MXPA00003853A - Tin-bearing free-machining steel - Google Patents
Tin-bearing free-machining steelInfo
- Publication number
- MXPA00003853A MXPA00003853A MXPA/A/2000/003853A MXPA00003853A MXPA00003853A MX PA00003853 A MXPA00003853 A MX PA00003853A MX PA00003853 A MXPA00003853 A MX PA00003853A MX PA00003853 A MXPA00003853 A MX PA00003853A
- Authority
- MX
- Mexico
- Prior art keywords
- tin
- steel
- sulfur
- process described
- manganese
- Prior art date
Links
- ATJFFYVFTNAWJD-UHFFFAOYSA-N tin hydride Chemical group [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 title claims abstract description 252
- 229910052718 tin Inorganic materials 0.000 title claims abstract description 251
- 229910000915 Free machining steel Inorganic materials 0.000 title claims abstract description 83
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 269
- 239000010959 steel Substances 0.000 claims abstract description 269
- 229910000529 magnetic ferrite Inorganic materials 0.000 claims abstract description 116
- 229910000859 α-Fe Inorganic materials 0.000 claims abstract description 116
- 238000000034 method Methods 0.000 claims abstract description 97
- 206010040844 Skin exfoliation Diseases 0.000 claims description 120
- 238000004299 exfoliation Methods 0.000 claims description 120
- NINIDFKCEFEMDL-UHFFFAOYSA-N sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 claims description 98
- 229910052717 sulfur Inorganic materials 0.000 claims description 98
- 239000011593 sulfur Substances 0.000 claims description 98
- PWHULOQIROXLJO-UHFFFAOYSA-N manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 claims description 74
- 229910052748 manganese Inorganic materials 0.000 claims description 74
- 239000011572 manganese Substances 0.000 claims description 74
- RYGMFSIKBFXOCR-UHFFFAOYSA-N copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 69
- 229910052802 copper Inorganic materials 0.000 claims description 69
- 239000010949 copper Substances 0.000 claims description 69
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 65
- 239000000203 mixture Substances 0.000 claims description 58
- 150000004763 sulfides Chemical class 0.000 claims description 40
- 229910052760 oxygen Inorganic materials 0.000 claims description 38
- 239000001301 oxygen Substances 0.000 claims description 38
- MYMOFIZGZYHOMD-UHFFFAOYSA-N oxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 claims description 38
- OKTJSMMVPCPJKN-UHFFFAOYSA-N carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 36
- IJGRMHOSHXDMSA-UHFFFAOYSA-N nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 36
- 229910052799 carbon Inorganic materials 0.000 claims description 35
- 239000012535 impurity Substances 0.000 claims description 34
- 229910052742 iron Inorganic materials 0.000 claims description 32
- 238000003754 machining Methods 0.000 claims description 31
- 238000001816 cooling Methods 0.000 claims description 28
- OAICVXFJPJFONN-UHFFFAOYSA-N phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 claims description 19
- 229910052698 phosphorus Inorganic materials 0.000 claims description 19
- 239000011574 phosphorus Substances 0.000 claims description 19
- 229910052757 nitrogen Inorganic materials 0.000 claims description 18
- 229910052710 silicon Inorganic materials 0.000 claims description 18
- 239000010703 silicon Substances 0.000 claims description 18
- 229910052782 aluminium Inorganic materials 0.000 claims description 17
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminum Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 17
- 239000012141 concentrate Substances 0.000 claims description 14
- VCTOKJRTAUILIH-UHFFFAOYSA-N manganese(2+);sulfide Chemical compound [S-2].[Mn+2] VCTOKJRTAUILIH-UHFFFAOYSA-N 0.000 claims description 13
- 238000004519 manufacturing process Methods 0.000 claims description 12
- 230000001376 precipitating Effects 0.000 claims description 9
- 230000001131 transforming Effects 0.000 claims description 7
- 230000014759 maintenance of location Effects 0.000 claims description 6
- 229910001566 austenite Inorganic materials 0.000 claims description 5
- 239000002244 precipitate Substances 0.000 claims description 3
- 238000005520 cutting process Methods 0.000 abstract description 29
- 230000000694 effects Effects 0.000 abstract description 12
- 230000002708 enhancing Effects 0.000 abstract 2
- 230000002441 reversible Effects 0.000 abstract 1
- 239000000523 sample Substances 0.000 description 29
- 238000005553 drilling Methods 0.000 description 7
- 229910052751 metal Inorganic materials 0.000 description 7
- 239000002184 metal Substances 0.000 description 7
- VLTRZXGMWDSKGL-UHFFFAOYSA-N Perchloric acid Chemical compound OCl(=O)(=O)=O VLTRZXGMWDSKGL-UHFFFAOYSA-N 0.000 description 6
- 238000005296 abrasive Methods 0.000 description 5
- 125000004429 atoms Chemical group 0.000 description 5
- 238000007906 compression Methods 0.000 description 5
- 230000000875 corresponding Effects 0.000 description 5
- 238000005336 cracking Methods 0.000 description 5
- 238000009826 distribution Methods 0.000 description 5
- 150000002500 ions Chemical class 0.000 description 5
- 238000010438 heat treatment Methods 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- 238000002844 melting Methods 0.000 description 4
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 4
- 238000007711 solidification Methods 0.000 description 4
- 238000009628 steelmaking Methods 0.000 description 4
- QTBSBXVTEAMEQO-UHFFFAOYSA-N acetic acid Chemical compound CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 description 3
- 230000005540 biological transmission Effects 0.000 description 3
- 230000015572 biosynthetic process Effects 0.000 description 3
- 238000005755 formation reaction Methods 0.000 description 3
- GNVXPFBEZCSHQZ-UHFFFAOYSA-N iron(2+);sulfide Chemical compound [S-2].[Fe+2] GNVXPFBEZCSHQZ-UHFFFAOYSA-N 0.000 description 3
- 238000005259 measurement Methods 0.000 description 3
- 239000002245 particle Substances 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- CADICXFYUNYKGD-UHFFFAOYSA-N sulfanylidenemanganese Chemical compound [Mn]=S CADICXFYUNYKGD-UHFFFAOYSA-N 0.000 description 3
- POAOYUHQDCAZBD-UHFFFAOYSA-N 2-Butoxyethanol Chemical compound CCCCOCCO POAOYUHQDCAZBD-UHFFFAOYSA-N 0.000 description 2
- VZGDMQKNWNREIO-UHFFFAOYSA-N Carbon tetrachloride Chemical compound ClC(Cl)(Cl)Cl VZGDMQKNWNREIO-UHFFFAOYSA-N 0.000 description 2
- JCXGWMGPZLAOME-UHFFFAOYSA-N bismuth Chemical compound [Bi] JCXGWMGPZLAOME-UHFFFAOYSA-N 0.000 description 2
- 229910052797 bismuth Inorganic materials 0.000 description 2
- 230000001680 brushing Effects 0.000 description 2
- OYPRJOBELJOOCE-UHFFFAOYSA-N calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 description 2
- 239000011575 calcium Substances 0.000 description 2
- 229910052791 calcium Inorganic materials 0.000 description 2
- 239000003795 chemical substances by application Substances 0.000 description 2
- 230000001276 controlling effect Effects 0.000 description 2
- 238000003379 elimination reaction Methods 0.000 description 2
- 238000005242 forging Methods 0.000 description 2
- 238000009413 insulation Methods 0.000 description 2
- 238000010030 laminating Methods 0.000 description 2
- 229910000464 lead oxide Inorganic materials 0.000 description 2
- 239000000155 melt Substances 0.000 description 2
- 238000000465 moulding Methods 0.000 description 2
- YEXPOXQUZXUXJW-UHFFFAOYSA-N oxolead Chemical compound [Pb]=O YEXPOXQUZXUXJW-UHFFFAOYSA-N 0.000 description 2
- 238000005498 polishing Methods 0.000 description 2
- 238000001556 precipitation Methods 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- 239000011135 tin Substances 0.000 description 2
- 229910000997 High-speed steel Inorganic materials 0.000 description 1
- 229910001209 Low-carbon steel Inorganic materials 0.000 description 1
- OGIDPMRJRNCKJF-UHFFFAOYSA-N TiO Inorganic materials [Ti]=O OGIDPMRJRNCKJF-UHFFFAOYSA-N 0.000 description 1
- PNEYBMLMFCGWSK-UHFFFAOYSA-N al2o3 Chemical compound [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 230000003466 anti-cipated Effects 0.000 description 1
- 238000005266 casting Methods 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 239000002826 coolant Substances 0.000 description 1
- 230000003247 decreasing Effects 0.000 description 1
- 230000002939 deleterious Effects 0.000 description 1
- 230000001627 detrimental Effects 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 238000007667 floating Methods 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 239000003517 fume Substances 0.000 description 1
- 230000004927 fusion Effects 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- 230000000977 initiatory Effects 0.000 description 1
- 230000001788 irregular Effects 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 230000001050 lubricating Effects 0.000 description 1
- 238000005461 lubrication Methods 0.000 description 1
- 238000000691 measurement method Methods 0.000 description 1
- TXKRDMUDKYVBLB-UHFFFAOYSA-N methane;titanium Chemical compound C.[Ti] TXKRDMUDKYVBLB-UHFFFAOYSA-N 0.000 description 1
- 238000007431 microscopic evaluation Methods 0.000 description 1
- 238000003801 milling Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000006011 modification reaction Methods 0.000 description 1
- TWXTWZIUMCFMSG-UHFFFAOYSA-N nitride(3-) Chemical compound [N-3] TWXTWZIUMCFMSG-UHFFFAOYSA-N 0.000 description 1
- 150000004767 nitrides Chemical class 0.000 description 1
- 239000010451 perlite Substances 0.000 description 1
- 235000019362 perlite Nutrition 0.000 description 1
- 230000001902 propagating Effects 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 238000005204 segregation Methods 0.000 description 1
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
- 229910052814 silicon oxide Inorganic materials 0.000 description 1
- UCKMPCXJQFINFW-UHFFFAOYSA-N sulphide Chemical compound [S-2] UCKMPCXJQFINFW-UHFFFAOYSA-N 0.000 description 1
- 238000005496 tempering Methods 0.000 description 1
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- 239000010936 titanium Substances 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
- 229910001929 titanium oxide Inorganic materials 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
- 230000003313 weakening Effects 0.000 description 1
- 238000004804 winding Methods 0.000 description 1
Abstract
The invention relates to free-machining steels which do not rely on lead as a means of enhancing machinability. Instead, the steels of the invention employ concentrations of tin at ferrite grain boundaries to replicate a role of lead, which the inventors have discovered, in enhancing machinability. This role is to cause an embrittlement at the localized cutting zone temperatures by changing the fracture mode from transgranular to intergranular at those temperatures. The invention's use of concentrations of tin at ferrite grain boundaries of the steel permits the machinability-enhancing effect to be obtained while employing bulk tin contents below levels at which hot tearing becomes problematic. The invention improves over lead-bearing, free-machining steels in that the machinability-enhancing embrittlement produced by concentrating tin at ferrite grain boundaries is both controllable and reversible. The invention also relates to methods of producing the described tin-bearing, free-machining steels and the products of those processes.
