PROGRAM AND PROCEDURE FOR CREEP AND RUPTURE TESTS ON HIGH-TEMPERATURE MATERIALS MANUFACTURED IN JAPAN

 The creep and rupture properties of materials, expressed as creep-rate, rupture time, etc., vary widely depending upon the kind of material, the testing temperature, and the applied stress. As the knowledge of these properties is important for designing machines which are used under elevated-temperature and high-stress conditions, efforts have been made in many countries to carry out creep and rupture tests based on systematic programs as well as to gather such data as is available on the materials produced in their own countries.

 In Japan the work of generating and collecting creep data has begun rather recently. Collections of data on low alloy steels and stainless steels were published in 1964 and 1968, respectively, by the 129th Committee of the Japan Society for the Promotion of Science. A collection of data on welded joints was published by the High Pressure Institute of Japan in 1967. The Japanese data collected at the request of ISO by the Committee on Creep of the Iron and Steel Institute of Japan are contained in a 1967 ISO publication.

 These data, however, are the results of tests conducted by steelmakers and fabricators for their own purposes and are not the results of a systematic test program. Therefore, it was felt highly necessary to carry out a systematic program of creep and rupture tests for defining more exactly the properties of materials in practical use.


 Since its establishment in 1956, the National Research Institute for Metals has been especially active in research on the high-temperature properties of metallic materials. Complying with the above situation, a systematic and coordinated test program for the preparation of creep data sheets was planned at NRTM in 1964. The plan was to obtain creep and creep-rupture strengths up to 100,000 hrs by actual long-term tests on high-temperature materials produced in Japan.

 To carry out this program a new creep laboratory was built at NRIM in 1967 and the installation of testing facilities was completed in 1968. The creep testing facilities of this laboratory comprise 900 single-specimen tensile creep testing machines (0.3, 0.75, 1.5, 3, and 5 ton loading capacity), 150 multi-specimen tensile creep-rupture testing machines with 12 or 18 test specimens for each machine, about 50 testing machines of other types including some with 50 ton loading capacity, internal pressure (biaxial stress) creep testing machines, and 10 ton stress relaxation testing machines. The total number of these machines is about 1,100 which corresponds to about 3,500 testing points. The laboratory is equipped with air conditioning and power generating units of 2,500 KVA are available in case of a failure of the normal power source.

 According to the program the tests were started in 1968, and the program is now under way with regard to 32 kinds of steels as shown in the appended Table. Included are 6 kinds of plate steels, 12 kinds of pipe and tube steels, 4 kinds of forgings and bars, 2 kinds of cast steels, and 8 kinds of heat-resisting alloys.

 The items of testing for the program, such as the steel types, manufacturers, manufacturing conditions, typical use, dimension and product form of the materials sampled, the position within the product where the specimens were collected, test temperature, and test duration, were decided considering the opinion of the Committee on Creep of the Iron and Steel Institute of Japan.

 At present, for 6 among the 32 steel types, data up to 10,000 hr rupture times have been obtained and they are continuing in long-term creep-rupture tests aimed at 30,000 and/or 100,000 hr rupture times.

 These long-term creep data obtained at NRIM will be published as the results of the 10,000, 30,000, and 100,000 hr tests for each kind of material are obtained.