What Does a Mill Operator Do?

The medium-sized rolling mill is a rolling mill that mainly rolls 40-80mm square steel, round steel, I-beams, channel steel below 120mm high, 50mm × 50mm 100mm × 100mm angle steel, 11kg / m light rail and other profiles. 580 medium-sized rolling mill is one of the oldest medium-sized rolling mills in China

The 580 medium-sized rolling mill is one of the oldest medium-sized rolling mills in China. It was put into production in 1935. After the liberation, with the reform and update of process equipment, the accumulation of operating experience and the improvement of proficiency, production is continuously developing, but compared with foreign advanced similar rolling mills, the product variety, quality and various technical and economic indicators are all There is a big gap. The key is the low level of equipment. Therefore, a technical transformation plan was proposed as early as the 1970s. However, due to the financing of the transformation, etc., it has not been achieved so far. ^[1]

Due to the increasing requirements of steel products for the quality of steel products, the worldwide energy shortage, and metallurgical companies' efforts to reduce costs, save construction investment and improve economic efficiency have promoted the development of steel rolling technology and equipment. The rapid development of contemporary science and technology, especially the widespread use of computers and the improvement of smelting and continuous technology within the steel industry, has created favorable conditions for this. The development of foreign medium-sized steel rolling technology has the following characteristics:

1. H-shaped steel, light thin-walled and other economical section steels have developed rapidly;

2. The degree of homogeneity and dimensional accuracy of section steel are further improved;

3. To achieve continuous or semi-continuous and automatic rolling;

4. The rolling mill body is developing towards diversification and high rigidity;

5. Online testing has received widespread attention;

6. The complicated finishing process of the work content realizes long-foot cooling, long-foot straightening, cold sawing, and automatic stacking and bundling;

7. Using continuous casting slab as raw material, realizing hot feeding and hot charging when conditions permit;

8. Quickly and widely apply electronic technology;

9. Gradual promotion of controlled rolling and cooling technology.

The medium-sized rolling mill of Chup, Texas, which started in 1979, currently has

The annual output of medium-sized factories increased from 100,000 tons in 1943 before the liberation to 678 thousand tons in 1987, and the products developed from 24 specifications of 6 varieties to 236 specifications of 37 varieties. Due to the continuous adoption of new technologies and processes, dozens of special-shaped cross-section steels urgently needed by the country have been trial-rolled, and the product quality has also been continuously improved. Hot-rolled section steel and shipbuilding ball flat steel have been rated as national high-quality products, and some products are exclusively produced in China . Therefore, the 580 rolling mill has been considered as a medium-sized rolling mill with high output, many varieties and high technical level, and most of its technical and economic indicators have taken the lead in the country.

However, with the deepening of reform and opening up, continuous medium-sized rolling mills have been introduced into the company, and many plants have undergone technological transformation. Some new processes, new technologies, and folding equipment have been adopted. The level of equipment has been greatly improved. For example, rolling bearings are used for rolling. The application of pre-stressed or short-stress-line high-rigidity stands, etc., has greatly improved the rolling accuracy.

The 580 mill faces challenges, and its advantages are gradually disappearing, and the gap is even larger than that of similar rolling mills. The main gaps are:

1. Product backwardness, first of all, the product standard is backward. Although the international standards for work, groove and angle steel have been implemented, they are only limited to the technical conditions such as dimensional tolerances. In terms of varieties, specifications, and cross-section dimensions, they are basically the former Soviet Union's FOCT standard series in the 1930s. The distribution of metal on the section is unreasonable, and waste metal amounts to 10-15%. The former Soviet Union had re-formulated standards in the 1960s and 1970s, changing to light series, and our country has been using them to this day.

2. Poor physical quality. With the advancement of science and technology, the steel processing department is increasingly moving towards high speed and automation, requiring the supply of steel with precise and homogeneous dimensions. In order to adapt to market competition, foreign companies put product quality first. The physical material of the product is higher than the corporate standard, and the corporate standard is higher than the published industry or national standard. However, we are only satisfied to meet domestic standards and produce in actual production. China even exceeds the standard allowable range and cannot withstand strict inspections. Except for 7.5 × 8 angle steel, the thickness fluctuation range is less than 1.0, which exceeds the current standard. The thinner and wider the product, the greater the fluctuation range. There is also a large gap in sawing, packaging, bundling, and appearance quality of our steel. Our packing and bundling cannot meet the requirements of long-distance transportation and reversing. In the dock loading and unloading, a large number of loose bales are difficult to export.

In addition, the straightness of the profile and the regularity of the shape of the two ends have a great influence on the use. The end deformation of the steel during hot sawing often cannot be corrected during straightening, which brings a lot of trouble to the user.

