High temperature materials

Through pre-normative projects, the Belgian Welding Institute contributed to implement high temperature steel materials in the harmonised standards EN10216: "seamless steel tubes for applications under pressure". The main objective of the research projects was to generate data on base materials and welded joints as input for European standards.

Overview of the pre-normative research projects:

  • 2002-2003 "New generation 2¼ Cr steels – Weldability and high temperature properties" (T23/T24)
  • 2004-2005 "New generation of 12Cr steels – Weldability and high temperature properties" (VM12)
  • 2009-2010 "New generation austenitic steels – Weldability and high temperature properties" (Super 304HCu 304H/DMV)
  • 2011-2012 "New generation austenitic steels – Weldability and high temperature properties" (HR3C/DMV310N)
  • 2013-2014 "New generation nickel alloys – Weldability and high temperature properties" (617Mod/617B)

This resulted in the introduction of e.g. T23 and T24 (7CrWVNb 9.6) (7CrMoVB 10.10), and also T/P92 (X10CrWMoVNb 9.2). This is important for the Belgian manufacturers who wish to use these steels. After the implementation of these materials in this standard, manufacturers don’t need to prove that their product meets the requirements of the PED directive (Pressure Equipment Directive). This directive specifies the essential safety requirements to be met by new installations under pressure. The results of previous standards projects were internationally published and presented.

9% Cr Martensitic Steel T/P92 currently has the highest creep strength of all ferritic steels and is suitable for steam temperatures up to 620°C in non-corrosive environments. In superheater tubes, in addition to steam oxidation and creep strength, also the high temperature corrosion plays an important role. The maximum application temperature for T/P92 is 580°C in superheater tubes. The 12% Cr steel VM12-SHC (commercial name for VM12) developed within COST536 by Mannesmann & Vallourec, is by its high chromium content more resistant to oxidation and corrosion than T/P92 and is suitable for higher steam temperatures, but has a lower creep resistance than T/P92. For reheater tubes, austenitic steels, such as Super 304H (X10CrNiCuNb18-9-3) and HR3C (X6CrNiNbN25-20), are therefore required.

Previous standards projects have contributed to the implementation of the newer ferritic steels. Now that these ferritic steels have found their way to industrial applications, it has also become clear which heterogeneous material combinations in welded joints with austenitic steels will be used now or in the near future. The use of intermediate parts from nickel alloy 617mod is an possibility.

The above projects are part of the long research strategy of the research center of the Belgian Welding Institute in the domain of the high temperature materials and could count on a broad industrial interest.

 
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