Industry + Work | 1950 | Sound | Colour
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Steel Industry in Sheffield England A fascinating account of the three steel making processes used in the 1930s,
the seimens open hearth process, the electric arc process, the high frequency induction process. Comprehensive and detailed accounts of the steelmaking processes listed above are provided, 1950's
voice over " A million feet of factory space are occupied by Firth Brown in Sheffield for the melting of high quality steel. For the melting of these steels Firth Brown use the following smelting process; the Siemens open hearth process. Cut to intertitle : Part One: Siemens Open Hearth Process. Huge masses of plain carbon or low alloy steel are melted in gas fired , acid lined , Siemens open hearth furnaces up to 100 tons in weight. During the process of steel making temperatures of up to 1006.50 degrees can be reached and to withstand these high temperatures Fern's walls must be of a refractory or heat resistant nature. This voice over uses good imagery of a man stoking a furnace with a close up of an open hearth furnace. For this purpose special silica bricks are used. The hearth which carries the charge in which the steel is made is formed as a lining of fused silica sand. The fuel in this type of furnace is a mixture of producer gas and air which before reaching the combustion chamber is preheated. This voice over works over a series of images showing close ups of the furnace. There are three different charges used in the furnace ( voice over slightly obscured here ) of 60, 80 and 100 tons capacity, and they're combined output will be used for the casting of an ingot of well over 200 tons in weight. Mechanical charges are feeding into the furnaces. Controlled proportions of iron ore , pig iron and steel scrap of high grade and known composition. We see the melting of the gas in the furnace under the action of the gas flames in unique interior shots takes through the door of the furnace. Development of colour photography has made it possible to reveal these stages in steelmaking . Shot of a man pushing a lever towards the camera, used to control the reversal of the gas flow. Midway the gas is shot off and at this point temperature readings are taken with an optical pyrometer and fuel adjustments made to suit. During the course of the progress visual observations are made of the bath or charge of steel and furnace atmosphere at frequent intervals. Cut to shots of the inside of the furnace with the charge completely melted. From the time that the bath is fully melted samples of metal and slag are taken at regular intervals for laboratory test and analysis. Excellent footage of a man retrieving a long handled plate from the furnace. Considerable skill is employed when extracting these bath samples to ensure they are representative of the bath conditions. A sample is retrieved and poured into a casket to be taken away for analysis. Drillings of the samples are taken and subjected to laboratory tests. Here the carbon content is being determined by burning the drillings in oxygen, absorbing the gases and weighing them. Cut to shot of scales. The carbon content is about 1.7%. After the carbon content has been checked further additions of iron ore are made. Cut to shot of men quickly shovelling iron ore into the furnace. They wear long coats but do the work with out masks . By adding iron ore the carbon content in the bath is reduced, the reduction being obtained by the reaction of the oxygen in the iron ore producing carbon monoxide gas. Lime is added at this point to provide the correct type of slag or protective coating for the bath. The function of this is to protect the metal from the contaminating effect of the flame and the furnace atmosphere. This slag is formed from the association of the added lime with the other slag producing materials already present in the bath. The part of the voice over is comprehensively covered by footage of showing the addition of new compounds. It is similar in appearance to molten glass and has a dark brown or greenish colour. The addition of ore and lime to the bath produces active chemical reaction and the liberation of the carbon monoxide gas brings about an appearance of boiling in the furnace. Cut to footage of this boiling reaction in the furnace interior. For recording the temperature deep in the bath a mobile immersion pyrometer is used . This resembles a Howitzer gun. The temperature is transferred from the thermo- couple to the furnace and can be read in a meter. This mechanism is so tolerant that it can pick up temperature differences of between one or two degrees, even when working in the range of around 1630 degrees Celsius. Panning shot down a large furnace. The product of three furnaces will be combined to provide an ingot of over 200 tons in weight, and the ingot mould must be correctly prepared, pre-heated and carefully inspected and finally lowered into position in the casting pit, so that it is ready to receive the molten steel shortly to be tapped from the furnaces. The total weight of this specially tapered mould will itself not be less than 200 tons. The feeder head is next lowered onto a position on top of the cast iron mould, and will accommodate some 40 tons of metal in a fluid position. As the metal in the ingot mould solidifies and contracts, the formation of cavities is presented by the slower additional metal union flows from the feeder head. All this part of the voice over is done over detailed shots of this part of the production process. The size of the machinery dwarfs the men adjusting the equipment. It is essential that the metal in the furnaces is brought to a state of identical composition condition and temperature. This entails the closest so-operation between the melters, the technical staff, whilst continual temperature and inspection readings must be maintained, and adjustments made on laboratory tests. A montage of different shots which have been used earlier in the film are put together here. The sample processor? Records the process of the three heats and co-ordinates their workings until a stage is reached when the carbon values of each is within specified requirements certain other steelmaking alloys must be weighed in carefully , calculated quantities