US2360271A - Alloy steel article - Google Patents

Description

Patented on. 10, 1944 Q 2,360,271

my STEEL ARTICLE Otto N. Peterson, Flint, Mich, asslgnor to General Motors Corporation, Detroit, Miclm, acorporation oi' Delaware No Drawing. Application August 2 1940, Serial No. 350,083

12 Claims. (01. 1 .48-21.55)

This invention relates to alloy steel articles and methods of making and of treating the same. For a number of years it has been common practice for certain purposes in the automotive binations oi alloying constituents to manganese steels during the manufacture thereof further improves the properties thereof for parts such as gears and the like which require low drawing tem- .peratures on the order of temperatures up to about 500, F. The addition of a small-amount of an alloy mixture containing vanadium, titanium and aluminum as essential constituents to the'molten manganese steel, prior to or after pouring into ingot form results in a manganese steel that when hardened and subjected to drawing temperatures up to about 500 F. has exceptional properties especially adapted for gears and the like. Manganese steels made as just described are also highly suitable for parts requiring higher drawing temperatures, but at the lower drawing temperatures the properties are outstanding as compared with similar manganese steels made without the use of the addition agent.

A steel in accordance with the present invention is exceptional in hardenability'as compared without the use of the.

with similar steels made addition agent. The hardenability maybe determined by a method similar to that described in an article in Transactions of The American Society for Metals, volume 26, beginning on page 574 (1938) and'in Hardenabllity of Alloy Steels, published bythe American Society for Metals (1939), commencing on page 66. In this method an elongated bar 3 inches in length and 1 inch in diameter is heated to a hardening temperature and cooled by means of a Jet of water contacting one end face-only of the bar. The hardness of the bar is then measured at various disindustry to utilize steels containing larger tances from the water cooled end. The greater amounts of manganese than employed in the the distance from the water cooled end at which plain carbon steels. Such steels are known as h dn ss s above a s a fi the eate manganese alloy steels and when properly made th flammability 0f the steel.

. and heat treated are as good as, or better than, In addition to its exceptional hardenability as other alloy steels that are much higher priced. compared with similar steels made without the For example, manganese steels have been used a iti n a nt, the eel of t e present i e commercially to a rather large extent for such tion when hardened and drawn at temp r r automotive parts as steering knuckles, steering up to about 500". F. is exceptional as regards arms, supports, main shafts, etc. For these ductility and imp t V e- Moreover, the usages the manganese steels have proven exultimate strength is high, although ordinarily ceptionally good. For such usage the parts are not appreciably greater than similar steels first hardened by heating and quenching. This A made without the addition agent. The comis followed by a drawing treatment at a tembination of high ultimate strength with the perature of about 800 F. to 1200 F. More reexcep p ties of hardenabflity, duct t cently manganese steels have been used commerand impact value makes an extremely good macially for parts requiring lower drawing temperaterial for gears and similar articlestures, say up to about 500, F. In this field the One convenient method by which the alloy manganese steels have also proven highly sucmixture containing vanadium, titanium, and alucessful. minum may be added to the steel is to add it to I have found that the addition of certain comthe molten steel while i t ladle before n ing the steel into the ingot molds. The vanadium, titanium and aluminum combination is commercially available as an alloy mixture composed of about 25% vanadium, about 15% titanium, about 12% aluminum, about 2% of silicon and carbon together and the balance iron plus traces of impurities.

ceptional properties. Amounts as low as two pounds per ton have also been used with success. Higher and lower amounts may be used also, the amount varying somewhat depending on the condition of the bath, andother factors. ,Due to the increased cost occasioned by the larger amounts it is desirable to restrict the amount as much as possible and still obtain the desired.

properties in the finished article.