Description
STEEL STEELS OF FREE iVIAQUiNADO
BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a free machining steel that does not use lead to increase the machinability. More specifically, the invention relates to a free-machining steel having tin concentration in the ferrite exfoliation plane of the steel, which has machinability comparable to or better than that of conventional free-machined lead steel. The present invention also relates to a process for producing the aforementioned free machining steel.
Description of the related art Free machining steel is used in the machining of different components by means of fast cutting machine tools. The free machining steel is characterized by a good machinability, that is, (i) by its ability to produce relatively little deterioration of the cutting tool and therefore extend the life of the cutting tool, and (ii) by the large quality of the surface. The little wear of the tool allows the use of higher cutting speeds, which result in greater productivity. The extension of the useful life of the cutting tool also reduces the production costs, allowing the saving in the cost of the cutting tools, and
avoiding the interruption period associated with the change of tools. Machinability is a complex property and not entirely understood. The total understanding of the machinability requires that several factors be taken into account, including the effect of steel composition, elastic tension, creep, the mechanics of breaking of the piece of metal to be welded, and the cutting dynamics that It takes place when the steel is machined by cutting tools in such operations as transforming, molding, laminating, drilling, reaming, drilling, brushing, and filleting. Due to the complexities of the cutting process and the inherent difficulties in real-time observations at the microscopic level, knowledge of the scope of the range of mechanisms that affect machinability is also incomplete. The metallurgists believed for a long time that the machinability of the free machining steel could be improved by modifying the chemical composition of the steel to optimize the size, shape, distribution, and chemical composition of the inclusions to increase the chip's fragility and increase the lubrication in the interface of the tool / chip. In addition, they sought to avoid the formation of abrasive inclusions that could increase wear on the tool. Therefore, it has been common to use steels of
Free machining in which soft inclusions, such as sulphide manganese, are dispersed. Manganic sulfide inclusions extend the useful life of the cutting tool, producing effects such as propagating cracks, reducing tool deterioration by lubricating the tool surface, and avoiding welds at the tool edge. In contrast, hard inclusions of oxide or carbonitride, such as silicon oxide, aluminum oxide, titanium oxide, titanium carbonitride, which have higher hardness than those of the cutting tool, act as fine abrasive particles to waste and damage the cutting tool, thereby reducing the useful life. Thus, free-machining steels are generally not subject to strong deoxidation during steelmaking to keep the content of hard inclusions low. Historically, lead has been added to free-machined steels containing manganese sulfide inclusions to increase the machinability of these steels. However, the use of lead has serious problems. Lead and lead oxide are dangerous. Precautions must be taken during steel fabrication and any other processing step involving high temperatures. Those steps in the process produce lead and / or oxide fumes. Atmospheric control procedures must be incorporated into the processing at high temperatures of the lead steels. The
Removal Mstgúinado chips from free-machining steels are also problematic due to the lead content of the chips. Another serious problem is that lead is not evenly distributed along conventional steel products. This occurs because the lead is not soluble in the steel and, due to its high density, it goes to the bottom during the processes of pouring into the mold and solidification, which results in segregation or irregular distribution within the steel. The ability of lead to increase machinability has been attributed to the flowing effects of a combination of the low melting temperature of lead and its tendency to surround inclusions of manganic sulfide as a soft phase. Thus, previous efforts to replace lead in free-machining steels have focused on repeating this combination of characteristics. Accordingly, free-machining steels were developed in which a soft phase, such as a low melting metal such as bismuth or a plastic oxide, such as a complex oxide containing calcium, took the place of lead in surrounding the sulfide inclusions. manganic
COMPENDIUM OF THE INVENTION The inventors discovered that lead plays a decisive role in increasing the machinability of
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free machining steels that are not related to the tendency of steel to form a soft phase around the sulfide inclusions. The inventors discovered that lead causes a brittle effect in free-machining steels at temperatures corresponding to the temperatures of the localized cutting zone that take place during machining. Through the use of hot compression tests, the inventors verified that, for free-machined lead steels, a point of brittleness occurs in the temperature range of about 200 ° C to about 600 ° C where the mode of rupture changes from a relatively ductile transgranular mode to a relatively fragile intergranular mode. Figure 1 shows a graph of hot compression test results for two similar grades of conventional free-machining steels, one of which, grade AISI 12L14, contains lead, and the other, grade AISI 1215, no. The deep depression of the graph for grade 12L14 indicates a zone of fragility. Through a microscopic examination of the fracture surfaces, the inventors discovered that the brittleness of lead grade 12L14 was due to a change in the mode of rupture in the area of brittleness temperature of the transganular to intergranular break. The inventors further discovered that lead causes this change in fragility of the rupture mode by being present and weakening the ferrite exfoliation plane of the
, ~, - «t ~.» - »"
free machining steel plume. Thus, the inventors discovered that lead resides in the ferrite exfoliation plane of steel where, because the cohesive force of the exfoliation plane decreases, it causes the break mode to change from transganular to intergranular in the temperature range corresponding to the localized temperatures that take place in the cutting area during machining. Fragile intergranular rupture requires relatively little energy compared to ductile, transgranular rupture. Consequently, the inventors also discovered that lead, acting to make the steel brittle at localized machining temperatures, improved machinability by reducing the energy received from the cutting tool needed to cut the steel, which results in less wear of the tool cutting machine It is important that, due to the discovery of this mechanism by which lead acts to improve the machinability of free machining steels, the inventors were able to discover and solve a problem that was previously not detected by those skilled in the art. The inventors discovered that in order to solve the problem of finding a substitute for lead in free machining steels, it was necessary to determine what could replace lead as an agent that resides in the exfoliation plane to cause the break mode to change from transgranular to intergranular in the margin
~ «^" ^ TiSSÉ. ^ ÍSr ..: m »fm-
temperatures corresponding to the localized temperatures that take place in the cutting area during machining. This discovery allowed the inventors to invent the free machining steels of the present invention upon discovering afterwards that the tin could act as that agent and thus replace the lead to increase the machinability of the free machining steels. Thus, the inventors made the surprising discovery that tin could increase machinability in the same way as lead in free-machining steels. In addition, the inventors discovered that the effectiveness of a relatively sticky amount of tin to increase machinability could be increased through the use of thermal processes that act to concentrate tin in the ferrite exfoliation plane of the steel. By employing that tin concentration in the ferrite exfoliation plane, the inventors were able to avoid the deleterious effects, such as hot cracking, that occur with a higher tin content. The inventors obtained the surprising result that the effect of increasing the machinability within the temperature range of localized machining temperatures, which results from the concentration of tin in the ferrite exfoliation plane, can be considerably reversed through the use of thermal
that act to redistribute tin more homogeneously throughout the steel. Thus, the inventors discovered that, by means of a first thermal process, the machinability of the steel can be improved by causing embrittlement in the temperature range of the localized machining temperatures, concentrating the tin in the ferrite exfoliation plane of the steel, and then , by means of a second thermal process after machining, this embrittlement can be controllably eliminated, redistributing tin from the ferrite exfoliation plane more homogeneously throughout the steel. In other words, the inventors made the surprising discovery of how to controllably increase the machinability of steel, reversibly concentrating tin in the ferrite exfoliation plane of steel. One of the objects of the following invention is to provide machinability in free machining steels comparable to that of free machining steels or better than theirs, without the need to use lead to increase machinability and, therefore, to avoid objectionable disadvantages associated with the use of lead. Another objective of the invention is to produce a free-machining steel with a lead substitute that fulfills the role of lead in the ferrite exfoliation plane of the steel, causing a change in the mode of rupture from transgranular to intergranular in the range of temperatures
corresponding to the localized temperatures that occur in the cutting area during machining. Another objective of the invention is to provide an increased machinability in free machining steels without the need to use a soft phase around the sulfide inclusions, such as a low melting metal such as lead or bismuth. or a plastic oxide, such as a complex oxide containing calcium, to improve the machinability in the free machining steel. Another object of the invention is to provide a free machining steel in which a embrittlement of the machinability increase can be controllably caused in the steel before machining and then can be removed from the steel controllably after machining. Another object of the invention is to provide a free machining steel from which it is possible to eliminate, after machining, the embrittlement of the temperature range of 200 ° to 600 ° C experienced by free-machined lead steels. Another object of the invention is to provide a free machining steel that does not present the problems of free machining steels, that is, the elimination of machining chips containing lead. Another object of the invention is to provide a free machining steel that uses tin to increase the
machinability Another object of the invention is to provide a free machining steel that uses tin to improve the machinability in which the tin content of the steel has been minimized to avoid the harmful effects, such as hot break, which occur with high contents tin. Another object of the invention is to provide a free-machining steel in which it is possible to increase the machinability controllably using low tin content, reversibly concentrating the tin in the ferrite exfoliation plane of the steel. Another object of the present invention is to provide a free machining steel that can be machined into parts that are useful as machined steel parts. Another objective of the invention is to provide processes for the production of free-machining steels that meet the aforementioned objectives. Another objective of this invention is to provide products obtained from these processes. The present invention fulfills the above objectives by supplying free machining steels using a tin concentration in the exfoliation plane of ferrite together with the inclusions of manganese sulphide in the steel to provide machinability comparable to that obtained with conventional free machining steels. or better
than her, and supplying processes to make those steels. The present invention encloses a free machining steel having a composition consisting essentially of (weight percentage): carbon up to almost 0.25; copper up to almost 0.5; manganese from almost 0.01 to almost 2; oxygen from almost 0.003 to almost 0.03; sulfide from almost 0.002 to almost 0.8; and tin from almost 0.04 to almost 0.08. The balance consists essentially of iron and possible impurities, in which a proportion of the manganese content to the sulfide content is from almost 2.9 to almost 3.4 and a total of the sulfur plus tin plus copper is not greater than almost 0.9, the composition being characterized by a microstructure having a tin concentration in the exfoliation plane of ferrite in an amount of at least about ten times the content
volumetric tin of steel. The present invention also encompasses processes for preparing free-machining steels comprising the steps of supplying a steel containing tin as an element, precipitating sulfide inclusions in the steel,
developing ferrite exfoliation planes in the steel, and concentrating the tin in the ferrite exfoliation plane. The present invention also encompasses processes that also comprise steps of machining steel and controllably redistributing tin most homogeneously throughout the
steel. This last step controllably eliminates
embrittlement of the machinability increase resulting from tin concentration in the steel exfoliation ferrite plane. The present invention also includes free machining steels resulting from the use of the processes encompassed by the present invention. These and other features, aspects and advantages of the present invention will be better understood with reference to the following definitions, descriptions of the preferred embodiments, examples, appended claims, and accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 shows a graph of the results of the hot compression tests conducted in conventional free-machining AISI grades 1215 and 12L14 within the temperature range of room temperature to 600 ° C. Figure 2 shows an example of an index chart C. Figure 3 shows a graph of the results of the hot compression tests performed on embodiments of the present invention compared to the results of similar tests performed on grades AISI 1215 and 12L14 of conventional free machining steel within the temperature range of the ambient temperature to 600 ° C.