including ferro- silicone, ferro- maganese. Ferro- chrome, and ferro- nickel. After these finishings have melted final samples and pyrometer readings are taken. The furnaces are now ready for tapping. Cut to shot of first furnace being taped, in a flurry of sparks. The other two furnaces are apped soon after and the molten steel makes its way down the launders or channels into the waiting ladles. Once again optical pyrometer readings are taken during tapping because the temperature in the ladle will have an important bearing on the selected rate of flow into the ingot mould. The shots used over this part of the voice over are of particular interest showing the scale of the production process and the machinery used. When tapping is completed, the ladles move over to the waiting mould in the casting pit. The metal in the free mould ladles is noe teemed into the mould. Excellent footage on the process being watched by managerial figures high up on gantries above the moulds. The first ladel opens out into a trough. At this point the soundtrack stops. Molten steel is poured into a channel. There is a controlled stream entering the mould. Cut to shot of second stream poring into the mould. Finally a third ladel will be brought into a central position over the mould. Kodachrome stock used in this production means that the colours are particularly vibrant with very strong reds and yellows. From a position above the mould the progress of the steel is viewed by more senior managers (possibly scientists) holding visors close to their faces. Metal from all three ladels flows into a larger mould. Temperature recordings of each stream are made throughout the entire casting operation. Cut to a young man holding up a measuring tool. The behaviour of the metal in the mould is also checked to confirm the teeming speed is correct. The work of casting ingots of this size will usually take up to 3/4 of an hour. Very bright image as the molten iron is poured into the mould. The mould starts to fill up. Very good short brief shots of the men working on the process. After casting is completed the ingot remains on the e mould and is allowed to cool then the feeder head is removed and finally the ingot is lifted from the mould. The timing of these operations has been so accurately determined so that solidification of the body and head of the ingot is complete. Slow panning shot up length of ingot. Good shot of the ingot being transferred to the forge re-heating furnace. (The structure of the building in particular the roof of the steel plant is clear in long shot here) for the production of a solid forging or alternatively to heat treatment furnaces for careful kneeling to obtain a cold ingot free from the danger of cracking. Such ingots when kneeled and cold will often under go various machinery operations to prepare them for conversion to hollow forging . This extract from the voice over shown over images of the transportation of the steel ingot over rail. While cold the ingots will sometimes undergo various machinery operations to prepare them for conversion to hollow forging. An ingot from which the head and part of the body have been discarded. The centre of the ingot has also been removed as a solid core by a pre-panning operation, the core subsequently to be used for examination purposes. After this machinery and further re-heating the prepared ingot is worked between a mingle passing through the bore and a tool mounted in a large hydraulic press. Shot of the ingot being withdrawn from the reheating furnace, with a mingle placed in the centre hole, and moved towards the 6000 pound press under which the material will be gradually shaped to make a large hollow forging. As the ingot is moved slowly from one end of the plant to the next, the voice over explains that whilst the forming of these components is in progress numerous re-heatings are necessary owing to the very limited temperature range in which such forging can take place. Excellent shot of the molten ingot in the foreground, a man standing in the front of it, and in the background the blue of the transportation machinery, contrasting with the vivid red of the molten steel. The time allowed for raising the steel to forging heat is determined by previous experience on similar jobs, the temperature varying with different compositions of metal. Great care must be taken to ensure completely uniform temperature is achieved. We see the forging after initial expansion being withdrawn from the furnace for further working. Very bright shot of white molten steel being slowly retrieved from the furnace. As the core is enlarged so larger mingles are inserted accordingly. On these mingles the steel will be progressively forged out to the desired length and wall thickness. To obtain correct symmetry of wall thickness internal and outside dimensions and straightness reliance is placed on the experience and skill of the forge men who by applying pressure at the correct spot maintains by eye a straightness over great lengths which must be seen to be believed. As the pressure is applied to the molten steel the scale falls away leaving the hot metal below. Good shot of this. Scale now removed in this way is taken off manually. The more closely final dimensions are approached, the more important it becomes to dispense with scale. The molten steel is revolved around a drum. At intervals pressure from the press is applied and the steel is forced into shape . Final shaping is nearly complete, so partial heating is only necessary to complete the process. Despite appearing rough the steel can be machined without the removal of an undue amount of material from the siemens open hearth furnaces of capacities up to 100 tons efficiently large ingots can be produced to form these large forgings of which the one we see is typical. We see a large yellow ingot dwarfing the men around it being scrapped. The development of the large modern engineering project such as power stations, motor and steam ships, chemical works demanding the use of high pressure boiler drums, motor shafts, marine propeller shafts, chemical reaction chambers is to a great extent is dependent on the skill and experience of the steel maker and forge master for it is his duty to divide the large masses of material to a standard of quality which is