Progress in the application of continuous casting molds on surface plating technology

[Abstract ] Surface treatment of crystallizer can greatly improve its service life. Electroplating technology is the main surface technology in the field of crystallizer surface treatment. The application development space of the surface electroplating technology of continuous casting mold was analyzed. The application status and development direction of the surface electroplating technology of the mold were expounded from the aspects of product performance, production orientation and user orientation. It is believed that in the future field of continuous casting mold surface treatment, electroplating technology will coexist with other surface technologies and complement each other. Electroplating technology will still have a good development and application prospect.

0 Preface

Continuous casting mold is the core equipment of the whole continuous casting production, and its quality directly affects the quality of the casting blank and the working rate of the continuous casting machine. The surface of the crystallizer is modified by electroplating, thermal spraying, etc., and the surface-processed remanufactured crystallizer not only repairs the size of the crystallizer, but also has high strength, high toughness, superior corrosion resistance, wear resistance and The surface functional coating of the mold with high thermal fatigue resistance can also greatly improve the surface performance of the crystallizer, which greatly prolongs the life of the crystallizer, improves the grade, technical content and added value of the crystallizer, and also improves the efficiency of steel production. And continuous casting billet quality, energy saving materials [1].

The literature [2-4] introduces the research and application progress of the surface treatment technology of continuous casting mold. At present, in the surface treatment technology of continuous casting molds, electroplating technology is still the most widely used, mature and reliable. In this paper, the application progress of the surface electroplating technology of continuous casting mold is discussed and prospected.

1 Application space for crystallizer surface plating technology

In the past 20 years, surface technology has been vigorously developed, especially some emerging surface technologies, such as thermal spraying technology, laser cladding technology, PVD technology, CVD technology, surfacing technology, etc. have been widely developed and applied. The development of emerging surface technology has brought great impact to traditional electroplating technology. The pattern of surface decoration and protection in electroplating technology has been broken, showing the competition of various surface technologies. However, it is this kind of competition that promotes the continuous development and improvement of each technology. Therefore, the result is the formation of the overall prosperity of surface technology, and the existence of various surface technologies in various application fields.

At present, in the field of surface treatment of crystallizers, electroplating technology is no longer the only surface treatment technology. Thermal spraying technology has been applied to the industrialization of short-side copper plates of crystallizers. Other surface technologies are also in the research and development stage, and there are reports of crystallization. The long-side copper plate has achieved industrialization of all-ceramic coatings [5] (what technology is used to obtain all-ceramic coatings unknown). Therefore, doubts and reflections on the application prospects of electroplating technology in the field of crystallizer surface treatment are inevitable.

Electroplating technology remains the primary surface technology in the field of crystallizer surface treatment. The most fundamental technical advantage of electroplating technology is that it can be carried out in low temperature (<100 °C) plating solution, effectively avoiding the deterioration of coating and matrix materials caused by high temperature, low equipment investment, low production cost and high utilization rate of raw materials. Process implementation is continuous and easy to automate production. Based on these basic technological advantages, electroplating technology can also obtain a wide variety of coatings, which has great potential in the development of high-performance new coatings. The coating obtained by the crystallizer copper plate electroplating technology has good adhesion to the substrate, good resistance to cold and heat fatigue, and high comprehensive cost performance. However, the current crystallizer surface plating technology also has the disadvantages of low deposition rate and long production cycle.

Like electroplating technology, thermal spray technology is also a very effective mold surface treatment process. The coating obtained by the thermal spraying technology of the short-side copper plate of the crystallizer has the advantages of good wear resistance and strong corrosion resistance, and the deposition rate of the coating is high. However, compared with the electroplating technology, the thermal spraying technology has a low bonding strength between the coating and the base material, and because the deposition environment is a high temperature environment, thermal stress is easily generated on the workpiece, causing thermal deformation of the workpiece. In order to compensate for the defects of bonding strength and thermal stress, the copper plate must be subjected to a relatively long heat treatment process. After the high temperature heat treatment of the copper plate, the deformation correction is difficult, the substrate material is damaged, the fatigue layer required to repair the cutting is increased, and the copper plate is reduced. The service life. Since the area of ​​the long-side copper plate is much larger than that of the short-side copper plate, these problems will be magnified. It can be seen that the application of thermal spraying technology on the long side copper plate of the crystallizer is not a matter of course.

In summary, in the future field of crystallizer surface treatment, electroplating technology will still have a good development and application prospects. Electroplating technology will coexist with other surface technologies and complement each other.

2 Application status and development direction of crystallizer surface plating technology

The process of modern manufacturing is carried out throughout the life cycle of the product. The development of technology can no longer be limited to the internal manufacturing workshop, but should follow all aspects of the product life cycle. The development of the mold surface plating technology for the product life cycle was analyzed, as shown in Figure 1. It can be seen from the figure that the application and development of the surface electroplating technology of the crystallizer should be a closed-loop, comprehensive technology application and development from demonstration design to manufacturing, to user use, and then to demonstration design.

2.1 Product-oriented performance

The surface electroplating technology of the crystallizer begins with the initial plating of Cr. At present, several main coatings of Ni plating, Ni Fe plating, Ni Co plating, and Co Ni plating are gradually formed, and the performance of the product is gradually improved. With the rapid development of the steel industry, there is an increasing demand for the performance of the surface of the crystallizer material. The development of the crystallizer will continue to the direction of high mechanical strength, good thermal conductivity, wear resistance and corrosion resistance. development of. In order to meet such requirements, new electroplating technology and new materials will come into being. In the field of electroplating technology, the development direction of nano-composite plating technology [6 7], pulse plating technology [8] and new alloy plating technology [9] is in good agreement with the development requirements of future crystallizers. In Figure 2, the crystallizer plating is analyzed. The development history and direction of technology believes that the future development of crystallizer surface plating technology will focus on the development and application of micro- and nano-composite plating, pulse plating and new alloy plating technology.

