Metallurgic crane as key and essential equipment in metallurgic industrial for safe and normal production.
Its working reliability, safety, advancement have always been highly valued by us, 
With the deepening of reform and opening up, a large number of foreign advanced technologies have been introduced, and the modern metallurgical cranes also have changed greatly.
This article discusses the development trend of metallurgical crane based on the improvement of metallurgical process of domestic metallurgy enterprise and the demand of end user.
The metallurgy cranes mainly refer to the casting crane, charging cranes, slab handling cranes, steel coil clamp cranes, magnet cranes of the metallurgical enterprises and othermodel overhead cranes serving for metallurgic plants with heavy working class.
Now, we will go on some preliminary analysis of the development trend and cranes used by metallurgical enterprises.
1 The general development trend
1.1 Upsizing lifting capacity, high working speed
One of the maindevelopment trendof modern metallurgical cranes is that large lifting capacity and high working speed.
With the development of society, the demand for metallurgical enterprises is also gradually improving, not only reflect on the quantity of metallurgical products, but also on the quality and variety of metallurgical products.
Due to increasing social demand, which facilitate the technical renovation and technological progress of metallurgical enterprises.
With application of large converter, continuous casting, rolling technology, higher demand on the large-scale and high speed of metallurgical crane.
This paper makes a simple statistics on the development of casting crane of major metallurgical crane in China.

Time	Main hook (t)	Main hook (m／min)	Long travling (m／min)	Cross traversing (m／min)
1950s～1970s	200	2～5	70	40
1980s	280	10	80	40
1990s	450	12	80	40

From the table above, the lifting speed and weight of the main hook have been greatly improved.
1.2 Adopt speed regulating system in lifting and traveling mechanism.
In the early 1970s ~1980s, with the development and maturity of AC speed regulation technology, various famous crane manufacturers from foreign countries made the promise on the speed adjustment of various institutions.
The speed regulating ranges differ from the speed regulating methods.

Speed adjustment model	Speed adjustable range	instructions
Eddy-current brake	1/5～1/10	Energy dissipation, not suitable for long time use, tends to be eliminated
Stator voltage regulation	1/10～1/20	Energy dissipation，the speed regulating performance is better, most in use…
Inverter control	＞1／20	The speed regulating performance is good, renewable energy can be achieved, in developing…

Now, the most design solution adopt stator voltage regulation and frequency control system, in lifting mechanism mainly adopt stator voltage regulation and frequency control in traveling mechanism.
Some evident advantages after adopt speed control system.
a) Mechanism start and brake smoothly. Which is a good advantage for casting cranes to lift steel ladle
b) Effectively reduces the wear of brake block.
c) Locate the object accurately
d) Reduce the impact on metal structures (bridge or trolley frame) and transmission systems, exlarge the lifespan.
e) Effectively imporve the working conditions for workers.
f) Reduce the impact on power grid when starting.
Some problems also caused as followings:
a) Crane cost increase;
b) High technical level on maintenance electricians.
Although causing costincreasing after adopt speed regulating system and make the maintenance difficult, the cost of the speed regulating system is also decreasing gradually as the technology progresse and its advantages become more and more obvious.
1.3 Monitoring and sensory control technology are widely applied, Usability and reliability are greatly improved.
With the progress of science and technology, various monitoring and sensing control technology have been widely used in metallurgical cranes, so as to make use of the crane performance greatly improved, which change the metallurgical crane from previous simple material handling tools into the equipment of logistics, information flow integrated transmission.
1.3.1 Weighting system:
Setting up digital weighting system on metallurgic cranes, small displayer installed inside the cabin and big displayer intalled under the main girder and toward the ground, showing the liquid steel weight at any time, associated this data to the computer, on one side, which can accumulate the daily output, on the other side, it can recommend weight of liquid steel based on weight and size of steel billet to reduce the waste.
