| 摘要 |
1456661 Continuous casting ALCAN RESEARCH & DEVELOPMENT Ltd 22 Jan 1974 [24 Jan 1973] 3699/73 Heading B3F An ingot 12 of light metal, such as Al-Mn, Al-Mg, Al-Cu, Al-Zn-Mg or Al-Mg-Si, is cast in a horizontal or vertical mould 10 and is directly chilled by coolant (water from a slot 22 in a jacket of an Al mould 10) as it emerges; at one stage it is withdrawn at a speed below the crack propagating speed (C.P.S.) for a sufficient distance to ensure the formation of a crack-free centre in a length of the emerging ingot, the speed then being increased to above the C.P.S. and below the crack-initiating speed (C.I.S.). "Hot short" tendencies of the alloys referred to cause centre cracking of the first few inches of the ingot 12 but unless the C.P.S. is exceeded the crack should terminate. Once it has terminated, however, the speed can be exceeded and as long as the C.I.S. is not exceeded no fresh crack should form. The C.P.S. and C.I.S. values are established empirically. A high initial withdrawal speed with resultant crack might be acceptable if followed by a low speed to terminate the crack before increasing the speed. Figures relating withdrawal speeds to stages of withdrawn lengths in terms of ingot diameter thickness are given together with speed increment details. The compositions of Al-Mg-Si alloys used are also given. An hydraulic ram 20 lowers a starting stool 19 from the mould 10. Wire supports 38 restrict the descent of a float 30 which bears a baffle bar 36 below a pouring tube 28 from a launder 26 to regulate the flow to provide the proper level of metal in the mould. |