As an example of one type of manganese steel that may be treated in accordance with my invention, reference may be made to the T1300 series. This type containsabout 1.60% to 1.90% manganese, carbon as desired depending on the use and up to the top limit of, carbon present in steels generally, silicon about .15% to and the balanceiron plus traces of ordinary impurities. Generally such impurities will include up to to .45% may be employed; about .40% carbon having proven especially suitable. In case the manganese steel is to be used for a part such as a ring ear that is to be case carburized the carbon conte tpf the part before carburizing may be lower, say about .10% to .30%. Other types of manganese steel may be employed, also, with considerable variation in the quantity of manganese present. Good results have been obtained with a manganese range of 1.35% to 1.65%, with the carbon and silicon as described for the T1300 series. Amounts of manganese as low as 1.00% have also been usedwith success. Greater amounts of silicon may be present, if desired. In special applications it may be as high as 1 or 2%, for example. Small amounts of other alloying elements such as chromium, nickel, molybdenum, etc. may sometimes be present.

The vanadium, titaniumjalumlnum mixture may be added to the manganese steels in the ladle before pouring the same into the ingot molds. The steel ingots thereafter may be rolled or otherwise shaped into bar form in the usual way. The bar stock may be forged or shaped in any desired manner into the form of a gear blank or other article. The forged blank is preferably normalized and thereupon machined to shape. Heating to a temperature of about 1600" F. to 1650 F. followed by slow cooling is a suitable normalizing treatment. The temperature to be employed in any particular instance will depend somewhat on the carbon and manganese contents and other factors. Ordinarily the higher the carbon content up to about .85% carbon, the lower the normalizing temperature.

The machined part is then heated to a hardening temperature and rapidly cooled ,or quenched to harden the same. The proper hardening temperature will vary somewhat depending on the carbon and manganese contents and other factors.

about 35% to .45% carbon is to heat the parts to 1550" F., for about one hour and oil quench.

For gears and the like the parts are then subjected to a low drawing temperature up to about tanium and aluminum. Heats of steel have been made up with the separate addition of vanadium, titanium or aluminum and the result in each case is a steel that, while good, has little, if any, advantage over similar steels without the addition agent. Apparently, also, the exceptional properties of the product of the. present invention are not due to the traces of vanadium, titanium and aluminum remaining in the product. Chemical analyses indicate that but traces of the aluminum and titanium remain in the end product. Al parently these constituents are removed du g A hardening treatment that has proven satisfactory for the manganese steels containing A the deoxidization of the steel. Tests indicate that the product contains most of the added vanadium, but the presence of this constituent by itself in the amountremaining is insumcient to have any 5 great effect as has been proven by making up heats of manganese steel and adding an equivalent amount of vanadium in the form of ferro-.

vanadium.

Microscopic examination of samples. of the steel made with the use of the vanadium, titanium,

aluminum addition agent have been made. Whether annealed or hardened and drawn, one thing that stands out is the uniformity of structural constituents. When oil quenched and drawn at about 450 F., the structure is martensitic, with practically no ferrite out of solution. It appears that the martensite is more readily obtainable in a non-needle like form in a steel produced in accordance with the present invention than in a similar steel made without the addition agent.

I claim: 1. As a new article of manufacture, a hardened manganese steel article that has been drawn at 5 a temperature less than about 500 F., said article having been made from a manganese steel having added thereto in the manufacturing process a small but effective amount up to about 4 pounds per ton of steel of an addition agent containing vanadium, titanium andaluminum, said article having high ultimate strength combined with outstanding properties of ductility, hardenability and impact value. i

2. As a new article of manufacture, a gear of hardened manganese steel characterized by the combination of high ultimate strength with exceptional ductility, hardenability and impact value, said gear having been drawn at a temperature less than about 500 F. and having been.

40 made from a manganese steel to which has been added in the manufacture thereof a small but eflective amount up to about 4 pounds per ton of steel of an addition agent containing vanadium, titanium and aluminum.

3. A method of making and heat treating an article which comprises forming a molten manganese steel, adding thereto a small but effective amount up to about 4 pounds per ton of steel of a mixture containing vanadium, titanium and aluminum, pouring said composition into ingot form, forming said manganese steel ingot into bar form, forging an article of manganese steel from said bar, heating said article to a hardening temperature, rapidly cooling said heated article to harden the same, and drawing the hardened article at a temperature less than about 500 F.

