US3163565A - Process for producing a tough steel for low temperatures - Google Patents
Process for producing a tough steel for low temperatures Download PDFInfo
- Publication number
- US3163565A US3163565A US203444A US20344462A US3163565A US 3163565 A US3163565 A US 3163565A US 203444 A US203444 A US 203444A US 20344462 A US20344462 A US 20344462A US 3163565 A US3163565 A US 3163565A
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- United States
- Prior art keywords
- steel
- temperature
- aluminum
- nitrogen
- weight percent
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- 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
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
-
- 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
- C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
Definitions
- a steel has a transition temperature which is determined by its constituency and will absorb high energy at the time of breaking on the higher side of the transition temperature and'low energy on the low temperature side. Therefore, it is considered necessary that a steel to be used at low temperatures should have a transition temperature low enough for the conditions which it is to be used under and further, should be tough.
- a steel which has been extensively used for this purpose contains more than 2.5% nickel in order to keep the transition temperature low.
- the alloying element nickel is added, the steel becomes costly and, further, special consideration is required for refining, ingoting, heating and rolling in the production of the steel and therefore the production cost is high.
- the object of the present invention is to eliminate the aforementioned defects and to provide low-temperature tough steel which is easy to heat-treat and is low in cost.
- a steel according to the present invention can easily be made by melting in an open-hearth furnace, electric furnace or pure oxygen converter. Its chemical composition is approximately less than 0.14%' carbon, less than 0.5% silicon, 1.0 to 1.5% manganese, 0.01 to 0.04% aluminum and 0.008 to 0.020% nitrogen, less than 0.20%- of one or more of the elements niobium, tantalum and vanadium if required with the remainder being iron and unavoidable impurities. Small amounts of somespecial element may be added when required. Steel having such acomposition is produced by first melting, then rolling or forging, then heating to a temperature above 880 C., then quenching, further reheating to 600 to 700 C. and then cooling by air or the like.
- the first of the fundamental features of the present invention is that when the aluminum and nitrogen are in a solid solution and supercooledin the steel they are deposited as aluminum nitride by heating from 600 to 700 C., which is below the A transformation point, and then cooling so that the toughness at low temperatures may be improved.
- the method of increasing the toughness by depositing aluminum nitride below the A, transformation point, as in the present invention is far more effective than any known conventional method.
- the present invention is the first to discover and apply such fact.
- the above mentioned heating temperature is below 600 C., the deposition of aluminum nitride will be volumetrically insufficient.
- the structure will become austenite and the structure and deposited state will be nonuniform and undesirable.
- United States Patent More particularly the present invention relates "ice
- the second of the features is to produce a steel having a fine ferrite structure. That is, said aluminum nitride will be highly effective when, it is deposited in ferrite. Therefore, the steel is rapidly cooled from above 880 C. so that the steel will not have so-called hardened structure such as martensite or bainite but rather, should have a ferrite structure and that, before treating to deposit the aluminum nitride both the nitrogen and aluminum should be in solid solution in the steel.
- the heating temperature above 880 C. in the heat-treatment of the steel according to the present invention is determined therefore. It is preferable that the heating time is as short as possible. However, as described later, the heating temperature must be kept in such range as will not make the crystal grain size coarse.
- the heating temperature before cooling is recommended to be about 880 to 950 C.
- the cooling rate should be so rapid that no aluminum nitride will be deposited during cooling and must be controlled so that fine ferrite will appear and no hardened structure is made. A cooling rate of about 5 to 50 C./sec. is recommended. Further, in order to prevent aluminum nitride from being deposited, the COO1-' below the A transformation point. The carbon content.
- the silicon content is below 0.5%.by weight which is the normal requirement in steel making.
- the manganese content is as high as is possible and is about 1.0 to
- a small amount e.g., less than 0.2% by weight of one or more of the elements niobium, tantalum and vanadium each of which will form a fine carbide, stable even at high temperatures, and will reduce the hardenability, accelerate the production of fine ferrite and, at the same time, improve the weldability of the'steel.
