4.1.1 This Section gives the specific requirements for compacted or vermicular graphite iron castings.
4.1.2 These requirements are generally applicable to castings intended for use at ambient temperatures.
4.2.1 Where castings do not meet the specified mechanical property requirements in the as-cast condition, a corrective heat treatment may be carried out. This is to be restricted to a single heat treatment and the test coupons must be heat treated with the castings.
4.3.1 The test samples are to be as detailed in Table 7.3.1 Type A (U-type) test samples, Table 7.3.2 Type B (Double U-type) test samples or Table 7.3.3 Type C (Y-type) test samples. The dimensions of the test specimens and testing procedures used are to be in accordance with Ch 2 Testing Procedures for Metallic Materials. Test samples of other dimensions may be specially agreed with the Surveyor.
4.3.2 The test samples may be either gated to the casting or separately cast.
4.3.3 Where separately cast test samples are used, they are to be taken towards the end of pouring of the castings.
4.4.1 The tensile strength and elongation are to be determined and are to comply with the requirements of Table 7.4.1 Mechanical properties for acceptance purposes: compacted or vermicular graphite iron castings. Minimum values for the 0,2 per cent proof stress are also included in this Table but are to be determined only if included in the specification. Typical ranges of hardness values are also given in Table 7.4.1 Mechanical properties for acceptance purposes: compacted or vermicular graphite iron castings and are intended for information purposes.
4.4.2 Castings may be supplied to any specified minimum tensile strength grade.
Note Proof stresses need only be determined if specifically requested.
4.5.1 Samples for metallographic examination are to be prepared for compacted or vermicular graphite iron castings. These samples are to be representative of each ladle used and may conveniently be taken from the tensile test specimens. Alternative arrangements for the provision of these samples may, however, be adopted subject to the concurrence of the Surveyor. They are, however, to be taken towards the end of the pour.
4.5.2 Examination of the samples is to show that at least 80 per cent of the graphite is in a dispersed, compacted or vermicular form. The remaining 20 per cent of the graphite may be in spheroidal forms. Details of typical matrix structures are given in Table 7.4.1 Mechanical properties for acceptance purposes: compacted or vermicular graphite iron castings and are intended for information purposes.