STEEL HORIZONS

[Music] [Music] well i've watched quite a few melts of stainless steel being tapped since the first day i walked into a steel mill that was a good many years ago too i was fresh out of college oh what a thrill i got that day i talked about it for weeks it's such an impressive sight it sort of scares you at first spectacular isn't it it's hard to believe that this red yes even white hot stream is really steel even the men who work each day with this operation can't help but be fascinated as i stood beside this 75 ton electric furnace showing some friends around the plant i watched how wide-eyed they were suddenly my business took on a completely new perspective you might say that i'd been taking too many things for granted by here in this ladle 75 tons of molten steel is being positioned for the tv this operation which we call teaming is really a casting of liquid steel into ingot molds it's just one of the hundred steps necessary to make stainless steel yes i had a new perspective for now i began to realize that every job regardless of how simple had to be precisely handled you see these ingots must be cooled so they can be stripped from their molds and then they're charged into these circular soaking pits where they're reheated looking into one of these seething soaking pits you can see 60 tons of glowing inkans the pits are charged most of the time which means plenty of stainless ingots always on the ready line with one of them on its way we decide to follow its reduction into slabs a ram pushes the ingot from the car onto the roller table of the mill then the two operators up in their puppet take over this is a 40 inch blooming mill remotely controlled by finger tip touch one man controls the direction of the steel and the other the space between the rolls well it's almost like rolling dough for a pie crust back and forth the ingot goes being squeezed under tremendous pressure the amount of reduction being carefully gauged by the operators and checked with each pass now watch that ingot being passed back and forth compress thinner and thinner each time i mentioned a while back that this steel was called an ingot but due to this rolling it will now be known as a slab you know it takes two 3000 horsepower motors to drive this mill the couplings spindle arms and rolls attached to each motor weigh more than 60 tons and yet it's pretty obvious that the operator can select the passes and reverse the direction easily and swiftly we have a separate motor room to house and protect the machinery that operates this mill the rolls can be reversed from full speed in one direction to full speed in the other direction in a matter of five seconds this is done by changing the flow of current which in turn changes the electrical field of the motors without damage to the ponderous machinery you see a little manipulation performed by this operator and the slab is flipped up and starts to receive its edging pass this edging pass controls the width and tends to prevent cracking now the sink head or end of the slab which contains possible impurities is cropped off by the shear the slab moves on past the shears the other end is cropped and it goes on to the first roughing stand of the breakdown mill this hot strip mill consists of three two high roughing stands and four four high finishing stands we mean by too high just this the two rows through which the steel is now passing exert the pressure to reduce the gauge and elongate the slab by stand we mean the upright castings containing the two rolls we'll pass the steel through three such stands as the slab continues to be reduced in gauge to about seven eighths of an inch the vertical edging rolls control the width they squeeze it to size and also aid in shaping the edges [Music] this is the finishing part of the mill containing four stands and four rolls per stand each roll which comes in contact with the steel has a backup roll for exerting more pressure and greater reduction thus it's a four high four stand mill as the strip emerges from the last stand its gauge is down to one hundred eighty thousandths of an inch and it's traveling at more than eight hundred feet a minute as it hits the automatic feed coiler now this same steel which was an ingot then a slab is now a strip in the form of a coil if you look closely you can see the deep red heat of the steel as it's cooling down it's marked with its identification melt number size and type this steel has many more hours of treatment ahead of it before it leaves the plant and all the time the surface will be improving through each operation stainless steel is quite hard after the hot rolling and for further working it must be in a dead soft condition so the hot rolled strip is continuously annealed in a furnace heat of 2000 degrees fahrenheit the steel is passed through the furnace at just the right speed so it'll be under the heat just long enough emerging it passes under a water spray and is recoiled remember that this is a slow heat soaking process which softens the material so that it can be cold reduced to a still thinner gauge but from the hot rolling and annealing a scale has formed on the surface now this is unwanted and must be removed [Music] this isn't a simple matter by any means the hot rolled annealed coils are first immersed in a hot salt bath and water quenched then they're immersed in sulfuric acid and water washed after which they'll go into a nitric hydrofluoric acid bath [Music] as you probably know nitric hydrofluoric acid is very potent so here in a close-up you can see what really happens to the scale when the steel is immersed see how the acid seeps under the preconditioned scale and slowly starts attacking the metal surface [Applause] [Music] look at those gas pockets developing under the scale as the reduction takes place [Music] slowly the scale starts rolling off the surface but no violent attack of the surface occurs in this operation as takes place in most pickling bats looks like it could peel off in a sheet doesn't it well in a matter of two minutes at the very most all the scale has fallen away from the steel and after rinsing in water the crane will pick up the rack and the coils will emerge clean and bright well there they are in perfect condition for cold rolling pretty haunting this now looks like the stainless steel we all know doesn't it well as a matter of fact these coils could be used in this condition but the gauge and the finish are not yet right by this i mean the surface would be too rough and the thickness too great for the application so we'll trail right behind this coil of strip and keep pretty close tab on it it's destined for a fabricator of a popular consumer product requiring a particular finish and further processing therefore it's now fed through a roller leveler which straightens the strip before it enters the cold rolling mill this mill is a four high reversing mill one of the finest of its kind in the world used for both roughing and finishing of high alloy strip this is a cold reducing job and in order to get a fine finish the mill operates at a reduced speed stainless is so tough that only by working at reduced speeds can the rolls reduce the gauge and at the same time improve the finish however this mill