Non-metallic inclusions in GCr15SiMn steel

Abstract

The GCr15SiMn steel is a kind of low carbon steel – chromium bearing steel grade. It has been widely used in the production of mechanical components due to its good mechanical performance and wear resistance. It is well known that the nonmetallic inclusions in the GCr15SiMn steel have great influence on its properties. Subsequently, this paper carries out a comprehensive research on the nonmetallic inclusions in the GCr15SiMn steel. Its various nonmetallic inclusions and its effects on mechanical properties are introduced firstly. Then, the formation mechanism of the nonmetallic inclusions in the GCr15SiMn steel is discussed from the oxidation rate and inclusion shape. Furthermore, the measuring methods and influencing factors of nonmetallic inclusions in the GCr15SiMn steel are elaborated. The purpose of this paper is to provide useful reference for further research and production of GCr15SiMn steel.

Keywords： GCr15SiMn steel; Nonmetallic Inclusions; Mechanical Properties

Introduction

GCr15SiMn steel is a low carbon bearing steel grade. It is often used in the production of mechanical components such as bearings, and due to its superior mechanical properties and wear resistance, it is quite popular in this industry. However, it is well known that the nonmetallic inclusions in the GCr15SiMn steel have great influence on its properties. Some studies have shown that the number, distribution and chemical composition of nonmetallic inclusions in the GCr15SiMn steel are decisive factors of its mechanical behaviors. Manufacturing process, casting environment, etc. are common influencing factors of nonmetallic inclusions in the GCr15SiMn steel. Therefore, the research of nonmetallic inclusions in the GCr15SiMn steel is essential for further research and production of GCr15SiMn steel.

Classification of Nonmetallic Inclusions in GCr15SiMn Steel

Nonmetallic inclusions in GCr15SiMn steel are mainly classified as oxide inclusions, sulphide inclusions, silicate inclusions and miscellaneous inclusions. The oxide inclusions are mainly composed of iron oxide, manganese oxide, calcium oxide, titanium oxide and rare earth oxide. In general, they have round or ellipsoidal shape, and have red, gray or white color. The sulphide inclusions are mainly composed of iron sulphides, manganese sulphides and calcium sulphides, and usually take the form of network. The silicate inclusions are mainly composed of calcium silicates and aluminium silicates, and usually take the form of plates or block. The miscellaneous inclusions include nap whorls and nonmetallic materials, such as precipitates and dust particles.

Effects of Nonmetallic Inclusions in GCr15SiMn Steel

The nonmetallic inclusions in the GCr15SiMn steel have great influence on the mechanical properties. First, the nonmetallic inclusions affect the fatigue strength of the GCr15SiMn steel. The larger the number and diameter of nonmetallic inclusions in the GCr15SiMn steel, the lower the fatigue strength. Second, the nonmetallic inclusions affect the wear resistance of the GCr15SiMn steel. The heavier the nonmetallic inclusions deposits on the GCr15SiMn steel, the lower the wear resistance. Third, the nonmetallic inclusions in the GCr15SiMn steel can also affect the toughness of the steel. The more nonmetallic inclusions in the GCr15SiMn steel, the lower its toughness.

Formation Mechanism of Nonmetallic Inclusions in GCr15SiMn Steel

The nonmetallic inclusions in GCr15SiMn steel are mainly formed in three ways: first, the nonmetal oxides are generated by the activity of oxygen-bearing compounds in air; second, when the temperature is too high, the reaction between nonmetallic elements and oxygen will take place, which will generate various nonmetallic oxides; third, the nonmetallic inclusions are generated by the reaction between different elements.

The reason why the oxide inclusions are dominant in GCr15SiMn steel is mainly reflected in two aspects. On the one hand, the oxidation rate of Mn-C-Si and Ce-used alloy steel is fast when they encounter oxygen in high-temperature molten steel. On the other hand, molding process requires the steel to be in a fully continuous liquid state. Therefore, the amount of oxygen dissolved in the molten steel is enough to cause oxidation reaction, resulting in various oxide inclusions.

Measuring Methods of Nonmetallic Inclusions in GCr15SiMn Steel

The measuring method of nonmetallic inclusions in GCr15SiMn steel is mainly optical microscope method. First of all, the steel with different carbon content is heated and then cooled with the water, so that it can be observed under the light optical microscope. Then, the number and size of nonmetallic inclusions in the steel can be counted, and the detailed information of the shape, size, quantity and composition of the inclusions can be obtained.

Influencing Factors of Nonmetallic Inclusions in GCr15SiMn Steel

The influencing factors of nonmetallic inclusions in GCr15SiMn steel are mainly related to the manufacturing process, casting environment, metallography and chemical composition of the steel.

The manufacturing process is an important factor affecting the nonmetallic inclusions in GCr15SiMn steel. First, appropriate casting temperature and casting speed should be selected to ensure that enough oxidation time of the nonmetallic elements in the steel can be provided; second, it is necessary to ensure that the cooler is clean and pollutants are prevented from entering the GCr15SiMn steel; third, the flow speed of the molten steel should be slow, which is favorable for the assembly and growth of nonmetallic inclusions.

The other important influencing factor of nonmetallic inclusions in GCr15SiMn steel is the casting environment. In order to reduce the number of nonmetallic inclusions in the GCr15SiMn steel, the casting environment should be kept at a low oxygen partial pressure and kept clean to avoid the pollution of dust, iron oxide and other pollutants.

Conclusion

In conclusion, the nonmetallic inclusions in GCr15SiMn steel have great influence on its properties, so it is important to research and properly control the nonmetallic inclusions. This paper has comprehensively expounded the classification, effects, of nonmetallic inclusions in GCr15SiMn steel, formation mechanism, measuring methods and influencing factors. It is hoped that this paper can provide useful reference for the further research and production of GCr15SiMn steel.

GCr15SiMn steel is non-magnetic, chammfered and heat treatable. It is a low-alloy chromium steel with a high carbon content that makes it stronger than carbon steel but still ductile and resistant to fatigue. Its physical properties make it ideal for applications such as gears, valves and pumps.

GCr15SiMn steel is a fairly low-alloy steel and its various components include iron, carbon, manganese, silicon and chromium. The chromium content makes this steel corrosion and wear resistant, whereas the addition of manganese and silicon gives it some strength and flexibility. It is also easy to weld and heat treat.

GCr15SiMn steel is prone to contain non-metallic inclusions, which can affect its performance. These inclusions may be present due to the added material or may form due to stress and strain during production. Non-metallic inclusions are decreases the toughness of the steel, reducing its yield strength and making it more brittle.

In order to reduce the effect of non-metallic inclusions on GCr15SiMn steel, several steps must be taken throughout production. Various deoxidation methods should be incorporated to reduce the amount of oxygen present when the steel is being formed, reducing the likelihood of inclusions forming. Proper alloy composition must also be maintained and grain size should be minimized. The steel should not be overworked and the cooling rate should be properly controlled.

With the right precautions and proper production methods, GCr15SiMn steel can be used in many applications and industries. Its excellent strength and formability, resistance to wear and corrosion, and easy machinability make it an ideal choice for many manufacturing needs.