CA1086991A - Abrasion resistant stainless steel - Google Patents
Abrasion resistant stainless steelInfo
- Publication number
- CA1086991A CA1086991A CA285,202A CA285202A CA1086991A CA 1086991 A CA1086991 A CA 1086991A CA 285202 A CA285202 A CA 285202A CA 1086991 A CA1086991 A CA 1086991A
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- Canada
- Prior art keywords
- titanium
- carbon
- silicon
- steel
- abrasion resistance
- Prior art date
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/36—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.7% by weight of carbon
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- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Heat Treatment Of Steel (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A stainless steel having excellent abrasion resistance in a heat hardened state consists essentially of about 1.8% to about 10% carbon,up to about 1.0% manganese, greater than 1.7% to about 4.5% silicon, about 11.5% to about 18% chromium, up to about 1% nickel, 1% to about 10%
titanium, up to about 1.5% molybdenum, and balance iron, except for incidental impurities. A method of increasing the abrasion resistance of heat hardenable chromium-bearing stainless steel, comprises adding silicon and titanium to a stainless steel melt containing from 0.75% to 10% carbon, 11.5% to 18% chromium, and balance essentially iron, silicon being from greater than 1.7% to about 4.5%, titanium being from about 1% to about 10%. The additions are proportioned relative to the carbon content to obtain a synergistic improvement in abrasion resistance.
A stainless steel having excellent abrasion resistance in a heat hardened state consists essentially of about 1.8% to about 10% carbon,up to about 1.0% manganese, greater than 1.7% to about 4.5% silicon, about 11.5% to about 18% chromium, up to about 1% nickel, 1% to about 10%
titanium, up to about 1.5% molybdenum, and balance iron, except for incidental impurities. A method of increasing the abrasion resistance of heat hardenable chromium-bearing stainless steel, comprises adding silicon and titanium to a stainless steel melt containing from 0.75% to 10% carbon, 11.5% to 18% chromium, and balance essentially iron, silicon being from greater than 1.7% to about 4.5%, titanium being from about 1% to about 10%. The additions are proportioned relative to the carbon content to obtain a synergistic improvement in abrasion resistance.
Description
This invention rela~es to a me~hod of increasing the abrasion reslstance of a chromium-bearing heat hardenable stainless steel while retaining good corrosion resistande and ability to be readily converted to wrought products by hot and cold working with conventional steel mill equipment. Steel treated by the method of the invention is martensitic in the heat hardened condition. The invention further relates to a steel of critical composition which has particular utility for fabrication into bearings,ball joints, tire ~tuds, cutlery, materials processing equipment such as mining and ore pro-cessing machinery, and similar products of ultimate use wherein the above combination of properties is needed.
Currently available alloys capable of withstanding high stress, abrasive conditions are produced as castings onl~ and are not amena~le to production in wrought form.
Among~such prior art iron base alloys are chromium-~olybdenum white cast iron (analyzing about 3.2% carbon, about 0.6~
silicon, a~out 15.0% chromium, about 3.0% molybdenum, and balance iron), and high chromium white cast iron (analyzing about 2.7% carbon, about 0.65~ silicon, about 27.0~ chromium, and balance ironl. Other such alloys are tool steels, e.g.
AISI Type ~-2 (1.50-1.60% carbon, 0.30-0.45% silicon, 11.50-:.
12.50% chromium, 0.75 0.85~ molybdenum, 0.70-0.90~ vanadium, and balance iron), and AISI ~ype D-4 (2.0-2.30% carbon, 0.20-0.45~ ~ilicon, 11.50-12.50% chromium, 0.70-0.90 molybdenum, 0.30-0.50~ vanadium and balance iron).
Prior art martensitic stainless steels classified as wrought steels, such as AISI Types 440 A, B and C, actually can be~hot and cold worked in standard mill equipment only with great dificulty. Moreover, these steels, which .
~ 699~ ~
contain up to about 1.2~ carbon, are deficient in abrasion resistance under very high stress, abrasive conditions.