consistently high. This section of voice over works over a montage of exterior daylight shots of the large steel ingots waiting to be transported by train. Smaller ingots from similar quality open hearth steel are also cast for the manufacture of smaller components. We see one of these being cast in the form of a disc or wheel which has been partially forged and a hole punched through the centre to form after rolling, railway locomotive tyres. This disc is now rough to shape on this special rolling mill and afterwards finished on a horizontal finishing mill. In the case of railway locomotive tyres such close limits can be maintained that the outside form and diameter need no further operation before the tyre is put into service . Excellent shot of large locomotive tyres or wheels being carefully stacked up. Railway axles , crankshafts and connecting rods and heavy duty springs together with all the types of marine and engine forgings are produced with the same technique and care and are thus particulary suitable to rigorous service conditions which they have to undergo. Panning shot of locomotive tyres on locomotive number: 21C101. intertitle: "Electric Arc Process The electric arc process is used for the production of high quality steels, for the aircraft, motor and general engineering industries. In addition , heat and acid -resisting steels, and steels for tools, dies , hobs , etc, are made by this process . The electrical process is capable of producing steel of a distinctly higher degree of purity than the siemens open hearth furnace. This part of the voice over told over medium shot of workers standing beside furnace . Undesirable elements such as sulphur and oxygen are more readily controlled. It is for this reason used for the production of high alloy steel for the aircraft , motor and precision engineering industries. These applications demand steel of a known and very closely controlled specification and standard of purity and cleanliness. Scrap and pig iron are charged into the furnace by a mechanical charger. The scrap is graded not only in respect to chemical composition but according to physical characteristics. The heavier scrap is charges into the furnace first because it is less subject to oxidisation. Detailed footage of these events is shown. The light scrap is then charged. Afterwards suitable amounts of lime and iron ore are added to provide the controlled oxidisation effect. The lime forms a greater proportion of the slay coal in the electric hearth process than it does in the open hearth type. Detailed shots of the lime and pig scrap being inserted into the furnace. Close up of the engineer stoking the furnace and adjusting the flow of air. The charge is melted and refined by the enormous heat developed by the electric arc. The temperature of the arc is about 3000 Degrees centigrade. Close up the measuring equipment mounted on a wall to give accurate predictions and the metal melts at approximately 1500 centigrade. The arc from the 16 inch graphite e,ectrodes stokes the charge with an intensity of light which is almost blinding . It is for this reason that dark blue glasses are worn by the operators . Montage sequence showing the hearth in long shot and close up . Electric current of 25,000 amperes is maintained during the melting period controlled by automatic equipment. After two and a half hours, the bath is completely molten and further carefully adjusted amounts of lime and iron ore are added to meet the oxygen requirements of the melt. Owing to the violent reaction brought about by these additions only small quantities can be added at one time. Various and multiple shot of the materials being added to the furnace. Such additions are calculated according to the capacity of the furnace which may vary from three to thirty tons. By skill learnt by much practice the melter distributes these additions uniformally over the bath. Further uniformity is obtained later through the thorough ravelling or stirring of both slag and bath. The reaction of the iron ore on the carbon in the bath is profoundly affected by temperatures and as the heat increases so the reaction will commence, carbon monoxide will be given off, and the bath will appear to boil. Slow motion shot showing the action of one the large electrodes in the furnace. The temperature in the bath immediately under the electrodes is higher than anywhere else and therefore the boiling action is more pronounced in that region. A period of reaction in the furnace is followed by the taking of samples from laboratory analysis and and visual examination. These samples are taken in a sampling spoon (shown) . Before immersion in the metal the spoon must first be coated with slag from the furnace to avoid the risk of the sample being contaminated with contact with the iron spoon. To ensure that the sample is truly representative of the bath conditions, thorough mixing must take place before the sample is cast into a small mould and when cold drillings are made and taken to the laboratory for rapid and accurate analysis. The drillings are then dissolved in acid to obtain particulars of the contents of various elements. Meanwhile another sample is taken for fracture tests and visual examination by the sample passer. His long experience enables him to judge the exact condition of the bath by the crystaline appearance of the broken sample. After sufficient time has elapsed to allow the necessary reactions to take place the intial slag with the impurities so far absorbed is removed. For this purpose the furnace is tilted slightly so that the face of the metal is just below the door sill. By this means the molten slag is free to flow through the door and down into the slag pan. This flow is assisted by the use of iron ravels which are used to rake the slag towards the door. Good shot of furnace team dragging the slag towards the door. The heat from the open furnace and molten slag is so intense that the operators face and neck have to be protected. Thus is the function of the sweat rays or neck towels which are worn. A wooden ravel is used to skim the remaining traces of slag from the surface of the bath. It is very important that all traces of the slag should be removed to make sure that none of the impurities there can find their way back into the bath. Immediately