will operate up to 1500 feet per minute this dust panel gives the operator a continuous check and touch control of all operations and the flying micrometer relays to the panel the gauge of the steel this mill is equipped to give a high surface finish to stainless steel with each pass on this reversing mill a carefully worked out amount of reduction is called for and attained so to make sure it's conforming to the demands put upon it the operator keeps a wary eye out for any deviation from the normal now there are two main reasons why this is one of the most efficient mills made for cold rolling of stainless strip first for power expended its results are phenomenal and secondly the fact that it is a reversing mill means no delaying transfer from the take up end of the mill back to the payoff end this reversing operation gives complete flexibility to the working of the strip the strip makes repeated passes through the rolls back and forth as many times as necessary to bring about the type of surface finish desired by the customer now the uniformity of thickness speed voltage on the motors and the current the motors draw are indicated by the gauges in front of the operator each pass reduces the thickness so that the total reduction in five such passes would bring the steel down to about one half of the original thickness [Music] on the final pass paper is fed into the coil of strip to protect the finish against the scraping action of the two metal surfaces coming together and the flying mic keeps a constant check right down through the last production permitting the operator to make accurate adjustments for uniformity and thickness up to this point the thickness of the metal has been reduced just about in half almost 50 percent and as you might have guessed all this rolling has made the steel extremely hard something has to be done about that so it's annealed again to make it soft once more consequently the stainless strip enters the continuous annealing furnace you see this cycle of rolling and heat treating is repeated over and over as the steel is worked and brought down engage look at that bright finish on the surface the rolling imparted that finish but some of the brilliance will be removed by this annealing and pickling process here's a diagram of what actually happens the strip enters the heating chamber and reaches a temperature of 2000 degrees fahrenheit and emerges for rapid cooling by air jets then a pickle first sulfuric acid followed by a water spray then into the nitric hydrophoric bath another water spray then the finished annealed and pickled strip passes over the inspection table to the take-up reel you see that final spray removed all traces of acid so the steel emerges clean and ready for further cold rolling to see how much reduction was taken in the first cold rolling operation let's compare the original hot roll thickness against this cold rolled gauge the comparison shows 160 thousandths of an inch down to 80 thousandths of an inch now since many applications require strip which varies greatly in width thickness and finish it isn't surprising to walk past hundreds of coils of stainless strip all sizes and types awaiting further reduction by cold rolling on this four stand four high tandem mill this mill works stainless strip down to a thickness of 50 thousandths of an inch with a speed up to 1120 feet per minute as it begins to roll through the operator at number one stand checks the thickness of the strip its speed and the tension between the first two stands these are indicated on the control panel and require frequent adjustment a tension indicator shows the lengthwise pull on the strip between the stands so it's kept under control either by adjusting strip thickness or script speed the next operator similarly watches the tension indicators the operator at the third stand makes the same checks and the man at number four is the key man under the roller supervision he's responsible for the accuracy of the finished gauge and for surface quality [Music] this is a pretty busy quartet shouldering the responsibility of controlling the finishing touches on all the work that's gone into the strip up to now again it's the flying mic which conveys the information about the steel to the panel board at this point my guest asked oh then the stainless is ready for shipment i had to laugh i'll bet his feet were tired because believe me we'd covered some mileage i said politely with a small grin not quite but bear with me because here's where all this effort really shows results now not to repeat myself but just to continue with a number of steps we again go through the continuous anneal because again the stainless has become hard due to rolling and it must be softened for further cold rolling now look here's how much we've reduced the thickness this time from 80 thousandths of an inch to 30 thousandths of an inch the strip is now fine grained thoroughly softened and with a slightly lustrous surface and in perfect condition for many applications now since stainless strip has so many uses customer requirements are many invariant the customer for this trip wants a 36 inch wide 25 000 of an inch thick stainless sheared into sheets 120 inches long after passing through the final annealing and pickling line the steel is cut to size and at the same time gone over very carefully for surface defects the steel is highly corrosion resistant has a good finish now over here in another part of the plant is a still different type of a cold milk which produces cold rolled strip with an even brighter finish the rolls in contact with the steel smaller in diameter and made of high speed steel are extremely hard and have a brilliant luster as the stainless passes between these rolls their high polish is imparted to the stainless itself [Music] this is a large planishing mill which serves two purposes to improve the finish and add a slight stiffness to the metal the finish or surface obtained on this steel is fully dependent upon the smoothness of the rolls in the mill itself so we merely impress the extreme luster of the polished roll upon the less smooth steel strip the result is the finest finish that can be rolled on stainless steel [Music] when you see this mirror-like surface beautifully reflected and know that the same time it's highly corrosion-proof you realize that this is just about the ultimate in beauty and utility [Music] now many customers require stainless in narrower widths than we've seen being cold rolled for such items as molding trim for boxes and refrigerators automotive trim and grill work so high-speed steel knives slit a wide processed stainless strip into desired narrower widths when the knives have done their work the customer's steel is just the way he wants it well folks now i have a new perspective and i believe you have a better picture of steel making you've seen how a tremendous tonnage of stainless steel strip is produced each day today's steel is likely to become on the moral cabinets clinical sinks and coffee makers dental instruments and drain boards pails pans and pasteurizers mixers mirrors moldings and milking machines for the number of uses is as infinite as the limitless steel horizons which stretch ahead beyond tomorrow [Music] you