Mill Line Research Articles

Rolling characteristics of new compact multi-reduction mill.

Increasing the rolling reduction in thickness in one mill stand contributes to realize a compact mill line and less initial and running cost.For this purpose many studies about the effect of the work roll diameter in case of conventional mill were tried out and it was recognized that the maximum rolling reduction per stand is about 45-55% at most.In order to achieve the high reduction over 70% in one cold rolling stand, “The three-gap rolling method” has been investigated. This New Compact Multi-Reduction Mill (NCM) consists of four work rolls arranged vertically in one housing and the strip is threaded through three roll gaps.The practical stable rolling condition has been accomplished on a test mill by regulating the tension, roll speed difference, rolling force, etc. Such rolling characteristics as the number of work rolls to be driven, the conditions to realize the optimum inter-gap tensions, and the position of the neutral points have been investigated theoretically. Further the rolling characteristics such as rolling force, torque, tensions, forward slip, rolling energy, and the optimum rolling conditions have been investigated experimentally.The new compact multi-reduction mill enables the high reduction over 70% in one stand and gives sound strip surfaces by applying improved lubrication.Finally the possibility of practical applications for tandem cold mills and reversing cold mills are discussed.

Development of regimes of induction heat treatment for electric-welded stainless-steel pipe in the mill line

A continuous furnace was replaced with an induction furnace for heat treatment of stainless steel pipes in the line of an argon-arc welding mill. The replacement was implemented for reasons of increased furnace reliability and decreased downtime and subsequent startup power consumption. After welding and induction heat treatment, the mechanical and service properties, microstructure, stresses, percent oxidation loss, and susceptibility of the pipes to intercrystalline corrosion were studied. The mechanical properties of the pipes met all standards within a broad range of temperatures after induction heat treatment. Satisfactory results were obtained in all processing tests, flattening, flanging, and spreading to which the pipes were subjected and from an x-ray diffraction analysis.

Grinding experience at Afton

This sums up briefly our experience with the Afton grinding circuit. We are still in the experimental stage with the combination rubber-steel mill lining, and we are certain that this experiment will generate a lot of interest by other operators by autogenous and semi-autogenous circuits.

アルミ熱延における材料温度計算

Fundamental experiments on air cooling, spray cooling and hot rolling of aluminum are performed for determining the heat transfer coefficients in hot rolling. And using these heat transfer coefficients, the temperature change of aluminum strip in hot strip mill line is calculated by the method of finite differences. The calculation results show that except in the roll gap, there is almost no temperature difference between the surface and the cross section center of the strip in case of aluminum, unlike in case of steel.Therefore, for computer control, temperature model for calculating the mean strip temperature is necessary.

ホットストリップミル用形状計の実用化

A practical shape meter to measure the manifest shape of running strip on a hot strip mill line with high accuracy has been developed. Structures and operating results of the meter are reported.The points of designing were getting good stability of an eddy current type displacement meter, protecting sensor heads and sensor positioning mechanism, and so on. Moreover the following functions were given; automatic sensor positioning, remote calibration of the displacement meter, statistical data processing of steepness data, and communication to a process computer.From the results of performance in Kakogawa Works, measuring accuracy of ±0.16% in steepness and time between failures more than 100 00 h have been obtained.

Use of new safety spindle in the main line of a Pilger mill

During service, the safety spindles fail 5-7 times a month. They fail with a slant fracture of infinite (dangerous) length, formed during overloads of the mill line (cold semifinishedproduct, gripping of a large volume of metal, fracture of the mandrel head, etc.). A significant portion of the length of the spindle is displaced when these slant fractures occur, so that additional breakage of various parts and components in the main line of the mill also takes place.

Improving the accuracy of cutting hot-rolled plate in the mill line

Improving the accuracy of cutting hot-rolled plate in the mill line

Examination of Slab Temperature Change, Rolling Power and Rolling Capacity in a Hot Strip Mill with Mill Arrangement Equivalent to Semi Continuous Type

A mathematical model is proposed for the mill arrangement equivalent to semi continuous type in a hot strip mill. The rolling schedule is arranged so that a slab is rolled from 230mm into 60mm in bar thickness by 3 passes roughing with only one reverse mill and 60mm into 1.2mm, 2.0mm, and 2.5mm in final thickness by 7 passes finishing. The possibility of rolling in this case is analytically examined in due consideration of slab weight, temperature change, rolling power, rolling capacity, and rolling speed. As a result, the rolling of the comparably heavy slab with 30t/m in unit weight is enabled, and the temperature condition is sufficiently fulfilled. The length of the rolling mill line can be geometrically shortened very much in comparison with the case of other type hot strip mill.

