Steels continued ferritic, martensitic

Grade 91 steels and their equivalents, along with some other conventional ferritic-martensitic steels, are implemented in the major structural design codes in the world, such as the ASME Code, RCC-MRx, and the JSME Code. These codes are continuously improving their provisions to further meet the requirements of Generation IV projects. The current major issue on ferritic-martensitic steels application is the extension of time-dependent allowable stresses to 500,000 h. In conjunction with this, provisions on items that involve time-dependent material properties such as weldment... 

Austenitic steels are produced as castings, ingots of all sizes and as continuously cast billets and slabs. The other types of stainless and heat resistant materials mentioned in table 4.1 are cast predominantly as ingots of a moderate size, although martensitic and ferritic-austenitic steels are also commonly used as castings. 

Fig. 3.1-113 Continuous-cooling-transformation (CCT) diagram for a 4130 grade low-alloy steel. Acs and Ac signify the temperatures of the y/ y+a) and eutectoid reation, respectively. A - austenite, F - ferrite, B - bainite, P - pearlite, M - martensite. The cooling rate is measured at 705 °C. The calculated critical cooling rate is 143 K/s [1.80]...

ConcBpt Check 10.4 Briefly describe the simplest continuous cooling heat treatment procedure that would be used to convert a 4340 steel from (martensite + bainite) into (ferrite + pearlite). 

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