Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
  • C22C38/54—Ferrous alloys, e.g. steel alloys containing chromium with nickel with boron
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
  • C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten

Definitions

• the present invention relates to alloy steels and, more particularly, to martensitic low alloy steels of relatively low cost which in the quenched and tempered condition manifest a combination of metallurgical properties of such magnitude that the steels are especially suitable as plate steels in section sizes up to at least 1 inch in thickness for general industrial and commercial use.
• quenched and tempered plate steel is used in a substantial number of diversified industrial and commercial activities, including transportation, machinery, mining, power, petroleum, etc., and, thus, represents a significant tonnage item of the steel industry. More recently, it would appear that the rapidly developing field of cryogenics holds considerable potential for plate steels which are of low cost and which manifest good impact properties at low temperatures. Because of the versatile role characteristic of plate steels, it is not unexpected to find that they must possess a combination of properties capable of meeting the varying requirements imposed by the increasingly stringent demands of industrial and commercial use. In this regard, a satisfactory plate steel, of say 1 inch in thickness, should, in the quenched and tempered (at 1150 F.
• the steels are of relatively low cost, can be processed without difficulty and the properties characteristic thereof are reproducible from heat to heat. These additional factors render the steels particularly attractive for use as steel plates.
• alloy steels having the following most advantageous composition: about 0.15% to about 0.22% carbon, about 0.65% to about 1% manganese, about 0.2% to about 0.35% silicon, about 0.7% to about 1% nickel, about 0.2% to about 0.35% chromium, about 0.15% to about 0.3% molybdenum, about 0.02% to about 0.06% aluminum, about 0.0005 to about 0.004% boron, and the balance essentially iron.
• the alloy ranges set forth above be maintained.
• the carbon content should not be appreciably lower than 0.15
• carbon contents e.g. 0.1%
• free ferrite can form readily enough to give a marked reduction in hardenabi'lity.
• processing difficulty can be encountered with carbon levels of say 0.1%, as opposed to 0.15%. With 0.15% carbon a much cleaner steel is provided because less oxygen is needed in producing it than would be required in producing the steel if it were to contain 0.1% carbon.
• the amount of silicon not exceed 0.35%.
• Silicon should be added prior to the aluminum for good preliminary deoxidation, accompanied by fiuxing and removing silica to the slag. This insures minimizing retention of dissolved oxygen and keeping it to a low level, thereby forming only small amounts of alumina. High silicon contents adversely affect certain properties and give rise to dirty steels which are known to be difficultly processable.
• the siilcon content should always be less than 0.5%.
• Manganese, nickel, chromium and molybdenum contribute to afiording high tensile strengths (hardness), high yield strengths and high hardenability.
• nickel greatly contributes to the toughness of the steels, especially to good impact properties at low temperatures.
• Each of these elements retard softening upon tempering although molybdenum and chromium are most effective in this regard.
• amounts of these four elements significantly above the aforedescribed ranges will undesirably lower the M temperature of the steels and tend to cause cracking upon quenching from austenitizing temperature.
• Alloy steels within the foregoing ranges have more than an adequate degree of hardenability since they harden to at least 90% martensite upon quenching sections up to at least 1 inch thick from austenitizing temperatures. This is important in order to afford good impact properties and a high yield strength to tensile strength ratio, e.g., 0.8
• the steels are characterized by a yield strength (0.2% offset) of at least 90,000 p.s.i., good toughness as shown by a Charpy V-notch impact strength of at least 40 and as high as 90 ft.-lbs. at room temperature and, more importantly, of
• the invention provides a low alloy steel which when quenched and tempered develops a high yield strength usually in excess of 95,000 or 100,000 p.s.i., with an impact transition temperature below -150 F. in plate form and in weldments.
• the foregoing properties obtain in sections of at least 1 inch thickness, are reproducible from heat to heat and, thus, the steels are especially adaptable for use as plate steels.
