Українська   Русский
DonNTU   Masters' portal

Abstract

Content

Introduction

The presence of longitudinal forces in the rumblings between adjacent stands to continuous hot rolling mills are the result of it is not exposed to and / or supported by the right the ratio of the drive motors speeds. This leads to the fact that the rolled material is subjected to uncontrolled deformation and process starting to be unstable and is in danger zone of failure, for example drilling or damage to equipment.

1 Theme urgency

The development of rolled production processes in the areas of flexible high-speed technological schemes, while tightening the requirements for quality performance profiles (primarily, accuracy) makes it relevant to complex tasks for finding effective methods of targeting technological process factors.

Keep in mind the increasing development and application of process control systems, which requires a relatively simple, versatile, fast, easy and reliable model, supplemented, meeting the requirements of object-oriented software. However, the ambiguous relationship of many technological parameters of rolling in calibers varying complexity limits the development and implementation of complex systems analysis and management with high-quality rolling. The implemented system are highly specialized, do not always agree with each other, poorly adapted to the changing technological conditions of production, does not allow a rapid analysis of alternative technological schemes. Therefore adaptivity is should be considered in two aspects [3]:

2 Observing rolling mill process

2.1 Rolling production. Common definitions and concepts.

Rolling – process of plastic deformation of bodies on the rolling mill between the rotating driving rolls (the part of rolls can be not driving). Words driving rolls mean that the energy necessary for deformation implementation is transmitted through the rolls connected to the engine of the rolling mill. The deformable body can be stretched also through not driving (idle) rolls, but it will be not process of rolling, but drawing process. Rolling is among the main ways of processing of metals pressure. Rolling receive products (rolling) of a various form and the sizes. As well as any other way of processing of metals pressure rolling serves not only for receiving the necessary form of a product, but also for formation at him a certain structure and properties [6].

2.2 Classification of processes of rolling

Processes of rolling classify by the following signs [6]:

3 Analysis of high-speed modes of operation of electric drives of continuous rolling mill group

Metal rolling refers to metal forming by pressure. The method consists in changing geometric dimensions of roll during the passage between the rotating shafts. As a result, increases the rolling width and length of the metal.

During metal forming it is assumed that the volume of the body during plastic deformation remains permanent. This makes it possible to link the size of the body before deformation with body size after deformation.

Formulates the law of constancy-second volume in the following way: the volume of metal flowing per unit time through the certain cross section deformation zone, which is formed by the working tool, it does not change when passing from one section to another in a continuous processing mode.

Mathematically, the law of constancy-second volume is expressed by:

Vi * Fi = const,

where Vi – average speed of movement of the metal in the i-th cross-sectional area of the deformation zone Fi [1].

On the basis of this law establish the relationship between the speed of movement of the metal and changes cross-sectional size of the deformable substrate in continuous processing mode.

Figure 1 is a technological scheme of metal rolling in a six-stand mill, consisting of a series alternating horizontal and vertical stands [2]. Such technological scheme is designed to form the desired product profile in height and width.

pic1

Figure 1 – Structural scheme of metal forming by pressure
Figure 1: Wi*Fi – law of conservation of second-volume of metal in the stands;
Vi – linear speed of metal;
Fi – sectional area of the deformation zone;
Vi & ndash; the volume of metal in interstand space.

Speed management of the main drives of the rolling stands is one of the main functions of automated process control system (PCS) of continuous rolling mill. Its task - for given strip speed at the exit of the final stand, based on the mode and compresses law constancy Seconds volumes strip speed calculated in each stand, and then, based on advancing, to identify and select a speed of rotation of the rolls. Its task - for given strip speed at the exit of the final stand, based on the mode of compresses and law constancy second-volumes, strip speed calculated in each stand, and then, based on advancing, to identify and select a speed of rotation of the rolls [2].

The cross section of the deformation zone Fi area is defined by the calibration of rolls of the stands, so the linear velocity of the electric drive must be strictly maintained in accordance with a change in cross-section passing metal.

Requirements to the drive of rolling mills:

  1. wide margin of speed control;
  2. high overload capacity at the torque;
  3. good operational reliability;
  4. minimum inertia;
  5. high starting torque;
  6. rigid mechanical characteristics.

In strict observance of speed limits by means of the electric drive, the metal will be rolled freely. An indication of compliance with free-rolling conditions can be static electric current of the first stand. If he hasn't changed after metal capture by rolls of the subsequent cage at simultaneous rolling in two cages, then rolling goes freely – there are no efforts of extension or tension. At change of static current of the ED of the first cage in the big party there is a redistribution of loading – the first cage assumes part of loading of the following cage. At the same time there is an effort of extension in a inter-stand interval. For his elimination it is necessary or to increase the angular speed of the drive of the second cage, or to reduce the angular speed of the first.