United States Patent ~o. 3,692,515 issued September 19, 1972 to S.G. Fletcher et al, cliscloses a steel alleged to have improved abrasion resistance, forgeability and work-ability consisting essentially of about 1% to about 4.25 carbon, about 1.5% maximum silicon, about 1.5~ maximum manganese, about 10~ to about 15~ chromium, less than 2%
molybdenum, about 0.5% to about ~% titanium, less than 3%
tungsten, less than 3% nickel, less than 5% cobalt, less than 5~ vanadium, up to 0.25% sulfur, and balance iron with residual impurities. A preferred composition contains 2O9 carbon, 0.4% silicon,0.4% manganese, 12.5% chromium, 1.1~
molybdenum, 3% titanium, and balance substantially iron with residual impurities. It is stated that carbon is added in excess of that necessary to ~ive a desired hardenability and that such excess carbon is combined with titanium in a weight ratio of 4:1 and vanadium in a weight ratio of 4.2 (V-l):l.
The cast alloy is reduced in cross sectional area by at 2Q least 5% by working, and heat treated by austenitizing at 1600 to 1950F and tempering at 900 to 950~F.
The maximum austenitizing temperature of 1950F
disclosed in the ~letcher patent limits the amount o~ dis-solved carbon to about 0.7~ to 0.8% maximum. If no vanadium is present, the excess carbon content in the preferred practice would be Ti/4, or 3/4 (th~ preferred titanium content being 3%), i.e. 0.75~. Thus the total carbon content should be 1.45~ to 1~55~. Since the excess carbon cannot all be dis-solved and since ~he amount~of titanium is insufficient to combiné with all the excess carbon, that portion of the ca~bon - , ~
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not in solution and not in the form of titanium carbides would appear as ledeburitic carbides of iron, chromium, and such optional elements as vanadium, molybdenum and tungsten.
The limited disclosure of the Fletcher patent regarding heat treatment gives no indication of the micro-structure of the tempered product and would apparently result in the presence of retained austenite.
There is thus a real need for a method of increasing the resistance to erosion by mechanical and/or mechanical-chemical abrasion in a heat hardenable stainless steel, which also exhibits ease of manuacture and abrication into articles ~f ultimate use, and good corrosion resistance.
It is the principal object of the present invention to provide a method of increasing the abrasion resistance of a heat hardenable stainless steel which, by selection of heat treatment, and observance of critical proportioning of carbon, titanium. and silicon, will exhibit a degree of hardness and abrasion resistance suited to a particular application, toge~her with good hot and cold workability and good corrosion resistance.
It is a further object to provide a stainle~s steel which in heat hardened and stre~s relieved condition exhibits excellent abxasion resistance by reason of a sub-stantially fully martensitic matrix and an absence of ledeburitic carbides.
The above and other incidental objects of the invention, which will be apparent from the discus~ion which follows, are.obtained in a method o~ increasing the abrasion resistance of a heat hardenable stainless ~teel while retaining good c~rrosion re6tstance~ which comprises the steps of providing a stainless st~el mel~ containing, in weight percent, from : ~ . . ......... . . . . ............... . . .
.. . . . . .
., . , . . ~ .
108~9~L
about 0.75% to about 10~ carbon, up to about 1,0% manganese, about 11.5~ to about 18% chromium, up to about 1~ nickel, up to about 1.5% molybdenum, up to about 0.1% phosphorus, up to about 0.05% sulfur, and balance iron except ~or inci-dental impurities, adding silicon in the range of greaterthan 1.7~ to about 4.5~, adding titanium in the range of about 1% to about 10%, proportioning the silicon and titanium additions relative to the carbon content in such manner as to obtain a synergistic improvement in abxasion resistance, casting the steel, heat treating the steel by austenitizing within the temperature range of about 1600 to about 2250F to dissolve sufficient c~rbon to prevent lowering the martensitic transformat~on point and to leave a predetermined proportion of undissoIved carbon in the form of uniformly dispersed partiales of titanium-rich carbides of microscopic siz~, and cooling at a rate sufficient to form a substantially fully martensitic matrix.