• steels of the following composition about 0.14% to about 0.24% carbon, about 0.6% to about 1.2% manganese, about 0.10% to less than about 0.5% silicon, about 0.6% to about 1.5% nickel, from 0.18% to less than 0.4% chromium, about 0.15% to about 0.35% molybdenum, about 0.015% to about 0.1% aluminum, about 0.0005% to about 0.005% boron, and the balance essentially iron.
• the steels should be austenitized at about 1625 F. to about 1750 F. and preferably between 1650" F. and 1700 F. Holding at such temperature for about 20 minutes or more is quite adequate. Quenching should be conducted sufficiently rapid to insure a structure of at least 90% martensite. Water quenching is quite adequate and is desirable in quenching sections /z-inch thick and above for optimum results. Tempering at a temperature of 1000 F. to 1200 F. provides a steel which does not manifest an appreciable decrease in impact properties at ambient temperatures. All factors considered, tempering at 1100 F. to 1175 F., e.g., 1150 F., is quite satisfactory, although actual tempering temperature will be dictated by commercial application. The steels should be held at tempering temperature for a period consistent with good commercial heat treating practice. Periods of '1 to 2 hours have been found quite adequate although shorter periods, e.g., onehalf hour, can be used satisfactorily.
• a series of alloys was prepared having compositions of boron, tends to or is capable of reducing the impact as given in Table I.
• This steel was austenitized at between 1625 F. and 1675 F. and the tempering temperature was maintained at between 114- 0" F. and 1160 F.
• This commercial heat had the following properties: a yield strength of 103,000 p.s.i., a tensile strength of 112,000 p.s.i., a tensile elongation (2- inch gage length on 0.505-inch bar) of 23%, a reduction Table III illustrates the relatively small dilference in tensile ductility. Thus, severe forming operations can be performed in either direction with assurance. It should be pointed out that a 2-inch gage length was used in measuring ductility. If the conventional or standard gage length of 1.4 inches were used (since the specimens were 0.3 inch thick), the elongation values would be over 20%.
• Weld-ability is a most important commercial characteristic of plate steels. If a plate steel is prone to or susceptible to cracking, or if, for example, strength properties are appreciably reduced as a result of welding, the effectiveness of the plate steel and its commercial acceptability are obviously impaired. Moreover, many steels require a stress-relief treatment subsequent to the. welding operation. It stress-relieving of the heat-affected zone can be avoided, the overall cost of the final product is considerably reduced. Further, stress-relieving large articles of manufacture is a most tedious and difficult task. To illustrate the good weldability characteristics and the effect of welding upon alloys within the instant invention, alloys were produced having compositions given in Table IV. Alloy D is an alloy within the invention whereas Alloy N 0. 1 responds to a prior art nickel-free alloy steel which is outside the present invention.
• alloy steels within the invention have an excellent combination of properties from the commercial aspect.
• the plates were cut into lengths of about 13 inches and were given the following heat treatment: austenitized at 1675 F., water quenched, tempered for two hours at 1200 F. and thereafter water quenched.
• the plates were machined (including top and bottom surfaces) to 4 /2 inches wide and a groove was machined along the vertical face of one of the 13-inch edges of each plate which left a lip of about -inch.
• the grooves had a radius of about fii-inch and flared out at an angle of about 15 to the 11016 electrode.
• the Welding current was 190 amperes and the welding voltage was 25 volts.
• the bead sequence consisted of a series of about passes to fill the groove, the final pass being made down the middle of the weld.
• the welded plate was then turned over and a single root bead was deposited on the reverse side. Subsequent to the welding operation the plates were cut in half, one-half being tested as-welded while the other half was tested after being stressrelieved at 1100 F. for two hours. No pre-heating was used prior to the Welding operation.
• Charpy V- notch specimens were cut from the transverse direction of the plate and were notched perpendicular to the surface. The specimens were machined to about 0.394- inch square blanks and macroetched to reveal the heataffected zone. The entire heat-affected zone as Well as a small amount of the weld metal and base metal were under the Charpy V-notch.
