US2283299A - Manufacture of steel - Google Patents

Description

y 1942- NQF. TISD ALET 2,283,299

' MANUFACTURE or" STEEL Filed July '51. 1940 .002 sow/v v Pt: 77? 7mm 0F HARONESS //v INC/IE5 :wogzy syn/aw 77.749006 INVENTOR MFA IAN E 7750,91:

' TTORNEYS Patented May 19, 1942 PATENT OFFICE 2,283,299 MANUFACTURE OF s'ram.

Norman Fenwick Tisdale, Mount Lebanon, 1a.,

assignor' to Molybdenum Corporation of America. N ewYork, N. Y., a corporation of Delaware Application July 31, 1940, Serial No. 348,635

5 Claims.

The invention relates to a method ---forthe production of irons and steels. I More particularly, it pertains to the production of alloy irons and steels, and includes correlated improvements and discoveries whereby their qualities are :enhanced.

-The desirable properties of irons and having a content of boron have been recited in the literature for some time past. However, such products have not been manufactured commercially. This may be attributed to the fact that the usual procedure for the manufacture-and handling of iron and of steel entailed the addition of ferro-boron, or other boron-containing material in a manner which led to such a loss of the boron that practically all found its way into the slag rather than into the finished iron product. Or, if large amounts of ferro-boron were added, an indefinite amount of boron entered the steel to give a brittle and undesirable product. Consequently, when calculated amounts of ferro-boron were added to a steel in a reverbratory furnace, little or no boron was found in th( finished steel. Rather, because of its ready oxidizability and capability of uniting with nitrogen, it went into the slag. Similar results attended production in a blast furnace or in a foundry cupola. Moreover, thereare methods described in technical and patent literature in which boron compositions are added to steel for the purpose of deoxidizing and denitridingthe provide a method whereby boron may be introduced into a steel and therein act as a deep hardening element.

A more particular object of the invention is the provision of a procedure-whereby a definite percentage of boron will be present in a finished iron or steel through addition of definite amount of a boron containing composition, such as a ferro-boron, and which may be readily, efliciently and economically carried out to a desired extent.

Other objects of the invention are to provide a process for the production of irons and steels, which entails first a thorough degasification of an iron or steel melt, followed by a combination of boron therewith.

melt. Consequently, the obtainment of .an iron' or steel with a boron content is attended with great difficulty, especially when a definite percentage of boronis to be a part of the iron or steel.

It is an object of the present invention to provide a method in accordance with which boron may be combined with andbecome a component part of irons and steels.

Another object of the invention is the provision of a method whereby boron may be introduced into an iron or steel melt with a minimum of loss. a

A further object of the invention is to provide a process forthe manufacture of an iron or steel which possesses shallow hardening characteristics with a content of a deep hardening element, i. e., boron.

A still further object of the invention is the treated is provision of a method which will lead to the production of an iron or steel having a combination of deep hardening with some of the de-,

sirable properties of shallow hardening steels.

Other objects of the invention will in part be V I obvious and will in part appear hereinafter.

The invention accordingly comprises the several steps and the relation of one or more of such steps with respect to each of the others, and the article possessing the features, properties, and

the/relation of'elements, which are exemplified addition of a suitable material which may contain aluminum, silicon, zirconium, titanium, or vanadium, more especially fer'ro-titanium, ferrozirconium, as well asother materials, such as manganese, calcium, barium and the like. the event that aluminum is employed an amount of from lb. to 1% lb. per ton of the metal usually sufiicient for the degasification, and when, silicon is utilized the quantity depends on the desired silicon content and this, for example, in open hearth practice, may be up to 3%, whereas in acid furnace practice it would be slightly higher.

