The temperature of inelastic transformation of the material

GB150 specifies the water temperature requirements during pressure testing in 10.9.4.3, taking into account the material’s temperature at which ductility loss occurs. Regarding the specific inflection temperature for ductility loss of materials, it is difficult to obtain such information except from material research institutions. In actual design, the material is selected based on the operating temperature and design temperature, by referring to standards such as GB150 and HG20581, along with relevant experience.

Is this question referring to the \"brittle transition temperature\"? If it is the brittle transition temperature, this value varies for different metal materials; in fact, some materials do not have a brittle transition temperature at all. This temperature is usually expressed as a temperature range. This is generally not calculated; for each material, there are usually specific charts available for reference. Definition of the brittle transition temperature according to Baidu: The temperature range at which a metal material changes from a ductile state to a brittle state as the temperature decreases; it is also known as the ductile-brittle transition temperature. Above the brittle transition temperature range, metal materials are in a ductile state, and the mode of fracture is primarily ductile fracture ； Below the brittle transition temperature, the material is in a brittle state, and the mode of fracture is primarily brittle fracture (such as cleavage). The lower the brittle transition temperature, the higher the steel’s resistance to cold brittleness. 　　The brittle transition temperature is determined through a series of impact tests at different temperatures. Depending on the method used for determination, there are various ways of expressing it, mainly: ① Energy criterion method: It is defined as the temperature at which the impact absorption energy (Ak) drops to a certain specific value; for example, the temperature corresponding to Akma×0.4 is often denoted as Tk. 　　② Fracture morphology criterion method: It specifies the temperature at which the relative area of the fibrous region to the crystalline region on the fracture surface reaches a certain ratio; for example, the temperature corresponding to 50% of the total area being occupied by the crystalline region is used, and this is denoted as FATT (Fracture Appearance Transition Temperature). 　　③ Drop hammer test method: The temperature at which 100% of the fracture surface on a rectangular plate-shaped specimen broken by a drop hammer is a crystalline fracture is defined as the temperature of no plastic transformation, denoted as NDT (nil ductility temperature). 　　The brittle transition temperature is related to the method of representation, in addition to other factors. It is also related to the sample size, loading method, and loading speed; different materials can only be compared under the same conditions. In engineering applications, to prevent brittle fracture of components, materials with a brittle transition temperature lower than the minimum operating temperature of those components should be selected. For materials that contain high levels of impurity elements such as nitrogen, phosphorus, arsenic, antimony, and bismuth, and are prone to phenomena like aging embrittlement and temper embrittlement over time, their brittle transition temperature increases as operation time progresses. Therefore, the brittle transition temperature and the increase in the brittle transition temperature have become one of the criteria for evaluating the performance of structural materials.

This post was last edited by ztr1118 on 2011-10-24 at 19:30. The brittle transition temperature is determined through experiments. The brittle transition temperature varies for each material; even for the same material, different thicknesses and different heat treatment conditions result in differences in the brittle transition temperature. There is no such thing as a ductile transition temperature, a brittle transition temperature, or a tough-brittle transition temperature; in engineering terms, these refer to the same concept, just with different names. As for the testing methods, “Lao Wu” upstairs has already explained them in great detail.

This post was last edited by Pinocchio on 2011-10-24 at 22:33. The method standards for these two drop-weight tests can be downloaded from the Internet. ASTM E208 Standard method for determining the temperature of non-ductile transition (NDT) in ferritic materials by drop-weight test. GBT 6803-2008 Method for determining the temperature of plasticity transition of ferritic steels by drop-weight test. GBT 6803 was formulated with reference to E208.

Who can provide information on where I can find data regarding the ductile-to-ductile transition temperature? Is ordinary carbon steel 10, 20 suitable for -40 degrees? What is Q345?

China currently lacks data in this area; relevant testing is underway, which requires a large amount of money. Just wait!

Who knows what the yield transition temperature of S30408 is?

I use it too for pressure testing; the regulatory standards specify an increase of 30 degrees above the temperature at which no ductile transition occurs