- EXAMPLE A'steel containing the ingredients shown in Table 1 was produced by heating in an electric furnace to a temperature 'of 930 C. in 20 minutes. The steel was then rapidly cooled at a rate of 15 C./sec., then heated to a temperature of 625 C. for 30 minutes and was then cooled in air.
- Ferrite-grain size No. 911 (A.S. T.M.).
- sample 3 is the same as sample 1 except it was heated to 930 for 20 minutes and then rapidly cooled and sample 4 is the same as sample 3 except it was heated to 625 C. for 30 minutes and then cooled in air.
- sample 4 is the same as sample 3 except it was heated to 625 C. for 30 minutes and then cooled in air.
- Table 4 there is shown the relationship between the amount of aluminum nitride and the press notch Charpy broken surface tran sition temperature on the rolled sample and the sample heated to 930 C. for-20 minutes and rapidly cooled, both of which were heated to 625 C. for 30 minutes and then cooled in air for the depositing treatment.
- a process for producing a tough steel for low temperature service comprising heating a low carbon steel containing 0.01 to 0.04 weight percent aluminum, 0.008 to 0.02 weight percent nitrogen, less than 0.50% silicon and less than 0.14 weight percent carbon to a temperature of about 88010 950 C, quiclily cooling said steel at a cooling rate of from 5 to 50 degrees centigrade per second to a temperature below 600 C. wherehythere is produced a fine ferrite structure in said. steel and the liberated aluminum and nitrogen are insolid solution; reheating the cooled steel to a temperature of about 600 to 700 C. and cooling the steel to room temperature whereby the aluminum and nitrogen are deposited in said steel as aluminum nitride.
- a process for producing a tough steel for low temperature service comprising heating a steel containing 1.0 to 1.5 weight percent manganese, 0.01 to 0.04 weight percent aluminum, 0.008 to 020 Weight percent nitrogen, less than 0.14 weight percent carbon, less than 0.50 weight percent silicon with the remainder being iron and incidental impurities to a temperature of about 880 to 950 C. and quickly cooling said steel at a cooling rate of from 5 to 50 degrees centigrade per second to a temperature below 600 C. whereby there is produced a fine ferrite structure in said steel and the liberated aluminum and nitrogen are in solid solution; reheating the cooled steel to a temperature of about 600 to 700 C. and cooling the steel to room temperature whereby the aluminum and'ni-,
- trogen are deposited in said steel as aluminum nitride.
- a process for producing a tough steel for low temperature service comprising heating a steel containing 1.0 to 1.5 weight percent manganese, 0.01 to 0.04 weight percent aluminum, 0008 to 0.20 weight percent nitrogen, less than 0.14 weight percent carbon, less than 0.50 weight percent silicon and at least one alloying element selected from the group consisting of niobium, tantalum and vanadium, the total amount of said alloying elements T5 6 being less than 0.20 weight percent with the remainder References Cited by the Examiner being iron and incidental impurities to a temperature of UNITED TATE PATENTS about 880 to 950 C.
Description
3,153,565 PRGCESS FQR PRODUUNG A TUUGH STEEL FOR LQW TEMPERATURES Kamelrichi Wada, Yawata, Japan, assignor to Yawata Iron & Steel Co., Ltd, Tokyo, Japan, a corporation of Japan No Drawing. Filed June 19, 1962, Ser. No. 203,444 Claims priority, application Japan, June 22, 1961, 3/22,237 4 Claims. (Cl. 148-143) This invention relates to the process for producing steel having high weldability and toughness at low temperatures. to a process for producing tough steel for low temeperature service which contains no costly nickel and is easy to produce, simple to heat-treat and low in cost.
