外文翻译美国钢铁公司神户制钢冶金钢包的安装及运营

Installation and operation of a ladle metallurgy facility at USS/Kobe SteelINSTALLATION of a ladle metallurgy facility (LMF) at Lorains continuous caster spanned 90 days from groundbreaking to the first successful heat of steel. The primary reason for this relative short installation and start-up time was the cooperation and communication between engineering, operating and maintenance departments, and the installation contractors.The Lorain facility, formerly a USS Div. of USX Corp., is now a joint partnership (50/50) between USS and Kobe Steel Ltd.The plant occupies 2.70 sq miles on the south side of the city of Lorain, Ohio, approximately 25 miles west of Cleveland, near Lake Erie.The plant is a primary source of bar products mostly directed at automotive and fastener industries as well as seamless and ERW pipe for oil country and other petrochemical applications. It has three operable blast furnaces (2 x 1500tons/day and 1 x 3600 tons/day), two 220-ton BOF vessels and a continuous caster.The caster produces a variety of cross-sections and steel grades for sourcing the plants finishing facilities as well as customers. Caster capacity is 750,000 tons/year, but it has already achieved 900,000 tons in a calendar year. The balance of the raw steel produced, approximately 2 million tons/year, is converted to 11-ton ingots which are rolled at the 46/40-in. tandem breakdown rolling and sizing mills. Finishing facilities include one 12-in. and one 10-in. bar mill for rounds rated at approximately 750,000 and 420,000 tons/year, respectively. Bar mill product ranges in.size from 0.464 to 3.0625 in. Tubular facilities include two seamless piercing mills producing product from 2 to 26-in. OD with a cornbined annual capacity of 540,000 tons and one ERW mill for product in the 2 to 6-in. OD range with an annual capacity of approximately 110,000 tons.Attempts to justify a buffer between the BOF and caster, whether a ladle furnace or a plasma torch heating unit had been an ongoing objective for many years. A low budget, plasma torch installation had been made but found to be inadequate. A ladle furnace was required but the cost of a new facility could not be fully justified. However, a simplified ladle furnace consisting, in part, of used components that provided the required operating conditions could be justified. In addition, it could be installed and operational within six months from the date of authorization.Justification for the LMF expenditure was governed by three principal conditions: Achieving more stringent composition and temperature requirements.Locating an acceptable site.Establishing an appropriate method of construction and installation.Composition and temperature requirements - A 6-strand round and billet caster was started up at Lorain in Dec. 1983. Initially, only three different product sizes with easily castable compositions were made. Aborted caster heats were ingot poured and relatively few problems were experienced.Since that time, conditions have changed. Five more section sizes and a large number of grades were added to the product mix. The quality assurance department would not permit the ingot teeming of aborted caster heats and, in addition, the market was developing for low carbon/high sulfur free machining steels as well as high carbon/high alloy grades.With the steelmaking process 1 to 2 hr in advance of opening the ladle at the caster, the operating window at the BOF shop was small. Thus, the BOF became essentially dependent on the caster which, in turn, limited steelmaking productivity. The twofold problem to be resolved was narrowing of the bandwidth of final temperature and composition requirements for quality steel immediately prior. to casting and,to minimize the operating time dependence between the BOF and caster which was adversely affecting the productivity of both units.It was considered that an electric ladle furnace combined with a wire feeder ahd alloy trimming capabilities would probined a satisfactory buffer between the two operations. A capital expenditure authorization request was accordingly prepared. It was based on: reduced BOF tap to tap times; reduced BOF tap temperature,fewer caster heats recycled to the BOF for missed composition and/or temperature;increased BOF lining life;and increased caster productivity.Cost increases considered in the authorization request as a result of the new facility included those due to increased ladle refractory consumption and porous川ug wear as well as increased electricity consumption, alloy additions, electrode consumption and man-hours for operating and maintenance personnel.The cost benefits were considerably greater than the increase in operating costs and a high return on investment was established due, in part, to the capital expenditure being approximately one-half that of similar facilities (discussed subsequently) and construction in one-third the time.Location- Primary objectives in selecting a location for the ladle metallurgy facilities were: Closest and easiest transportation method to casting turret. 。