Experimental design of tube steels characterization and validation test at cryogenic temperatures by means of Small Punch Test
Hydrogen is considered an energy vector, that is, a means to store and transport energy. However, hydrogen storage and transportation remain important barriers to the development of a full hydrogen economy due to the conditions it is in (in a liquid state and at very low temperature).
Therefore, the materials and components that are in contact with this medium must be tested at cryogenic temperatures. This is the case of large diameter seamless tubes.
With this development, the work team made up of Tubos Reunidos and AZTERLAN aims to assess the suitability of the Small Punch Test (SPT) to carry out screenings of steels for use in cryogenic conditions.
Authors:
Marcelo López Belver (Tubos Reunidos Group), Itziar Berriozabalgoitia (AZTERLAN), Garikoitz Artola (AZTERLAN).
Keywords:
Steel, behavior, cryogenic temperatures, small punch test, hydrogen.
Small Punch Test
The Small Punch Test (SPT) is a non-destructive mechanical test used to evaluate the mechanical properties of materials. It consists of hitting a small sample with a punch and measuring the resulting deformation. This test is often used when only a small amount of material is available or when traditional tensile testing is not feasible.
During the test, a small punch is pressed against the sample, causing it to deform. Punch force and displacement are measured and from this data mechanical properties such as yield strength, tensile strength and ductility can be estimated.
The Small Punch Test has diverse applications ranging from quality control or material characterization to evaluation of component integrity.
Design of the experimental trial
The research team has designed an experimental test for the characterization and validation of seamless tube materials at the temperature of liquid hydrogen using the Small Punch Test (SPT). The work carried out includes:
- The definition of the test scheme
- The development of specific tooling for the execution of the test
Definition of the test scheme, development of tooling and execution of the test using liquid nitrogen
Results
- It is possible to use the SPT technique to perform screenings of steels for use in cryogenic conditions.
- It has been possible to work successfully down to -196ºC (using liquid nitrogen) and the same concept is in the testing phase for -262ºC with liquid helium (a temperature analogous to that reached by the walls of tanks, valves and conduits in contact with liquid hydrogen )