3. High energy consumption. At present, the energy consumption of a medium-sized plant is 83kg standard coal / t, which is 45.6% higher than the world advanced level of 57kg standard coal / t. Such a large gap is due to the fact that hot feeding and hot charging cannot be implemented; on the other hand, there is a large gap in the energy saving technology of the heating furnace, and the thermal efficiency is low. The current thermal efficiency is only close to 50%, and the advanced level in foreign countries can reach 70%.

4.Low level of mechanization and automation, heavy manual labor, especially the finishing process, before and after the straightening machine, stacking and bundling are all manual operations, with high labor intensity and occupying a lot of people. Compared with similar foreign mills, the difference is very large .

5. Outdated equipment, backward technology. The manual adjustment of the three-roller horizontal rolling mill basically has no online detection device.The operation of the rolling mill completely depends on the experience and proficiency of the workers. The roller bearings are rubber tiles, which wear quickly, have large deformation, and wear out when the arch windows are worn. With a jump value of 3mm, the rolling process is very unstable. The operator frequently adjusts the rolling mill, and the slightest sloppy will cause the most oversized quality accident. Therefore, it is not only difficult to roll light thin-walled sections, but even conventional products are difficult to ensure compliance.

The finishing process is still very backward a few days ago. The rolled products are sawed in the hot state, and the quality of the steel ends cannot be guaranteed, resulting in a large number of vertical cuts. This wastes steel and increases labor intensity, and the steel cutting rate also decreases.

6. Restricted by external conditions, fine rolling cannot be performed. The surface defects of the supplied slabs are serious, and unconditional and comprehensive sorting is carried out before the furnace is installed, which can only be carried out with waste rolling, resulting in an increased workload of finishing and sorting, and nearly 100 tons of poor steel scraps per month. According to the regulations, the curvature of the billet is 2%, which cannot be controlled in actual production. As a result, the furnace is turned over, and the 90 × 90mm billet is particularly serious. The length of the incoming material varies, and the cut-to-length billet only reaches 70%. The short-cut billet cannot pass the continuous rolling mill, which results in an increase in intermediate waste products. The rolled product also varies in length. The cut-to-length rate of the steel is only 50% -60%. Non-fixed-length steels of varying lengths are considered waste products abroad, but are now issued as qualified products, transferring trouble and waste to users.

At present, the price reform of metallurgical products, the first and second class prices have been merged, and even completely opened, coupled with China's imminent restoration of seats in the GATT countries, the situation is even more severe in the face of many powerful players at home and abroad. If the product lags behind and the quality is low, there is a danger of being eliminated in the fierce market competition. Therefore, it is necessary to hurry up and speed up the technological transformation. The transformation is imperative ^[3]

Technological transformation follows the principles of advanced, practical, economical and effective, and strives to grasp the general direction of domestic and foreign professional technology, accurately analyze and analyze the application conditions, scope and development prospects of various new technologies. Starting from the actual situation of our factory, Adopt advanced technology, practical and reliable technology and equipment to create higher economic benefits. In the implementation of the plan, pay attention to careful calculation and minimize the amount of engineering and renovation investment. In principle, the increased equipment is based on domestic manufacturing. For key equipment that cannot be manufactured in China or the quality is the most difficult to guarantee, import from abroad.

When formulating a technical transformation plan for a medium-sized plant, proceed from the following actual conditions:

1. The area of the factory area cannot be expanded. The east and west sides are adjacent to the factory buildings, and the north and south ends are roads. The reconstruction can only be performed in the existing factory buildings.

2. Maintain the existing production scale and product plan, and appropriately expand special-shaped steel sections such as light rail.

3. The relationship between the billet supply remains unchanged, and energy is basically not increased.

4. In order to maintain production, the transformation can only be carried out in conjunction with large and medium repairs ^[2]

Restricted by the transformation funds and construction period, the transformation risk is minimized. The transformation plan is implemented in stages. Considering that the finishing process is the most backward process and equipment of the whole plant, it is the current three outstanding quality, metal consumption and labor intensity The focus of the problem is that the difficulty and risks of the transformation are also smaller than those of steel rolling, and it can accumulate lessons for the next transformation. Therefore, it is decided that the first stage of the transformation and reforming process. The second phase of the reformation of heating furnaces and rolling mills, focusing on solving the problems of reducing energy consumption and improving rolling accuracy. The second phase of the project was also implemented in two steps. In the first step, the finishing mill was transformed, and the two three-roller finishing mills were changed to three two-roller short stress line rolling mills. Second, an online detection device was added. The second step was to transform the heating furnace and change the two former rolling mills into six continuous rolling mills, and the transformation plan was fully completed ^[2] .