Within the above bxoad composition range, a pxacticable upper limit of 5~ carbon should be observed for wrought products formed by hot and cold working in standard mill equipment. With carbon contents above S~, the steel can be produced in th2 cast-to-shape condition, or in a ~m suitable for powder metallurgy techniques, and can be hardened and tempered.
An important aspect of the present invention is the discovery that the increase in abxasion resistance re-sulting ~rom addition of ti~anium alane is ;~estri~ted to a rekatively narrow range and that an increase in th2 titanium content above this range (which varies with the carbon content) results in a decre~se in abrasion resistance, i.e., a reversal of the desired effect~ However, in accoxdance with the present invention, addition of silicon in amounts grea~er than 1.7%
results in progressive increases in abrasion resistance with progressive increases in titanium content. The combined silicon and titanium additions, within the limits defined herein, must thus be reqarded as synergistic, i.e., better abrasion resistance is achieved th~n with addi~ion of an equal amount of either silicon or titanium alone.
In accordance with the invention, a stain-less steel having good coxrosion resistance andexcellent abrasion resistance in a heat hardened state consists essentially of, in weight percent, from about 1.8%
to about 10~ carbon, up to ~bout 1~0~ mangane~e, greater than l.t~ to about 4~5~ silicon, ab~ut 11.5% to about 18%
chromium, up to about 1~ nickel, from about 1% to a~out 10% tltanium, up to about 1.5% molybde~um, up to 0.1%
phosphorus, up to 0.05~ sul~ur, and balance iron except for incidental impurities.
Reference is made to the accompany~drawing wherein;
Fig~ 1 is a graphic illustration of the effects of varying titanium ~nd silicon addition~ on abrasion xesis-tance in a chromium-iron alloy conta~ng about 1% carbon, and Fig. 2 i5 a graphic illustration of the effects of varying titanium and silicon additions on abrasion resis-tance in a chromium-iron alloy containing about 2~ carbon.
While not wishing to be bound by theary, it i5 believed that the function of silicon in impro~ing abrasion or wear resistance is the de~elopment of greater oxidation .
10~91 resistance during wear testing. This results in decrease in ~ -the loss of matrix metal by an oxidation process and provides extended holding o~ the small titanium-enriched carbide particles in place within the matrix. Thus, silicon additions lower the rate of loss of matrix me~al which, in turn, lowers the rate of loss of carbide particles by mechanical erosion.
The stabilizing influence of silicon in retaining or improving abrasion resistance at higher titanium levels is believed to be due to the formation of silicon-titanium intermetallic compounds which apparently pr~ovide continued abrasion resistance.
The reason for the decrease in abrasion resistanc observed for high titanium addit~ons (withou~ compensating increases in silicon content) is unknown but may be due to depletion of the carbon contant of the matrix metal, or lowering of the martensitic transformation temperature thus r sulting in retained austenite in the heat treated product.
Heat treatment of a steel of ~he broad and preferred composition ranges set forth above produces a mar-tensitic stainless steel matrix, containing uniformly dispersedextremely hard abrasion resistant particles of titanium carbide.
These titanium carbide particles are micrsscopic in size and roughly sperical in shape. The creation of a martensitic matrix of high hardness and high compressive yield strength has been found to be necessary to provide the desired high abrasion resistance. In this condition the hard particles of titanium carbide are not forced into the matrix under applied heauy service loads.
Since titanium combines with carbon in a 1 1 atomic ratio, and since titanium carbide is o~ extreme hardness, a .
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~086~a~L
highly efective resistance against abrasion can be achieved at a relatively low alloying level. Moreover, the degree of abrasion or wear resi~tance can be preselected for any given application by varying the carbon and titanium contents and by the heat treatment to which the steel is subjected, there-by controlling the hardness of the martensitic steel matrix and the relative volume of small titanium carbides di~persed in`the ~atrix.
