Page 1 |
Previous | 1 of 4 | Next |
|
small (250x250 max)
medium (500x500 max)
Large
Extra Large
large ( > 500x500)
Full Resolution
All (PDF)
|
This page
All
|
40 SCIENTIFIC AMERICAN SUPPLEMENT No. 2011 July 18, 1914 The Manufacture of Crucible Steel Its History and Technology By George H. Neilson T H E pioneers in crucible melting are said to have been the Chinese, who used the process many centuries ago. But the art in China never progressed beyond the initial stage. The real father of the crucible steel industry was Daniel Huntsman, of Sheffield, Eng., a clock-maker, who found it impossible to get uniform steel from which to make his springs, and he hit on the idea of fusing blister steel in a crucible. This was in the latter part of the eighteenth century, and the melting of crucible steel has changed but little since that time. The details have Fig. 1.—Detail of hole in a crucible furnace. changed somewhat but the actual process is much the same. The material to bo melted is loaded in a crucible, covered with a cap to keep out the gases, and placed in a hot hole and left there until melted. The crucibles have changed, the holes also have been changed in shape and size, and the method of heating is not tho same, but the process is practically unchanged. Clay crucibles were the first of which we havo any definite knowledge. They held aboul 50 or 75 pounds and lasted but one heat, and very often cracked and went to pieces before the steel was melted. Clay crucibles of the present day are much more durable and arc extensively used in Europe, but little in this country. They have one decided advantage * Address of the Retiring Chairman of the Mechanical.Section ot the Engineers' Society of Western Pennsylvania., published in the February, 1914, Proceedings, page. 00. over the plumbago, or graphite, crucibles inasmuch as they do not throw off any carbon during the melting process. The plumbago crucible, which is the most generally used in this country, consists of about equal parts of plumbago and clay. The greater part of the plumbago is imported from Ceylon. These crucibles are capable of withstanding a very severe heat, and can be used a number of times, depending greatly on the nature of the mix and also whether the crucibles arc replaced in the furnace before they get cold. The usual practice is to get as manj' heats as possible from the crucible without letting it cool. As soon as the melted steel is poured out, it is re-charged by hand, or by means of a mechanical shaker, and the crucible returned to the melting hole. Furnace. Tho modern crucible furnace is of the regenerative type and is heated by gas, generally producer gas, although where natural gas can be obtained it is often used. Natural gas is probably a more costly way to run a furnace, but it has many advantages over producer gas. It is easier to regulate, as the flow is constant, which is not the case with producer gas unless a large holder is used. It is free from tho poisonous fumes of the producer gas and is much cleaner. I a m not in a position to say whether or not it is harder on the crucibles and furnace than producer gas. The capacity of a. furnace is spoken of in pots. That is a 24 pot, 36 pot or 60 pot furnace. That is the number of crucibles the furnace will accommodate at one lime. The furnace holes, in which the crucibles are placed, hold o crucibles, so a 36- pot furnace is one of (1 boles. Tho gas enters the holes at tho bottom on one side, mixing witli the air immediately before entering the melting hole, and passes out at the opposite side and then through checker work to tho stuck. When the valve is reversed, the direction of tho s flow of the gas is reversed. This is done every 15 or 20 X minutes, and, in this way, the checker work on both t sides is kept hot. The gas should not be pulled through 1 the melting hole too rapidly. If it is, it will cut the port 3 holes and also cut the crucibles. The gas should fill the a melting hole and show a small flame around the covers. 3 This is a sure indication that the gas is getting around a the crucible and not pulling across tho bottom. The 1 detail of the hole is shown in Fig. 1, and a modern 36-pot 3 furnace in Fig. 2. Charge or Mix. The basis of good crucible steel is iron, ^ and, consequently, the better the iron the better will be L tbe steel. Therefore, it is vitally necessary that iron low in phosphorus and sulphur be used. As the crucibles generally in use hold from 100 to 12.") pounds, the mix or charge is weighed up in lots of that weight and placed r in pans, called weigh pans, from which if is transferred 5 to the crucibles. In order to get the exact analysis, (be weighing must be carefully done, in many cases to the exact ounce. When tho crucible is filled it is covered with a cap. This is done to exclude deleterious gases which otherwise would impregnate the steel. When the material to be melted is weighed up, the amount of carbon given off by the crucible must bo taken into consideration. If this is not done, the carbon content of the ingots will run higher than expected. The new pots, as a rule, do not throw off as much carbon as they will tho second time used, and after the. third heat the amount thrown out will be