Section 8 Aluminium Alloys

801. Aluminium alloys

1. Application

(1) These requirements are to apply to the aluminium alloy plates and extruded shapes(hereinafter referred to as "aluminium alloys") intended to be used in the construction of hulls, super- structures, other marine structures and tanks of liquefied gas carriers.

(2) Where aluminium alloys exceeding the maximum value of plate thickness or size specified in

Table 2.1.98 and Table 2.1.99. are manufactured, a new approval test is required by the Society. See Guidance

(3) Aluminium alloys having characteristics differing from those specified in 801. are to comply

with the requirements in 101. 2.

2. Kinds

The aluminium alloys are classified as specified in Table 2.1.97.

Table 2.1.97 Kinds

3. Chemical composition

(1) The chemical composition of

Table 2.1.98.

aluminium alloys is to comply with the requirements given in

Table 2.1.98 Chemical Composition

(2) When the aluminium alloys are not cast in the same works in which they are manufactured in- to semi finished products, the Society Surveyor shall be given a certificate issued by the works in question which indicates the reference numbers and chemical composition of the heats.

4. Heat treatment

The heat treatment(hereinafter referred to as "temper condition") of the aluminium alloys is to com- ply with the requirements given in Table 2.1.99 and Table 2.1.100.

5. Mechanical properties

(1) The mechanical properties in tension tests are to comply

2.1.99. and 2.1.100.

with the requirements given in Tables

Table 2.1.99 Mechanical Properties for Rolled Products(1)

Tensile test

Grades Temper condition(2)

Thickness,

(mm)

Yield strength (N mm )

Tensile strength (N mm )

Elongation(%)

( ) ( )

5083P

5383P

5059P

O 3 50 125 min. 275 350 16 min. 14 min.

H111 3 50 125 min. 275 350 16 min. 14 min.

H112 3 50 125 min. 275 min. 12 min. 10 min.

H116 3 50 215 min. 305 min. 10 min. 10 min.

H321 3 50 215 295 305 385 12 min. 10 min.

O 3 50 145 min. 290 min. - 17 min.

H111 3 50 145 min. 290 min. - 17 min.

3 50

H116 or

H321 220 min. 305 min. 10 min. 10 min.

O 3 50 160 min. 330 min. - 24 min.

H111 3 50 160 min. 330 min. - 24 min.

H116 or

H321

3 20 270 min. 370 min. 10 min. 10 min.

20 50 260 min. 360 min. 10 min. 10 min.

5086P

O 3 50 95 min. 305 min. 16 min. 14 min.

H111 3 50 95 min. 305 min. 16 min. 14 min.

3 12.5 125 min. 250 min. 8 min. -

H112

5754P

12.5< 50 105 min. 240 min. - 9 min.

H116 3 50 195 min. 275 min. 10 min.(3) 9 min.

O 3 50 80 min. 190 240 18 min. 17 min.

H111 3 50 80 min. 190 240 18 min. 17 min.

3 6.3 130-205 290-365 16 min. -

O

6.3 50 125-205 285-360 16 min. 14 min.

3 30 230 min. 315 min. 10 min. 10 min.

(1) Aluminium alloy may be subject to any other standards in lieu of the requirements given in this Table where they are approved by the Society.

(2) Symbols used in temper condition are as follows See Guidance : O : Annealing

H 111, H 112, H 116 : Work hardened

H321 : Stabilizing treatment after work hardened

(3) % for thicknesses up to and including 6.3 mm.

Table 2.1.100 Mechanical Properties for Extruded Shapes(1)

(2) Where deemed necessary by the Society, other tests may be required in addition to the specified tests. See Guidance

6. Selection of test samples

(1) For test samples for rolled products, if the weight of one lot exceeds 2 tonnes, one extra test specimen is to be taken from every 2 tonnes of the product or fraction thereof, in each lot ex- cept where specially approved by the Society.