半連続式と同じミル配列の熱間圧延設備におけるスラブの温度変化, 圧延動力および圧延能力の検討

A mathematical model is proposed for the mill arrangement equivalent to semi continuous type in a hot strip mill. The rolling schedule is arranged so that a slab is rolled from 230mm into 60mm in bar thickness by 3 passes roughing with only one reverse mill and 60mm into 1.2mm, 2.0mm, and 2.5mm in final thickness by 7 passes finishing. The possibility of rolling in this case is analytically examined in due consideration of slab weight, temperature change, rolling power, rolling capacity, and rolling speed. As a result, the rolling of the comparably heavy slab with 30t/m in unit weight is enabled, and the temperature condition is sufficiently fulfilled. The length of the rolling mill line can be geometrically shortened very much in comparison with the case of other type hot strip mill.

Energy Saving in Rolling Process of the Three Quarters Continuous Type Hot Strip Mill

The total length of the rolling mill line and the state of slab temperature change are analytically discussed by means of a mathematical model for two different types o f hot strip mill: the quasi continuous type, which is usually called the three quarters continuous type, and the quasi continuous tandem type in which the last rougher and the finishing train are connected in tandem for shortening the rolling mill line.In the quasi continuous tandem type, the total length in the roughing process can be shortened to 56% compared with the case of the normal quasi continuous type. For a given reheating temperature, the slab temperature at the entrance of the first finisher remains much higher in the quasi continuous tandem type so that the reheating temperature can be lowered. Consequently, the quasi continuous tandem type is considered to be effective not only for the shortening of the length in a rolling mill line, but also for the energy saving in the rolling process.Finally, it is suggested on the basis of mill layout that the semi continuous type hot strip mill, which is insufficient in the rolling capacity and consumes a relatively large quantity of energy, can be remolded into the quasi continuous tandem type with comparative ease.

Analysis of Slab Temperature Change and Rolling Mill dine Length in Quasi Continuous Hot Strip Mill Equipped with Two Roughing Mills and Six Finishing Mills

The length of the rolling mill line and the slab temperature change are theoretically compared between the quasi continuous type equipped with 3 rougher mills, of which the first one is reversible, and 6 finisher mills and the quasi continuous 4 passes type equipped with 2 rougher mills, of which the first is reversible, and 6 finisher mills for a mathematical model that a slab is rolled from the initial thickness 230mm to the final thickness 2.5mm.In the quasi continuous 4 passes type, the total length in the roughing process can be shortened to about 60% compared with the case of the quasi continuous type. For a given reheating temperature, the slab temperature at the entrance of the first finisher remains much higher in the quasi continuous 4 passes type so that the reheating temperature can be reduced over 100°C. Finally, one conclusion is that the quasi continuous 4 passes type is much profitable not only for the shortness of the rolling mill line but also for the energy saving in the rolling process.

Process Computer System of Kawasaki's New Seamless Pipe Mill

Kawasaki Steel Corporation installed a new scaralcaa pipe mill - 16 in. plug mill - at the Chita Works and started commercial production in May 1978. A process computer (HIDIC 80) was incorporated in the new mill line. Optimum temperature control of rotary hearth furnace, automatic gauge control of rollings, and piece cracking systems were developed by using the process computer connecting with digital controllers and various sensors. Quality and dimension of pipes are outstanding. Productivity, yield and energy saving have been improved.

Truing angles in the 360 mill line

Truing angles in the 360 mill line

Durability of the ball mill lining

Durability of the ball mill lining

New developments in eddy current testing of hot wire rod and tubes

NDT of hot wire and hot tubes is described as a cybernetic process because of the high material speeds and high test-data-flow in on-line testing. The basic concept of a new eddy current test unit for the high speed testing of hot materials is described. Results of experience in many rolling mills with this unit when used for tests of ferrous, austenitic and non-ferrous hot wires and hot tubes (temperature 300–1200°C) in the diameter range from 5–60 mm are given. Artificial defects are used for initial tests. Correlations are derived between eddy current indications and depth of defects, which have been examined by eddy current as well as by visual and microscopical methods. Typical statistical relations between defect depth and the percentage of defects detected by eddy current result from this investigation. Finally, further applications of evaluated eddy current test results in the production line are discussed. These include automatic control of a rolling mill line, optimizing the cutting of defective wire ends, and the automatic cutting of welded tubes in the production line.