immaterial. Melting. The length of time necessary to reduce the mix to a molten state varies, depending on the makeup of the mix itself, and will lake anywhere from 2 to 5 hours. When the sfeel becomes Quid, it is usually good practice lo "kill it," or, in other words, drive out the gases which would otherwise resulf in blow holes in the ingot. This process of '•killing" usually takes from 20 minutes to one hour or longer. Molds. The niohls in general usr an- known as split angle molds. They are made in two pieces, held together by rings and wedges - one ring at the top ami one at the bottom. The three essential qualities are long life, smooth finish and light joints. If tl„, jnsirle finish is not smooth, the ingot will have a rough surface which may result in defects in the finished bar. If the joints are not tight, the hoi metal will work through and form a fin on the ingot. This fin will have to be removed, which means added cost. If it is not removed, it will work into the steel and cause complications. The smaller molds have the bottoms cast with the sides. The larger molds, 7-ineh and over, have no bottoms as a rule, the molds being set up on removable bottoms. Before the molds aro used, the general practice is to smoke them with rosin,_or some other heavy, greasy, smoke-making material. This prevents the ingots from sticking, and also makes a smoother surface. The molds should also be warmed before using. Iteming or Pouring. Teeming is a very important feature and is not merely dumping the hot steel from the crucible into the mold in a haphazard way. In the first place, the si ream must be steady; if it is stopped and then started again there will be a weak spot iu the ingot. The Fig. 3.—A 10-inch bar mill. Fig. 2.—A 36-pot furnace.
Object Description
Author | Neilson, George H. |
Title | The manufacture of crucible steel : its history and technology |
Other Title | Scientific American. Supplement |
Contributors | Scientific American |
Publisher | New York : Munn & Co., 1914. |
Date of Publication | 1914 |
Date Created | 2011 |
Physical Description | pages 40-43 : illustrations ; 41 cm |
Notes | Title from caption.; Article appearing in: Scientific American supplement, vol. 78, no. 2011 (July 8, 1914). |
Subjects | Steel -- Metallurgy.; Crucibles. |
Material Type | Article |
Call Number | TN735.N45 1914eb |
Sierra Bib Record No. | b3057013x |
OCLC Number | 742347801 |
Collection | Pittsburgh Iron & Steel Heritage Collection |
Contributing Institution | Carnegie Library of Pittsburgh |
Rights | http://rightsstatements.org/vocab/InC-EDU/1.0/ |
Sponsorship | This Digital Object is provided in a collection that is included in POWER Library: Pennsylvania Photos and Documents, which is funded by the Office of Commonwealth Libraries of Pennsylvania/Pennsylvania Department of Education. |
Contact | For more information about these collections contact Carnegie Library of Pittsburgh at 412.622.3114 or info@carnegielibrary.org |
Description
Title | Page 1 |
Publisher | New York : Munn & Co., 1914. |
Collection | Pittsburgh Iron & Steel Heritage Collection |
Contributing Institution | Carnegie Library of Pittsburgh |
Rights | http://rightsstatements.org/vocab/InC-EDU/1.0/ |
Sponsorship | This Digital Object is provided in a collection that is included in POWER Library: Pennsylvania Photos and Documents, which is funded by the Office of Commonwealth Libraries of Pennsylvania/Pennsylvania Department of Education. |
Transcript | 40 SCIENTIFIC AMERICAN SUPPLEMENT No. 2011 July 18, 1914 The Manufacture of Crucible Steel Its History and Technology By George H. Neilson T H E pioneers in crucible melting are said to have been the Chinese, who used the process many centuries ago. But the art in China never progressed beyond the initial stage. The real father of the crucible steel industry was Daniel Huntsman, of Sheffield, Eng., a clock-maker, who found it impossible to get uniform steel from which to make his springs, and he hit on the idea of fusing blister steel in a crucible. This was in the latter part of the eighteenth century, and the melting of crucible steel has changed but little since that time. The details have Fig. 1.—Detail of hole in a crucible furnace. changed somewhat but the actual process is much the same. The material to bo melted is loaded in a crucible, covered with a cap to keep out the gases, and placed in a hot hole and left there until melted. The crucibles have changed, the holes also have been changed in shape and size, and the method of heating is not tho same, but the process is practically unchanged. Clay crucibles were the first of which we havo any definite knowledge. They held aboul 50 or 75 pounds and lasted but one heat, and very often cracked and went to pieces before the steel was melted. Clay crucibles of the present day are much more durable and arc extensively used in Europe, but little in this country. They have one decided advantage * Address of the Retiring Chairman of the Mechanical.Section ot the Engineers' Society of Western Pennsylvania., published in the February, 1914, Proceedings, page. 00. over the plumbago, or graphite, crucibles inasmuch as they do not throw off any carbon during the melting process. The plumbago crucible, which is