. "ÍSS - * - * •:" «- *
Definitions 1. Volumetric content of tin. The phrase "volumetric content of tin" refers to the total amount of tin present in the steel as determined by a chemical analysis of a steel sample. 2. C index. The "C index" is a measurement value to evaluate the machinability of a steel. The index value C of a steel is determined on the basis of a number of machining tests where the cutting speed is varied and the amount of material removal is determined by a fixed amount of wear of the cutting tool. The scale of measurement of the C index has been selected so that a theoretical reference steel that has 200 cubic cm of material removal at a cutting surface velocity of 100 meters per minute has a C index of 100. Therefore, steels having C index values greater than 100 have higher machinability than the reference steel and those steels having C index values less than 100 have lower machinability than the reference steel. The method to measure the value of index C is as follows. For a selected cutting speed, a single-ended reamer milling cutter that uses a cutting tool
16 steel, high speed and standard, a standard coolant, and a standard feed rate are used to cut the surface of a cylindrical test sample that has a diameter of 25.4 millimeters (1 inch). Cutting is carried out until the tool part shows 0.7 mm lateral wear. The volume of matter removed from the test sample is measured. The test is repeated after using other cutting speeds. The results of the tests are plotted on a graph in coordinates: the volume of matter removed is plotted on the ordinate and the cutting speed is plotted on the abscissa, as shown in Figure 2. The chart contains a reference line which is logarithmically graduated with C index values. A line is drawn through the plotted test points and, if necessary, it is extended so that it crosses the reference line. The intersection of this line passing through the test points and the reference line gives the index value C for the test material. The test conditions used to determine the C-index values are described in detail in "The Volvo Standard Machinability Test", Std. 1018,712, The Volvo Laboratory for Manufacturing Research, Trolhattan, Sweden, 1989, which are included herein by way of reference . However, that publication describes the measure of what is referred to there as "index B". The only difference between the methods of
test of index B and index C is the diameter of the test sample: index C uses a test sample of 25.4 mm (1 inch), while index B uses a test sample of 50 mm in diameter . The graph of index B found in the cited publication is used to determine the index C when using the size of the test sample of index C. 3. Tin concentration in the ferrite exfoliation plane. The phrase "concentration of tin in the plane of exfoliation of ferrite" and syntactic inflections of that phrase refers to the amount of tin located in the exfoliation plane of ferrite of the steel measured according to the technique described in the following paragraphs. In order to understand the present invention, it is essential to differentiate the tin content of the steel and the concentration of tin in the exfoliation plane of ferrite. The concentration of tin in the ferrite exfoliation plane is measured as follows. A steel sample is electro-polished on needle samples using a solution of 25% perchloric acid in acetic acid floating on carbon tetrachloride and a voltage of 15-20 volts DC. As the electropolishing progresses, the steel sample narrows in the interface between these two immiscible liquids until it finally divides into two needles. Then, one of the needles is sharpened by electropolishing
using 2% perchloric acid in 2-butoxyethanol and a voltage of 10-15 volts DC. The needle is then examined with a transmission electron microscope to determine if a ferrite exfoliation plane is within 300 nanometers of the tip of the needle. If there is not a ferrite exfoliation plane within 300 nanometers of the end of the needle tip, then the needle sample is micro-electropolished using 2% perchloric acid in 2-butoxyethanol and a voltage of 10 volts DC . The voltage is supplied by a pulse generator for which the interval can be controlled in the order of milliseconds. The tip of the needle is again examined with the transmission electron microscope. The cycle of micro-electropolishing and transmission electron microscope is extended until a plane of exfoliation of ferrite is within 300 nanometers of the end of the tip of the needle. The exfoliation plane of ferrite is then examined in an Atom Probe Field Ion Microscope by means of which a raw value of tin concentration, Cr. Is measured. This crude value, Cr, is then multiplied by a correction factor, K, to obtain a corrected value of the tin concentration in the ferrite exfoliation plane, Ce. The correction factor, K, is the ratio of the area of the ferrite exfoliation plane observed to the opening area of the Atom Probe Field Ion Microscope That is, K is equal to the observed area of the plane of
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ferrite exfoliation divided by the observation field of the Atom Probe Field Ion Microscope. A) Yes, ? "Agh / A« = (1 xt) / (px r2) and Ce = K x CR where, K is the correction factor, Agh is the observed area of the exfoliation plane visible in the observation field, Aa is the area of the opening of the Atom Probe Field Ion Microscope, that is, the area of the observation field, 1 is the length of the exfoliation plane visible in the observation field, t is the width of the exfoliation plane visible in the observation field, is the radius of the observation field, Cc is the corrected tin concentration in the ferrite exfoliation plane, and CR is the raw value of the tin concentration, within the opening area containing the ferrite exfoliation plane, measured by the Atom Probe Field Ion Microscope The above steps are repeated until a corrected value, Cc, is obtained for each of the four to six steel exfoliation planes, then an average of all the corrected values obtained is obtained. in this way for
determine the average tin concentration in the steel exfoliation planes. This average value is called here "tin concentration in the ferrite exfoliation planes". 4. Concentrate the tin in the ferrite exfoliation planes. The phrase "to concentrate tin in the planes of exfoliation of ferrite" and the syntactic inflections of that phrase refer to subjecting a tin-bearing steel to thermodynamic and kinetic conditions resulting in tin atoms residing in the ferrite exfoliation planes of the steel in large quantities such that the amount of tin in the ferrite exfoliation planes exceeds the tin content in the steel. In other words, a step that concentrates the tin in the ferrite exfoliation planes results in a concentration of tin in the ferrite exfoliation planes that, measured according to the measurement technique described above, exceeds the volumetric content of tin in the steel . 5. Equivalent diameter. The concept of an "equivalent diameter" is used to correlate heating and cooling times, or to acquire a particular metallurgical condition, when it is determined that a cylindrical sample of a metal becomes a non-cylindrical sample of that metal. The phrase "equivalent diameter" refers to the diameter that would have
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a cylindrical sample, of the same metal as the non-cylindrical sample of the metal under study, which would acquire the same metallurgical condition as the non-cylindrical sample when subjected to the same heating or cooling conditions. Thus, the equivalent diameter of a given piece of steel would be the diameter of the cylindrical sample that would correspond to the piece of steel for the purpose of determining the heating or cooling conditions necessary to reach a desired metallurgical condition in that piece of steel. 6. Possible impurities. The phrase "eventual impurities" refers to those impurities present in the steel as a result of the steelmaking process. 7. Reconcentration of tin in the ferrite exfoliation plane. The phrase "to concentrate the tin in the plane of exfoliation of ferrite" and the syntactic inflections of that phrase refer to subjecting the steel, once the steel was subjected to a process of redistribution of the tin in the steel, to thermodynamic conditions and kinetics, leading to homogenize the distribution of tin in the steel for a fairly long time to decrease the concentration of tin in the exfoliation plane of ferrite, and then to cool the steel at a fairly fast speed to avoid
that the tin is reconcentrated in the ferrite exfoliation plane of the steel. 8. Redistribute tin in steel The phrase "redistribute tin in steel" and the syntactic inflections of that phrase refers to subjecting steel to thermodynamic and kinetic conditions, leading to homogenize the distribution of tin in steel for a time long enough for the concentration of tin in the ferrite exfoliation planes to decrease, and then to cool the steel at a fairly fast rate to prevent the tin from being reconcentrated in the ferrite exfoliation planes of the steel. 9. Type I Manganic Sulfide Inclusions The phrase "Type I Manganic Sulfide inclusions" refers to manganese sulfide inclusions that have a globular shape and are formed when the oxygen content is about 0.01 weight percent or greater. The globular shape of the manganic sulfide inclusions will be determined when the steel is in the solidified state, that is, before the steel is subjected to deformation processes that may cause some change in the shape of the manganic sulfide inclusions. 10. Inclusions of manganic sulfide Type II The phrase "inclusions of manganic sulfide Type II" refers to inclusions of manganic sulfide in the
steel that have a rod-like shape and are formed when the oxygen content is between almost 0.003 and almost 0.01, percentage by weight. The rod-like shape of manganese sulfide inclusions will be determined when the steel is in a solidified state, that is, before the steel is subjected to deformation processes that may cause a change in the shape of the inclusions of the steel. Manganic sulfide
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention include free machining steels that use a tin concentration in the ferrite exfoliation planes of the steel along with a dispersion of manganic sulfide inclusions to provide a machinability comparable to that obtained with free machining steels, convention, or better than it. These embodiments have compositions in which certain elements are controlled within specific margins and the contents proportions of some interrelated elements are also controlled. It should be understood that where a margin is described, the inventors contemplate that each increment between the ends of the margin should be understood to be part of the invention. A preferred embodiment of the present invention consists of a free machining steel having a