With the application of various large and high-precision electronic scales, the metallurgical crane can also realize the statistics of production, overload power and alarm and other functions except for lifting goods.
1.3.2 Fault display and record and print device
In a continuous production of steel mills, time is money.
After the crane has broken down, the maintenance time will be reduced to the shortest.
Fault display device can display components and parts name on the display screen of drive’s cabin, maintenance personnel immediately know failure parts, which can greatly shorten the maintenance time.
Quick-wear part of the electrical and mechanical parts, the owner can make a list, crane manufacturer should be in accordance with the requirements of the owner settingfault display , once monitored component failure ,which will be displayed on the screen, to avoid the happening of greater fault.In addition to the display function, the device also has a record and printing function, which can be used for finding fault reasons and check the responsibility.
1.3.3 Three-dimensional positioning device
Sling position can be displayed by this device in the cabin’s screen, positioning accuracy can be controlled under ±10mm, which can meet the technological requirements of all kinds of automatic production line.
Drivers can visually determine whether sling or object has reached the location through the figure displayed on screen, which could shorten the operation time, also avoid shaking of the object, and can effectively improve production efficiency.
1.3.4 Anti-collision device
In the past, to prevent two crane collisions,  only install the limit switch and buffer, now, we have Laser or radar collision device.
Install a launch device on a crane, and set accept or reflectors device on another crane, when two cranes reach pre-set distance, which will givingalarm and avoid a crash.
1.3.5 Safety brake 
When lifting importantobjects, e.g. nuclear materials, liquid metal, large hydropower generator rotor, which need to set safety brakeon the drum in the main lifting mechanism of crane.
In one side of the flange braking torque can be set up one pair, 2 pairs and even 3 pairs of brake shoe, controlled by the hydraulic station.
When starting, safety brake opens first, the working brake then open that installed on high speed shaft.
When braking, working brake first, safety brake lag brake for a few more seconds.
The function of safety brake is to ensure any transmission parts damaged or broken that work in all chain link between working brake and safety brake, the objects that lifted can be safe.
Apply various monitoring, sensing technology appropriately on the crane, implementation control of metallurgy crane with wire or wireless,which is not only the developing direction of modern metallurgy crane, but also become a design goal that workers should strive for.
1.4 Programmed control technology, remote control technology used in special environment
With the development and perfection of computer hardware and software technology,which make procedural control cranes become possible, and its control scope has become increasingly widespread, control function also has become increasingly perfect, all kinds of metallurgical craneperforming certain tasks has become a reality according to the model human setting in advance
In order to completion of various tasks more accurate and instantly, all kinds of metallurgical crane linkaged with main control equipment by wire or wireless.
The remote-controlled metallurgical cranes have been used in some metallurgical enterprises. It is mainly used in some high dust and high pollution hazard areas, such as steel mills
The program control metallurgy cranes are used in some occasion with high efficiency. It can improve the service life of the crane, reduce the impact and improve the accuracy of the operation, operation efficiency and improve the driver's operation environment, process control and remote control crane crane will get certain development in some degree and will be gradually adopted by metallurgical enterprises
1.5 Standardization of structural type and internationalization of production mode
The reason we put "standardization of structural type and internationalization of production mode" as the main development trend of modern metallurgy crane , mainly due to following two aspects:
a) The objective demand of market economy for metallurgical crane, because of the economic operation system has been shifted from planned economy to market-oriented economy,providing strong and favorable conditionsto allow the equipment procurement unit using the bidding forms to choose high quality and low price products in a short period of time.
b) The development of information and communication technology provides sufficient material and technical support for it.
1.6 Generalization of crane type, customization of lifting attachment.
It is mainly due to the renewal of the rolling technology of metallurgical enterprises, namely, from traditional ingots, deingots, cast, hot rolled, and continuous castings. Match with the traditional process, metallurgical enterprises need to equipped with bridge cranes, container cranes of feeding, casting crane, stripping crane, soaking pit pliers peel crane crane, soaking furnace cranes to complete the process.