One lot is made up of rolled products of the same alloy and from the same cast, of the same

thickness, manufactured by the same process and having been submitted simultaneously to the same temper condition. For single plate or coil weighting more than 2 tonnes each, one lot is made up of a single plate or coil.

(2) For test samples for extruded shapes with a nominal weight of less than 1 kg/m, except where specially approved by the Society, one test specimen is to be taken from each 1 tonne, or frac-

tion thereof, in each lot. For nominal weights between 1 and 5 kg/m, one test specimen is to

be taken from each 2 tonnes or fraction hereof, in each lot. If the nominal weight exceeds 5 kg/m, one test specimen is to be taken for each 3 tonnes of the product or fraction thereof, in

each lot.

One lot is made up of rolled products of the same alloy and from the same cast, of the same dimension, manufactured by the same process and having been submitted simultaneously to the

same temper condition.

(3) Test samples are to be taken out of the place at one third of the width from a longitudinal

edge of rolled of the thickest

products, or in the range 1/3 to 1/2 of the distance from the edge to the centre part of extruded products.

(4) After removal of test samples, each test specimen is to be marked in order that its original identity, location and orientation is maintained.

7. Selection of test specimens

Tensile test specimens are to be taken according to (1) to (4) below.

(1) One test specimen is to be taken out of each test sample.

(2) For rolled products, the longitudinal axis of the test specimen is to be taken transversely to the rolling direction. If the width is insufficient to obtain transverse test specimen or in the case of strain hardening alloys, however, the longitudinal direction may be taken parallel to the rolling direction.

(3) For extruded shapes, the longitudinal axis of the test specimen is to be taken parallel to the ex- truding direction.

(4) For thickness of test sample up to and including 40 mm, the longitudinal axis of the test speci- men is to be located at a distance from the surface equal to half of the thickness. For thickness of test sample over 40 mm, the longitudinal axis of the test specimen is to be located at a dis-

tance from one of the surfaces equal to one quarter of the thickness.

8. Drift expansion tests

The manufacturer has to demonstrate by macrosection tests or drift expansion tests of closed profiles performed on each batch of closed profiles that there is no lack of fusion at the press welds.

(1) Every fifth profile shall be sampled after final heat treatment. Batches of five profiles or less shall be sampled one profile. Profiles with lengths exceeding 6 m shall be sampled every pro-

(2)

(3)

file in the start of the production. The number of tests may be the results from the first 3-5 profiles are found acceptable.

Each profile sampled will have two samples cut from the front profile.

The test specimens are to be cut with the ends perpendicular

edges of the end may be rounded by filing.

reduced to every fifth profile if

and back end of the production to the axis of the profile. The

(4) The lengths of the drift expanding test specimens are to be equal to 1.5 times the external di-

ameter(D) of the test specimen in accordance with KS B ISO 8493. The test piece may be shorter provided that after testing the remaining cylindrical portion is not less than 0.5D.

(5)

(6)

Testing is to be carried out at ambient temperature and is to consist of expanding the end of

the profile by means of a hardened conical steel mandrel having an included angle of at least 60°.

The sample is considered to be unacceptable if the sample fails with a clean split along the weld line which confirms lack of fusion.

9. Corrosion testing

(1) Testing procedures

(a) Rolled 5xxx-alloys of type 5083, 5383, 5059, 5086 and 5456 in the H116 and H321 tem- pers intended for use in marine hull construction or in marine applications where frequent direct contact with seawater is expected are to be corrosion tested with respect to exfoliation and intergranular corrosion resistance. The manufacturers shall establish the relationship be- tween microstructure and resistance to corrosion when the above alloys are approved.

(b) A reference photomicrograph taken at 500x, under the conditions specified in ASTM B928, Section 9.4.1, shall be established for each of the alloy-tempers and thickness ranges relevant.

(c) The reference photographs shall be taken from samples which have exhibited no evidence of

exfoliation corrosion and a pitting rating of PB or better, when subjected to the test de- scribed in ASTM G66 (ASSET).

