Analytical Method of Process Capability for Steel

Abstract

The mechanical properties of steel are the most important factor in the safety of structures that must be stable and appropriate. In order to investigate whether the process capa- bility of steel production meets the quality requirements or not, Sung et al. proposed a procedure to evaluate the production and quality control of steel manufacturing. This evaluation model uses statistics to judge the quality of steel objectively. However, there are various types of steel which can satisfy the engineering requirements of design and con- struction, but procedures are lacking with which to evaluate the multi-process capability of the whole steelwork. In this paper, the objective evaluation methods proposed by Sung and Vannman are modified appropriately and extended by using the principles of statistical inference. A procedure to evaluate the quality of the multi-process capability analysis method is proposed. This evaluation method not only completely evaluates the process capability and quality, but it also improves the production process and quality control capability, and so can reduce production loss. A steel structure is more reliable than a wooden structure or a reinforced concrete structure for resisting earthquake-induced forces (1,2). According to these results, steel will be widely used in the construction industry in Taiwan and Japan. Carbon steel, high strength-low alloy steel and heat treatment-low alloy steel are often used as constructional materials for frame structures. Additionally, in order to promote the earthquake resistance capability of a structure, new steels for construction have been developed such as: low yielding ratio steel; narrow yielding stress variation steel; and low yielding stress steel. To increase the strength and provide special functional characteristics to steel, alloying elements other than carbon are added to produce steels of various yielding stress. Quenching and tempering heat treatment procedures can also be used to obtain higher yielding steel. The key aspects of the production process are puddling and heat treatment after crushing. These techniques affect the mechanical properties of the steel. In order to ensure the quality of the steel, the analyses of chemical composition and mechanical behaviour are tested. The test of steel monotonically loaded in tension is widely used to ascer- tain the quality of steel that has a major effect on the safety of structures. Although there are some analytical methods for evaluating the production process control of steel, there is still a lack of evaluation methods to estimate the efficiency of the production processes control involved. The purpose of this work is to propose a procedure to evaluate the quality and control capability of the multi-processes of steelworks. At this time, many new evaluation methods are continually being developed to enhance the analysis and the evaluation of a satisfactory production process, for the loss function of the production process and for the index of production capability. The technology of engineering quality analysis is very mature for assessing the production capability. Effective methods for evaluating production processes are provided by many workers such as Kane (3), Chan et al. (4), Chou and Owen (5), Boyles (6), Pearn et al. (7), Boyles (8), Greenwich and Jahr-Schaffrath (9), and Chen (10). Sung et al. (11) proposed indices of accuracy and precision to evaluate the quality and tensile strength of steel bars. A new index, the quality index, for the tensile strength of steel reinforcing bars is created to evaluate the production quality and efficiency of steel bar manufacture by combining these two indices. This method is useful for