While the presence of iron and chromium make it difficult to develop "pure" -titanium carbides as the bearing-particle or a~rasion-resistance phase, nevertheless this condition can be approached to the extent that only very small pro-portions of iron and chromium exist in the carbide phase. As is well known, the weight ratio of titanium to carbon in titanium carbide is about 4:1. In order to harden and strengthen the matrix a selected carbon level associated with iron and chromium needs to be taken into solution at the hardening temperature. Thus the titanium content will be less than 4 times the total carbon content. The solubility of Z carbon in iron increases with an increase in hardening temp-erature, and this provides the mechanism for controlling the proportion of carbon combined with titanium and hence the relative volume o~ the titanium carbide or bearing- ~
particle phase. At a selected temperature level of soluble ;
carbon, tha undissolved or insoluble carbon is combined with the titanium in the form of titanium carbide or titanium-enriched carbides. It should also be understood that any nitrogen present as an impurity will also react with titanium to produce some titanium cyanonitrides and/or titanium nitxides under ordinary commercial melting practice.
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More specifically, heat treatment temperatures ~or hardening the martensitic matrix range from about 1600 to about 2250F. A greater proportion of carbon is dissolved at the upper limit of this range, and some chromium is dissolved with the carbon, thereby improving the corrosion resistance and hardness of the matrix. On the other hand, titanium car-bides cannot dissolve in the matrix until temperatures higher than about 2050F are attained. While not wishing to be bound by theory, it is believed that about 0.10~ carbon is dissolved at 1600F, about 0.8% carbon is dissolved at 1900F, and about 1.5~ carbon is dissolved at 2200F. Any undissolved carbon remains in the form of titanium carbide. After the desired hardening temperature is reached the steel is cooled by any conventional system including air, a moving gas stream, oil and the like. Thereafter, stress-relieving heat treatment at about 550 to 700F may be applied to hardened sections, as needed for specific applications.
It is an essential feature of the invention that the heat treatment or ~ustenitizing temperature be ~ selected as to take enough carbon into solution that the martensite transformation temperature (Ms) will not be lowered, thus insuring the formation of a substantlally ~ully martensitic matrix on cooling. The cooling rate is not a limitation since the rate of martensite transformation is the governing factor, and thi~ is~dependent on the alloy content of the steel. In general, a cooling rate at least as rapid as air cooling is preferred.
Assuming a steel having a total carbon content of not greater than 5~, after melting and casting, it can be hot rolled, cold rolled, heat treated to dissolve a predetermined . 9 : ~ ' ' ' 9~
percentage or proportion of carbon in the matrix and to leave a selected proportion of the total carbon content in the form of titanium carbides. Alternatively, at relatively low carbon contents, all the carbon can be clissolved by hea~ treatment and a selected proportion can be precipitated as titanium carbide by a controlled cooling rate from the hardening temperature, or by a selected secondary heat treatment.
Exemplary hea~ treatments which may be applied are as follows:
A ~ heat to 1900F, hold 30 minuteS, air cool B - heat to l9Q0F, hold 30 minutes~ air cool, stress relieve at 600F
C - heat to 19009F, hold 30 minutest air cool to 1300QF, hold 1 hr., and air cool or oll ~uench to room temperature D - heat to l900~F, hold 30 minutes, air cool to 1300F, hold 1 hx., air cool or oil quench to room temperature, and stress-relieve at 600~F
As will be apparent from ~he above discussion, the titanium, silicon and carbon contents, and critical propor-tioning thereof, with conse~uent ~ormation of titanium oarbide particles and formation o~ a hard matrix, are responsible for the excellent abrasion re~istance of the steel of the invention.