(d) The samples shall also have exhibited resistance to intergranular corrosion at a mass loss no

greater than 15mg/cm2, when subjected to the test described in ASTM G67 (NAMLT).

(e) Upon satisfactory establishment of the relationship between microstructure and resistance to corrosion, the master photomicrographs and the results of the corrosion tests are to be ap-

proved by the Society. Production practices shall not be changed after approval of the refer- ence micrographs.

(f) Other test methods may also be accepted at the discretion of the Society.

(2) Acceptance criteria

(a) For batch acceptance of 5xxx-alloys in the H116 and H321 tempers, metallographic examina- tion of one sample selected from mid width at one end of a coil or random sheet or plate is to be carried out in accordance with ASTM B928 or equivalent standards agreed by the Society. The microstructure of the sample is to be compared to the reference photomicro-

(b) If the microstructure shows evidence of continuous grain boundary network of alumi- nium- magnesium precipitate in excess of the reference photomicrographs of acceptable mate- rial, the batch is either to be rejected or tested for exfoliation-corrosion resistance and inter- granular corrosion resistance subject to the agreement of the Surveyor.

(c)

Corrosion tests with respect to exfoliation and intergranular corrosion resistance are to be in accordance with ASTM G66 and G67 or equivalent standards agreed by the Society. See

Guidance

(i) The samples have exhibited no evidence of exfoliation corrosion and a pitting rating of PB or better when subjected to the test described in ASTM G66.

(ii) The samples shall also have exhibited resistance to intergranular corrosion at a mass loss no greater than 15 mg/cm2, when subjected to the test described in ASTM G67.

If the results from testing satisfy the acceptance criteria, the batch is accepted, else it is to be rejected.

(d) As an alternative to metallographic examination, each batch may be tested for exfolia- tion- corrosion resistance and intergranular corrosion resistance, in accordance with ASTM G66 and G67 under the conditions specified in ASTM B928, or equivalent standards. If this alternative is used, then the results of the test must satisfy the acceptance criteria stated in

(c) above.

10. Surface inspection and dimensional tolerance

(1) Surface inspection and verification of dimensions are left to the responsibility of the manufacturer.

(2) The under-thickness tolerances of rolled products are to comply with the requirements given in

2.1.101. The under-thickness tolerances of extruded shapes and other dimensional tolerances are to be as deemed appropriate by the Society. See Guidance

Table 2.1.101 Under-thickness Tolerance for Rolled Products

(3) Dimensional tolerance except those specified in (2) above is left to the discretion of Society. See Guidance

11. Quality

(1) Aluminium alloys are to be of uniform quality and free from internal and surface harmful fects prejudicial to the use of the concerned material for the intended application.

(2) Slight surface imperfections may be removed by smooth grinding or machining as long as

thickness of the materials remains within the tolerances given in Table 2.1.101.

12. Retest procedures

the

de- the

(1) When the tensile test from the first piece selected fails to meet the requirements given in Table

2.1.99 and 2.1.100, two further tensile tests may be made from the same piece. If both of

these additional tests meet all of the requirements, the piece and the remaining pieces from the same lot may be accepted.

(2) If one or both of the additional tests referred to above (1) are unsatisfactory, the piece is to be

rejected. However, the remaining materials from the same lot may be accepted provided that two of the remaining pieces in the lot selected in the same way, are tested with satisfactory results.

13. Marking

(1) Aluminium alloys which have satisfied with the required tests are to be marked with the identi- fication mark in accordance with the requirements in 110. 1. In this case, the mark of temper conditions is to be put subsequent to the mark of material grade. (ex : 5083 P H321)

(2) For aluminium alloy, which have satisfied with the corrosion resistance tests specified in 801. 9,

the

M)

mark of [M] is to be put subsequent to the mark of the temper condition (ex : 5083 P H321