| Horizontal continuous casting is the main method of billet produced for the modern big steel (tube) factories as well as copper alloy mould is the most critical consumable parts of horizontal continuous casting equipment. In the course of usage, the inner surface of the copper alloy mould is working on very poor conditions, it contacts directly with 1475~1570℃high temperature liquid steel, which is very easy to produce various forms of failure. The main forms of the failure are generating heat crack, wear, peeling, scratching, corrosion and so on. The quality of copper alloy mould directly affects the steel-making efficiency, effectiveness and labor intensity. With the rapid development of horizontal continuous casting from 1980s, many domestic and international steel companies and research institutes did lots of work, which mainly included enhancing the quality of the material, surface strengthening as well as surface modification, in order to improve the life of copper alloy mould. This paper mainly according to some problems emerging from steel production at a large domestic steel factory, studying on heat treatment of CuCo2Be alloy and Surface modification-arc spraying strengthening process of copper alloy mould on the basis of comprehensively analyzing the form of failure and the mechanism for the copper alloy mould. The results are shown as follows:(1) The main reason for the failure of copper alloy mould is that it occurs within the scratch, the peeling and thermal crack. The form of scratch and peeling relates to the material, the former mainly formed by the scratch mechanism, the latter mainly formed by the scratch mechanism and the adhesive mechanism of the formation of joint action; the formation of heat crack related to low melting compounds which exists in grain boundary, transverse thermal crack is produced under the thermal stress. Metallurgical defects exist in grain boundary and forging defects, which led to fatigue failure of copper alloy moulds.(2) Comprehensive performance of CuCo2Be alloy can be acquired after solution treatment of 960℃×1.5h+30% cold deformation+480℃×4h aging. At this condition, hardness is HB256, conductivity reaches 48.75%IACS, tensile strength reaches 859MPa, yield strength is 800MPa, elongation is 17%, softening temperature is 540℃, tensile fracture is ductile fracture.(3) the optimized processing parameters of the arc spraying Ni-Cr-Ti coating are:spray current 140A ,spray voltage 35V and spray distance 150mm; Spray voltage, spray current, spray distance have different effected on the anchoring strength of Ni-Cr-Ti coating Under constant pressure in the air, and the higher anchoring strength, the better thermal shock resistance. The highest strength 34.1MPa of Ni-Cr-Ti coating can be obtained using the optimized parameters, and the coating has no cracks or spalling after thermal shock 41 times. The coating displays good Properties, has the typical layers structure characteristic and good thermal shock resistance, the highest hardness reaches 390.65HV. |
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