M composition consisting essentially of (percentage by weight): carbon up to almost 0.25; copper up to almost 0.5; manganese from almost 0.01 to almost 2; oxygen from almost 0.003 to almost 0.03; sulfur from almost 0.002 to almost 0.8; tin from almost 0.04 to almost 0.08; with a remnant of iron and possible impurities, where a proportion of manganese to sulfur is from almost 2.9 to almost 3.4 and a total of sulfur plus tin plus copper does not exceed almost 0.9, characterizing the composition by a microstructure having a tin concentration in the exfoliation planes of ferrite in an amount of at least about ten times the tin content of the steel. In a more preferred embodiment of the present invention, the composition of the free machining steel consists essentially of (weight percent): carbon from about 0.01 to about 0.25; copper up to almost 0.5; manganese from almost 0.5 to almost 1.5; oxygen from almost 0.003 to almost 0.03; sulfur from almost 0.2 to almost 0.45; and tin from almost 0.04 to almost 0.08; with a residual of iron and possible impurities where a proportion of manganese to sulfur is almost 2.9 to 3.4 and a total of sulfur plus tin plus copper does not exceed almost 0.9, the composition being characterized by a microstructure which has a tin concentration in the exfoliation plane of ferrite in an amount of at least ten times the content of tin in the steel. In a still more preferred embodiment, the
The composition of the free machining steel consists essentially of (percentage by weight): aluminum up to almost 0.005; carbon from almost 0.01 to almost 0.25; copper up to almost 0.5; manganese from almost 0.5 to almost 1.5; nitrogen to almost 0.15; oxygen from almost 0.003 to almost 0.03; phosphorus from almost 0.01 to almost 0.15; silicon to almost 0.05; sulfur from almost 0.2 to almost 0.45; tin from almost 0.04 to almost 0.08; with a remnant of iron and possible impurities, where a proportion of manganese to sulfur is from almost 2.9 to almost 3.4 and a total of sulfur plus tin plus copper does not exceed almost 0.9, characterizing the composition by a microstructure having a tin concentration in the exfoliation planes of ferrite in an amount of at least about ten times the tin content of the steel. The composition of each preferred embodiment of the present invention is characterized by a microstructure having a tin concentration in the ferrite exfoliation planes. Preferably, the concentration of tin in the ferrite exfoliation planes of the steel is at least ten times the tin content. More preferably, the concentration of tin in the exfoliation planes is at least 0.5 weight percent. Preferred embodiments of the present invention increase machinability using a tin concentration in the ferrite exfoliation planes
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together with manganic sulfide particles dispersed throughout the steel. The type of manganic sulfide inclusions in these preferred embodiments are preferably "Type I manganic sulfide inclusions" and "Type II manganic sulfide inclusions" or a combination of both types. The importance of the specific elemental margins in these preferred embodiments is described in more detail below. Unless stated otherwise, the stipulated content is the content of the elements in the steel. The content of tin in these embodiments is preferably in a range between 0.04 and 0.08 weight percent. Below this margin, the increase in machinability obtained from the concentration of tin in ferrite exfoliation planes decreases. Above this margin, the steel becomes more susceptible to hot breakage during hot work. More preferably, the tin content is in the range of almost 0.04 to almost 0.06 weight percent. In addition, when the combined total of the content of tin, sulfur and copper, in percent by weight, exceeds almost 0.9, the susceptibility of steel to hot cracking increases. Thus, it is preferred that, in these preferred embodiments of the present invention, the total tin, sulfur, and copper content, in percent by weight, does not exceed about 0.9.
The content of anganesium in these preferred embodiments of the present invention is preferably not less than 0.01 in percent by weight so that a sufficient amount of manganese sulfide inclusions to promote machinability can be precipitated in the steel by precipitation from the melt. . Furthermore, it is preferred that the manganese content does not exceed about 2 percent by weight, since increasing the manganese content by over 2 percent by weight can increase the hardness of the steel and, therefore, decrease the machinability. In more preferred embodiments of the invention, the manganese content is from about 0.5 to about 1.5 weight percent. The sulfide content in these preferred embodiments is preferably not less than about 0.002 percent by weight, so that a sufficient amount of manganese sulfide inclusions to promote machinability can be precipitated in the steel by precipitation from the melt. Since the excess sulfide can form iron sulfide, which can cause hot breakage of the steel, it is also preferred that the sulfide content does not exceed about 0.8 weight percent. In more preferred embodiments of the invention, the sulfide content is from about 0.2 to almost 0.45 weight percent. Since some fraction of manganese and sulfur combine to form sulfide inclusions
Manganic, which contribute to the machinability, it is convenient in these preferred embodiments of the present invention to control the ratio of the manganese content to the sulfide content from almost 2.9 to almost 3.4. Limiting the proportion of the manganese content to the sulfur content to this range of proportions also helps to prevent the excess element from causing harmful effects. When the ratio is less than 2.9, the manganese content may be insufficient to combine with the sulfide to supply the desired manganese sulfide inclusions, and the excess sulfide may form iron sulfide, which can make the steel susceptible to cracking during hot work. When the proportion is greater than 3.4, the excess manganese can increase the hardness of the steel and therefore decrease the machinability of the steel. The oxygen content in these preferred embodiments of the present invention is preferably in the range of from about 0.003 to about 0.03 weight percent. Keeping oxygen within this range helps minimize the amount of abrasive oxide inclusions present in the steel. Keeping oxygen in this range also helps ensure that manganic sulfide inclusions are of types that promote machinability. That is, when the oxygen content is maintained within this range, it is likely that the manganic sulfide inclusions
precipitates are "Manganic Type Sulfide inclusions Type!" * "Type II Manganic Sulfide inclusions" or a combination of both types All steels contain some carbon In preferred embodiments of the present invention, it is advisable that the carbon content be up to almost 0.25 weight percent, to optimize the ferrite content of the steel and hence promote machinability, More preferably, the carbon content in the preferred embodiments is from about 0.01 to about 0.25 weight percent Copper can reduce the ductility of steel, It is therefore preferred in some embodiments of the present invention that the copper content does not exceed about 0.5 weight percent Phosphorus is usually added to free-machining steels for improve the regularity of the machined surface, however, excessive amounts of phosphorus can reduce the ductility of the steel, therefore, it is advisable in some embodiments of the present invention that the phosphorus content is in the range from about 0.01 to about 0.15 weight percent. Nitrogen is known to promote chip cracking capacity. However, nitrogen can react with other elements to form nitrides or
tow.
carbonitrides that can increase the wear of the tool and therefore, decrease the machinability. Therefore, in some preferred embodiments of the present invention, it is preferred that the nitrogen content does not exceed about 0.015 weight percent. Silicon can form abrasive oxide inclusions that can be harmful to the useful life of the tool. Therefore, it is preferable that the silicon content be kept as low as possible, and in some preferred embodiments of the present invention, more preferably be limited to no more than about 0.05 weight percent. Aluminum can also form abrasive oxide particles that can be detrimental to lifespan
of the tool. Therefore, it is preferable that the aluminum content be kept as low as possible, and in some preferred embodiments of the present invention, more preferably be limited to no more than almost 0.005 weight percent. Some preferred versions of a process for preparing free machining steels in accordance with the present invention comprise the steps of supplying a steel containing tin as an element, precipitating the inclusions of manganese sulfide in the steel, developing plans of exfoliation of ferrite in the steels. steel, and concentrating tin in
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the exfoliation planes of ferrite. While in different embodiments of the present invention these steps can be performed in many ways, a number of preferred ways to accomplish these steps will be described below. The step of supplying a steel containing tin as an element is preferably fulfilled by producing, by conventional steelmaking methods, a molten steel which in its composition includes tin. Preferably, the steel provided will have a composition described above for preferred embodiments of the present invention. This step is important since it determines the stage for the remaining steps of the process. The step of precipitating inclusions of manganese sulfide in the steel is accomplished by precipitating inclusions of manganese sulfide from the molten steel composition during the solidification of the steel. Preferably, this step results in inclusions of manganese sulfide Type I or inclusions of manganese sulphide Type II or a combion of both types dispersed throughout the steel. This step is important as it results in steel containing manganic sulfide inclusions that contribute to the machility of the steel. The step of developing the ferrite exfoliation planes in the steel is preferably accomplished by cooling the steel from above the transformation temperature of the steel.