However, in addition the titanium and carbon aontents are further responsible ~or the ease with which the steel can be hot and cold wor~ed. Parenthetically it should be noted at ~his point that: no prior art martensitic stainless steel con-taining more than about 2.5% carbon can be produced in wrought 9~
form. (The previously mentioned Fletchex patent, while allegingworkability up to 4.25% carbon, actually discloses carbon contents of only 2.35% and 2.7~ in the specific examples.) Accordingly, a permissible increase in carbon up to and including the S% level, while still retaining hot and cold workability, represents a significant contribution to the art~ In the practice of the present invention the tLtanium addition increases the workability o the steel by raising the temper-ature at which the alloy can be hot w~rked. By way of example, the previously mentioned AISI D-2 and D-4 tool steels are hot worked or forged from 1950F and ~rom l~OO~F~ respectively, whereas the steel of the present invention is hot worked from 2100F to 2250F. If the prior art D-2 and D-4 ~tool steels were hot worked from 2150 to 2250F, they would over- -heat and break up during working. Moreover, the titanium addition significantly increases the cold workability of the steel. For example, AISI Type 440C (containing about 1%
carbon) can accept only 15% cold reduction between anneals, whereas a steel of the present lnvention containing about 2%
carbon and about an equal amount o~ titanium can be cold reduced 40~ between anneals.
It is believed th~t the beneficial ef~ects of titanium on the hot and c~ld workabllity of the steel ari~e ; from the shape and size o~ the titanium carbides in the matrix.
Since these are small and spherical in shape the titanium carbides permit easy ~low of the matrix around them during hot and cold working~ Prior art cast alloys and so-called wrought Types ~40 A, B or C contain ledeburitic carbide structures, i.e., large platelets, which impede the ~low of metal around them, ~hereby causing craaking and breaking of the matrix during : , .
~L~86991 hot and cold working. Such ledeburitic caxbide st~uctures are common to hypereutectoid steels generally.
Chromium is also an essential element, a minimum of about 11.5% being necessary to impart good corrosion reqistance and haxdenability to the matrix. In this respect chromium lowers the eutectoid carbon level (from about 0.78% carbon in pure iron) to about 0.35% carbon at about 13~ chromium. More than 18% chro~ium is undesirable since it would ad~ssely affect the hot and cold working propert~es of the steel and unnec-essarily increase the cost of the alloy with no attendantbenefit.
Silicon functions in the same manner as chromium in lowering the eutectoid carbon level and appax~ntly is synergistic with chromium ~n ~his function.
Manganese, nickel, phosphorus and sulfux are non-essential elements in the steel of the invention. A maximum of about 1~ manganese can be tolerat~d and about 0~30% is preferred. Manganese in excess of 1% would he harmul because of its effect of stabilizing the high temperature phase austenite~ Up to a~out 1~ nickel may be present as an impurity without adverse effect/ and phosphorus and sulfur samilarly can be tolerated in amounts up to about 0.10% and 0.005~, respectively.
zirconium may be substituted in part for titanium.
Other carbide formers auch as vanadium and molybdenum may also be added br substituted in part for ~itanium, in amounts up to about 1.5% each, for ~pecial purposes such as increase in corrosion resistance. Columbium should not be added since it adversely affects the hot workability of the steel.
The critic~l proportioning of carbon, titanium and .~ .
.i . .
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silicon, and the synergistic e~ect of silicon additions together with titanium i~ improving abrasion resis~ance, are shown by a series of test heats of steels within and outside the ranges of the invention, the compositions and w~ar test results of which are set forth in Table I. For all samples, spea~s were hot for~ed to 1~2 inch diameter, annealed at 1450F, ma~hined, heat treated by austenitizing at 1850F, held for 30 minutes, and then oil quenched. The surfaces of the specimens were smoothed with 120 grit paper, and abrasion resistance tests were conducted on the Taber Met-Abrader Model 500.
A consideration of the data of Table I showS
that addition of increasing amounts of either silicon or titanium improves the abrasion resistance of a nominal 1~
carbon, chromium-bearing steel (comparison of Sample 1 with Samples 2-71, but that if the titanium addition exceeds about 1.5% and silicon is low ~less than 1.7%), abrasion resistance decreases Samples 8 and 9). However, if silicon is added in excess of 1.7~ when titanium exceeds 1.5%, then abraslon resis~ance is greatly imp~oved (compare Sample 8 and 9 with Sample 10), This efect is illustrated graphicall~ in Fig. 1 ~hich is plotted from the data of Table I. It will be noted therefrom that titanium con~ers a greater increase in abrasion resistance (in amounts up to about 1.5%) than silicon, but that silicon and titanium together, with silicon greater than 1.7% and titanium greater than 1.5%, exhibit a synergistic ef~ect (Samples 10-12).
