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 .
||11 January 2017
|PDF File Size:
|ePub File Size:
||Free* [*Free Regsitration Required]
Just remember that these tests were devised for specific groups of alloys and should not be applied to all CRAs! The Huey test method C is only for molybdenum-free grades, such as L, as alloys with molybdenum show high rates of attack in this test. ASTM G28 does not require samples to be heat treated. ISO is the most rigorous in terms of defining test methods, and says which alloys should use which test methods as follows:.
Intergranular Corrosion Tests for CRAs
For many alloys, the onset is at 0. Table 1 below shows the various methods for four common standards: Good material should have a corrosion rate substantially less than the threshold value. The latter is a German is, but it is often called up in European projects. Where a bend test is required, the sample must be bent over a mandrel of a diameter related to the specimen diameter, without any cracking, as determined by inspection under a low power microscope and a microsection in any suspicious areas.
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.
It can be seen that some alloys fall into two categories, and no guidelines are given for selecting the most appropriate.
The test solutions and exposures for some common intergranular corrosion tests. These tests were introduced when the carbon content in CRAs typically hit 0. It has been used for the duplex stainless steel UNS Swhich has been used for nitric acid cooler tubes. The Tests Table 1 below shows the various methods for four common standards: 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.
This means that carbide formation during welding is highly unlikely, and modern CRAs should easily pass one of these tests. 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 duplex and super austenitic stainless steels, are queried.
This document describes all three of these tests for four common standards, and describes the differences. The effect of post weld surface treatments on the corrosion resistance of super duplex stainless steel welds in sea water ASTM A was designed for austenitic stainless steels, specifically the series alloys.
Alternatively, a welded test-piece in the as-welded condition may be tested. Make an Enquiry Notice: Suggested test methods for different corrosion resistant alloys. 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.
There are a number of recognised tests when it comes to the intergranular corrosion testing of corrosion resistant alloys CRA. Get in Touch Contact us by Phone or Email to find out how we can help your industry. ISO is the most rigorous in terms of defining test methods, and says which alloys should use which test methods as follows: 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.
Conducting the Tests When a test has been selected, follow the detailed directions in that standard for making up the test solution, the preparation of test samples and the finish to be used.
The specifications for bend testing are shown in Table 4. 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 that the selection of a suitable test method is difficult. The test methods in Table 1 were designed with specific alloys in mind, but the proliferation of new CRAs has meant that the selection of a suitable test method is difficult. R Baboian, Corrosion Tests and Standards: Some standards require the test sample to be aged prior to testing, to simulate the precipitation that might occur during welding.
SEP also gives guidance on which of its methods apply to which alloys: When a test has been selected, follow the detailed directions in that standard for making up the test solution, the preparation of test samples and the finish to be used. ASTM G28 was designed for nickel-based alloys, and a list of applicable alloys for methods A and B is in the standard.
Where no specific test is specified, Table 5 suggests the most appropriate alongside a second choice, if the first is declined. This test should be avoided for most CRAs, except in the circumstances described below, in section 4. Methods B and E are 365-12 for all grades of series austenitic alloys, while method F is suggested for cast type alloys. The most convenient size is often a cylinder 10mm diameter by mm long, but other dimensions are possible to suit particular product forms.
Hence, it is normally only used for stainless steels intended for nuclear service, or another application involving nitric acid. The exception io this is ASTM G28 method A, where rates for the onset of intergranular corrosion are described in reference 1. 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.
All bend tests require a tensile test machine or similar, with suitable grips and sufficient strength to bend the strongest alloy. This document also points out which alloys the tests are intended for, and recommends the most appropriate test when none is specified.
Bend test criteria for several standards. ISO is specifically for duplex and all austenitic stainless steels, and recommends ageing at two different temperatures:. It does not say what to do about duplex or super austenitic alloys. Why were these tests designed?
More suitable alternatives are offered in Table 5, below. None of these are identical and cross substitution of results is not possible.
ASTM G28 method B is a more aggressive test than method A and is intended for more corrosion resistant alloys, as listed in the document.