the austenite, A B3, after the steel was worked hot or heat treated, although it is also within the contemplations of the present invention that the exfoliation planes are developed during the cooling of the solidification of the steel. This step is important because it results in the formation of ferrite exfoliation planes that, when weakened by a concentration of tin at localized machining temperatures, participate in the intergranular break through which the machility of the steel is increased. To accomplish this step, it is necessary that the cooling rate used of the margin of the austenite of the steel is not so fast that the formation of ferrite can be avoided. Preferably, a cooling rate of the austenite margin will be chosen so that the microstructure of the steel, after cooling, contains at least about 80 percent of the volume of ferrite and the rest of the perlite. The step of concentrating the tin in the ferrite exfoliation planes is important, since it locates sufficient quantities of tin in that portion of the microstructure from which the tin can effect an increase in machility by causing the intergranular break to take place at temperatures of machining located in a similar way to what occurs with lead in free-machined lead steels. This step can be fulfilled in many ways, two of the
Preferred forms will be described below. A preferred way of concentrating tin in the ferrite exfoliation planes is to cool the steel at a cooling rate of less than about 1 ° C per second through the temperature range of from almost 700 ° C to almost 400 ° C. More preferably, the cooling rate through this cooling range is almost 28 ° C per hour, a cooling rate that accompanies a common coiling practice for bar steel. The cooling can be carried out after the steel is subjected to high temperatures such as during solidification, hot treatment, or hot working operations. Preferably, cooling is performed after some hot working operation of the steel, such as hot-curing or hot-forging *, "has been completed at temperatures above about 900 ° C, and more preferably when the End temperature is within the range of almost 900 ° C and almost 950 ° C. Under these circumstances, a preferred way of performing the cooling is to cool the steel under blankets or insulated bedspreads. Another preferred way of concentrating tin in the ferrite exfoliation planes is to keep the steel in the temperature range of from about 425 ° C to about 575 ° C for a long enough time to concentrate the tin in the exfoliation planes of Ferrite
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Preferably, the retention period is at least about 0.4 hours per centimeter (1 hour per inch) of the equivalent diameter of the steel. The retention period necessary for a given temperature exposure for a particular piece of steel can be determined by analyzing the amount of tin in the ferrite exfoliation planes in the manner specified above to determine whether the time was sufficient to concentrate the tin in the ferrite exfoliation planes. Ferrite exfoliation plans. Alternatively, it can be evaluated whether the time was long enough or not to concentrate the tin in the ferrite exfoliation planes by determining if the machinability reached the expected level for the steel. What the preferred forms described of fulfilling the step of concentrating tin in the exfoliation planes of ferfite have in common is that they all subject the steel to kinetic and thermodynamic conditions that result in tin atoms residing in the exfoliation planes of ferrite in large quantities so that the concentration of tin in the ferrite exfoliation planes exceeds the tin content.In general, within the specified temperature ranges, the amount of tin concentrated in the ferrite exfoliation planes will increase asymptotically to as the exposure periods increase, thus, in the preferred versions of the present invention described above, the concentration of tin in the
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Ferrite exfoliation planes will increase asymptotically as the rate of cooling through the temperature range from almost 425 ° C to almost 575 ° C is decreased or as the retention period in the temperature range from almost 425 ° C C at almost 575 ° C is increased. Thus, it is possible to control the amount of tin concentration in the ferrite exfoliation planes by controlling the amount of time the steel is exposed to these temperature ranges. Preferably, the step of concentrating the tin in the ferrite exfoliation planes results in concentrating the tin in the exfoliation planes at a concentration that is at least ten times the tin content. More preferably, the step results in concentrating the tin in the exfoliation planes of ferrite at a concentration of at least about 0.5 weight percent. Other preferred versions of a process for preparing free-machining steels in accordance with the present invention further comprises the steps of machining the steel and then redistributing the tin into the steel, in addition to the above-mentioned steps of supplying a steel having tin as an element , precipitating inclusions of manganese sulphide in the steel, developing planes of exfoliation of ferrite in the steel, and concentrating the tin in exfoliation planes of ferrite. While in different embodiments of this
invention, these steps can be performed in many ways, preferred forms will be described below. The step of machining can be accomplished by any means known to those skilled in the art. These means include, but are not limited to, such machining operations as transforming, molding, laminating, drilling, reaming, drilling, brushing and filleting. It is not necessary that all the machining that has to be done to the steel is done during the machining step. For example, additional machining can be conducted in the steel after the redistribution step resulted in a complete or partial redistribution of tin in the steel. The step of redistributing tin into steel involves subjecting the steel to thermodynamic and kinetic conditions, leading to homogenize the distribution of tin in the steel, for a long enough time so that the concentration of tin in the exfoliation planes of ferrite decreases or the ferrite exfoliation planes are removed, and then to cool the steel at a speed fast enough to prevent the tin from being reconcentrated in the ferrite exfoliation planes. The purpose of this step is to controllably eliminate, partially or totally, the embrittlement of the increase in machinability in the temperature range of almost 200 ° C to almost 600 ° C that resulted from the concentration of tin in the
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Ferrite exfoliation plans. Optimally, the thermodynamic and kinetic conditions are maintained until the concentration of tin in the ferrite exfoliation planes is essentially the same as the tin content. This optimal way of practicing the results of this step results in the more complete elimination of the embrittlement of the increase in machinability, and consequently, in the total restoration of the ductility and / or the hardness of the steel in the temperature range from almost 200 ° C to almost 600 ° C. However, it is not necessary for the practice of these versions of the present invention that the step of redistributing tin is employed so that the redistribution of tin is brought to this optimum state. For example, under circumstances where some improvement in ductility is desirable for the steel service request but some additional machining operations are anticipated after the steel redistribution step, it may be useful to controllably redistribute the tin only partially to retain a portion of the machinability increase while recovering the necessary ductility for steel to operate properly in service. A preferred way to accomplish the step of redistributing tin in steel is to heat the steel to a temperature above the transformation temperature of steel austenite, Ac3, by at least 0.4 hours per
centimeter (1 hour per inch) of steel equivalent diameter and then cool the steel at a speed faster than 1 ° C per second through the temperature range of almost 700 ° C to almost 400 ° C. This rate of cooling prevents a reconcentration of tin in the ferrite exfoliation planes. The various thermal practices explained above can be performed by any method known to those skilled in the art. For example, all or some of these thermal practices can be performed in furnaces of refractory lines and controlled temperature, which are heated electrically or through the combustion of a fuel. The cooling rates described can be performed by any method known to those skilled in the art, by means of which cooling periods and temperatures can be controlled. For example, cooling rates can be achieved through the use of furnace cooling or by surrounding the hot steel with insulation materials during cooling. In some preferred embodiments of the present invention, insulation blankets are placed on the steel at the end of the hot coil or hot forging process to control the cooling rate.
EXAMPLES The following examples are merely illustrative and are not intended to limit the scope of the present invention. EXAMPLE 1 Embodiments of the present invention having different compositions were made by vacuum induced fusion using standard steelmaking practices. The nominal compositions of these embodiments appear in Table 1. TABLE 1
* All compositions are payroll and are in percentage by weight. In making these embodiments, the raw material was charged to the melting furnace in two stages. First, a base charge consisting of graphite, ferrophosphorus (with 25% phosphorus), iron sulfide (50% de-sulfide), pure copper and electrolytic iron was charged into the furnace and melted. Once the base charge was melted, the remaining elements were added in the following order: electrolytic manganese, pure silicon and pure tin. The molten steel was poured into 22.4 kilogram (50 lb) casting molds. The solidified ingots were heated to almost 1232 ° C (2250 ° F) for almost 2.5 hours and then hot-threaded between almost 1232 ° C (2250 ° F) and almost 954 ° C (1750 ° F) on a rounded bar with a final diameter of almost 29 mm (1 1/8 inches) in ten passes. The bars were then cooled to a
! < ** speed of almost 28 ° C per hour (50 ° F per hour) at room temperature. Test samples, each 152 mm (6 inches) long by 25.4 mm (1 inch) in diameter, were prepared from each heating. Comparison samples of AISI grades 1018 and 1215 hot-screwed and 12L14, obtained from commercial sources, were also machined to achieve the size of the test sample. The AISI 1018 grade is a low carbon steel that is not considered to be free machining. The AISI 1215 grade is a conventional free-machined steel, without lead. The nominal compositions of these three commercial grades are set forth in Table 1. The C index values, as defined above, of each of the samples were determined. The values of index C are indicated in Table 2. TABLE 2
The results of the test clearly show that the machinability of the embodiments subjected to the test of the following invention correspond to those of the conventional free machining steels tested or exceeded. The results also demonstrate that the machinability of some of the embodiments under test of the present invention greatly exceeds the machinability of the conventional free machining steel under test. The results also demonstrate that the embodiments of the present invention tested greatly exceed the machinability of the AISI 1018 grade of conventional steel that is not free-machined and has been tested.
Example 2 Experiments were performed to determine the effect of thermal practice on the machinability of some embodiments of the present invention. A comparison sample having a composition of the present invention except that it did not have concentrated tin in the exfoliation plane of ferrite was also tested. The samples were prepared as described in Example 1, except that the thermal practice of the samples was varied. The final hot coiling temperature of the Sn60M and Sn80M samples was almost 954 ° C (1750 ° F). Some of the samples were cooled slowly from the final temperature of hot coiling to almost 28 ° C per hour at room temperature, simulating a cooling speed used with commercial rod winding operations. Other samples were cooled from the hot coiling temperature to room temperature at a rate of almost 1 ° C per second. Even so, other samples, after being cooled from the temperature of hot coiling to room temperature at a rate of almost 1 ° C per second, were heated to almost 500 ° C for about two hours and then cooled by air to room temperature. The Sn60 samples were hot coiled with a final temperature of almost 900 ° C (1650 ° F) and then cooled by air at almost 5 ° C per second at temperature
ambient. This rapid cooling rate did not allow the tin to concentrate in the ferrite exfoliation planes. One of these samples was tested in the cooled state in that way and used as the comparison sample. The other Sn60 sample was heated to almost 450 ° C (842 ° F) for almost one hour to concentrate tin in the ferrite exfoliation planes according to the present invention and then cooled by air at room temperature before being tested . Measurements of index C were made in each sample. The results are in Table 3.