afterwards a fresh slag has to be built up to protect the exposed metal and to reduce further the hydrogen and phosphorous content. Excellent shot of slag being put into the furnace. After this second slag has in its turn been removed the final and reducing slag is made up. It is during this refining process that the bulk of the oxygen and sulphur content is removed. Samples of both slag and metal are taken again and analysis are made. When these results are known and furnace conditions are satisfactory, carefully weighed additions of nickel and ferro-alloys such as silicone, manganese and chronium, tungsten are ordered by the sample passer. These finishings ae calculated on the basics of certain specific factors which are the amount required in the finished steel, the amount already present in the bath, slight losses which might occur in the final stages, the amount present in other additions. Two good shots of the furnace being stoked and of the material bubbling in the furnace. Meanwhile the pre-heated refractory ladel is lowered into position so that it will be ready to receive the molten charge as soon as the sample passer is satisfied with condition and temperature samples, gives the order for tapping to begin. When the temperature is correct and the steel calm the electrodes are raised the furnace tilts and 30 tons of molten metal pour in the waiting ladel. During this process of tapping it is important that accurate measurements of temperature are taken and the condition of the metal is watched. The tipping of the furnace must be closely watched and controlled. It is of great importance to maintain a steady stream into the ladel to avoid trouble by allowing the metal to eddy and splash during this operation. In cases where ingots larger than 30 tons are required for example up to sixty tons additional furnaces must be tapped at the same time into other ladels as shown earlier. The preceding sequence offers some particularly vivid images which differ from 'standard' notions of steel production as these are imbued with vivid colours used in Kodachrome film stocks of the time. The ladel stoppers or refractory covered plungers are shown in screen. These stoppers extend down to the bottom of the ladel and cover the nozzles or outlets through which the molten metal will pass. To control a close control of rate of the flow into the moulds, a secondary or smaller nozzle is fitted over the ladel nozzle by a special device which is shown. A stopper is opened and the steel is allowed to steam into the mould below. Temperatures of the stream of the ladel are taken by the optical pyrometer and the time taking for crafting the ingot are carefully recorded. The moulds are prepared with meticulous care and are fitted with a larges ratio feeder head. Again the moulds are prepared with great care so again a perfect fit will result. After preparation a cover is placed over the mould to exclude any foreign matter and is removed only immediately before teeming begins. An initial cooling period is allowed to elapse and then the ingots are lifted and kneeled in suitable furnaces and taken to the rolling mill for conversion to rolled bars or strips, or sheets or to the forge for conversion to forgings or billetts. The engineer will select this high quality electric steel for the production of components he knows must reliably perform those functions. Intertitle: High frequency Induction Process… High grade tool and special purpose steels are made in high frequency induction furnaces in quantities of up to five tons. The high frequency induction furnace is also an electric steel making process, but instead of arcs being used for processing and heating the charge is placed in a refractory crucible which is surrounded by an electric coil. Alternating currente of high frequency is passed through the coil causing by induction a secondary current in the charge which is sufficient to melt it. This type of steel melting furnace represents the most recent development of steel making methods ( in the 1930s) . Early difficulties associated with the capacity of these furnaces have been overcome to a large extent, where as the original types had a capacity of 500 pounds, ingots of eleven tons in weight have now been produced by this method of melting. These furnaces found their greatest use for the production of relatively small ingots of soecial quality high alloy steel of the type often used for cutting tools, small dye blocks, aero engine valves and valve springs. The high frequency furnace is particularly well suited to the production of such steel, because it is possible to exercise extremely close control over the temperature and composition of the bath. It is also found that steels produced in these furnaces are very uniform in character for the production of smaller ingots of high alloy analysis, the steel is taken from the furnace in small quantities by hand. Crucible pots used in the early days of quality craft steel making are still employed for teeming these small ingots. As we have already seen the temperature and speed at which the casting of steel into the ingot mould takes place is of great importance and so in the hand teeming of these important special purpose steels the skill and experience of the teemer plays a vital part. Excellent shots of the men working in unison as a team on the multitude of jobs the task requires. The personal skill of arm and eye of the teemer for which Brown and Sheffield are justly proud. A great difference in size between the 200 ton ingot and the hand teemed ingots is evident , but this difference illustrates the wide range of steel products which Firth Brown are equipped to manufacture. All types of cutting tools are made from high speed and alloy tool steel and melted in the high frequency furnace. Slitting saws and slotting cutters (shown) saws , inserted booth cutters, drills, rimmers and other types of small tools. From other types of high frequency steel aero engine valves and valve springs. All the above tools are shown and drills in operation are filmed. Film ends with an advertisement of the Firth Brown Company, which at this point has been in existence for 100 years. Closing sequences show the factory chimneys over upbeat stately music.
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