It is of import that the combination of boron should be brought about only after oxygen and nitrogen have been removed to substantial completion, since otherwise there will be an attending loss of boron due to its ready reaction with oxygen and nitrogen and passage in large meas- I are into the slag. Introduction of the boron may An additional object of the invention is to be through the medium of a'suitable boron-containing material, and as an example a ferroboron containing to 12% boron and 1.5 to 2.5% carbon. This alloy has a low melting point, dissolves readily in liquid metal, and protects the boron from the oxygen and nitrogen by reason of its high carbon content. The ferro-boron may be of various types, such as high boron-high carbon, high boron-low carbon, low boron with various percentages of carbon. boron, manganese-boron, aluminum-boron and in some instances, borax may also be used.

A procedure found to be especially advantageous is to prepare an iron or steel melt and, following blocking of the molten charge, to tap it into a ladle. The melt is run into the ladle until it is about one-third full, at which time an addition of silicon is completed. It is now degasified thoroughly by rapidly adding the required amount of aluminum, or other degasifying element, and thereafter ferro-boron may be introduced. These additions should be completed before the ladle is three-quarters full, in order to prevent slag from coming intocontact with the boron with an attendant loss thereof. The ferroboron introduced may contain from 10 to 12% boron and from 1.5 to 2.5% of carbon, and the amount introduced is such as to give the steel a desired boron content which may be from .0005% to .01%, and preferably about .0025%. Addition of the ferro-boron may be in the form of lumps, and satisfactory results have also been attained when the boron material is placed in a can and plunged into the melt at the end of a rod.

The method is well adapted for utilization in the manufacture of various irons and steels, and has been more particularly employed for the production of carbon steels having relatively large cross-sections, as crank shaft steels, and in the production of cast iron rolls, to which the addition of boron in amounts of .03% to .12%, and especially .05%, imparts highly advantageous properties, as a clear, chill-like structure on the surface without increasing the combined carbon of the core. Combination may also be effected with alloy steels, as manganese, nickel, molybdenum, chromium, tungsten and vanadium steels.

Furthermore, the iron or steel is carefully melted and the refinement thereof is performed in like manner. There is a gradual elimination of the non-metallic elements, and the liquid metal is then blocked and made ready to be placed in a ladle. When the ladle is approximately one-third full a proper amount of final deoxidizer and degasifer, as silicon, ferro-silicon, ferro-manganese, or aluminum, may be added whereby the oxygen and other occluded gases are substantially completely removed. In addition to the amount required to deoxidize and degasify the melt completely there is introduced a small extra amount in order to insure the absence of oxygen or other gas which would react with and occasion a loss of boron. When the deoxidizing and degasifying action is finished, the full amount of boron-containing material is added. However, the boron addition should not be made too late, since then it will react and enter into the slag with attending loss.

It is significant that the amount of deoxidizer and degasifier be such as completely to remove the occluded gases, particularly oxygen, prior to addition of the boron, because otherwise oxidation of the boron will take place and lead to loss.

Consequently, the boron is not added with the I charge, nor is it introduced into the furnace Also, nickelwhile the metal is molten and before theheat has been blocked and/or deoxidized. Not only is removal of oxygen required, but of nitrogen as well, since it unites with boron, and loss due thereto would also ensue. Therefore, removal of nitrogen must be efiected as well as of oxygen. The liquid steel absorbs oxygen readily, and in view thereof the boron should not be added until the melt is ready to be cast, since otherwise the boron would be oxidized by any oxygen absorbed.

Furthermore, slags usually have a high oxygen content, and the boron, hence, should be all dissolved in the melt before the slag from the furnace comes in contact with the steel in the ladle, and casting should be carried out immediately to obtain high utilization of the boron.

As an illustrative embodiment of a manner in which the invention may be practiced, the following examples are iven:

Example I A carbon steel was produced in an open hearth furnace by melting therein an initial charge comprising hot metal and #2 heavy melting scrap in appropriate amounts. During the heating of the charge there may be added to the furnace suitable quantities of spiegeleisen, ferro-silicon containing about 15% silicon, and ferro-manganese containing about of manganese. When the furnacing is complete and the molten charge has been blocked it is tapped into a ladle. During the withdrawal into the ladle there may be added ferro-silicon containing 50% of silicon and aluminum, in order to complete degasification of the molten metal. Carbon, in the form of coal, and ferron-boron having a boron content of about 11% in an amount of .003% based upon the weight of the charge were also introduced into the ladle. Steel so obtained consists preponderatingly of iron and may contain 0.39 to 0.43% carbon, 0.55 to 0.75% manganese, up to about 0.03% phosphorus, up to about 0.045% sulfur, and 0.18 to 0.25% silicon, and is well adapted for the manufacture of crank shafts.