Turning next to a consideration of a nominal 2%
carbon, chromium-bearing steel, it i~ evident that addition of increasing amounts of either silicon or titanium increases 99~
~b~asion resistance (again w~ith titaniu~ ha~ing a gxeater effect), but that when titanium exceeds about 4% and silicon iS 1QW (less than 1.7%) abrasion resistance decreases (compare Samples 13-15 with 16?. Thi~ is shown graphically in Fig. 2 which is plotted fxom Table I If silicon is added in excess of 1,7~o when titaniu~ exceeds about 4%, abrasion resistance is improved (compaxe Samples 15 and 16 with Samples ~O and 23~ The synergistic effect of silicon and - titanium at higher carbon levels is thus also evident. Figs.
- 10 1 and 2 contain curves in which titanium plus silicon are plotted against abrasion resistance, and progressive increases in the sum total of both cause a synergistic increased abrasion resistance throughout the range investigated.
In the preferred method of the present invention, the~step of proportioning the silicon and titanium additions relative to the carbon content thus comprises adding silicon, in excess of 1,7~O~in direct proportion to titanium when the titanium addition exceeds about 1.5% with a nominal 1% caxbon content, and adding silicon, in excess of 1.7%, in direct proportion to titanium when the titanium addition exceeds about 4% with a nominal 2% carbon c~ntent.
:, .
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~69~1 TABLE I
Compositions - Weight Perc~nt and Abrasion Resistance Wear Number mg/100 cycle Taber Met-Abrader Sample C 9i Cr Ti Model 500 1 0.96 0.65 12.31 0.01 22,000
Currently available alloys capable of withstanding high stress, abrasive conditions are produced as castings onl~ and are not amena~le to production in wrought form.
Among~such prior art iron base alloys are chromium-~olybdenum white cast iron (analyzing about 3.2% carbon, about 0.6~
silicon, a~out 15.0% chromium, about 3.0% molybdenum, and balance iron), and high chromium white cast iron (analyzing about 2.7% carbon, about 0.65~ silicon, about 27.0~ chromium, and balance ironl. Other such alloys are tool steels, e.g.
AISI Type ~-2 (1.50-1.60% carbon, 0.30-0.45% silicon, 11.50-:.
12.50% chromium, 0.75 0.85~ molybdenum, 0.70-0.90~ vanadium, and balance iron), and AISI ~ype D-4 (2.0-2.30% carbon, 0.20-0.45~ ~ilicon, 11.50-12.50% chromium, 0.70-0.90 molybdenum, 0.30-0.50~ vanadium and balance iron).
Prior art martensitic stainless steels classified as wrought steels, such as AISI Types 440 A, B and C, actually can be~hot and cold worked in standard mill equipment only with great dificulty. Moreover, these steels, which .
~ 699~ ~
contain up to about 1.2~ carbon, are deficient in abrasion resistance under very high stress, abrasive conditions.
United States Patent ~o. 3,692,515 issued September 19, 1972 to S.G. Fletcher et al, cliscloses a steel alleged to have improved abrasion resistance, forgeability and work-ability consisting essentially of about 1% to about 4.25 carbon, about 1.5% maximum silicon, about 1.5~ maximum manganese, about 10~ to about 15~ chromium, less than 2%
molybdenum, about 0.5% to about ~% titanium, less than 3%
tungsten, less than 3% nickel, less than 5% cobalt, less than 5~ vanadium, up to 0.25% sulfur, and balance iron with residual impurities. A preferred composition contains 2O9 carbon, 0.4% silicon,0.4% manganese, 12.5% chromium, 1.1~
molybdenum, 3% titanium, and balance substantially iron with residual impurities. It is stated that carbon is added in excess of that necessary to ~ive a desired hardenability and that such excess carbon is combined with titanium in a weight ratio of 4:1 and vanadium in a weight ratio of 4.2 (V-l):l.
