2,500 Words Essay on Allowable Deviation in Chemical Composition Analysis of Steel
Introduction
Steel is an important industrial material used in the production of various products including construction, automotive, aeronautics, electrical and electronic equipment, structural components and machine components. Ensuring the steels chemical composition is within the allowable deviation is of utmost importance and thus regular chemistry analysis is necessary. This essay will provide an overview of the allowable deviation in chemical composition analysis of steel. The discussion will include an introduction to chemical composition analysis and the classification of steel, an explanation of allowable deviation in chemical composition, a description of the various accuracy grades of chemical composition analysis, and a summary and conclusion.
Overview of Chemical Composition Analysis and Steel Classification
Chemical composition analysis is a testing method used to determine the chemical characteristics of a sample, including its elemental composition and impurity content. In the industry, chemical analysis is mainly used for the quality control of raw materials and the control of the production process. Steel is one of the most critical materials used in industry and it is classified into four major types – low carbon steel, medium carbon steel, high carbon steel and alloy steel – according to its carbon content.
Allowable Deviation in Chemical Composition
The allowable deviation in chemical composition depends on the requirements of the end-user and the application of the steel. The allowable deviation in the chemical composition is specified in steel standards, such as the ASTM A6/A6M-17 Standard Specification for General Requirements for Rolled Structural Steel Bars, Plates, Shapes, and Sheet Piling and the ASTM A572/A572M-18 Standard Specification for High-Strength Low-Alloy Columbium-Vanadium Structural Steel. The allowable deviation is also specified in company standards and customer specifications.
For example, the allowable deviation in carbon content is usually specified as a percentage of the nominal value; for silicon content, the allowable deviation is usually 0.20 or 0.50; for manganese content, the allowable deviation is usually 0.10. The allowable deviation for other chemical elements is typically 0.01-0.05%, with certain exceptions such as sulfur, phosphorus, and oxygen.
The allowable deviation in chemical composition is not uniform for different steel grades, and different uses also require higher accuracy of the chemical composition. For example, pipelines require more accurate chemical composition with small allowable deviation than structural steel.
Grades of Accuracy in Chemical Composition Analysis
Based on the requirements for the accuracy of the chemical composition, chemical composition analysis can be divided into three scales of accuracy – high precision, medium precision, and low precision.
High precision analysis, or Class I analysis, is used in high-end applications such as aerospace and nuclear power plants, where small allowable deviation and trace elements are required. It is the most accurate and reliable type of chemical composition analysis and is performed using the highest accuracy criteria.
Medium precision analysis, or Class II analysis, is used for regular applications with medium accuracy requirements. This type of analysis is only used for steel without secondary phase or other complex elements. Low precision analysis, or Class III analysis, is used for regular applications with low accuracy requirements. It does not require strict accuracy of the chemical composition, but it is still necessary to ensure the quality of the steel.
Conclusion
In conclusion, chemical composition analysis is an important testing method used to ensure the quality of steel and is used in the production of various products in the industry. The allowable deviation in chemical composition depends on the requirements of the end-user and the application of the steel, and accuracy can be graded according to the specific needs of the application. Additionally, the categories of allowable deviation include carbon content, silicon content, manganese content and other elements. Chemical composition analysis is necessary to ensure that the steel’s chemical composition is within the allowable deviation and for the production of high-quality steel products.