If static current of the EDS of the first cage has changed in the smaller party, therefore, the following cage has assumed part of loading of previous. At the same time there is an effort of a tension in an inter-stand interval. For his elimination it is necessary or to increase the angular speed of the previous cage, or to reduce the angular speed of following.

The sequence of correction of speeds can be both on the rolling process course, and against him:

  1. Correction of speed on the course of rolling process is carried out by method of fine tuning of subsequent (i+1)-th cages under the previous i-th cage. That is, change the angular speed of rotation of rolls (i+1)-th to a cage in relation to cage i-th.
  2. Correction of speed against the course of rolling process means change of angular speed of rotation of rolls of the previous i-th cage in relation to the speed of rotation of rolls of subsequent (i+1)-th cage.

4 Aftermath of inaccuracy settings for speed modes of electric drives

4.1 Excessive bending force

pic2

Figure 2 – Consequences of excessive effort of extension in metal on an inter-stand interval

The result of excessive effort of extension is drilling, i.e. the rolled metal has not come into the following cage and has begun to be bent. For avoiding of consequences of drilling, as a rule, using a special device for catching metal. In case of their absence damage to machinery, postings is possible, and there is also a threat of life of service staff.

4.2 Excessive tensile load

pic3

Figure 3 – Tension crack

 pic4

Figure 4 – The deformation gap

The consequences of excessive tensile force may be several events.

The crack of tension and deformation gap are defects of rolling process and owing to them the rolling mill receives defective products.

Tension crack (figure 3) appears, as a rule, when rolling a corner. It arises at worn-out working rolls because of which the effort of compression enclosed to metal, unevenly on all its area. In other words, working rolls roll one party of a corner quicker, than another.

The deformation gap (figure 4) arise at sharp acceleration of rotation of working rolls of a cage at metal capture. Actually, there is a slipping and metal is getting licked.

Goals and objectives master's project

Taking into account everything is higher stated, in the degree project it is planned to choose the most rational control algorithm of the high-speed control modes and to consider the possibility of realization of automatic system of regulation of angular speeds of working rolls for draft group of the continuous rolling mill 390 of the Makiivka branch of Yenakiieve iron and steel works. Also, in system of regulation of angular speeds of working rolls for draft group compensations of efforts in metal in inter-stand intervals have to be considered [7].

Objectives master's project:


At the time of writing this abstract of master's work is not yet complete.

The estimated date of completion of the master's work: June 2017. The full text of work and materials on the topic can be obtained from the author or his manager after that date.

References

  1. Теория обработки металлов давлением: Конспект лекций и варианты заданий для выполнения курсовой работы / сост. Н. Н. Загиров, Э. А. Рудницкий. - Красноярск: Сиб. федер. ун-т, 2011. - 5 стр.
  2. Pазработка математической модели взаимосвязанных электромеханических систем черновой группы прокатного стана. Андрюшин И. Ю., Шубин А. Г., Гостев А. Н. / Электротехнические системы и комплексы. Вып. № 3 (24) 2014 г. - С 24–30.
  3. Тулупов О. Н., Способ задания скоростного режима непрерывной группы прокатных клетей стана горячей прокатки металла с обеспечением минимального натяжения в межклетевых промежутках: Обработка металлов давлением. д-р технич. наук. Магнитогорский гос. техн. унив. им. Г.И. Носова, Магнитогорск, 2001 г.
    Режим доступа: Техносфера – библиотека технических наук.
  4. Бурьков В. В., Юнгер И. Б. - Способ задания скоростного режима непрерывной группы прокатных клетей стана горячей прокатки металла с обеспечением минимального натяжения в межклетевых промежутках, 2007 г.
    Режим доступа: FindPatent.ru – патентный поиск, 2012-2016.
  5. Цены на готовую продукцию компании КТ-СТАЛЬ.
    Режим доступа: База металлопроката КТ-СТАЛЬ.
  6. Редакционная статья, прокатное производство, 2013 г.
    Режим доступа: Международное издание Metallurgical and Mining Industry.
  7. Шубин А. Г., Гостев А. Н., Храмшин Р. Р., Одинцов К. Э. – Исследование системы компенсации межклетевых усилий в черновой группе прокатного стана методом математического моделирования // ЭС и К. 2015. № 4 (29).
    Режим доступа: КиберЛенинка – научная электронная библиотека.