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* "HR" means "hot rolled" under the conditions described in Example 1. "RT" means "room temperature". The results prove that each of the embodiments tested of the present invention demonstrated excellent machinability under all test thermal conditions. In contrast, the comparison sample of Sn60 that does not It had concentration of tin in the exfoliation planes of ferrite showed notoriously little machinability. The results also show that the samples cooled to almost 28 ° C per hour and the samples subject to 500 ° C had better machinability than the samples cooled to 1 ° C per second. This indicates that the machinability can be controlled by controlling the time that the steel is subjected to thermodynamic and kinetic conditions conducive to concentrating the tin in the ferrite exfoliation planes. A) Yes, the results show that a longer exposure to the temperature margins at which tin is concentrated in the ferrite exfoliation planes results in higher concentrations of tin in the levels of
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&A exfoliation of ferrite and in a better machinability of steel.
Example ? A test was carried out in a complex and high-volume production environment for machine manufacturing and production. In the test, one embodiment of the present invention, Sn80, was compared to traditional 12L14 lead steel. The machine used was the rotary transfer machine of sixteen stations Hydromat model HB 32/45 high volume, which was able to perform various functions of machining. The production speed was approximately 300 pieces per hour. The machining of each piece consists of the following functions: 1) cutting, 2) preliminary transformation, 3) final transformation, 4) beveling, 5) polishing, 6) drilling, 7) reaming, 8) preliminary drilling, 9) final drilling , 10) counterbore, ll) ~ bordered, and 12) polish. The tools used were l) high speed steel, 2) titanium carbide covered with nitride, 3) uncoated carbide, 4) steam tempering saw, and 5) a polishing tool equivalent to 52100. The results are found in Table 4
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TABLE 4
The results show that the embodiment under test of the present invention acts at least
with the conventional lead steel 12L14 and that the surface finish is smoother in both polished and non-polished conditions.
Example The hot ductility tests were carried out in an embodiment of the present invention to determine if there is embrittlement at temperatures corresponding to the temperatures of the localized cutting zone as is the case with the 12L14 grade of conventional free-machined lead steel. A conventional free-machining steel that does not contain lead, AISI grade 1215, was also submitted for comparison. The embodiment of the present invention tested was SnβO. The nominal composition of SnßO appears in Table 1. SnßO was prepared in the manner described in *** Example 1, except that three different thermal practice conditions were used to allow a determination of the effect of increasing tin concentrations in the exfoliation planes of ferrite in hot ductility. In the first condition, the SndO was hot rolled and then cooled at a rate of almost 2d ° C per hour at room temperature. The two remaining conditions started with SnßO in the hot rolled and cooled state at room temperature of the first condition. In the second condition, the steel was reheated to 500 ° C for a period of retention of
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two hours and then cooled by air at room temperature. Due to the increasingly long periods of exposure of the sample to temperature ranges at which tin is concentrated in the ferrite exfoliation planes, increasing amounts of tin concentrations were expected for the three conditions. The hot ductility tests were performed on flanged compression samples using a tension rate of 20 seconds "1 at temperatures between room temperature and 600 ° C. Hot ductility was determined by measuring the amount of Hoop strain (Hoop strain). ) in which the initiation of cracking occurred on the external surface of the flange The results of the tests are shown graphically in Figure 3. The results are also shown in Table 5 which indicates the 400 ° ductility loss. C from the ductility level at room temperature The loss of ductility at 400 ° C represents the depth of the embrittlement zone of the machinability increase The ferrite content of all the samples tested was around 95 volume percentage determined by means of a microscopic analysis of the image of polished metallographic samples.
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4 * TABL 5
The tests show that each embodiment subjected to the test of the present invention showed a behavior similar to that of free machined lead steel. The results also demonstrate that the deepened hollow for the embodiments under test of the present invention as the concentration of tin in the ferrite exfoliation planes increased. The results also show that the zone of fragility was absent
in the conventional free machining steel that did not contain lead. Microscopic examination of some of the rupture surfaces of the embodiments under test demonstrated that the rupture mode was transgranular outside the region of the embrittling and intergranular hollow within the region of the embrittlement hollow. The same behavior of the rupture mode was observed in the conventional free machining steel containing lead, that is, in the AISI 12L14 grade samples. However, the mode of fracture was transgranular throughout the range of temperatures tested for the free-machining steel, conventional that does not contain lead, that is, the sample of the AISI 1215 grade. While only a few embodiments and versions of The present invention has been shown and described, it is obvious to those skilled in the art that many changes and modifications can be made without departing from the spirit and scope of the present invention. Therefore, it is to be clearly understood that the present invention is not limited to the specific embodiments and versions described herein but may be enclosed and may be practiced within the scope of the following claims.
Claims (83)
- Claims 1. A free-machining steel composition consisting essentially of (weight percent): carbon up to about 0.25; copper up to almost 0.5; manganese from almost 0.01 to almost 2; oxygen from almost 0.003 to almost 0.03; sulfur from almost 0.002 to almost 0.8; tin from almost 0.04 to almost 0.06; and a residual of iron and possible impurities, where a proportion of manganese to sulfur is from almost 2.9 to almost 3.4 and a total of sulfur plus tin plus copper does not exceed almost 0.9, characterizing the composition by a microstructure having a tin concentration in the exfoliation planes of ferrite in an amount of at least about ten times the tin content of the steel.
- 2. The free-machining steel composition as described in claim 1, wherein the concentration of tin in the ferrite exfoliation planes is at least about 0.5 weight percent.
- 3. A free-machining steel composition consists essentially of (weight percent): aluminum up to almost 0.005; carbon from almost 0.01 to almost 0.25; copper up to almost 0.5; manganese from almost 0.5 to almost 1.5; nitrogen to almost 0.015; oxygen from almost 0.003 to almost 0.03; phosphorus from almost 0.01 to almost 0.15; silicon to almost 0.05; sulfur from almost 0.2 to almost 0.45; tin from almost 0.04 to almost 0.08; and a remnant of iron and possible impurities, where a The proportion of manganese to sulfur is from almost 2.9 to almost 3.4 and a total of sulfur plus tin plus copper is not greater than almost 0.9, the composition being characterized by a microstructure having a tin concentration in the Ferrite exfoliation planes in an amount of at least ten times the tin content of the steel.
- 4. The free-machining steel composition as described in claim 3, wherein the concentration of tin in the ferrite exfoliation planes is at least about 0.5 weight percent.
- 5. A process for preparing a free machining steel, comprising the steps of: a) supplying a steel containing tin as an element; b) precipitate inclusions of manganese sulfide in the steel; c) develop planes of exfoliation of ferrite in the steel; and d) concentrating the tin in the exfoliation planes of ferrite in an amount of at least about ten times the content of the steel. The process described in claim 5, wherein the step of precipitating manganese sulfide inclusions in the steel comprises precipitating sulfide inclusions Manganic of a type of at least one selected from the group of inclusions of manganic sulfide Type I and inclusions of manganic sulfide Type II. The process described in claim 5, wherein the step of concentrating the tin in the ferrite exfoliation planes includes concentrating the tin in the ferrite exfoliation planes at a concentration of at least about 0.5 weight percent. The process described in claim 5, wherein the step of concentrating the tin in the ferrite exfoliation planes comprises cooling the steel at a rate of less than about 1 ° C per second through a temperature range of almost 700 °. C at almost 400 ° C to concentrate the tin in the ferrite exfoliation planes. The process described in claim 5, wherein the step of concentrating the tin in the ferrite exfoliation planes comprises maintaining the steel in a temperature range from almost 425 ° C to almost 575 ° C for a sufficiently long time as to concentrate the tin in the ferrite exfoliation planes. The process described in claim 9, wherein the retention period of the steel in the temperature range from about 425 ° C to about 575 ° C is at least about 0.4 hours per centimeter of an equivalent diameter of the steel. 