Optimal crane service for operation and maintenance. Flexibility to bypass fatuity if the need arises to source the caster directly from the BOF. Minimal interference to BOF and caster during installation.The location selected was in the caster ladle aisle (Fig. 1).This location (in comparison with a site in the BOF shop)had the following advantages: a ladle crane available with alower utilization; and the operation would be under the supervision of caster personnel. A second transfer car was installed between the south teeming bay and south end of the ladle aisle to provide a bypass and also to avoid interference with the current operation during installation.Construction and installation procedure- A battery limits turnkey installation procedure was selected as the most desirable method of achieving, for this installation, the shortest installation time possible. With this procedure, the contractor would be responsible for everything within that zone of activity and Lorain personnel would be responsible for bringing all utilities to that zone.The advantage of this type of contract was that USS/Kobe did not have to wait for the award of the contract before beginning the installation of utilities and auxiliaries to the battery limits, most of which had system components with long delivery lead times. The contractor would only be concerned with installing a facility,the design of which could be based on previous installations and experience.In addition,the contractor would not have to become familiar with the plants utility and auxiliary systems.The significantly smaller investment,ously,referred to previously was achieved by using equipment that was removed ,reworked and then reused from either the Lorain facilities or other USS plants. In addition to utilizing the roof support, electrode hoist and power factor regulator from a 90-ton electric arc furnace at the Duquesne works, the contractor was also allowed to use a refurbished transformer.Concept, design and installationWithin battery limits- The turnkey supplier was responsible for the design,fabrication,erection and start-up of the LMF and for meeting predetermined criteria of acceptability.Design parameters included: Transformer capacity-25 Mva providing approximately 110 kva/ton. Power consumption-approximately 40 kwhr/ton. Power factor-70 to 75%/phase providing 16 to 18Mw. Pitch circle-36 in. dia. Thermal increase-guaranteed 5F/min during second part of arc reheating cycle.Additional features include reduced BOF slag carryover:addition of synthetic insulating slag (15 lb/ton). Composition and temperature control capabilities were to be achieved with two wire feeders, a check weigh hopper and chute for bulk additions, inert gas bubbling, and temperature and metal sampling equipment.The LMF builder disassembled an existing 90-ton, 20-ft dia electric arc furnace at the Duquesne works and removed,for reuse, the roof support, electrode hoist and power factor regulator. With a few minor modifications, the lift and swing-type roof ideally matched the 220-ton, 15-ft dia casting ladles at Lorain. The 18-in. dia electrode,housing equipment（drives, masts and arm assemblies) were also refurbished and reused although new bus tubes and electrode holders (interchangeable on any phase) were installed. The power factor regulator was .upgraded from an analog-based unit with no computer interface capability to digital micro-processor based circuitry with computer interface capability. The used transformer, a General Electric 25-Mva unit,was refurbished and installed with a 1-year operating guarantee. The LMF site is small: 80 x 65 ft. To conserve space, the transformer vault, which has a removable top hatch for removing the transformer (when needed), was built on top of the motor control center.All moving parts of the facility are electric motor driven or hydraulic. For safety reasons, a completely separate hydraulic system was used for the compression spring-loaded electrode holders. A patented water-cooled roof was installed that does not require any refractory or gunning with the ex-ception of a 3-hole refractory delta area.The high-voltage electrical system includes a no-load, motor-operated disconnect switch and vacuum contact switch with arc-over detection system. They are kirk-key inter-locked to the furnace main vacuum circuit breaker and a 3-phase ground switch for safe operation and maintenance. A600-amp motor control center was installed to distribute andcontrol the 480-v auxiliary power (Fig. 2).The LMF is fully automated and integrated with the process control host computer system for the iron and steelmaking division.All operations, with the exception of temperature and sample taking, are controllable from the operating pulpit.This includes control and/or monitoring of hydraulics, high and low-voltage electrical equipment, cooling water, wire feeders and bulk additions systems and fugitive emission control. The operator makes use of a full-function operators console, supervisory graphics computer and mainframe terminal to control the process.Utilities and auxiliaries to the battery limits- All utilities and auxiliary systems (Fig. 3) were designed by Lorain personnel or outside engineering subcontractors. These included electric power, cooling water, fugitive emission control and a bulk additions system.The electric power system required major modifications to the existing system principally at the remote substation where connection to the primary power source was required.These changes included: addition of high-voltage circuit breaker cubicles; 15-kv bus duct modifications; step-down transformer rewind and relocation; installation of a 14.4-Mvar capacitor bank from the Duquesne facility; and a 2000-ft twin-cable aerial run from the substation to the new facility. A dual-kirk key interlock system was introduced to make the electrical system safe to operate and maintain. A hook-up to a nearby caster motor control center was required to Installation and start-up - Highlightsbring the 480-v auxiliary power to the site.Cooling water is supplied by an existing system in the BOF shop that is used for cooling the vessel and hood. It is a closed, chemically treated system with dual cooling towers and precipitators. A supply return loop with a pressure reduciug station was installed utilizing 600 ft of 10-in.seamless pipe (produced by the Lorain seamless mill). A sixth pump and motor was added to the BOF cooling water system to provide the 1300 gpm delivery required at the LMF. The existing cooling towers provided sufficient thermal capacity for the additional load.Fugitive emission control was achieved by utilizing three modules of an existing 