Horizontal centrifugal casting is an effective method for the production of hollow metal with good mechanical properties, low defect, cast

to size and relatively cheap. The ability of a metal to satisfy the above requirements highly depends on its microstructure. In this study, the

relationship between microstructural parameters such as grain size and the amount of phases with bulk hardness of SnCu4Pb3 is concerned

in three areas of the product. Consequently, to achieve the desired hardness of the product in a particular area, the interaction of two

factors of the microstructure including, grain size and particles amount of the hard intermetallic compositions (Cu6Sn5) should be noted.

Different methods are used for production of bronze bearings. In terms of technical specifications, the success of each of these methods

depends on the bond’s strength and in terms of economic, the production method is important. In this study, the aim is to study the strength

and microstructure of steel-bronze thrust bearing bond that has been produced through the casting using pre-mold. In this study, in order to

bond, the raw metals are chemically washed with sulfuric acid solution for five minutes at first. Then, the molten bronze SAE660 is cast in

a structural steel S235JR pre-mold. The bond’s strength has been measured using the shear test three times; the measurement of bond’s

length has been done using field emission scanning electron microscope (FESEM). The results indicate that the strength of the bond is at

least 94.8 MPa and bond’s length is 0.45 micrometers. Therefore, this method was successful for trust bearing application.

Metallic bearing alloys have different types, most of which are tin (Babbitt) or bronze based. Bronze bearings are used at heavy duty conditions. The goal of this research is an investigation on the effect of cooling rate and pouring temperature (two important factors in casting production) on the Brinell hardness and pin-on-disc wear resistance (two important properties in bearing applications) of bronze SAE660. The melt had prepared by induction furnace. Then, it had poured in sand mold in four different casting conditions, including pouring temperatures of 950 oC and 1200 oC, and cooling with water and air. Finally, the microstructure, hardness and wear resistance of the SAE660 had investigated. The results indicated that if the maximum hardness, along with the minimum weight loss due to wear (or maximum wear resistance) is required; the contents of intermetallic compounds, lead phase and the solid solution phase should be more. In this way, the samples which are cooled in air and poured at 950 oC have the high hardness and the lowest weight loss.

Metal pieces wear out due to variable loading, because cracks formed on their surface of them. In order to increase useful life of metal

pieces with the help of different methods of welding, surface cracks are repaired. In this research, performance of the diffusion welding of

pure iron powder through magnetic induction evaluated for repairing structural steel surface cracks. First, four specimens prepared

including one control specimen and other three specimens grooved specimens in length of 6.25mm and in depth of 1mm and groove

width in the sizes of 0.5, 0.75 and 1mm. Then by a coil, the induced current created in the piece surface. After crossing the current, the

powder melted and the groove repaired due to diffusion welding. To prevent oxidation, the atmosphere inside the coil filled with argon

gas. The results show that after repairing surface groove, tensile strength of the repaired specimens reached to the tensile strength of

control specimen with the margin of 7.5%.

One of the methods to prevent unsuitable lubrication of moving components of devices and machinery is using bi-metal and three-metal

bearings. Centrifugal casting process is one of the manufacturing methods that is used for such bearings. In this study, the purpose is

microstructure evaluation of the bonding location and length determination of diffusion bond in structural steel-bronze. A mold made of

structural steel with inner diameter of 240mm, length of 300mm and thickness of 10mm was coated by a 6mm film of bronze under

centrifugal casting process. At first, a bronze ingot with dimension of 5mm×10mm×20mm is located inside of the hollow cylindrical mold

and then the two ends of it will be sealed. During mold rotation with the rate of 800 rpm, two high power flames are used for heating the

mold under Ar gas atmosphere to melt the bronze ingot at 1000˚C. After 15minutes, the system is cooled rapidly. Results showed that the

diffusion bonding of bronze in structural steel to depth of 1.2µm from the bonding line was obtained. In this bonding, copper element was

diffused to 50% of its initial concentration.

To improve mechanical properties and increasing useful life of metal pieces, different methods of welding are used for repairing surface

crack of metal pieces. In this research, performance of flame welding method by spraying pure iron powder evaluated for repairing surface

grooves of structural steel. First, four specimens including one control specimen and other three specimens grooved specimens in depth of

1mm and in length of 12.5mm and groove width in the sizes of 0.5, 0.75 and 1mm.were prepared then, powder melted using oxyacetylene

reducing flame and spraying iron powder in the flame path and attached to the inner surface of the groove and finally, the specimen

repaired. Results showed that after repairing surface groove, tensile strength of the repaired specimens were reached to the tensile strength

of control specimen with the margin of 2.5%.