11. The process described in claim 5, wherein the step of supplying a tin-containing steel as an element comprises supplying a steel having a composition consisting essentially of (weight percentage): carbon up to about 0.25.; copper up to almost 0.5; manganese from almost 0.01 to almost 2; oxygen from almost 0.003 to almost 0.03; sulfur from almost 0.002 to almost 0.8; tin from almost 0.04 to almost 0.08, and a rest of iron and possible impurities, where a proportion of manganese to sulfur is from almost 2.9 to almost 3.4 and a total of sulfur plus tin plus copper does not exceed almost 0.9. The process described in claim 6, wherein the step of supplying a tin-containing steel as an element comprises supplying a steel having a composition consisting essentially of (weight percentage): carbon up to about 0.25; copper up to almost 0.5; manganese "from almost 0.01 to almost 2, oxygen from almost 0.003 to almost 0.03, sulfur from almost 0.002 to almost 0.8, tin from almost 0.04 to almost 0.08, and a remnant of iron and impurities eventual, where a proportion of manganese to sulfur is from almost 2.9 to almost 3.4 and a total of sulfur plus tin plus copper does not exceed almost 0.9 13. The process described in claim 7, where The step of supplying a tin-containing steel as an element comprises supplying a steel having a composition consisting essentially of (weight percentage): carbon up to almost 0.25; copper'up to almost 0.5; manganese from almost 0.01 to almost 2; oxygen from almost 0.003 to almost 0.03; sulfur from almost 0.002 to almost 0.8; tin from almost 0.04 to almost 0.08, and balance iron and incidental impurities, wherein a ratio of the manganese to the sulfur is from 2.9 to nearly almost 3.4, and a total sulfur plus the tin plus the copper does not exceed almost 0.9. The process described in claim 8, wherein the step of supplying a tin-containing steel as an element comprises supplying a steel having a composition consisting essentially of (weight percentage): carbon up to about 0.25; copper up to almost 0.5; manganese from almost 0.01 to almost 2; oxygen from almost 0.003 to almost 0.03; sulfur from almost 0.002 to almost 0.8; tin from almost 0.04 to almost 0,0d and balance iron and incidental impurities, wherein a ratio of the manganese to the sulfur is from 2.9 to almost 3.4 almost a total sulfur plus the tin plus the copper not exceeds almost 0.9. The process described in claim 9, wherein the step of supplying a tin-containing steel as an element comprises supplying a steel having a composition consisting essentially of (weight percentage): carbon up to about 0.25; copper up to almost 0.5; manganese from almost 0.01 to almost 2; oxygen from almost 0.003 to almost 0.03; sulfur from almost 0.002 to almost 0, d; tin from almost 0.04 to ^ ^ almost 0.08, and a rest of iron and eventual, where a proportion of manganese to sulfur is from almost 2.9 to almost 3.4 and a total of sulfur plus tin plus copper does not exceed almost 0.9. 16. The process described in claim 10, wherein the step of providing a steel containing tin as gue element comprises providing a steel having a composition consisting essentially of (percent by weight): carbon 0.25 to almost; copper up to almost 0.5; manganese from almost 0.01 to almost 2; oxygen from almost 0.003 to almost 0.03; sulfur from almost 0.002 to almost 0.6; tin from almost 0.04 to almost 0.08, and a rest of iron and possible impurities, where a proportion of manganese to sulfur is from almost 2.9 to almost 3.4 and a total of sulfur plus tin plus copper does not exceed almost 0.9. ~~ ** 17. The process described in claim 5, wherein the step of providing a steel containing tin as element comprises providing a steel having a composition consisting essentially of (percent by weight): aluminum to nearly 0,005; carbon from almost 0.01 to almost 0.25; copper up to almost 0.5; manganese from almost 0.5 to almost 1.5; nitrogen to almost 0.015; oxygen from almost 0.003 to almost 0.03; phosphorus from almost 0.01 to almost 0.15; silicon to almost 0.05; sulfur from almost 0.2 to almost 0.45; tin from almost 0.04 to almost 0.08, and a remainder consisting of iron and Possible impurities, where a proportion of manganese to sulfur is from almost 2.9 to almost 3.4 and a total of sulfur plus tin plus copper does not exceed almost 0.9. 18. The process described in claim 6, wherein the step of providing a steel containing tin as element comprises providing a steel having a composition consisting essentially of (percent by weight): aluminum to nearly 0,005; carbon from almost 0.01 to almost 0.25; copper up to almost 0.5; manganese from almost 0.5 to almost 1.5; nitrogen to almost 0.015; oxygen from almost 0.003 to almost 0.03; phosphorus from almost 0.01 to almost 0.15; silicon to almost 0.05; sulfur from almost 0.2 to almost 0.45; tin from almost 0.04 to almost 0.08, and a residue consisting of iron and eventual impurities, where a ratio of manganese to sulfur is from almost 2, 9-to almost 3.4 and a total of sulfur plus tin plus copper does not exceed almost 0.9. The process described in claim 7, wherein the step of supplying a steel having tin as the element comprises supplying a steel having a composition consisting essentially of (weight percentage): aluminum up to almost 0.005; carbon from almost 0.01 to almost 0.25; copper up to almost 0.5; manganese from almost 0.5 to almost 1.5; nitrogen to almost 0.015; oxygen from almost 0.003 to almost 0.03; phosphorus from almost 0.01 to almost 0.15; silicon to almost 0.05; sulfur from almost 0.2 to almost 0.45; Tin from almost Hi? S? • > s - 0.04 to almost 0.08, and a residue consisting of iron and eventual impurities, where a ratio of manganese to sulfur is from almost 2.9 to almost 3.4 and a total of sulfur plus tin plus copper does not exceed almost 0.9. The process described in claim 8, wherein the step of supplying a tin-containing steel as an element comprises supplying a steel containing a composition consisting essentially of (weight percent): aluminum up to almost 0.005; carbon from almost 0.01 to almost 0.25; copper up to almost 0.5; manganese from almost 0.5 to almost 1.5; nitrogen to almost 0.015; oxygen from almost 0.003 to almost 0.03; phosphorus from almost 0.01 to almost 0.15; silicon to almost 0.05; sulfur from almost 0.2 to almost 0.45; tin from almost 0.04 to almost 0.08, and a rest consisting of iron and eventual impurities, where a proportion of manganese to sulfur is from almost 2.9 to almost 3.4 and a total of sulfur plus tin plus copper does not exceed almost 0.9. The process described in claim 9, wherein the step of supplying a tin-containing steel as an element comprises supplying a steel having a composition essentially in (weight percent): aluminum up to almost 0.005; carbon from almost 0.01 to almost 0.25; copper up to almost 0.5; manganese from almost 0.5 to almost 1.5; nitrogen to almost 0.015; oxygen from almost 0.003 to almost 0.03; phosphorus from almost 0.01 to -almost 0.15; silicon up almost 0.05; sulfur from almost 0.2 to almost 0.45; tin from almost 0.04 to almost 0.08, and a rest consisting of iron and eventual impurities, where the proportion of manganese to sulfur is from almost 2.9 to almost 3.4 and a total of sulfur plus tin plus copper does not exceed almost 0.9. 22. The process described in claim 10, wherein the step of supplying a tin-containing steel as an element comprises supplying a steel having a composition consisting essentially of (weight percent): aluminum up to almost 0.005; carbon up to almost 0.01 and almost 0.25; copper up to almost 0.5; manganese from almost 0.5 to almost 1.5; nitrogen to almost 0.015; oxygen from almost 0.003 to almost 0.03; phosphorus from almost 0.01 to almost 0.15; silicon to almost 0.05; sulfur from almost 0.2 to almost 0.45; tin from almost 0.04 to almost 0.08, and a residual - consisting of iron and eventual impurities, where a ratio of manganese to sulfur is from almost 2.9 to almost 3.4 and a total of sulfur plus tin plus copper does not exceed almost 0.9. 23. A process for preparing a free-machining steel comprising the steps of: a) supplying a tin-containing steel as an element; b) precipitate inclusions of manganese sulfide in the steel; c) develop exfoliation plans of ferrite in steel; d) concentrating the tin in the exfoliation planes of ferrite in an amount of at least about ten times the volumetric content of tin of the steel; e) machining tin; and f) redistribute tin in steel. The process described in claim 23, wherein the step of redistributing tin in steel comprises the steps of: a) subjecting the steel to temperatures exceeding the transformation temperature of the austenite, A ^, of the steel during minus 0.4 hours per centimeter in diameter - equivalent; and --- b) cooling the steel at a faster rate than almost 1 ° C per second through the temperature range of from almost 700 ° C to almost 400 ° C to prevent the re-concentration of tin in the exfoliation planes of ferrite. The process described in claim 23, wherein the step of precipitating the inclusions of manganic sulfide in the steel comprises precipitating manganic sulfide inclusions of at least one type selected from the group "Type I" or "Type II" manganic sulfide inclusions. The process described in claim 23, wherein the step of concentrating the tin in the ferrite exfoliation planes involves concentrating the tin in the ferrite exfoliation planes at a concentration of at least about 0., 5 percentage by weight. The process described in claim 23, wherein the step of concentrating the tin in the ferrite exfoliation planes comprises cooling the steel at a slower rate than almost 1 ° C per second through the temperature range of from about 700. ° C at almost 400 ° C to concentrate tin in the ferrite exfoliation planes. 2d. The process described in claim 23, wherein the step of concentrating the tin in the ferrite exfoliation planes comprises-keeping the steel within a temperature range of about 425 ° C to about 575 ° C for a sufficiently long time as to concentrate the tin in the ferrite exfoliation planes. 29. The process described in claim 26, wherein the retention period of the steel in the temperature range from about 425 ° C to about 575 ° C is at least about 0.4 hours per centimeter of an equivalent steel diameter. . 30. The process described in claim 23, wherein the step of supplying a steel containing tin as an element comprises supplying a steel having a composition consisting essentially of (weight percentage): carbon up to almost 0.25; copper up to almost 0.5; manganese from almost 0.01 to almost 2; oxygen from almost 0.003 to almost 0.03; sulfur from almost 0.002 to almost 0.6; tin from almost 0.04 to almost 0.06, and a remnant of iron and eventual impurities, where a proportion of manganese to sulfur is from almost 2.9 to almost 3.4 and a total of sulfur plus tin plus copper does not exceed almost 0.9. 31. The process described in the claim 24, wherein the step of supplying a tin-containing steel as an element comprises supplying a steel having a composition consisting essentially of (weight percentage): carbon up to about 0.25; copper up to almost 0.5; manganese from almost 0, 01 to almost 2; oxygen from almost 0.003 to almost 0.03; sulfur from almost 0.002 to almost 0, d; tin from almost 0.04 to almost 0.0d, and a remnant of iron and eventual impurities, where a ratio of manganese to sulfur is from almost 2.9 to almost 3.4 and a total of sulfur plus tin plus copper does not exceed almost 0.9. 