Rare metal metallurgy is the backbone course of non-ferrous metal metallurgy in rare metal metallurgy, and it is one of the required courses for metallurgical engineering majoring in rare metal metallurgy in Central South University, as well as one of the academic courses for other disciplinary directions (light metallurgy direction, heavy metallurgy direction and metallurgical physical chemistry direction). As a branch of metallurgical engineering, rare metal metallurgy mainly studies the principles and processes of metallurgical processes of rare metals, because there are 59 different kinds of rare metals.
However, due to the similarity of metallurgical processes of many metals, the course selects tungsten, molybdenum, titanium, zirconium, hafnium, tantalum, niobium and rare earth metals as the representatives of the course. This course is intended for junior students in the direction of rare metal metallurgy, with 64 hours, and the course name is “Rare Metal Metallurgy I”; for senior students in other metallurgy directions, with 32 hours, and the course name is “Rare Metal Metallurgy II”. The course of rare metal metallurgy is relatively strong in engineering and covers a wide range of contents.
If the traditional teaching method is used to explain the processes and technologies in the course one by one, the lecture content will be boring and the students will be impatient. What’s more, because students have no working background, they can’t have a deep experience of the process, especially because of the progress of technology and the lag of the textbook preparation, which makes students can’t really grasp the dynamics and direction of technology development. It is worth exploring how to link theory with practice as much as possible in the teaching session so that students can learn more interestingly and efficiently.
Originally originated from Harvard University, case teaching method is a form of participatory teaching mode and an important form of teaching in economics and management courses in developed countries in Europe and America. In recent years, it has been widely adopted in the teaching of economics, management and law in China. Case teaching is a teaching method that brings students into the scene of a specific event under the guidance of teachers, enter the role, reproduce the case scenario, and improve students’ practical operation ability through case analysis. It presents a unique and realistic existing scenario to students so that they can be exposed to practical problems in a short period of time without leaving school, thus effectively compensating for the lack of practice and one-sidedness of learning.
The case teaching method is mainly applied to economic and management courses, while case teaching is less often conducted in the teaching of engineering courses, which is perhaps due to the complexity of engineering technology. The so-called case teaching method of engineering courses is to choose specific engineering practical problems as the basic material, and in the principle of combining theory and practice, the content of the case must include the basic theory taught.
Feasibility of adopting case teaching in rare metal metallurgy courses
The suitable target of case teaching method is senior undergraduate students who have mastered certain professional theoretical knowledge. The course “Metallurgy of Rare Metals I” starts in the 6th semester, and “Metallurgy of Rare Metals II” is in the 7th semester, which means that before studying metallurgy of rare metals, students have already mastered the basic theoretical knowledge of metallurgy, and have completed the process of cognitive practice or production practice.
Therefore, it is feasible to introduce cases in the teaching of rare metal metallurgy course, which can not only improve students’ ability of comprehensive analysis and handling engineering practice, but also enable them to grasp the frontier of scientific and technological development and problems in this field.
Principles of case selection
(A) conform to the syllabus. The selection of cases should first meet the teaching requirements, not deviate from the syllabus, not too difficult, not too easy and targeted, so as to attract the attention of students in class, and then improve the enthusiasm of student participation, so as to receive a good teaching effect.
(2) Realistic and typical. The cases should be selected from the actual production or scientific research, not by virtue of personal imagination to make up. In the selection of cases to achieve fairness and objectivity, not to praise their own demeaning others.
Selection of cases
The selection of cases is different because of the different objects of face-to-face lectures on rare metal metallurgy. For students in the direction of rare metal metallurgy, they have already participated in the internship of rare metal metallurgy plant, so they have preliminary knowledge and understanding of the site, so in the selection of cases, they will combine the scientific research projects undertaken by teachers and engineering practice to choose, and explain the innovative ideas, the design of new processes, the problems encountered in industrial tests and the ideas to solve them. For example, when talking about the treatment of titanium metallurgy copper wire tower vanadium removal wastewater, we introduced the case of ion exchange and precipitation purification method developed by us and applied in Zunyi titanium plant: after adjusting pH to 3.0-4.0 by adding alkali, adding hydrogen peroxide to oxidize V(Ⅳ) to V(V), then adding Cu2+ to increase Cu/V molar ratio to 7.5-8.5, then adding alkali to neutralize to pH 7.5~8.5, stirred at room temperature for 20 min and filtered. The content of cu and V in the filtrate is less than 2.0 mg/L, which meets the national comprehensive sewage discharge standard; the filtrate contains 45%-60% Cu and 11%-15% V, which has high comprehensive recovery value. These cutting-edge technologies do not appear in the textbook, and the introduction of such cases not only increases students’ horizons, but also can effectively improve their learning motivation, make them feel that scientific research and innovation are not the kind of things that are out of reach, and cultivate their innovative thinking and ability to analyze problems comprehensively.