Generally, a steel has a transition temperature which is determined by its constituency and will absorb high energy at the time of breaking on the higher side of the transition temperature and'low energy on the low temperature side. Therefore, it is considered necessary that a steel to be used at low temperatures should have a transition temperature low enough for the conditions which it is to be used under and further, should be tough.
A steel which has been extensively used for this purpose contains more than 2.5% nickel in order to keep the transition temperature low. However, when the alloying element nickel is added, the steel becomes costly and, further, special consideration is required for refining, ingoting, heating and rolling in the production of the steel and therefore the production cost is high.
The object of the present invention is to eliminate the aforementioned defects and to provide low-temperature tough steel which is easy to heat-treat and is low in cost.
A steel according to the present invention .can easily be made by melting in an open-hearth furnace, electric furnace or pure oxygen converter. Its chemical composition is approximately less than 0.14%' carbon, less than 0.5% silicon, 1.0 to 1.5% manganese, 0.01 to 0.04% aluminum and 0.008 to 0.020% nitrogen, less than 0.20%- of one or more of the elements niobium, tantalum and vanadium if required with the remainder being iron and unavoidable impurities. Small amounts of somespecial element may be added when required. Steel having such acomposition is produced by first melting, then rolling or forging, then heating to a temperature above 880 C., then quenching, further reheating to 600 to 700 C. and then cooling by air or the like.
Thus, the first of the fundamental features of the present invention is that when the aluminum and nitrogen are in a solid solution and supercooledin the steel they are deposited as aluminum nitride by heating from 600 to 700 C., which is below the A transformation point, and then cooling so that the toughness at low temperatures may be improved. As already. known, it is possible to improve the toughness by depositing aluminum nitride near the A transformation point. However, the method of increasing the toughness by depositing aluminum nitride below the A, transformation point, as in the present invention, is far more effective than any known conventional method. The present invention is the first to discover and apply such fact. When the above mentioned heating temperature is below 600 C., the deposition of aluminum nitride will be volumetrically insufficient. When it is above 700 C., the structure will become austenite and the structure and deposited state will be nonuniform and undesirable.
United States Patent More particularly the present invention relates "ice The second of the features is to produce a steel having a fine ferrite structure. That is, said aluminum nitride will be highly effective when, it is deposited in ferrite. Therefore, the steel is rapidly cooled from above 880 C. so that the steel will not have so-called hardened structure such as martensite or bainite but rather, should have a ferrite structure and that, before treating to deposit the aluminum nitride both the nitrogen and aluminum should be in solid solution in the steel.
In order that the aluminum and nitrogen are well liberated, the thermal condition before the depositing treatment must be restricted. The heating temperature above 880 C. in the heat-treatment of the steel according to the present invention is determined therefore. It is preferable that the heating time is as short as possible. However, as described later, the heating temperature must be kept in such range as will not make the crystal grain size coarse. The heating temperature before cooling is recommended to be about 880 to 950 C.
The cooling rate should be so rapid that no aluminum nitride will be deposited during cooling and must be controlled so that fine ferrite will appear and no hardened structure is made. A cooling rate of about 5 to 50 C./sec. is recommended. Further, in order to prevent aluminum nitride from being deposited, the COO1-' below the A transformation point. The carbon content.
is below 0.14% by weight so that a ferrite structure is obtained at the time of rapid cooling.
The silicon content is below 0.5%.by weight which is the normal requirement in steel making. The manganese content is as high as is possible and is about 1.0 to
1.5% by weight so that, as already known, the toughness at low temperatures is increased and the weldability is improved.
Further, if necessary, there may be added a small amount, e.g., less than 0.2% by weight of one or more of the elements niobium, tantalum and vanadium each of which will form a fine carbide, stable even at high temperatures, and will reduce the hardenability, accelerate the production of fine ferrite and, at the same time, improve the weldability of the'steel.
