Section 9 Bars for welded chain cables

9.1.1 Provision is made in this Section for rolled steel bars intended for the manufacture of three Grades (U1, U2 and U3) of stud link chain cable for the anchoring and mooring of ships and five Grades (R3, R3S, R4, R4S and R5) of offshore mooring cable.

9.1.2 For the ship grades, U1, U2 and U3, approval will permit the supply of bars of the appropriate grades and size to any chain cable manufacturer.

9.1.3 For the offshore grades, R3, R3S, R4, R4S and R5, approval is confined to bar to be supplied to a nominated chain manufacturer and will be given only after successful testing of a completed chain. Separate approvals are required if bar is to be supplied to more than one cable manufacturer. Approval of a higher grade does not cover approval of a lower grade, as all grades must be individually approved. If it is demonstrated to the satisfaction of LR that the higher and lower grades are produced to the same manufacturing procedure using the same chemistry and heat treatment, consideration will be given to qualification of a lower grade by a higher grade. The parameters applied during qualification are not to be modified during production.

9.1.4 For all grades, approval is normally given for diameters of bars no greater than those of the bars used in procedure tests.

9.2.1 All grades of bar material are to be made from killed steel, and, all grades of bar material except for Grade U1 chain cables are to be fine grained. For Grades R3, R3S, R4, R4S and R5 the austenite grain size is to be 6 or finer, in accordance with ASTM E112 or equivalent grain size index in accordance to ISO 643. Measurements for circular sections are to be taken at one-third of the radius.

9.2.2 The bars are to be made to a specification approved by LR which should include the manufacturing procedure, deoxidation practice, heat treatment and mechanical properties.

9.2.3 The rolling reduction ratio of bars for Grades R3, R3S, R4, R4S and R5 must be at least 5:1.

9.3.1 For Grades U1, U2 and U3 the chemical composition should be generally within the limits given in Table 3.9.1 Chemical composition of killed steel bars.

9.3.2 For Grades R3, R3S, R4, R4S and R5 the chemical composition is to comply with an approved specification, see Ch 3, 9.2 Manufacture 9.2.2.

9.3.3 For Grades R4, R4S and R5 chain cable the steel should contain a minimum of 0,2 per cent molybdenum. The reported composition is to include the contents of antimony, arsenic, tin, copper, nitrogen, aluminium and titanium.

9.3.4 For Grades R4S and R5 the steel used must be vacuum degassed.

9.4.1 Unless stipulated otherwise, the bars are to be supplied in the as-rolled condition, but the supplier is to be advised by the chain manufacturer of the heat treatment to be used for the completed chain in order that the mechanical test specimens may be tested in the condition of heat treatment used for the chain.

9.4.2 For Grades U1 and U2, the samples selected from each batch may be tested either in the as-rolled condition, or after heat treatment where the chain is to be used in the heat treated condition, in full cross-section and in a manner simulating the heat treatment applied to the finished cable.

9.4.3 For Grades U3, R3, R3S, R4, R4S and R5 the sample is to be tested after heat treatment as detailed in Ch 3, 9.4 Heat treatment 9.4.2.

9.5.1 For Grades R3, R3S, R4, R4S and R5 the bar manufacturer is to provide evidence that the material is not susceptible to strain ageing or to temper brittleness under the conditions of manufacture of the chain. The results of the relevant tests are to be reported to LR at the approval stage. Approval will be restricted to the specified steel composition and if later this is altered then re-approval will be required. Temper brittleness testing may be waived if the chain is to be quenched after tempering.

9.5.2 Each heat of steel bars of grades R3S, R4, R4S and R5 is to be tested for hydrogen embrittlement (see Ch 2, 5.3 Hydrogen embrittlement tests). In the case of continuous casting, test samples representing both the beginning and the end of the heat are to be taken. In the case of ingot casting, test samples representing two different ingots are to be taken.

9.5.3 Each sample is to be heat treated in a manner simulating the heat treatment of the finished chain. From each sample two specimens are to be prepared from the mid-diameter of the bar and tested in accordance with Ch 2, 5.3 Hydrogen embrittlement tests.

9.5.4 The ratio Z ₁/Z ₂ is to be greater than or equal to 0,85, where Z ₁ is the reduction in area without baking and Z ₂ the reduction in area after baking.

9.5.5 If the requirement is not met, the material is to be subjected to a hydrogen degassing treatment which is subject to approval by LR. Further tests are to be performed after degassing.

9.6.1 Bars of the same nominal diameter are to be presented for test in batches of 50 tonnes or fraction thereof from the same cast. A suitable length from one bar in each batch is to be selected for test purposes. Test pieces are to be taken from the positions as shown in Figure 3.9.1 Sampling of steel bars.