• alloy steels within the invention are especially adapted for gas and liquid pipe lines, explosion bulge tests were conducted to further confirm that the steels in both the non-welded plate and welded plate conditions possess levels of toughness and resistance to brittle fracture of a magnitude sufficient to withstand the requirements of commercial use.
• the test specimens which had the composition given for the commercial heat set forth hereinbefore and treated as there described, were 14-inch squares, having a thickness of 0.281 inch and were of three types: (1) un-welded plate, (2) Welded plate in which the weld was deposited at a speed of 50 inches per minute, and (3) welded plate in which the weld was deposited at a speed of 75 inches per minute. Submerged arc welding technique was employed.
• weldments developed a hair-line crack along the edge of the weld bead and another showed cracking transversely acrossthe weld.
• fracture as would be expected, was more extensive. It required a 2 lb. charge at 15 inches to blow out the bulge area in the welded specimens and in each instance one-half of the area Was blown out.
• an alloy steel similar in composition to Alloys A, B and C of Table I and containing 0.18% carbon, 0.8% manganese, 0.15% silicon, 0.84% nickel, 0.36% chromium, 0.27% molybdenum, 0.029% aluminum, 0.003% boron (added), and the balance essentially iron was austenitized at 1700 F. for 1 hour, water quenched, tempered for 2 hours at 1200 F. and then water quenched.
• the steel was machined to a /2-inch thick specimen having a width of 1 inch and a length of 7 inches.
• the specimen was then subjected to a severe bend test which comprised bending the specimen over a /z-inch radius. Upon examination of the 180 bend, no cracks were observed and the test results confirmed the excellent formability characteristics.
• a further feature of the invention is that under normal conditions of tempering or stress-relieving when alloy steels within the invention are slowly cooled from tempering temperature, no problem of temper embrittlement is incurred as is the case with some other alloy steels.
• alloy steels of the invention can be slowly cooled from tempering temperature, e.g., air cooled to minimize distortion and then put into service.
• the steels are suitable for wide commercial application, including pressure vessels, fluid storage containers, heavy machinery, railroad cars, structural members, e.g., frames for trucks, ship framework, boom-s, materials requiring exceptional resistance to impact, e.g., penstocks, etc.
• the steels are especially useful as steel plate, particularly in the fabrication of oil, gas and other fluid pipe lines therefrom.
• a martensitic low alloy steel particularly adapted for use as steel plate in section sizes up to at least 1 inch in thickness and characterized when quenched and tempered at temperatures of at least 1100 F. by a yield strength (0.2% offset) of over 90,000 p.s.i., a tensile strength of over 100,000 p.s.i., a yield to tensile strength ratio of at least 0.8, a Charpy V-notch impact value of at least 40 -ft.-lbs. at room temperature and 15 ft.-lbs. at
• said alloy steel consisting essentially of about 0.15% to about 0.22% carbon, about 0.65% to about 1% manganese, about 0.2% to about 0.35% silicon, about 0.7% to about 1% nickel, about 0.2% to about 0.35% chromium, about 0.15% to about 0.3% molybdenum, about 0.02% to about 0.06% aluminum, about 0.0005% to about 0.004% boron, and the balance essentially iron.
• a low alloy steel adapted for use as steel plate and characterized by a martensitic structure in the quenched and tempered condition and by a good combination of mechanical properties, said alloy steel consisting essentially of from .14% to 0.24% carbon, 0.6% to 1.2% manganese, 0.1% to less than 0.5% silicon, 0.6% to 1.5% nickel, from 0.18% to less than 0.4% chromium, 0.15% to 0.35% molybdenum, 0.015% to 0.1% aluminum, 0.0005% to 0.005% boron, and the balance essentially iron.

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Heat Treatment Of Steel (AREA)
• Heat Treatment Of Articles (AREA)
• Heat Treatment Of Strip Materials And Filament Materials (AREA)

Priority Applications (8)

Applications Claiming Priority (1)

Publications (1)

Family

ID=22956831

Family Applications (1)

Country Status (8)

Cited By (5)

Citations (9)

Family Cites Families (1)

• 0
  • BE BE642783D patent/BE642783A/xx unknown
• 1963
  • 1963-01-21 US US252626A patent/US3258372A/en not_active Expired - Lifetime
• 1964
  • 1964-01-09 GB GB1081/64A patent/GB1034031A/en not_active Expired
  • 1964-01-18 DE DEJ25146A patent/DE1255929B/de active Pending
  • 1964-01-20 ES ES295490A patent/ES295490A1/es not_active Expired
  • 1964-01-21 DK DK30664AA patent/DK103594C/da active
  • 1964-01-21 NL NL6400420A patent/NL6400420A/xx unknown
  • 1964-01-21 LU LU45265D patent/LU45265A1/xx unknown

Patent Citations (9)

Also Published As

Similar Documents