For students from other directions, they take rare metal metallurgy more because they want to understand the similarities and differences between rare metal metallurgy and other metallurgical directions, and have a complete understanding of typical rare metal extraction processes through taking this course, so the selection of cases is different from that of students from rare metallurgy, such as the narration of tungsten metallurgy. In the textbook of rare metal metallurgy, tungsten metallurgy is written in stages according to the process flow of decomposition of tungsten mineral raw materials, production of pure tungsten compounds and tungsten metal powder. The advantage of this is that different technical methods can be compared horizontally, such as the decomposition of tungsten mineral raw materials by soda high-pressure leaching, caustic soda leaching, acid decomposition, and soda sintering in separate sections. This way of arrangement, for students who have some process foundation or have participated in internship, can let them fully understand the advantages and disadvantages of each technology and deepen the understanding of knowledge. Based on my teaching practice over the years, it is difficult for students of other metallurgical directions to form an overall grasp of tungsten metallurgy with such an arrangement. Therefore, in the process of explanation, I used the process of producing APT from wolframite in Xiangxi gold mine as a case to explain. Firstly, the pictures of the equipment and the connecting pipes at the site were shown in the process order, and on this basis, the process parameters and technical indexes of the production were explained, and the differences between the actual production and the theory were explained. The teaching practice shows that such teaching has got good effect, deepening the impression of students and motivating them.
Classroom Organization of Case Study Teaching
The success of case teaching depends on the joint efforts of teachers and students, and requires the active participation and cooperation of both sides. A successful case teaching not only requires teachers to prepare the lesson carefully before class and master the case content, but also requires students’ active participation during class. Therefore, when there is case teaching in the course, we adopt the following teaching links to ensure the smooth implementation of case teaching.
(i) Case reflection. After the introduction of the case, the teacher is responsible for organizing and guiding, and inspiring students to think independently, so that they can clarify the logical sequence of the case and the key technical aspects and the relationship with the learned basic theory.
(ii) Class discussion. Organizing students to discuss the cases is the key to the success of case teaching. Case teaching is different from example teaching, where the knowledge comes from the teacher’s explanation alone, while case teaching needs to come from the communication and discussion between the teacher and students. Through discussion, students can express their own views, recognize the views of others, broaden their horizons and deepen their understanding in the discussion. For example, in the case of alkaline phosphate high pressure leaching of tungsten from scheelite, the students first discussed the principle of the process and then asked them to find the difference points from the case. The theoretical principle is to add phosphate to sodium hydroxide solution to leach tungsten at high pressure, while the actual reagents used are sodium hydroxide and phosphoric acid. The discussion allows students to understand the difference between the economic factors and the theoretical practical existence, so as to clarify and explain the case with the example.
(iii) Review and summary. The purpose of case teaching is to practice on the basis of theoretical teaching. And the teacher’s summary review is the end of case teaching. Teachers in the summary review is to let students understand the implementation conditions of the technical route, the technical route of the development of ideas and the existence of advantages and disadvantages, so that students will learn the theoretical knowledge extended to the actual engineering, improve the students’ ability to analyze and solve problems.
Rare metal metallurgy is a highly specialized course, and it is necessary to explore and integrate various forms of teaching methods in order to obtain good teaching effects. In the early stage of teaching process, we have introduced the contrast teaching method into the course and received good results, and the introduction of case study teaching has increased the guarantee of good teaching effect. The introduction of case studies in the course of rare metals metallurgy has shown that, with the appropriate selection of cases and careful organization of teachers, the vividness and flexibility of the course can be enhanced, and the students’ enthusiasm to participate in the discussion of problems can be increased and the teaching level greatly improved.