US2013443A - High silicon and high manganese steel - Google Patents

Description

Patented Sept. 3, 1935 J UNITED s ArEs PATENT? OFFICE men SILICON .AND men MANGANESE STEEL' Abner C. Jones, Lebanon, Pa., assignor to Lebanon Steel Foundry, Lebanon, Pa., a corporation of Pennsylvania No Drawing.

Original application November 7,

1930, Serial No. 494,192. Divided and this application November 24, 1933, Serial No. 699,567

.3 Claims. (01. 75-'-1) This invention relates to steel products. This application is a division of my application, Serial No. 494,192, filed November 7-, v 1930, Patent -#1,94l,556 of January 2, 1934. Steel castings may be obtained from the steel that is produced 3.00% of manganese, about 0.50% to 3.00% of sili- 0.06% each of sulphur and V oxide and gases, such as carbon monoxide and face area is exposed to the moist sand of tin? mold.

Such sections are apt to show considerable porosity or pinholes.

It has been found that. this trouble of porosity can be avoided by the addition of aluminum to the molten steel, but the addition of suflicient aluminum to take care of this condition often results in decreased ductility of the steel. By the present invention, silicon-manganese steel is produced having the desired physical properties in which the trouble of porosity is obviated without the use of a deleterious amount of aluminum. The process is carried out so that the final product will contain less than about 0.20% of carbon and in such a way that the steel is deoxidized and degasified during its production by carbon and the introduction of silicon and manganese so that dissolved gases are removedand castings free from porosity can be obtained.

The following is given as a specific example of practicing this invention, but it is to be understood that the proportions can be varied over a considerdized condition able range: Steel scrap of about 0.20% to 0.30% carbon content is melted in an acid electric furnace. .Before the charge is completely melted,

. sufiicient iron ore is introduced into the bath so that the carbon content after the reaction brought about by the ore, will be about .12% After the charge is completely melted, a sufiiciept amount of silica sand is added to make the slag more siliceous and therefore less oxidizing. This increases its ability to hold iron oxides and thus decreases the amount of iron oxides in the bath metal. When the temperature reaches the point where the carbon reacts with the dissolved iron oxides obtained from the ore additions, the bath boils due to the formationof carbon monoxide gas which passes through the slag and reacts with oxides therein. forming carbon dioxide and thus reduces the oxiof the slag by decreasing its oxide content.

As the carbon gets lower to, say, about 0.12% in the molten bath, the reaction slows down due to the fact that the amounts of carbon and iron oxide in the bath decrease and the steel has a sufliciently great aflinity for the remaining carbon to prevent further reaction of the carbon with the iron oxide in the bath. 7

When the boiling subsides, more carbonis added to the bath, preferably in the fond of low silicon pig iron or wash metal, the latter being iron containing only about 4% of combined carbon. The carbon that is added reacts with more of the iron oxide of the bath and the bath is rabbled after the carbon is added to promote reaction between thecarbon and iron oxide. The amount of pig iron or other iron containing carbon is. about 1%% of the molten batch. Additional reaction between carbon and iron oxide takes place using up about half of the added carbon which passes of! as a gas in the form of an oxide of carbon. At the same time, other gases thathiay be present in the molten batch are swept out mechanically and non-metallic impurities are carried off and rise and become part of the slag.

As soon as the second boiling subsides, which usually requires about five or six minutes after the proper amount of pig iron or wash metal has been added with the desired carbon content, about 1% or sixty pounds of low carbon silica-manganese per five thousand pounds of metal is added and the bath rabbled for about a minute after the introductionof the silico-manganese to distribute it uniformly throughout the bath. The oxygen low bath of the electric furnace rise and enter pounds per square inch, an elongation of 32.8%,

the slag and manganese silicate is also formed, which rises and enters the slag. ,It has been found that the silicon content of the bath at this stage will be about 0.50%.

About ten minutes is permitted for the siliconmanganese reaction to take place and exercise its cleansing effect upon'the bath and then the temperature of the bath is slowly increased until the metal reaches approximately the temperature that is suitable for pouring small castings care being exercised to prevent the steel from becoming' overheated.

After the temperature of the bath has been increased almostto the temperature hot enough for pouring the castings, about 1 4% or seventy pounds of silico-manganese. to five thousand pounds of metal is added, together with an equal amount of 50% ferro-si licon. The amount of sillco-manganese and ferro-silicon introduced at this stage can be varied considerably, depending upon the final composition that is desired. The

bath is rabbled about a minute after the last addition to distribute the silicon and manganese throughout the steel and the furnace is tapped about two 'minutes after rabbling. By having the silicon and manganese distributed throughout the steel, very little, if any, iron oxide is formed when themolten metal passes from the furnace into the ladle, as oxygen from the air combines with the manganese and silicon rather than with the iron. If desired, an additional amount of silicon may be introduced into the ladle. The amount of silicon introduced into the ladle should not exceed more than about 2% of the charge by'weight because of the danger of ,chilling the steel. The presence of-the silicon and manganese not only helps to prevent the formation of pounds per square inch, a yield point of 53,000

a reduction of area of 64.7% and withstood a bend test of around a pin one inch in diameter. As an additional insurance against unusual conditionsof the mold that might result in porous castings, a small amount of aluminum may be introduced into the ladle after it has been filled, without changing the physical propertiesof the steel very much.

By this invention steel is made that has a low carbon content and a high silicon and high manganese content which can be poured into green sand molds to produce small size castings that are free from porosity. The steel is very ductile with high tensile strength and high ratio of yield point and .elastic limit to tensile strength.

Ferro silicon and low carbon manganese can be substituted for silico-manganese, but the best results were obtained with silico-manganese.

I claim:

1. Steel of high tensile strength and ductility containing about 0.12%;carbon, 1.76% silicon, 1.53% manganese, less than 0.06% of sulphur and phosphorouseach, and the remainder substantially all iron, said steel being capable of being cast into green sand molds when melted without becoming porous when it freezes.

2. Steel of high tensile strength and ductility containing about 0.12% carbon, about 1.76% silicon, about 1.53% manganese, lws than 0.06% of sulphur and phosphorous each, and the remainder substantially all iron, said steel being capable of being cast into green sand molds when melted without becoming porous when it freezes, said steel having a tensile strength over 75,000 pounds per square inch.

3. Steel of high tensile strength and ductility ABNER c JONES.