rolled intermediate rolls have to bear a lot of rolling stress during the working process. In addition, problems such as welds, inclusions, and edge cracks in the rolled piece can easily lead to instantaneous high temperatures, which make the work rolls subject to strong thermal shocks. Cause cracks, sticking, peeling and even scrapping. 

Therefore, cold-rolled work rolls and cold-rolled intermediate rolls must have the ability to resist cracking and spalling caused by bending stress, torsional stress, and shear stress, and also have high wear resistance, high contact fatigue strength, and high Fracture toughness and thermal shock strength, etc. 

Therefore, how to improve the service life of the roll has always been a major problem faced by the roll manufacturing industry.

Non-destructive testing of rolls is usually carried out with ultrasonic flaw detectors. In the flaw detection standards of cold-rolled work rolls and cold-rolled intermediate rolls, the roll body is usually divided into a surface area, a central area and an intermediate area according to the stress, and then the critical size of the allowable defects in each area is specified according to the principle of fracture mechanics. Flaw detectors should have knowledge of roll manufacturing in order to determine the nature of defects, and should also have knowledge of roll use in order to estimate whether these defects may cause service damage under specific conditions of use.

Leading Manufacturer of High-Performance Work Rolls - LMM GROUP 

What is adamite roll？

 

Adamite rolls are a type of rolling mill roll made from a material that combines the properties of both steel and cast iron. They are known for their excellent wear resistance, toughness, and ability to withstand high temperatures, making them suitable for various rolling mill applications. Here are the key aspects of adamite rolls:

Adamite roll Composition and Properties

Material Composition:

Carbon Content: Adamite rolls typically have a carbon content ranging from 1.2% to 2.3%.

Alloying Elements: They contain alloying elements such as chromium, nickel, molybdenum, and vanadium, which enhance their mechanical properties and wear resistance.

Microstructure: The microstructure of adamite rolls consists of a mixture of pearlite and carbide phases, providing a balance between hardness and toughness.

Properties:

Wear Resistance: Adamite rolls have good wear resistance, which helps in reducing roll wear and extending roll life.

Toughness: They exhibit high toughness, making them resistant to mechanical shocks and impacts during the rolling process.

Thermal Stability: Adamite rolls can withstand high temperatures, making them suitable for hot rolling applications.

Hardness: They have a hardness range typically between 40 to 60 HRC (Rockwell Hardness Scale), depending on the specific alloy composition and heat treatment.

Adamite roll Manufacturing Process

Casting: Adamite rolls are produced through a casting process, where molten metal is poured into molds to form the desired shape.

Heat Treatment: After casting, the rolls undergo heat treatment processes such as annealing, quenching, and tempering to achieve the desired mechanical properties.

Machining and Grinding: The rolls are then machined and ground to achieve the required dimensions, surface finish, and profile.

Applications

Adamite rolls are used in various rolling mill applications, including:

Hot Rolling Mills: Suitable for rolling hot metal slabs, billets, and blooms into desired shapes and sizes.

Section Mills: Used in rolling mills that produce structural sections such as beams, channels, and angles.

Bar and Wire Rod Mills: Employed in mills that produce bars and wire rods from billets.

Plate Mills: Used in rolling mills that produce metal plates of various thicknesses.

Roughing Stands: Often used in the roughing stands of rolling mills, where the initial deformation of metal takes place.

Advantages

Durability: The combination of wear resistance and toughness results in long-lasting rolls that require less frequent replacement.

Versatility: Suitable for a wide range of rolling mill applications, including hot and cold rolling.

Cost-Effective: The extended roll life and reduced maintenance requirements contribute to cost savings in rolling mill operations.

Consistent Performance: Adamite rolls provide consistent performance under varying rolling conditions, ensuring high-quality rolled products.

Author: LMM GROUP

LMM GROUP Online Automatic Steel Bar Counting And Separation System

 

1) The counting accuracy of our rebar counting machine is as high as 0.02%.

2) The system could work 24 hours/day continuously, Increasing productivity.

3) The system could control the number/weight of every bundle, and decrease the production cost.

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8) The free warranty period of one year, life-long free update system.

LMM GROUP Online Automatic Steel Bar Counting And Separation System

What is Indefinite Chilled Rolls(IC ROLLS)？

 

The Indefinite Chilled Rolls are manufactured by casting of the iron, This Rolls are cast iron grades containing graphite and carbides in a tempered martensitic matrix. Softer grades contain more graphite and less carbide. The graphite content is responsible for the excellent spall and fire crack resistance.

What is Definite Chilled Rolls？

Clear Chill Iron Rolls or better known as Definite Chill Iron Rolls have white and super-hard working surfaces, made of graphite-free cast iron. Cast iron is manufactured from eutectic carbide and austentite, which impart the quality of extra hardness and make the resultant metal alloy perfectly resistant to any kind of wear and tear.