Section 3 Approval test programme

3.1.1 Generally, the initial approval test programme is to be carried out on at least two casts of each product selected for approval testing. The testing is in respect of specific types of products and if, for example, a works requests approval for both plates and sections or bars, it will be necessary to carry out tests on two casts rolled into plates and two casts rolled into sections or bars.

3.1.2 The dimensions of the products from each cast submitted for approval tests are to be representative of the range which will be manufactured and should include at least one batch of material of the maximum thickness and width or diameter which it is proposed to supply, i.e. material where the amount of hot working is at the minimum value proposed by the manufacturer. If an example representing the maximum width or diameter cannot be included, then agreement needs to be made on the maximum width or diameter that will be granted manufacturing approval based on the samples supplied.

3.1.3 With the exception of hot coiled strip, approval tests are to be carried out on a minimum of two rolled products of different thickness or diameter from each cast. For plate, wherever possible, these tests are to be carried out on one plate 15–20 mm thick and on another of the maximum thickness that will be produced, up to 40 mm. If specified through-thickness properties are required to be approved, wherever possible the tests are to be carried out on one plate of approximately 25 mm thickness and on another of approximately 40 mm thickness. For ingot cast material, one plate is to be representative of the top of the first ingot and the other is to be representative of the last ingot from the ladle. Similarly, for continuous casting, one plate is to be representative of the beginning of a cast and the other of material poured when the ladle is nearly empty.

3.1.4 For hot coiled strip, materials for approval are to be taken from two coils selected from different casts. The coils selected are to be representative of material from an ingot top end and an ingot bottom end or, in the case of continuously cast material, from the beginning of one cast and from the end of the other. Additionally, one coil should be of the maximum thickness that it is proposed to supply. In the case of works approval for plate cut from coil, works with a de-coiling plant which is already approved for plate will be allowed a reduction in the number of tests required.

3.1.5 Testing shall be carried out according to Ch 3 Rolled Steel Plates, Strip, Sections and Bars of the Rules for the Manufacture, Testing and Certification of Materials, July 2022, or to an agreed National Standard or proprietary specification. Details of the applicable testing standards shall be submitted.

3.1.6 Applicable specification. Copies of any material specifications should be submitted where these are not National/International Standards. English copies are preferred, although documents annotated in English will be acceptable.

3.2.1 Type of tests

The tests to be carried out are indicated in Table 3.3.1 Tests on base material .

LR may require the additional tests to verify the relevant characteristics of high manganese austenitic steels compared with those of the conventional materials applied to cryogenic service.

3.2.2 Test specimens and testing procedure

The test specimens and testing procedures are to be in accordance with Ch 2 Testing Procedures for Metallic Materials and Ch 3, 1.7 Dimensional tolerances of the Rules for the Manufacture, Testing and Certification of Materials, July 2022.

In particular, the following applies:

1. Tensile test
   • Tensile test specimens are to be taken from one test sample.
   • Tensile tests are to be carried out at room temperature and −165°C.
   • Results of tensile tests at −165°C should be reported for reference.
   • Tensile tests should be carried out with a specimen of full thickness.

2. Impact test on non-aged specimens
   • One set of three Charpy V-notch impact specimens is required for each impact test.
   • The Charpy V-notch impact test temperature should include −196°C at least.
   • In addition to the determination of the energy value, the lateral expansion and the percentage crystallinity are also to be reported. The percentage of the ductile fracture surface at −196°C should be 100 per cent by fractography (SEM).
   • Additionally, for each location, Charpy V-notch impact tests are to be carried out with appropriate temperature intervals (−196°C, −165°C, −100°C and −65°C) to verify the properties of toughness at each temperature for reference.

3. Impact test on strain aged specimens
   • One set of three Charpy V-notch impact specimens is required for each impact test.
   • The test specimens which have been maintained for one hour at 250°C after a strain of 5 per cent has been applied, as a rule, are to be used.
   • The Charpy V-notch impact test temperature should include −196°C at least.
   • The result should be reported for reference.