EXAMPLE A'steel containing the ingredients shown in Table 1 was produced by heating in an electric furnace to a temperature 'of 930 C. in 20 minutes. The steel was then rapidly cooled at a rate of 15 C./sec., then heated to a temperature of 625 C. for 30 minutes and was then cooled in air.
Table 1.-Examples of Chemical Compositions in Percent Sample 0 Si Mn Al N Nb I V Ta signs 3 3 Table 2.--Examples of Mechanical Properties [As heated to 930 C. for 20 minutes, rapidly cooled, then heated to 625 C. [or 30 minutes and cooled in air] Press notch Charpy Sample Yielding Tensile Elongation broken signs point in strength in percent] surface lrgJnun. kg/mm. 200 mm. transition temperature in C.
observed. However, it is clearly seen that the sample which was rapidly cooled had better values than the rolled sample which is explained by the fact that there is a difference in the ferrite grain size between the two samples which is caused by the heating of the one sample to a T able 3.-Examples of Deposition of Aluminum Nitride in Weight Percent by Heat-Treatment Table 4.Examples of the Relation Between the Content of Nitrogen as Aluminum Nitride and Press Notch Charpy Transition Temperature [With the composition of Sample D in Table 1] (a) In the table below the sample as rolled was heated to 625 C. for 30 minutes and was cooled in air. Ferrite-grain size No. 79 (A.S.T.M.).
Content of nitrogen in weight percent as aluminum nitride .1 0. 0029 0. 0079 0. 0144 Press notch Charpy broken surface transition temperature in C 18 -21 -38 -42 (b) In the table below the steel was heated to 930 0. for minutes,
rapidly cooled, then heated to 625 C. for minutes and cooled in air. Ferrite-grain size No. 911 (A.S. T.M.).
Content of nitrogen in weight percent as aluminum nitride 0 0031 0.0083 0. 0152 Press notch Charpy fracture transition temperature in C 28 -34 61 .58
utes and then cooled in air, sample 3 is the same as sample 1 except it was heated to 930 for 20 minutes and then rapidly cooled and sample 4 is the same as sample 3 except it was heated to 625 C. for 30 minutes and then cooled in air. In (a) and (b) in Table 4 there is shown the relationship between the amount of aluminum nitride and the press notch Charpy broken surface tran sition temperature on the rolled sample and the sample heated to 930 C. for-20 minutes and rapidly cooled, both of which were heated to 625 C. for 30 minutes and then cooled in air for the depositing treatment. In both the rolled .sample and the rapidly cooled sample, after the depositing treatment, aluminum nitride was greatly deposited-and an increase in low-temperature toughness was Nitrogen as aluminum nitride Aoid- Sample 4 (as heated soluble Total Sample 2 (as heated Sample 3 (as heated to 030 C. for 20 aluminum nitrogen Samplel to 625 C. for 30 to 030 C. for 20 minutes, rapidly (as rolled minutes and cooled minutes and rapidly eooled,then heated only) in air) cooled) to 62 C. for 30 7 minutes and cooled inair) two below 600 C. whereby there is produced a fine ferrite structure in said steel and the liberated aluminum and nitrogen are in solid solution; reheating the cooled steel to a temperature of about 600 to 700 C. and cooling the steel whereby the aluminum and nitrogen are deposited in said steel as aluminum nitride.
2. A process for producing a tough steel for low temperature service comprising heating a low carbon steel containing 0.01 to 0.04 weight percent aluminum, 0.008 to 0.02 weight percent nitrogen, less than 0.50% silicon and less than 0.14 weight percent carbon to a temperature of about 88010 950 C, quiclily cooling said steel at a cooling rate of from 5 to 50 degrees centigrade per second to a temperature below 600 C. wherehythere is produced a fine ferrite structure in said. steel and the liberated aluminum and nitrogen are insolid solution; reheating the cooled steel to a temperature of about 600 to 700 C. and cooling the steel to room temperature whereby the aluminum and nitrogen are deposited in said steel as aluminum nitride.