2.2 Production oriented

While developing new technologies for plating new materials, it is necessary to pay attention to the improvement and improvement of electroplating technology in the production process. If the cost in the manufacturing process is not reduced and the product quality is not guaranteed, then the new plating materials, New technologies can only stop at the stage of envisioning and research, or greatly reduce their added value, thus losing competitiveness.

Japan's Mishima Photosynthetic Co., Ltd. has developed a continuous falling surface plating technology, which can flexibly obtain coatings of different thicknesses at different horizontal positions of the copper plate, changing the thickness of the plating of the existing fixed liquid level plating and causing material waste. The situation. Baosteel has developed technologies such as mold plate copper plate back plate or water tank integral plating. Compared with disintegration copper plate groove immersion plating method, the overall plating eliminates the copper plate disassembly and assembly process, shortens the production cycle, and reduces labor and management costs. Angang adopts the box-top plate electroplating technology [10], which implements the height-segmented thickness and cobalt content on the surface of the copper plate, thereby reducing the consumables and realizing the soft and hard characteristics of the copper plate coating.

The continuous casting mold copper plate needs to be subjected to pre-treatment processes such as degreasing and etching before electroplating, and the pre-treatment process is a key process for ensuring the quality of the plating layer and the plating layer. The usual pre-treatment process is first to remove the oil by hot alkali, and then pickled and etched after washing with water, that is, degreasing and etching are carried out separately. This method is not only cumbersome, but also covers a large area, and the cleaning water and chemical raw materials are used. The consumption is large. With the continuous research on the pre-plating treatment process, at present, the one-step degreasing process, that is, the process of simultaneously removing oil and etching in a pre-treatment liquid has been successfully applied to the mold copper plate electroplating enterprise. Compared with the step-by-step pretreatment technology, the oil removal and etching effect of the one-step degreasing method is excellent, the bonding strength of the obtained coating layer is very good, the pretreatment process is simplified, the equipment is reduced, the cleaning water and some chemicals are saved. raw material. However, at present, the research and development of one-step degreasing liquid and process in China is relatively weak, and the treatment liquid and treatment technology need to be imported from abroad. Therefore, from the perspective of cost reduction and efficiency, and energy conservation, the development of one-step degreasing and etching process for continuous casting mold copper plate is very promising.

2.3 User-oriented

Many problems that arise at the user's site provide a direction and platform for the development of electroplating technology.

The original crystallizer short-side copper plate of a continuous casting plant in Baosteel uses a front thermal spray alloy and then electroplated Ni on the side. As a result, it was found in the continuous casting production that the soft Ni-plated strip on the front edge is very easy to wear, which limits the short-side copper plate. Service life. In order to solve this problem, the copper plate was firstly plated and then frontally sprayed, and the plating process was changed accordingly. The short-edge copper plate obtained by the new method has improved wear resistance and extended service life. Baosteel used the finite element thermal analysis technology to analyze the user's original mold copper plate design when manufacturing the mold copper plate for a user. It was found that the 1 mm Ni Fe plating, the sink design and the cooling water flow on the copper plate were not reasonable enough. The temperature of the lower meniscus is too high. After further thermal analysis and analysis, the user was proposed to use the upper 0.3mm Ni Co coating, modify the original water tank and cooling water flow design, and the proposal to change the plating form was approved by the user.

The development of user-oriented crystallizer surface plating technology is relatively weak. On the one hand, there is a large professional span of mold manufacturing technology and continuous casting technology. The complex working conditions and management methods of the continuous casting site make the mold manufacturing technicians It is difficult to grasp the impact of various factors on the product and the degree of influence, and thus can not enter the next stage of product demonstration design. On the other hand, the reason is that the lack of product life cycle information chain or the efficiency of obtaining information is very low. As shown in Figure 1, without the intermediate link of product data information platform, technicians will not be able to obtain comprehensive product information, no data. As a guarantee, it is difficult to comprehensively analyze the problems that have occurred and will occur.

In view of the above reasons, the development of user-oriented crystallizer surface plating technology should be extended to the extent that it intersects with the application technology field of products. For the continuous casting technology, the core process is the heat exchange process in the crystallizer. Therefore, mastering the heat exchange law in the crystallizer will have an important guiding role in the design of the mold copper plate and the plating layer. In addition, it is very meaningful to build a database of crystallizer copper plate life cycle information. Japan's Mishima Light Products Co., Ltd. integrates the product life cycle information system including the on-site use information of the mold copper plate into the production management system of the enterprise, which not only facilitates management and marketing, but also greatly promotes the research and development of technology. Baosteel is also actively carrying out this work. The construction of the crystallizer copper plate life cycle information database will make electroplating technology easier to develop on the user-oriented platform, which is more conducive to the interactive development of electroplating technology and various technologies.

3 Conclusion

Electroplating technology is constantly developing and developing due to its unique technical advantages. In the future field of crystallizer surface treatment, electroplating technology will still have a good development and application. The electroplating technology will coexist with other surface technologies. Complementary. The application and development of future crystallizer surface plating technology can not be limited to the internal manufacturing workshop, but should be a closed loop that follows all aspects of the product life cycle, from demonstration design to manufacturing, to user use, to demonstration design. Comprehensive technology application and development.