Example II An open hearth furnace is suitably charged with a mixture of cold steel, pit and hot metal. During the furnacing of this charge additions of ore, spiegeleisen, ferro-silicon containing 10% silicon, and an 80% manganese may be made. Following maintenance of the charge in molten condition in the furnace for a suitable period, the melt is blocked and then tapped into a ladle. While the ladle is being filled, the molten metal may be degasified by adding ferro-silicon having a silicon content of 50%, and aluminum, and thereafter ferro-boron with a boron content of about 11% is added. Thereupon there is obtained a steel having a high manganese content and, in addition to iron, the relative percentages of other components are as follows:

The steel so obtained possesses the characteristics herein set forth, including deep hardening properties and a high precipitation hardness.

Example III Production of a nickel molybdenum steel is effected by charging an open hearth furnace with cold metal, #2 heavy melting scrap, ti nickelchromium, punch metal scrap, nickel-chromium scrap, and ti /2% nickel billets. The charge includes also limestone, burnt lime and spar. During the furnacing of this charge additions are made of iron ore, spiegeleisen, calcium molybdate, silicon-manganese and term-manganese. Following blocking of the melt it is tapped into a ladle, and silicon and aluminum added thereto for degasification. The silicon and aluminum are added in amounts to bring about substantially complete degasification of the molten metal, and then ferro-boron with about 11% boron is introduced. The steel produced is a typical nickelm'olybdenum steel, and in addition to the iron contains It has heretofore been found that boron, when added to steels, occasions a hot or red shortness. When the steel is hot-rolled, it disintegrates and a lapped surface is formed. This condition becomes more apparent as the content of carbon and of alloy elements increases, and is especially noticeable with carbide-forming elements. It has previously been found that an increase in boron also leads to similar bad efiects,

In accordance with the invention it has been found that there is a boron-content particularly suited for each type of structural steel, with attending enhancement of desirable properties without rolling defects. The quantity of boron added may be as little as .0005%, and thereby there is obtained an increase in the penetration of hardness. Furthermore, there is a definite range for the boron content, which is from .0005

to .0l% with attending increases in penetration of hardness and a useful percentage has been found to be .0025 this being the percentage of boron present in the steels produced in accordance with the foregoing examples.

As previously indicated, a good recovery of boron or introduction thereof into the iron or steel is attained when the melt is well deoxidized. It has further been found that in addition to deep hardening qualities which affect the physical properties of the steel through an increase in the elastic limit and tensile strength, there is a phenomenon known as precipitation hardness occurring through the use of boron. This is brought out by low drawing temperature, and may be done at a temperature as low as 150 F. A drawing of any kind usually results in a slight loss of hardness. However, the use of boron brings about an opposite effect so that the iron or steel may either retain the hardness present prior to drawing, or it may reduce the drop in with a boron content of about .002% the hardness at 7/8" was about 64 and that at 1" about 57. The marked effect of boron upon the hardness of the steel is thus well demonstrated, since without any boron the hardness at 7/8 was about 44, and at 1" about 42.