Figure 3.9.1 Sampling of steel bars

9.6.2 For all grades, one tensile test is to be taken from each sample length selected. Additionally, for Grades U3, R3, R3S, R4, R4S and R5 material, one set of three Charpy V-notch impact test specimens is to be prepared. Impact tests are also required for Grade U2 when the chain is to be supplied in as-welded condition.

9.6.3 The results of all tensile and, where applicable, impact tests are to be in accordance with the appropriate requirements of Table 3.9.2 Mechanical properties.

Table 3.9.2 Mechanical properties

Grade	Yield stress N/mm2 minimum	Tensile strength N/mm2	Elongation on 5,65% minimum	Reduction of area % minimum	Charpy V-notch impact tests
					Test temperature °C	Average energy J minimum	Average energy flash weld J minimum
U1	—	370–490	25	—	—	—	—
U2	295	490–690	22	—	0 (see Note 1)	27	—
U3	410	690 minimum	17	40	0	60	—
					–20 (see Note 2)	35	—
R3	410 (see Note 3)	690 minimum (see Note 3)	17	50	0	60	50
					–20 (see Note 2)	40	30
R3S	490 (see Note 3)	770 minimum (see Note 3)	15	50	0	65	53
					–20) (see Note 2)	45	33
R4	580 (see Note 3)	860 minimum (see Note 3)	12	50	–20	50	36
Grade R4S (see Note 4)	700 (see Note 3)	960 minimum (see Note 3)	12	50	–20	56	40
Grade R5 (see Note 4)	760 (see Note 3)	1000 minimum (see Note 3)	12	50	–20	58	42
Note 1. Impact tests may be waived when the chain cable is to be supplied in one of the heat treated conditions given in Table 10.2.3 Condition of supply and scope of mechanical tests for finished chain cables and fittings. Note 2. Testing may be carried out at either 0°C or –20°C, at the option of LR. Note 3. The ratio of yield strength to tensile strength should be 0,92 maximum unless specially approved. Note 4. The aim maximum hardness for R4S is to be HB330, and for R5 is to be HB340.

9.6.4 Failure to meet the requirements will result in the rejection of a batch of material, unless it is clearly attributed to improper simulated heat treatment. This is to be confirmed to be to the satisfaction of LR, and further heat treatment and testing will be required prior to acceptance.

9.7.1 For Grades R4S and R5, the following tests are to be carried out on each heat:

1. Assessment and quantification of the level of non-metallic micro inclusion. These must be acceptable for the final product.

2. Macro etching on a representative sample, in accordance with ASTM E381 or equivalent. This must be free from any injurious segregation or porosity.

3. Jominy hardenability tests in accordance with ASTM A255 or equivalent.

9.8.1 The tolerances on diameter and ovality of the bar are to be in accordance with Table 3.9.3 Dimensional tolerance of bar stock.

9.9.1 For the grades U1, U2 and U3 all bars are to be free from internal and surface defects that might impair proper workability, use and strength. Subject to agreement by the Surveyor, surface defects may be removed by grinding provided the acceptable tolerances are not exceeded.

9.9.2 For the R3, R3S, R4, R4S and R5 grades all bars are to be inspected by a magnetic particle or eddy current method and are also to be subjected to ultrasonic examination.

9.9.3 All non-destructive examination is to be carried out in accordance with approved procedures, in accordance with Ch 1, 5 Non-destructive examination.

9.9.4 All non-destructive examination operators are to be qualified in the method of non-destructive examination to a minimum of Level II in accordance with a recognised standard.

9.9.5 The bars are to be free from pipes, cracks, flakes, and injurious surface defects such as seams, laps, and rolled in mill scale. Longitudinal discontinuities may be removed by blending to a smooth contour provided that their depth is not greater than 1 per cent of the bar diameter, and that the required diameter tolerances are not compromised. The contour radiuses are to be a minimum of four times the excavation depth.

9.9.6 The frequency of non-destructive testing may be reduced at the discretion of LR, provided statistical evidence is available that the required quality is achieved consistently.

9.10.1 Each bar is to be identified in accordance with Ch 3, 1.12 Identification of materials and, in addition, is to be marked with the appropriate grade of chain cable.

9.11.1 Each consignment of bars is to be accompanied by a certificate of a type and in accordance with Ch 3, 1.13 Certification of materials but with the addition of the grade of chain cable, the rolling reduction ratio, the results of the hydrogen embrittlement, micro inclusion, macro etch and hardenability tests, where required by each grade.