Section 5 Iron castings for crankshafts

5.1.1 This Section gives additional requirements for cast iron crankshafts intended for engines and compressors. For both of these applications, details of the proposed specification are to be submitted for approval.

5.1.2 Crankshaft castings in grey iron and compacted graphite iron are acceptable only for compressors, and the specified minimum tensile strength is to be not less than 300 N/mm².

5.1.3 For crankshaft castings in spheroidal or nodular graphite iron, the specified minimum tensile strength is to be not less than 370 N/mm².

5.2.1 Details of the method of manufacture, including the arrangements proposed for the provision of test material, are to be submitted for approval.

5.2.2 Tests to demonstrate the soundness of prototype castings and the mechanical properties at important locations will be required.

5.3.1 In general, crankshaft castings other than those which are fully annealed, normalised or oil quenched and tempered, are to receive a suitable stress relief heat treatment before machining.

5.3.2 Where it is proposed to harden the surfaces of machined pins and/or journals of cast iron crankshafts, details of the process are to be submitted for approval. Before such a process is applied to a crankshaft it is to be demonstrated by procedure tests, and to the satisfaction of the Surveyor, that the process is suitably controlled and does not impair the strength or soundness of the material.

5.4.1 Unless otherwise approved, the dimensions of the test samples are to be such as to ensure that they have mechanical properties representative of those of the average section of the crankshaft casting.

5.4.2 For large crankshaft castings, the test samples are to be cast integral with, or gated from, each casting.

5.4.3 The batch testing procedure detailed in Ch 7, 1.6 Test material 1.6.2 may be adopted only where small and identical crankshaft castings are produced in quantity. Generally, the fettled mass of each casting in a batch is not to exceed 100 kg, and in addition to tensile tests, the hardness of each casting is to be determined. For this purpose, a small flat is to be ground on each crankshaft, and Brinell hardness tests are to be carried out. The results obtained from these tests are to comply with the approved specification.

5.5.1 Cast crankshafts are to be subjected to a full magnetic particle or dye penetrant examination after final machining and completion of any surface hardening operations.

5.5.2 Particular attention is to be given to the testing of the pins, journals and associated fillet radii.

5.5.3 Cracks and crack-like defects are not acceptable. Fillet radii are to be free from any indications.

5.6.1 Cast iron crankshafts are not to be repaired by welding, and blemishes are not to be plugged with a filler.

5.7.1 The chemical composition of ladle samples is to be given in addition to the other particulars detailed in Ch 7, 1.12 Certification of materials 1.12.2.