3. A process for producing a tough steel for low temperature service comprising heating a steel containing 1.0 to 1.5 weight percent manganese, 0.01 to 0.04 weight percent aluminum, 0.008 to 020 Weight percent nitrogen, less than 0.14 weight percent carbon, less than 0.50 weight percent silicon with the remainder being iron and incidental impurities to a temperature of about 880 to 950 C. and quickly cooling said steel at a cooling rate of from 5 to 50 degrees centigrade per second to a temperature below 600 C. whereby there is produced a fine ferrite structure in said steel and the liberated aluminum and nitrogen are in solid solution; reheating the cooled steel to a temperature of about 600 to 700 C. and cooling the steel to room temperature whereby the aluminum and'ni-,
trogen are deposited in said steel as aluminum nitride.
4. A process for producing a tough steel for low temperature service comprising heating a steel containing 1.0 to 1.5 weight percent manganese, 0.01 to 0.04 weight percent aluminum, 0008 to 0.20 weight percent nitrogen, less than 0.14 weight percent carbon, less than 0.50 weight percent silicon and at least one alloying element selected from the group consisting of niobium, tantalum and vanadium, the total amount of said alloying elements T5 6 being less than 0.20 weight percent with the remainder References Cited by the Examiner being iron and incidental impurities to a temperature of UNITED TATE PATENTS about 880 to 950 C. and quickly cooling said steel at a S S cooling rateof from 5 to 50 degrees centigrade per second 3,028,270 4/62 Monta 148 143 to a temperature below 600 C. whereby there is pro- 5 FOREIGN PATENTS duced a fine ferrite structure in said steel and the liberated 786993 11/57 Great Britain aluminum and nitrogen are in solid solution; reheating the 2/59 Great Britain cooled steel to a temperature 'of about 600 to 700 C. and cooling the steel to room temperature whereby the DAVID RECK, 'y Examineraluminum and nitrogen are deposited in said steel as 10 RAY K. WINDH AM Examiner aluminum nitride.
Claims (1)
1. A PROCESS FOR PRODUCING A TOUGH STEEL FOR LOW TEMPERATURE SERVICE COMPRISING HEATING A LOW CARBON STEEL CONTAINING 0.01 TO 0.04 WEIGHT PERCENT ALUMINUM, 0.008 TO 0.02 WEIGHT PERCENT NITROGEN AND LESS THAN 0.14 WEIGHT PERCENT CARBON TO A TEMPERATURE ABOVE THE A3 TRANSFORMATION POINT, QUICKLY COOLING SAID STEEL AT A COOLING RATE OF FROM 5 TO 50 DEGREES CENTIGRADE PER SECOND TO A TEMPERATURE BELOW 600*C. WHEREBY THERE IS PRODUCED A FINE FERRITE STRUCTURE IN SAID STEEL AND THE LIBERATED ALUMINUM AND NITROGEN ARE IN SOLID SOLUTION; REHEATING THE COOLED STEEL TO A TEMPERATURE OF ABOUT 600 TO 700*C. AND COOLNG THE STEEL WHEREBY THE ALUMINUM AND NITROGEN ARE DEPOSITED IN SAID STEEL AS ALUMINUM NITRIDE.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2223761 | 1961-06-22 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| US3163565A true US3163565A (en) | 1964-12-29 |
Family
ID=12077170
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| US203444A Expired - Lifetime US3163565A (en) | 1961-06-22 | 1962-06-19 | Process for producing a tough steel for low temperatures |
Country Status (3)
| Country | Link |
|---|---|
| US (1) | US3163565A (en) |
| DE (1) | DE1433818B2 (en) |
| GB (1) | GB1011794A (en) |
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3320099A (en) * | 1964-08-12 | 1967-05-16 | United States Steel Corp | Method of processing steel |