the most generally used in this country, consists of about equal parts of plumbago and clay. The greater part of the plumbago is imported from Ceylon. These crucibles are capable of withstanding a very severe heat, and can be used a number of times, depending greatly on the nature of the mix and also whether the crucibles arc replaced in the furnace before they get cold. The usual practice is to get as manj' heats as possible from the crucible without letting it cool. As soon as the melted steel is poured out, it is re-charged by hand, or by means of a mechanical shaker, and the crucible returned to the melting hole. Furnace. Tho modern crucible furnace is of the regenerative type and is heated by gas, generally producer gas, although where natural gas can be obtained it is often used. Natural gas is probably a more costly way to run a furnace, but it has many advantages over producer gas. It is easier to regulate, as the flow is constant, which is not the case with producer gas unless a large holder is used. It is free from tho poisonous fumes of the producer gas and is much cleaner. I a m not in a position to say whether or not it is harder on the crucibles and furnace than producer gas. The capacity of a. furnace is spoken of in pots. That is a 24 pot, 36 pot or 60 pot furnace. That is the number of crucibles the furnace will accommodate at one lime. The furnace holes, in which the crucibles are placed, hold o crucibles, so a 36- pot furnace is one of (1 boles. Tho gas enters the holes at tho bottom on one side, mixing witli the air immediately before entering the melting hole, and passes out at the opposite side and then through checker work to tho stuck. When the valve is reversed, the direction of tho s flow of the gas is reversed. This is done every 15 or 20 X minutes, and, in this way, the checker work on both t sides is kept hot. The gas should not be pulled through 1 the melting hole too rapidly. If it is, it will cut the port 3 holes and also cut the crucibles. The gas should fill the a melting hole and show a small flame around the covers. 3 This is a sure indication that the gas is getting around a the crucible and not pulling across tho bottom. The 1 detail of the hole is shown in Fig. 1, and a modern 36-pot 3 furnace in Fig. 2. Charge or Mix. The basis of good crucible steel is iron, ^ and, consequently, the better the iron the better will be L tbe steel. Therefore, it is vitally necessary that iron low in phosphorus and sulphur be used. As the crucibles generally in use hold from 100 to 12.") pounds, the mix or charge is weighed up in lots of that weight and placed r in pans, called weigh pans, from which if is transferred 5 to the crucibles. In order to get the exact analysis, (be weighing must be carefully done, in many cases to the exact ounce. When tho crucible is filled it is covered with a cap. This is done to exclude deleterious gases which otherwise would impregnate the steel. When the material to be melted is weighed up, the amount of carbon given off by the crucible must bo taken into consideration. If this is not done, the carbon content of the ingots will run higher than expected. The new pots, as a rule, do not throw off as much carbon as they will tho second time used, and after the. third heat the amount thrown out will be immaterial. Melting. The length of time necessary to reduce the mix to a molten state varies, depending on the makeup of the mix itself, and will lake anywhere from 2 to 5 hours. When the sfeel becomes Quid, it is usually good practice lo "kill it," or, in other words, drive out the gases which would otherwise resulf in blow holes in the ingot. This process of '•killing" usually takes from 20 minutes to one hour or longer. Molds. The niohls in general usr an- known as split angle molds. They are made in two pieces, held together by rings and wedges - one ring at the top ami one at the bottom. The three essential qualities are long life, smooth finish and light joints. If tl„, jnsirle finish is not smooth, the ingot will have a rough surface which may result in defects in the finished bar. If the joints are not tight, the hoi metal will work through and form a fin on the ingot. This fin will have to be removed, which means added cost. If it is not removed, it will work into the steel and cause complications. The smaller molds have the bottoms cast with the sides. The larger molds, 7-ineh and over, have no bottoms as a rule, the molds being set up on removable bottoms. Before the molds aro used, the general practice is to smoke them with rosin,_or some other heavy, greasy, smoke-making material. This prevents the ingots from sticking, and also makes a smoother surface. The molds should also be warmed before using. Iteming or Pouring. Teeming is a very important feature and is not merely dumping the hot steel from the crucible into the mold in a haphazard way. In the first place, the si ream must be steady; if it is stopped and then started again there will be a weak spot iu the ingot. The Fig. 3.—A 10-inch bar mill. Fig. 2.—A 36-pot furnace. |
Contact | For more information about these collections contact Carnegie Library of Pittsburgh at 412.622.3114 or info@carnegielibrary.org |
Tags
Comments
Post a Comment for Page 1