Find the most up-to-date version of ISO at Engineering ISOpdf – Download as PDF File .pdf) or read online. ASTM A method E is sometimes called the Strauss test, and is the same as ISO method A, except for the duration. As 15 hours is a difficult test period .
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For many alloys, the onset is at 0. There are other requirements in these standards over details that are not discussed in this document, and these should be followed, such as conducting bend tests.
ASTM A was designed for austenitic stainless steels, specifically the series alloys. Some standards require the test sample to be aged prior to testing, to simulate the precipitation that might occur during welding.
Intergranular Corrosion Tests for CRAs
ISO is specifically for duplex and all austenitic stainless steels, and recommends ageing at two different temperatures: This test should be avoided for most CRAs, except in the circumstances described below, in section 4. SEP does not require ageing, although it might be required in a specification calling up this standard. More suitable alternatives are offered in Table 5, below. Why were these tests designed? The exception to this is ASTM G28 method A, where rates for the onset of intergranular corrosion are described in reference 1.
Where no specific test is specified, Table 5 suggests the most appropriate alongside a second choice, if the first is declined. Suggested test methods for different corrosion resistant alloys. This means that carbide formation during welding is highly unlikely, and modern CRAs should easily pass one of these tests. Both of these tests should be followed by water quenching.
Some suggested criteria for the listed alloys are shown in Table 2, below. The most convenient size is often a cylinder 10mm diameter by mm long, but other dimensions are possible to suit particular product forms.
For alloys not listed in this standard, it will be necessary to carry out some tests on material in various conditions to determine the threshold. ISO is the most rigorous in terms of defining test methods, and says which alloys should use which test methods as follows: Make an Enquiry Notice: There are a number of recognised tests when it comes to the intergranular corrosion testing of corrosion resistant alloys CRA.
The specifications for bend testing are shown in Table 4. SEP method 3 is a special environment only suitable for the Ni-Mo alloys, as described below, in section 4. Test Samples Samples may be rectangular or cylindrical to suit the test vessel, but where a bend test is required, it is suggested that the sample be a minimum of mm long.
ISO is the most rigorous in terms of defining test methods, and says which alloys should use which test methods as follows:. Hence, it is normally only used for stainless steels intended for nuclear service, or another application involving nitric acid. Methods B and E are suggested for all grades of series austenitic alloys, while method F is suggested for cast type alloys. This document also points out which alloys the tests are intended for, and recommends the most appropriate test when none is specified.
Good material should have a corrosion rate substantially less than the threshold value.
This document describes all three of these tests for four common standards, and describes the differences. The Tests Table 1 below shows the various methods for four common standards: Alternatively, a welded test-piece in the as-welded condition may be tested. It has been used for the duplex stainless steel UNS Swhich has been used for nitric acid cooler tubes.
These tests were introduced when the carbon content in CRAs typically hit 0. Where a standard is included in a purchase specification, this must be followed, although it is advised that unsuitable tests, such as the Huey test for jso and super austenitic stainless steels, are queried.
SEP also gives guidance on which of its methods apply to which alloys: Samples may be rectangular or cylindrical to 36551-2 the test vessel, but where a bend test is required, it is suggested that the sample be a minimum of mm long.
It does not say what to do about duplex or super austenitic alloys.
Selection of a Test Method The test methods in Table 1 were designed with specific alloys in mind, but the proliferation of new CRAs has meant isp the selection of a suitable test method is difficult. For an alloy that is not listed, look for an alloy with a similar composition to a listed alloy to determine the most suitable test. R Baboian, Corrosion Tests and Standards: