EP0265402A1 - Calcium treated boron alloyed steel with improved machinability - Google Patents
Calcium treated boron alloyed steel with improved machinability Download PDFInfo
- Publication number
- EP0265402A1 EP0265402A1 EP87850292A EP87850292A EP0265402A1 EP 0265402 A1 EP0265402 A1 EP 0265402A1 EP 87850292 A EP87850292 A EP 87850292A EP 87850292 A EP87850292 A EP 87850292A EP 0265402 A1 EP0265402 A1 EP 0265402A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- boron
- steel
- titanium
- content
- calcium
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
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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
- C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
-
- 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
- C22C38/60—Ferrous alloys, e.g. steel alloys containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur
Definitions
- the object of the present invention is improved machinable calcium treated boron alloyed steel, wherein a free boron content sufficient for hardenability is obtained without Ti and/or Al contents disadvantageous to machinability. With this invention the weaknesses of the known techniques are avoided.
- the free boron content sufficient for hardenability is obtained by binding the dissolved nitrogen aluminium and/or titanium.
- the machinability of the known steels is poor for the following reasons: - As a result of titanium alloying (about 0.02-0.05 wt-%) required to protect boron, the steel contains extremely hard large TiN particles which have a disadvantageous effect on machinability. - The high Al content (0.05-0.1 wt-%) required to protect the boron impairs machinability. - The machinability of boron steels of these known types cannot be essentially improved by calcium treatment.
- the steel of the present invention amounts of Al and Ti added are so low that they do not bind all the dissolved nitrogen.
- the excessive part of nitrogen, which remains after the binding by titanium and aluminium, is bound to boron to give boron nitrides.
- a sufficient amount of boron is alloyed so that in addition to the boron in nitrides, the steel contains about 10-30 weight-ppm chemically free boron.
- Titanium alloying is restricted to prevent the precipitation of large so-called primary titanium nitrides in the molten state.
- the maximum amount of titanium added depends on the nitrogen content of the steel. If desired, the titanium may be left out altogether.
- At least 0.005 wt-% of aluminium is alloyed in order to kill the steel, to reduce the grain size and to obtain the correct type of non metallic inclusions. Aluminium contents of over 0.014 wt-% are not alloyed due to the deterioration of machinability.
- the steel of the present invention has been calcium treated in ladle.
- the calcium treatment improves the machinability of the steel. Full advantage is gained from the calcium treatment because high Ti or Al contents are not used.
- the steel of the present invention contains the following alloying elements shown below in percentages by weight: carbon 0.01 - 0.50% silicon 0.01 - 2.00% manganese 0.40 - 1.60% sulphur 0.01 - 0.30% chromium 0 - 2.00% molybdenum 0 - 0.80%
- the use of the steel determines the alloying element combination selected.
- Boron is an element which intensifies the hardenability of steel considerably with very low contents of chemically free boron.
- boron has a hardenability intensifying effect only when it is dissolved in steel in chemically free form, it should be ensured that boron is not bound in compounds - mainly BN or B2O3 - or that the free boron content is the said 0.001-0.004 wt-% also after a part of the boron is bound in the above-mentioned compounds.
- the obtaining of a stable hardenability effect of boron is ensured by adding nitrogen binding elements such as Ti and/or Al (also Zr, V, Nb) and a standa rd amount of boron after a thorough deoxidation.
- nitrogen binding elements such as Ti and/or Al (also Zr, V, Nb) and a standa rd amount of boron after a thorough deoxidation.
- Titanium forms extremely hard cubic TiN particles which wear machining tools abrasively. This is shown by the shorter tool life when machining titanium alloyed steels. Fig. 1.
- the calcium treatment does not, however, affect the titanium nitride particles. Therefore, the machinability of titanium protected boron steel cannot be improved by calcium treatment. Fig. 3.
- the steel of the present invention is also alloyed at least 0.01% sulphur because it is well known that sulphur addition improves machinability.
Abstract
Description
- The object of the present invention is improved machinable calcium treated boron alloyed steel, wherein a free boron content sufficient for hardenability is obtained without Ti and/or Al contents disadvantageous to machinability. With this invention the weaknesses of the known techniques are avoided.
- In the known heat treated boron alloyed steels the free boron content sufficient for hardenability is obtained by binding the dissolved nitrogen aluminium and/or titanium. The machinability of the known steels is poor for the following reasons:
- As a result of titanium alloying (about 0.02-0.05 wt-%) required to protect boron, the steel contains extremely hard large TiN particles which have a disadvantageous effect on machinability.
- The high Al content (0.05-0.1 wt-%) required to protect the boron impairs machinability.
- The machinability of boron steels of these known types cannot be essentially improved by calcium treatment. - A summary of the invention is presented in the following.
- In the steel of the present invention amounts of Al and Ti added are so low that they do not bind all the dissolved nitrogen. The excessive part of nitrogen, which remains after the binding by titanium and aluminium, is bound to boron to give boron nitrides. A sufficient amount of boron is alloyed so that in addition to the boron in nitrides, the steel contains about 10-30 weight-ppm chemically free boron.