Rolling of weighted drill pipes on a pilger mill line

Rolling of weighted drill pipes on a pilger mill line

Experience in installing a computer control system in a hot strip mill

It is highly desirable to reduce the application period of a computer control system to a hot strip mill. Completion of a hot strip mill computer control system chiefly depends upon the time when slab tracking is operative, and on the setup calculation method and its checking method. For slab tracking, many support programs were devised such as dump, on-line monitor, process input-output simulator, and mill line simulator. To confirm the efficiency of the setup calculation method, a unique checking procedure has been developed and has proven to be quite effective. With these preparations for the installation of a computer control system in Sumitomo's 80-inch hot strip mill, it took only five months in the field to put the full system into operation.

The role of cast alloys in resisting abrasion by cement clinker

The types of abrasive wear encountered by metallic materials are discussed. The role of alloy cast irons in resisting high-stress grinding abrasion is discussed with particular reference to the importance of both impact fatigue and abrasion resistance in cast alloys for cement mill linings and grinding media. Examples are given of the mode of abrasive wear observed in certain of the high carbon, high chromium alloy irons. Recent developments in abrasion-resistant irons are discussed in relation to their use in large modern mills of 3000 h.p. currently used in the cement industry.

Mechanization of the handling of hot metal from the mill line

Mechanization of the handling of hot metal from the mill line

The City in the Swamp: Aspects of the Site and Early Growth of Calcutta

Kipling's lines were written about Calcutta; they suited it well. Founded in 1690 on a small natural l vee thrown up by he Hooghly River, and set precariously on the edge of a deltaic swamp in a climate devastating to Europeans, Calcutta brought gold and death to many as the first city established in Asia on the modern Western commercial/urban model. Earlier European settlements such as at Surat, Goa, or Madras, were more nearly traditional trading factories and forts rather than fully developed urban bases of widespread commercial enterprise and investment. Situated with an eye to trade where it could best tap the great productivity of Bengal, Calcutta was indeed built by the river and founded its power in part on silt?the agricultural wealth of the Ganges delta. A 40-mile line of mills along the Hooghly, fed by deltagrown jute,l came in the nineteenth century to dominate the city's commercial/industrial structure. Silt was a chronic problem for shipping (see below), but the riverine gift of alluvium helped sustain the city with food and with earlier trade goods such as indigo. The dense network of waterways in Bengal, where virtually all settlement is riparian, made it possible to move these commodities to the city at low cost for export. Calcutta, like most of the port cities founded in Asia by Westerners, has always been primarily a service centre for export trade, a funnel for the collection and overseas distribution of commodities produced over a wide hinterland and financed and managed through commercial organizations in the city. Since about 1750, approxi? mately half of India's sea-borne trade has passed through Calcutta. The functions which the city performed were essentially new to India, as was to be the case with nearly all of the other Western-founded port cities in Asia which arose in the succeeding two centuries. Like most of them, Calcutta occupied a site which had received little or no attention from the indigenous inhabitants, one which maximized access to and from the sea ('Me the sea-captain loved*) and to and from those parts of the country which were actually or potentially productive of export goods. Port cities as such were rare in Asia before the advent of the Europeans; urban develop? ment was primarily inland, and European attention to the maritime fringes of each country after the fifteenth century was rewarded by the discovery of plentiful oppor? tunities for a commercially minded people to establish trade centres on their own models, responding to situational advantages for trade which had until then been largely neglected. One result was that the new port cities which arose, of which Calcu rta was the pioneer and prototype, were from the beginning alien, were dominated by Western traders as in effect outposts of the booming world of commercial/industrial Europe, and came in time to exert a revolutionary impact on the Asian host countries, an impact which extended far beyond the limits of economics. Kipling's mention of the sea-captain was appropriate. The most important tech? nical tool of the fifteenth century Renaissance in Europe was the new mastery of ships and sailing. Europe's command of the sea (commercial rather than naval) remained an important basis of its strength and prosperity into the present century, and ships