1.7 Rational man-machine engineering and the comfortable operation environment.
With the progress of the society, the improvement of environmental awareness and the labor protection consciousness, which put higher requirements on the man-machine engineering and comfortable operating environment in the process of metallurgy crane design, e.g. the driver cabin equipped with cold and warm air conditioning, heat insulation, ground wireless remote control, wire and wireless communication modules, aero seat ,rest room, crane with oblique ladder, electrical rooms equipped with heat insulation protection and air cooler, narrow walkway with anti-skid measures, installed repair lifting cage etc. Providing a good working environment and conditionsfor the operation and maintenance personnel.
2. The analysis and understanding of typical structure and transmission type
2.1 The development trend of lifting mechanism of casting crane
The main transmission of casting crane adopts star reducer,which will be a development trend of modern casting crane.
2.2 Clamping device for soaking pit crane
Gravity clamp, electric open closed gravity clamp, power tongs, three clamping device, due to the power tongs with high cost, its promotion is influenced to some extent, but because of its superior performance, especially the jaw can realize accurate three-dimensional tracking, pick up the trapezoidal billet reliably , high efficiency and no loss of lifting height, to achieve the automation of the metallurgical enterprise with incomparable advantages
Therefore, we believe that dynamic slab clamping crane will play an increasingly important role in the development of modern metallurgical cranes.
2.3 Wholistic processing of crane bridge and trolley frame 
Wholistic processing of crane bridges, trolley frame and other structural parts, which is an important measure and effective way to ensure the quality of metallurgical crane products.
Due to the particularity of metallurgy crane work, which require higher standard on quality, whole trolley frame processing refers to the motor base of trolley frame, brake basement, reducer bearing, drum bearing seat, and the trolley wheel bearing seat frame welding in line at once crossed, the shape between each other,dimensional tolerance guaranteed by machine, so the assembly work become easily.
In short, the shape tolerance between these components are ensured  by machine, whichhas nothing to do with the technical level  of assembly workers, ruled out the man-made factors, thus greatly improving the assembly precision and operational performance, at the same time, greatly shorten the maintenance time of users.
2.4 Basic drive and control
With the continuous production of metallurgical industry, metallurgical cranes are required with high reliability, good debugging and positioning performance, fault self-diagnosis, operation and comfortable and other functions
Control mechanism: industrial PC machine +PLC +basic transmission 
Basic transmission adopt inverter control.
Operation process from the traditional artificial speed control gradually transit to the accurate position control of PLC, job information will be automatically pass to the PC (industrial PC), finally connected with the whole plant management and control system ,which is a main development trend of metallurgical crane.
2.4.1 Basic transmission
All-digital controllable stator speed control and the variable frequency speed regulation are as the leading type in basic transmission.
The lifting mechanism will adopt inverter variable frequency control (e.g., Siemens AFE) 
The traveling will be based on variable frequency speed adjustment.
2.4.2 Automatic control
PLC will finish all the function of the automatic control, through field bus (PROFIBUS) realizing the control of speed and position, which with massive communication information, simple connection and high reliability.
For automatic stacking crane with slab continuous use, the rolled steel will be continuously automatic stacked, PLC will complete automatic timing, positioning automatic clamping, automatic positioning stacking according to the setting, the whole process will be done automatically, repeatedly, the system also has self-diagnosis function to ensure reliability.
In case of failure, the driver can switch to manual operation, and switch from any process point to the automatic processat any time, which will make the efficiency higher and equipment operation more reasonable.
2.4.3 Fault monitoring and control
The PC or touch-screen interface that installed in the driver's room will be able to display the malfunction information of the operating status of the various agencies and it can set the process instructions on the PC and download to PLC.
The automatic control process can be realized with automatic control function.
The industrial PC can also realize the automation of production management by means of communication network with the factory management.