The effect of the boron on the properties of the steel changes rapidly with increase of carbon and of alloy metals such as nickel, molybdenum,

manganese, tungsten, chromium and vanadium. Thus, witha 5% nickel carburizing steel there was an increase in hardness, penetration of hardness, tensile strength, elastic limit, and-in the hardness due to the precipitation hardness on drawing. The efficacy of the boron varies somewhat for difierent types of steel, but the effect and suitable range of boron can be readily determined by making similar heats of steel and, for example, gradually increasing the boron content. An effective range is from .0005 to .01%, more particularly between .001 and .003%. The application of these low percentages and limits of the boron content in steels, whether made in an electric, open hearth or crucible furnace, leads to beneficial results, such as increased depth of hardness and enhancement of general physical hardness; a clear chill-like structure on the chilled surface without increase of combined carbon in the core; a broken up radial or acicular structure; increased coarseness of the core crystals; greater resistance to impact; higher transverse strength, and a finer structure in the chill portion.

Since certain changes in carrying out the above process which embodies the invention may be made without departing from its scope, it is intended that all matter contained in the above description shall be interpreted as illustrative and not in a limiting sense.

It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described, and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.

Having described my invention, what I claim 'as new and desire to secure by Letters Patent is:

1. A method for production of irons and steels, which comprises blocking an iron containing melt, tapping until a substantial amount of he melt has been removed, then degasifying to substantial completion through incorporation of a degasifier in an amount sufficient not only to degasify that portion of the melt already tapped but in excess of that which is sufiicient completely to degasify the entire amount of melt to be tapped, then adding boron thereto in substantially full amount in order that the same may be incorporated in the melt whereby further oxidation of boron is minimized during continued tapping of the melt, and then continuing the tapping until it is complete.

2. A method for production of irons and steels, which comprises blocking an iron containin melt, tapping until a substantial amount of the melt has been removed, then degasifying to substantial completion through incorporation of a degasifier in an amount suificient not only to of the melt, and then continuing the tapping until it is complete.

3. A method for production of irons and steels, which comprises blocking an iron containing melt, tapping until a substantial. amount of the melt has been removed, then degasifying to substantial completion through incorporation of a degasifier in an amount sufiicient not only to degasiiy that portion of the melt already tapped but in excess of that which is sufiicient completely to degasify the entire amount of the melt to be tapped, then adding boron thereto in substantially full amount through the addition of a ferro-boron containing to 12% boron and 1.5 to 2.5% carbon in order that the same may be incorporated in the melt whereby further oxidation of boron is minimized during continued tapping of the melt, and then continuing the tapping until it is complete.

4. A method for production of irons and steels, which comprises blocking an iron containing melt, tapping until about one-third of the melt has been removed, then degasifying to substantial completion through incorporation of a degasifler in an amount sumcient not only to degasify that portion of the melt already tapped but in excess of that which is suflicient completely to degasify the entire amount of the melt to be tapped, then adding boron thereto in substantially full amount through the addition of a ferro-boron containing 10 to 12% boron and 1.5 to 2.5% carbon in order that the same may be incorporated in the melt whereby further oxidation of boron is minimized during continued tapping of the melt, and then continuing the tapping until it is complete.

5. A method for the production of irons and steels, which comprises blocking an iron containing melt, tapping until a substantial amount of the melt has been removed, then degasifying to substantial completion through incorporation of a degasifier in an amount suflicient not only to degasify that portion of the melt already tapped but in excess of that which is suflicient completely to degasify'the entire amount of the melt to be tapped, then adding boron thereto in substantially full amount to give a ferrous material having a boron content from about .0005 to 0.12% through the addition of a ferro-boron in order that the same may be incorporated in the melt whereby further oxidation of boron is minimized during'continued tapping of the melt, and then continuing the tapping until it is complete.

NORMAN FENWICK TISDALE.

, CERTIFICATE OF CORRECTION.

Patent No. 2,285,299. May 19, 1913.-

NORMAN FENNICK TISDALE.

It is hereby certified thet error appears in the printed specification of the above numbered patent requiring correction as follows: Page 5, first column, line 7, before "silicon-manganese" insert L'"; and that the said Letters Patent should be read with this correction therein that the same may confonn to the record of the case in the Patent Qffice.

Signed ani sealed this 114th day of July, A. D. 19112.

Henry Van Arsdale, (Seal) Acting Commissioner of Patents.

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