4. Drop weight test
   • Two specimens for drop weight test are to be taken from the surface of one test sample.
   • The test temperature is −196°C.
   • The test results should show no-break performance at −196°C.
   • Photographs of the test specimens are to be taken and enclosed with the test report.

5. Micro examination
   • One test specimen for micrographic examination should be taken from one test sample.
   • All micrographs are to be taken at × 100 magnification and where austenite grain size exceeds ASTM E112 index 10 or equivalent, additionally at × 500 magnification.
   • The austenite grain size should be measured and the non-metallic inclusions are to be examined.
   • The micrographs are to be representative of the full thickness.
   • The result should be reported for reference.

6. Chemical analysis
   • One test specimen for chemical analysis should be taken from one test sample.
   • Both the ladle and product analysis are to be reported.
   • The material for the product analysis should be taken from the tensile test specimen.

7. CTOD test
   • Test specimens for CTOD test are to be taken from one test sample.
   • One set of three CTOD specimens is required for each test.
   • CTOD minimum value should be in accordance with the design specification for testing at room and cryogenic temperatures as per design conditions. As a guide, a minimum CTOD value of 0,2 mm is often required.

8. S-N fatigue test
   • Sufficient number of test specimens to obtain an S-N curve are to be taken from test samples.
   • The test temperature is room temperature.
   • The S-N curve should be established and the result should be equal to or better than the FAT125-curve given by the International Institute of Welding (IIW) or C-curve in DNVGL-RP-C203-2020.
   • At the discretion of LR, on the basis of the available test results that at least three points from three stress ranges are sufficient to indicate that additional points are not needed and the available evidence is adequate to demonstrate fatigue properties, the S-N fatigue test may be waived.

9. Fatigue crack growth rate test
   • One test specimen for fatigue crack growth rate test should be taken from one test sample.
   • The test temperature is room temperature.
   • The result should be reported for reference.
   • At the discretion of LR, if a manufacturer can prove that the fatigue crack growth rate is superior to that of the conventional material used for the particular design application, or provide an ECA assessment for the suitability of the material for a particular application with available fatigue crack growth rate data, then the fatigue crack growth rate test may be waived.

10. General corrosion test
    • One test specimen for corrosion resistance should be taken from one test sample.
    • The result should be reported for reference.

11. Elastic modulus test
    • One test specimen for elastic modulus test should be taken from one test sample.
    • The test temperature should include room temperature and −165°C at least.
    • The result should be reported for reference.

12. Stress corrosion crack (SCC) test
    • One test specimen for stress corrosion crack test should be taken from one test sample.
    • The result should be reported for reference.

13. Sulphur prints
    • Sulphur prints are to be taken from plate edges which are perpendicular to the axis of the ingot or slab. These sulphur prints are to be approximately 600 mm long, taken from the centre of the edge selected, i.e. on the ingot centreline, and are to include the full product thickness.

14. Intergranular corrosion test
    • One test specimen for corrosion resistance should be taken from one test sample.
    • The result should be reported for reference.

3.2.3 Other tests

Additional tests may be required in the case of a newly developed type of steel, as deemed necessary by LR.

3.3.1 General

Weldability tests are required for plates and are to be carried out on samples of the thickest plate.

3.3.2 Preparation and welding of the test assemblies

In general, the following test assemblies are to be prepared:

The butt weld test assemblies are to be prepared with the weld seam longitudinal to the plate rolling direction, so that impact specimens will result in the transverse direction.

The bevel preparation should be preferably 1/2 V or K upon the test assembly thickness.

The welding procedure should be as far as possible in accordance with the normal welding practice used at the yards for the type of steel in question.

The welding parameters including welding process, consumables designation and diameter, preheating temperature, interpass temperature, heat input, number of passes, etc. are to be reported.

The maximum approved heat input level may be specified on the approval certificate.

3.3.3 Type of tests

The tests to be carried out are indicated in Table 3.3.2 Tests on weld material.

LR may require the additional tests to verify the relevant characteristics of high manganese austenitic steels compared with those of the conventional materials applied to cryogenic service.

Mechanical properties for butt weld tests are defined in Table 3.3.3 Mechanical properties for butt weld tests.

3.3.4 Test specimens and testing procedure