32. The process described in the claim 25, wherein the step of supplying a tin-containing steel as an element comprises supplying a steel having a composition consisting essentially of (weight percentage): carbon up to about 0.25; copper up to almost 0.5; manganese from ... issáaií = íssser "8« 8T- almost 0.01 up to almost 2; oxygen from almost 0.003 to almost 0.03; sulfur from almost 0.002 to almost 0.8; tin from almost 0.04 to almost 0.08, and a remnant of iron and possible impurities, where a proportion of manganese to sulfur is from almost 2.9 to almost 3.4 and a total of sulfur plus tin plus copper does not exceed 0.9. The process described in claim 26, wherein the step of supplying a tin-containing steel as an element comprises supplying a steel having a composition consisting essentially of (weight percentage): carbon up to about 0.25; copper up to almost 0.5; manganese from almost 0.01 to almost 2; oxygen from almost 0.003 to almost 0.03; sulfur from almost 0.002 to almost 0.8; tin from almost 0.04 to almost 0.08, and a remnant of iron and possible impurities, where a proportion of ~ manganese * 2To to sulfur is from almost 2.9 to almost 3.4 and a total of sulfur plus tin plus copper does not exceed almost 0.9. 34. The process described in claim 27, wherein the step of supplying a tin-containing steel as an element comprises supplying a steel having a composition consisting essentially of (weight percentage): carbon up to about 0.25; copper up to almost 0.5; manganese from almost 0.01 to almost 2; oxygen from almost 0.003 to almost 0.03; sulfur from almost 0.002 to almost 0.8; tin from almost 0.04 to almost 0.08, and a remnant of iron and impurities eventual, where a proportion of manganese to sulfur is from almost 2.9 to almost 3.4 and a total of sulfur plus tin plus copper does not exceed almost 0.9. 35. The process described in the claim 28, wherein the step of supplying a tin-containing steel as an element comprises supplying a steel whose composition consists essentially of (percentage by weight): carbon up to about 0.25; copper up to almost 0.5; manganese from almost 0.01 to almost 2; oxygen from almost 0.003 to almost 0.03; sulfur from almost 0.002 to almost 0.8; tin from almost 0.04 to almost 0.08, and a remnant of iron and possible impurities, where a proportion of manganese to sulfur is from almost 2.9 to almost 3.4 and a total of sulfur plus tin plus copper does not exceed almost 0.9. 36. The process described in the claim 29, wherein the step of supplying a tin-containing steel as an element comprises supplying a steel whose composition consists essentially of (percentage by weight): carbon up to about 0.25; copper up to almost 0.5; manganese from almost 0.01 to almost 2; oxygen from almost 0.003 up to almost 0.3; sulfur from almost 0.002 to almost 0.8; tin from almost 0.04 to almost 0.08, and a remnant of iron and possible impurities, where a proportion of manganese to sulfur is from almost 2.9 to almost 3.4 and a total of sulfur plus tin plus copper does not exceed 0.9. 37. The process described in the claim 23, wherein the step of supplying a tin-containing steel as an element comprises supplying a steel whose composition consists essentially of (weight percentage): aluminum up to almost 0.005; carbon from almost 0.01 to almost 0.25; copper up to almost 0.5; manganese from almost 0.5 to almost 1.5; nitrogen to almost 0.015; oxygen from almost 0.003 to almost 0.03; phosphorus from almost 0.01 to almost 0.15; silicon to almost 0.05; sulfur from almost 0.2 to almost 0.45; tin from almost 0.04 to almost 0.08, and a remainder consisting of iron and possible impurities, where a proportion of manganese to sulfur is from almost 2.9 to almost 3.4, and a total of sulfur plus tin more copper does not exceed almost 0.9. 38. The process described in the claim 24, wherein the step of supplying a steel containing tin as an element comprises supplying a steel whose composition consists essentially of (weight percentage): aluminum up to almost 0.005; carbon from almost 0.01 to almost 0.25; copper up to almost 0.5; manganese from almost or, 5 to almost 1.5; nitrogen to almost 0.015; oxygen from almost 0.003 to almost 0.03; phosphorus from almost 0.01 to almost 0.15; silicon to almost 0.05; sulfur from almost 0.2 to almost 0.45; tin from almost 0.04 to almost 0.08, and a rest consisting of iron and possible impurities, where a proportion of manganese to sulfur is from almost 2.9 to almost 3.4 and a total of sulfur '"ÍS * > 3Sk¿ ^? SsS plus tin plus copper does not exceed almost 0.9. 39. The process described in the claim 25, wherein the step of supplying a tin-containing steel as an element comprises supplying a steel whose composition consists essentially of (percentage by weight): aluminum up to almost 0.005; carbon from almost 0.01 to almost 0.25; copper up to almost 0.5; manganese from almost 0.5 to almost 1.5; nitrogen to almost 0.015; oxygen from almost 0.003 to almost 0.03; phosphorus from almost 0.01 to almost 0.15; silicon to almost 0.05; sulfur from almost 0.2 to almost 0.45; tin from almost 0.04 to almost 0.08, and a remnant of iron and eventual impurities, where a ratio of manganese to sulfur is from about 3.4 and a total of sulfur plus tin plus copper does not exceed almost 0 , 9. 40. The process described in the claim 26, wherein the step of supplying a tin-containing steel as an element comprises supplying a steel whose composition consists essentially of (percentage by weight): aluminum up to almost 0.005; carbon from almost 0.01 to almost 0.25; copper up to almost 0.5; manganese from almost 0.5 to almost 1.5; nitrogen to almost 0.015; oxygen from almost 0.003 to almost 0.03; phosphorus from almost 0.01 to almost 0.15; silicon to almost 0.05; sulfur from almost 0.2 to almost 0.45; tin from almost 0.04 to almost 0.06, and a remainder consisting of iron and possible impurities, where a proportion of the manganese to the sulfur is from almost 2.9 to almost 3.4 and a total of sulfur plus tin plus copper does not exceed almost 0.9. 41. The processes described in the claim 27, wherein the step of supplying a tin-containing steel as an element comprises supplying a steel whose composition consists essentially of (weight percentage): aluminum up to almost 0.005; carbon from almost 0.01 to almost 0.25; copper up to almost 0.5; manganese from almost 0.5 to almost 1.5; nitrogen to almost 0.015; oxygen from almost 0.003 to almost 0.03; phosphorus from almost 0.01 to almost 0.15; silicon to almost 0.05; sulfur from almost 0.2 to almost 0.45; tin from almost 0.04 to almost 0.06, and a remainder of iron and possible impurities, where a proportion of manganese to sulfur is from almost 2.9 to almost 3.4 and a total of sulfur plus tin plus copper does not exceed almost 0.9. 42. The process described in the claim 28, wherein the step of supplying a tin-containing steel as an element comprises supplying a steel whose composition consists essentially of (percent by weight): aluminum up to almost 0.005; carbon from almost 0.01 to almost 0.25; copper up to almost 0.5; manganese from almost 0.5 to almost 1.2; nitrogen to almost 0.015; oxygen from almost 0.003 to almost 0.03; phosphorus from almost 0.01 to almost 0.15; silicon to almost 0.05; sulfur from almost 0.2 to almost 0.45; tin from almost 0.04 to almost 0.08, and a remnant of iron and impurities the 8 eventual, where a proportion? manganese to sulfur is from almost 2.9 to almost 3.4 and a total of sulfur plus tin plus copper does not exceed almost 0.9. 43. The process described in claim 29, wherein the step of supplying a tin-containing steel as an element comprises supplying a steel whose composition consists essentially of (weight percentage): aluminum up to almost 0.005; carbon from almost 0.01 to almost 0.25; copper up to almost 0.5; manganese from almost 0.5 to almost 1.5; nitrogen to almost 0.015; oxygen from almost 0.003 to almost 0.03; phosphorus from almost 0.01 to almost 0.15; silicon to almost 0.05; sulfur from almost 0.2 to almost 0.45; tin from almost 0.04 to almost 0.08, and a rest consisting of iron and possible impurities, where a proportion of manganese to sulfur is from almost 2.9 to almost 3.4 and a total of sulfur plus tin plus copper does not exceed almost 0.9. 44. A free-machined steel produced by the process described in claim 5. 45. A free-machined steel produced by the process described in claim 6. 46. A free-machined steel produced by the process described in claim 7. 47. A free-machined steel produced by the process described in claim d. 4d.A free machining steel produced by the The process described in claim 9. 49. A free machining steel produced by the process described in claim 10. 50. A free machining steel produced by the process described in claim 11. 51. A free machining steel produced by the process described in claim 12. 52. A free machining steel produced by the process described in claim 13. 53. A free machining steel produced by the process described in claim 14. 54. A free machining steel produced by the process described in claim 15. 55. A free machining steel produced by the process described in claim 16. 56. A free machining steel produced by the process described in claim 17. 57. A free machining steel. produced by the process described in claim 18. 58. A free-machined steel produced by the process described in claim 19. 59. A steel of free machining produced by the process described in claim 20. 60. A free machining steel produced by the process described in claim 21. 61. A free-machined steel produced by the process described in claim 22. 62. A free-machined steel produced by the process described in claim 23. 63. A free-machined steel produced by the process described in claim 24. 64 A free machining steel produced by the process described in claim 25. 65. A free machining steel produced by the process described in claim 26. 66. A free machining steel produced by the process described in claim 27. 67. A free machining steel produced by the process described in claim 28. 68. A "free machining steel" produced by the process described in claim 29. 69. A free machining steel produced by the process described in the claim. 30. 70. A free-machined steel produced by the process described in claim 31. 71. A free-machined steel produced by the process described. pto in claim 32. 72. A free-machined steel produced by the process described in claim 33. 73. A free-machined steel produced by the process described in claim 34. 74. A free machining steel produced by the process described in claim 35. 75. A free machining steel produced by the process described in claim 36. 76. A free machining steel produced by the process described in the claim 37. 77. A free-machined steel produced by the process described in claim 38. 78. A free-machined steel produced by the process described in claim 39. 79. A free-machined steel produced by the process described in claim 40. 80. A free-machined steel produced by the process described in claim 41. 81. A free-machined steel produced by the process described in claim 42. 82. A free-machined steel produced by the process described. in claim 43. 83. A free-machined steel produced by the process described in claim 44.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US08972154 | 1997-11-17 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| MXPA00003853A true MXPA00003853A (en) | 2001-12-04 |
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