4. A method of making and heat treating a I the hardened gear at a temperature less than 7 about 500 F. r

5. A method of making and heat treating an article which comprises forming a molten manganese steel, adding thereto a small but ective amount up to about 4 pounds per aluminum, forming a manganese steel article therefrom, heating said manganese steel article to n of steel ofra mixturecontaining vanadium tanium and a hardening temperature, rapidly cooling said heated article to harden the same, and drawing the hardened manganese steel article at a temperature less than about 500 F. a

6. As a new article of manufacture, a gear of hardened and drawn manganese steel containing about .35%-.45% carbon, about 1.00%1.90% manganese, about .15%-.30% silicon, balance iron plus minor amounts of impurities, said manganese steel having had a small but effective amount up to about 4 pounds per ton of steel of an addition agent containing vanadium, titanium and aluminum added thereto in the manufacture thereof, said gear having been drawn at a temperature of approximately 450 F. and being characterized by outstanding properties of ductility, hardenability and impact value as compared with similarly treated manganese steels made without the addition agent. v

7. As a new'article of manufacture, a hardened and drawn manganese steel article containing about .35%.45% carbon, about 1.00%-1.90% manganese, about .15%-.30 silicon, balance iron plus minor amounts of impurities, said manganese steel having had added to each ton of steel in the manufacture thereof about 2 to 4 pounds of an addition agent composed of about 25% vanadium, about l5% t itanium, about 12% aluminum, about 2% of silicon andcarbon together and the balance iron plus traces of impurities, said article having been drawn at a temperature of not more than about 500 F. and being characterized by exceptional properties of ductility, hardenability and impact value as compared with similarly treated manganese steels made without the addition agent.

8. A method of making and heat treating an article which comprises forming a molten manganese steel composed substantially as follows: .35% to .45% carbon, 1.00% to 1.90% manganese. .15% to 30% silicon and the balance iron plu minor amounts of impurities; adding to said molten manganese steel about 2 to 4 pounds per ton of an addition agent composed substantially as follows; 25% vanadium, 15% titanium, 12%

aluminum, 2% of carbon and. silicon together, balance iron plus traces of impurities; forming a effective amount of titanium not greater. than about .03%, a small but effective amount of aluminum not greater than about .024%, a small but effective amount of vanadium up to about .05%, balance iron plus traces of ordinary impurities; said article having been drawn at a temperature less than 500 F. and being characterized by outstanding properties of ductility, hardenability and impact value.

10. A method of making and .heat treating an article which comprises forming a' molten mixture composed substantially as follows: 35% to .45% carbon, 1.00% to 1.90% manganese, .15% to .30% silicon, and the balance iron plus traces of ordinary impurities; adding to each ton of said molten mixture about .50 to 1.00 pound of vanadium, about .30 to .60 pound of titanium, and about .24 to .48 pound ofaluminum; forming a manganese steel article from the mixture thus treated; heating said manganese steel article to a hardening temperature; rapidly cooling the article to harden the same; and drawing the hardened manganese steel article at atemperature less than about 500 F.

11. A method of making and heat treating an article which comprises forming a molten mix- 'ture consisting essentially as follows: .35-.45%

carbon, 1.00-1.90% manganese, .15-.30% silicon, balance iron plus minor amounts of impurities; adding a small but effective amount up to about four pounds per ton of steel of an alloy addition agent containing vanadium, titanium and aluminum, forming an article from the mixture thus treated, heating said article to a hardening temperature, rapidly cooling the heated article to harden the same, and drawing the hardened arti-.

cle at a temperature less than about 500 F.

12. A method of making and heat treating a gear which comprises forming a molten manganese steel composed substantially as follows: .35 to .45% carbon, 1.00 to 1.90% manganese, .15 to .30% silicon and the balance iron plus minor amounts of ordinary impurities, adding to said molten manganese steel in the proportion of about two to four pounds per ton of steel an addition agent composed substantially as follows: 25% vanadium, 15% titanium, 12% aluminum, 2% of carbon-and silicon together, balance iron plus traces of impurities, pouring the molten manganese steel treated with said addition agent into ingot form, forming said ingot into bar form, forming a gear from said bar, heating the gear to a temperature of about 1550 F. for about one hour, quenching said heated gear in oil to harden the same, and drawing said hardened gear ata temperature of about 450 F.

" O'I'IO N. PETERSON.