12-module baghouse system relocated from the idled cokemaking plant. These modules were located at a separate site from the LMF and required an approximately 100-ft run of 48- in. dia duct to the LMF (Fig. 3)and a 480-v hook up to the nearby BOF motor control center.Two of the three 40,000-cfm modules are used when theLMF is operating with one module on standby and to facilitate cleaning and maintenance. The emission control system was integrated with the main process controller that provided maximum capture during arcing and trimming, minimizing pencilling of electrodes, and gas pickup by the steel due to overdrafting with the furnace idle.The bulk addition system was installed after the start-upof the LMF, and brought into operation approximately sixmonths later. Located inside the BOF north teeming bay,200 ft west of the LMF, the system includes six compartment hoppers feeding a weigh hopper which, in turn, feeds material onto a 600-ft conveyor belt that transports the material onto a 600-ft conveyor belt that transports the material to a check weigh hopper at the LMF.It has a design delivery rate of 50 tons/hr based on material density of 1501b/cu ft.Fully automated with tare weighing capability,it is directly linked to the main process computer for remote control by the LMF operator.Installation and start-up - Highlights of the facility installation included:Order placed with furnace builder-July 1987. Second transfer car installed and operational-Sept.1987. Ground breaking-Sept. 1987.Utilities and auxiliaries system available at battery limits-Dec. 1987.First arc struck -Dec. 21, 1987.Striking the first arc was followed by a 5-day trial operation, check out and start-up. A 2-turn operation began immediately, followed, eight days later, by 3-turn operation. Concurrent with the start of the 3-turn operation, the temperatures at th BOF were reduced by 50F on caster heats and an additional 30 to 40F one week later for a total reduction of 80 to 90F.A key to both the short start-up of the facility and a short learning curve to maximum operating level was the fact that,all control software was written, debugged and documentedby USS/Kobe personnel and that operators were given preliminary training on a duplicate, simulated control system.In addition, operators were transferred from CAB stations in the BOF shop where composition and temperature control practices are similar as well as staffing the operation with maintenance personnel having electric furnace experience.Personnel involved with the project had also toured other steel facilities with LMF to familiarize themselves with the operation. Initial operationThe overall start-up and early operation of the LMF was considerably better than expected and the anticipated objectives were easily accomplished within the first three weeks.There were,however,some problems.Recognizing that a used,refurbished transformer was being operated,coupled with the early problems experienced,a practice was established that involved full electrical and insulation testing on a monthly basis to diagnose potential problems,take corrective action or predict change-out with a recently acquired,new spare transformer having a higher capacity.Control interlocks and permissives were resequenced to allow full process flexibility and maintain a high degree of safety.There were two arcing problems.Arcing of the lubrication and hydraulic lines caused by insufficient electrical insulation,hydraulic and water leaks caused by arcing of the center phase bus tube to the mast arm assembly,and arcing from the electrodes to the roof.The arcing problem between the electrodes and roof opening was of such magnitude that the water leaks would cause a shutdown ofthe LMF.Refractory gunning of the roof,especially in the electrode area,was usually successful(as a temporary measure)except when the operating rate of the LMF would not provide sufficient time for the gunning operation.The 3-piece refractrory detla was redesigned as a 1-piece,quick change unit.Operating practice - A typical,fictitious,operating practice for a continuously cast heat is illustrated in Fig.4.Although the temperature-time profile at the LMF is not linear from the arrival of the heat to departure,it can be approximated by two linear profiles during that overall period.During the first stage ,when the ladle and LMF refractory systems,and electrodes are relatively cold,the steel can be heated at a rate of approximately 3 to 3 1/2F/min.During the second stage,when the refractory and electrodes are soaked out,the heating rate increases to 5 1/2 to 6F/min.Nitrogen pickup - Initially,excessive nitrogen pickup was experienced on some caster heats,especially boron grades.A low nitrogen practive was implemented that included:Additional insulating slag to further shied the steel surface in the ladle from the environment.Nitrogen monitoring throughout the process.Reduction in BOF charge fuels and fluxes.Automatic control by the main process controller over fugitive emission control systems to reduce draft while furnace is idle.This practice minimized electrode pencilling and reduced drafting in the ladle freeboard where gas pickup occurred.Ladle modifications - To accommodate the agitation of the steel bath at the LMF,a 9-in.increase in freeboard was added to all steel ladles.Also,due to potential thermal and electromagnetic stresses,a third belly band with gusset stiffeners was installed and the size of the lip ring increased to handle the slag slop from furnace agitation.Only small changes were made to the ladle refractory lining.A wroking lining of 70% alumina on the walls and 80% on the bottom was employed together with dual porous plugs and dual rotary nozzles.The safety lining was unchanged with 50% alumina throughout,except for the use of dolomitic brick at the slag line.The major change was made to the slag line of the wroking