| US3472707A (en) * | 1964-04-09 | 1969-10-14 | British Iron Steel Research | Alloy steels |
| US3539404A (en) * | 1967-05-15 | 1970-11-10 | Youngstown Sheet And Tube Co | Method of making a low alloy steel |
| US3713812A (en) * | 1970-08-03 | 1973-01-30 | Steel Corp | Ferritic stainless steels with improved drawability and resistance to ridging |
| DE1533252B1 (en) * | 1965-10-26 | 1973-04-05 | Nippon Steel Corp | LOW-ALLOY STEEL HIGH NOTCH TOUGHNESS FOR WELDED CONSTRUCTIONS EXPOSED TO THE CORROSIVE INFLUENCE OF HYDROGEN SULFUR |
| US3773500A (en) * | 1970-03-26 | 1973-11-20 | Nippon Steel Corp | High tensile steel for large heat-input automatic welding and production process therefor |
| US5533770A (en) * | 1992-10-10 | 1996-07-09 | Man Gutehoffnungshutte Aktiengesellschaft | High-strength solid wheels and tires for railroad traction vehicles and cars |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB786993A (en) * | 1954-11-22 | 1957-11-27 | Mannesmann Ag | Improvements in or relating to low-alloy steels |
| GB808556A (en) * | 1954-05-17 | 1959-02-04 | Mannesmann Ag | A process for the heat treatment of an unalloyed or low-alloy structural steel containing from 0.03% to 0.12% of aluminium nitride |
| US3028270A (en) * | 1958-08-25 | 1962-04-03 | Yawata Iron & Steel Co | Production of high tensile strength, high notch toughness steel by low temperature anneal |
-
1962
- 1962-06-18 GB GB23356/62A patent/GB1011794A/en not_active Expired
- 1962-06-19 US US203444A patent/US3163565A/en not_active Expired - Lifetime
- 1962-06-22 DE DE19621433818 patent/DE1433818B2/en active Pending
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB808556A (en) * | 1954-05-17 | 1959-02-04 | Mannesmann Ag | A process for the heat treatment of an unalloyed or low-alloy structural steel containing from 0.03% to 0.12% of aluminium nitride |
| GB786993A (en) * | 1954-11-22 | 1957-11-27 | Mannesmann Ag | Improvements in or relating to low-alloy steels |
| US3028270A (en) * | 1958-08-25 | 1962-04-03 | Yawata Iron & Steel Co | Production of high tensile strength, high notch toughness steel by low temperature anneal |
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3472707A (en) * | 1964-04-09 | 1969-10-14 | British Iron Steel Research | Alloy steels |
| US3320099A (en) * | 1964-08-12 | 1967-05-16 | United States Steel Corp | Method of processing steel |
| DE1533252B1 (en) * | 1965-10-26 | 1973-04-05 | Nippon Steel Corp | LOW-ALLOY STEEL HIGH NOTCH TOUGHNESS FOR WELDED CONSTRUCTIONS EXPOSED TO THE CORROSIVE INFLUENCE OF HYDROGEN SULFUR |
| US3539404A (en) * | 1967-05-15 | 1970-11-10 | Youngstown Sheet And Tube Co | Method of making a low alloy steel |
| US3773500A (en) * | 1970-03-26 | 1973-11-20 | Nippon Steel Corp | High tensile steel for large heat-input automatic welding and production process therefor |
| US3713812A (en) * | 1970-08-03 | 1973-01-30 | Steel Corp | Ferritic stainless steels with improved drawability and resistance to ridging |
| US5533770A (en) * | 1992-10-10 | 1996-07-09 | Man Gutehoffnungshutte Aktiengesellschaft | High-strength solid wheels and tires for railroad traction vehicles and cars |
Also Published As
| Publication number | Publication date |
|---|---|
| DE1433818A1 (en) | 1968-11-28 |
| DE1433818B2 (en) | 1970-03-19 |
| GB1011794A (en) | 1965-12-01 |
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