- Titanium alloying is restricted to prevent the precipitation of large so-called primary titanium nitrides in the molten state. The maximum amount of titanium added depends on the nitrogen content of the steel. If desired, the titanium may be left out altogether. At least 0.005 wt-% of aluminium is alloyed in order to kill the steel, to reduce the grain size and to obtain the correct type of non metallic inclusions. Aluminium contents of over 0.014 wt-% are not alloyed due to the deterioration of machinability.
- It is also characteristic for the steel of the present invention that it has been calcium treated in ladle. The calcium treatment improves the machinability of the steel. Full advantage is gained from the calcium treatment because high Ti or Al contents are not used.
- It is furthermore characteristic for the steel of the present invention that it contains the following alloying elements shown below in percentages by weight:
carbon 0.01 - 0.50%
silicon 0.01 - 2.00%
manganese 0.40 - 1.60%
sulphur 0.01 - 0.30%
chromium 0 - 2.00%
molybdenum 0 - 0.80% - The use of the steel determines the alloying element combination selected.
- In the following the technological background of the invention and the test results obtained with the steels relating to the invention will be described.
- Boron is an element which intensifies the hardenability of steel considerably with very low contents of chemically free boron.
- It is characteristic for the hardenability intensifyig effect of boron that maximum effect is obtained with a certain free boron content (0.001-0.004 wt-%) and that the obtained increase in hardenability diminishes as the carbon and alloying element contents increase.
- Since boron has a hardenability intensifying effect only when it is dissolved in steel in chemically free form, it should be ensured that boron is not bound in compounds - mainly BN or B₂O₃ - or that the free boron content is the said 0.001-0.004 wt-% also after a part of the boron is bound in the above-mentioned compounds.
- In the established steel making technique, the obtaining of a stable hardenability effect of boron is ensured by adding nitrogen binding elements such as Ti and/or Al (also Zr, V, Nb) and a standa rd amount of boron after a thorough deoxidation.
- It is also possible to alloy so much boron that although a part of it is bound in BN, enough boron still remains to guarantee the hardenability effect. This requires, however, advanced steel making technique because insufficiently low boron alloying results in the loss of hardenability and excessively high alloying in a decrease in hardenability and furthermore makes the steel brittle.
- The increase in hardenability achieved by boron alloying, that is, the boron hardenability effect (Bf) is usually defined as the ratio of the ideal critical diameter (DI) measured by the Jominy-test (SFS-standard 2375) to the ideal critical diameter (DIchem) calculated on the basis of the chemical analysis (excluding boron):
Bf = DI/DIchem - The chemical analyses of the test steels are given in Table 1 and the results of their hardenability tests are shown in Table 2. The test results clearly show that the boron hardenability effect is achieved on exceeding a certain value of the ratio B/(N - Ti/3.4), wherein B is the boron content, N the nitrogen content and Ti the titanium content in percentages by weight. The intensity of the effect increases rapidly at first as the free boron content increases, but reaches then its maximum value which is dependent on the carbon and alloying element contents. The boron hardenability effect is thus achieved without Al and/or Ti alloying with a sufficiently high boron content.
- The conventional boron-protecting methods, titanium and/or aluminium alloying, impair machinability. Titanium forms extremely hard cubic TiN particles which wear machining tools abrasively. This is shown by the shorter tool life when machining titanium alloyed steels. Fig. 1.
- By means of calcium treatment the machinability of steel is improved by modifying non metallic inclusions. Oxides in untreated steels (aluminium oxides, silicates) are extremely hard and thus wear the machining tool abrasively. In calcium treated steels oxides are softer and in addition enveloped by a soft sulphide case. These modified non metallic inclusions cause less abrasive wear of machining tools. At high machining speeds the inclusions of calcium treated steel also form a protecting film on the surfaces of machining tools. Thus, the tool lives are substantially longer when machining calcium treated steels. Fig. 2.
- The calcium treatment does not, however, affect the titanium nitride particles. Therefore, the machinability of titanium protected boron steel cannot be improved by calcium treatment. Fig. 3.
- When aluminium is used to protect boron, the aluminium contents required are high which is known to impair the machinability of steel.
- When the protection of boron is carried out according to the present application by means of excess boron alloying fixed to the nitrogen content of the steel, high titanium and/or aluminium contents are not required. The impairment of machinability caused by the above-mentioned alloying elements can thus be avoided,and an overall improvement of machinability is achieved by calcium treatment. Fig. 4.
-
Claims (9)
carbon 0.01 - 0.5%
silicon 0.01 - 2.0%
manganese 0.4 - 1.6%
sulphur 0.01 - 0.3%
chromium 0 - 2.0%
molybdenum 0 - 0.8%
boron 0.002 - 0.02%
titanium 0 - 0 .015%
aluminium 0.005 - 0.014%
calcium 0.0015 - 0.01%
and in addition
B = (0.5 - 2) × (N - Ti/3.4)
wherein B is the boron content, N the nitrogen content and Ti the titanium content in percentages by weight.
boron 0.004 - 0.02%
titanium 0 - 0.005%.
boron 0.007 - 0.02%
titanium 0 - 0.005%.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
AT87850292T ATE66700T1 (en) | 1986-09-29 | 1987-09-28 | CALCIUM-TREATED BORON-CONTAINING STEEL WITH IMPROVED MACHINABILITY. |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
FI863918A FI75870C (en) | 1986-09-29 | 1986-09-29 | Calcium treated boron alloy steel with improved cutability |
FI863918 | 1986-09-29 |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0265402A1 true EP0265402A1 (en) | 1988-04-27 |
EP0265402B1 EP0265402B1 (en) | 1991-08-28 |
Family
ID=8523221
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP87850292A Expired EP0265402B1 (en) | 1986-09-29 | 1987-09-28 | Calcium treated boron alloyed steel with improved machinability |
Country Status (4)
Country | Link |
---|---|
EP (1) | EP0265402B1 (en) |
AT (1) | ATE66700T1 (en) |
DE (2) | DE265402T1 (en) |
FI (1) | FI75870C (en) |
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0487250A1 (en) * | 1990-11-16 | 1992-05-27 | Daido Tokushuko Kabushiki Kaisha | Steel suitable for induction hardening |
WO1996023084A1 (en) * | 1995-01-24 | 1996-08-01 | Caterpillar Inc. | Deep hardening boron steel article having improved fracture toughness and wear characteristics |
WO2012048917A1 (en) * | 2010-10-11 | 2012-04-19 | Schaeffler Technologies AG & Co. KG | Quenched and tempered steel, use thereof as bar material, threaded spindle, toothed rack, toothed rack elements and method for producing same |
CN104789878A (en) * | 2015-05-05 | 2015-07-22 | 内蒙古包钢钢联股份有限公司 | Seamless steel tube for high-hardenability oil casing coupling material and preparation method |
Families Citing this family (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP5837837B2 (en) * | 2012-02-08 | 2015-12-24 | Jfe条鋼株式会社 | High-hardness BN free cutting steel with a tool life of 300HV10 or higher |
Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2388214A (en) * | 1941-08-27 | 1945-10-30 | Bethlehem Steel Corp | Machining steels |
FR2088862A5 (en) * | 1970-04-18 | 1972-01-07 | Nippon Kokan Kk | Free cutting steel |
US3634073A (en) * | 1969-07-09 | 1972-01-11 | United States Steel Corp | Free-machining steel, articles thereof and method of making |
US4265660A (en) * | 1979-07-03 | 1981-05-05 | Henrik Giflo | High-strength free-cutting steel able to support dynamic stresses |
-
1986
- 1986-09-29 FI FI863918A patent/FI75870C/en not_active IP Right Cessation
-
1987
- 1987-09-28 DE DE198787850292T patent/DE265402T1/en active Pending
- 1987-09-28 AT AT87850292T patent/ATE66700T1/en not_active IP Right Cessation
- 1987-09-28 DE DE8787850292T patent/DE3772511D1/en not_active Expired - Lifetime
- 1987-09-28 EP EP87850292A patent/EP0265402B1/en not_active Expired
Patent Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2388214A (en) * | 1941-08-27 | 1945-10-30 | Bethlehem Steel Corp | Machining steels |
US3634073A (en) * | 1969-07-09 | 1972-01-11 | United States Steel Corp | Free-machining steel, articles thereof and method of making |
FR2088862A5 (en) * | 1970-04-18 | 1972-01-07 | Nippon Kokan Kk | Free cutting steel |
US4265660A (en) * | 1979-07-03 | 1981-05-05 | Henrik Giflo | High-strength free-cutting steel able to support dynamic stresses |
Cited By (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0487250A1 (en) * | 1990-11-16 | 1992-05-27 | Daido Tokushuko Kabushiki Kaisha | Steel suitable for induction hardening |
WO1996023084A1 (en) * | 1995-01-24 | 1996-08-01 | Caterpillar Inc. | Deep hardening boron steel article having improved fracture toughness and wear characteristics |
WO2012048917A1 (en) * | 2010-10-11 | 2012-04-19 | Schaeffler Technologies AG & Co. KG | Quenched and tempered steel, use thereof as bar material, threaded spindle, toothed rack, toothed rack elements and method for producing same |
US9267195B2 (en) | 2010-10-11 | 2016-02-23 | Schaeffler Technologies AG & Co. KG | Tempered steel |
CN104789878A (en) * | 2015-05-05 | 2015-07-22 | 内蒙古包钢钢联股份有限公司 | Seamless steel tube for high-hardenability oil casing coupling material and preparation method |
CN104789878B (en) * | 2015-05-05 | 2017-03-15 | 内蒙古包钢钢联股份有限公司 | A kind of high-hardenability oil casing collar material seamless steel pipe and preparation method |
Also Published As
Publication number | Publication date |
---|---|
EP0265402B1 (en) | 1991-08-28 |
DE3772511D1 (en) | 1991-10-02 |
ATE66700T1 (en) | 1991-09-15 |
FI75870B (en) | 1988-04-29 |
FI75870C (en) | 1988-08-08 |
FI863918A0 (en) | 1986-09-29 |
DE265402T1 (en) | 1990-02-08 |
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