The cast alloy is reduced in cross sectional area by at 2Q least 5% by working, and heat treated by austenitizing at 1600 to 1950F and tempering at 900 to 950~F.
The maximum austenitizing temperature of 1950F
disclosed in the ~letcher patent limits the amount o~ dis-solved carbon to about 0.7~ to 0.8% maximum. If no vanadium is present, the excess carbon content in the preferred practice would be Ti/4, or 3/4 (th~ preferred titanium content being 3%), i.e. 0.75~. Thus the total carbon content should be 1.45~ to 1~55~. Since the excess carbon cannot all be dis-solved and since ~he amount~of titanium is insufficient to combiné with all the excess carbon, that portion of the ca~bon - , ~
~ ' ~ . ' ' ' ' ' ' , ' , .
~q~8~99~
not in solution and not in the form of titanium carbides would appear as ledeburitic carbides of iron, chromium, and such optional elements as vanadium, molybdenum and tungsten.
The limited disclosure of the Fletcher patent regarding heat treatment gives no indication of the micro-structure of the tempered product and would apparently result in the presence of retained austenite.
There is thus a real need for a method of increasing the resistance to erosion by mechanical and/or mechanical-chemical abrasion in a heat hardenable stainless steel, which also exhibits ease of manuacture and abrication into articles ~f ultimate use, and good corrosion resistance.
It is the principal object of the present invention to provide a method of increasing the abrasion resistance of a heat hardenable stainless steel which, by selection of heat treatment, and observance of critical proportioning of carbon, titanium. and silicon, will exhibit a degree of hardness and abrasion resistance suited to a particular application, toge~her with good hot and cold workability and good corrosion resistance.
It is a further object to provide a stainle~s steel which in heat hardened and stre~s relieved condition exhibits excellent abxasion resistance by reason of a sub-stantially fully martensitic matrix and an absence of ledeburitic carbides.
The above and other incidental objects of the invention, which will be apparent from the discus~ion which follows, are.obtained in a method o~ increasing the abrasion resistance of a heat hardenable stainless ~teel while retaining good c~rrosion re6tstance~ which comprises the steps of providing a stainless st~el mel~ containing, in weight percent, from : ~ . . ......... . . . . ............... . . .
.. . . . . .
., . , . . ~ .
108~9~L
about 0.75% to about 10~ carbon, up to about 1,0% manganese, about 11.5~ to about 18% chromium, up to about 1~ nickel, up to about 1.5% molybdenum, up to about 0.1% phosphorus, up to about 0.05% sulfur, and balance iron except ~or inci-dental impurities, adding silicon in the range of greaterthan 1.7~ to about 4.5~, adding titanium in the range of about 1% to about 10%, proportioning the silicon and titanium additions relative to the carbon content in such manner as to obtain a synergistic improvement in abxasion resistance, casting the steel, heat treating the steel by austenitizing within the temperature range of about 1600 to about 2250F to dissolve sufficient c~rbon to prevent lowering the martensitic transformat~on point and to leave a predetermined proportion of undissoIved carbon in the form of uniformly dispersed partiales of titanium-rich carbides of microscopic siz~, and cooling at a rate sufficient to form a substantially fully martensitic matrix.
Within the above bxoad composition range, a pxacticable upper limit of 5~ carbon should be observed for wrought products formed by hot and cold working in standard mill equipment. With carbon contents above S~, the steel can be produced in th2 cast-to-shape condition, or in a ~m suitable for powder metallurgy techniques, and can be hardened and tempered.
An important aspect of the present invention is the discovery that the increase in abxasion resistance re-sulting ~rom addition of ti~anium alane is ;~estri~ted to a rekatively narrow range and that an increase in th2 titanium content above this range (which varies with the carbon content) results in a decre~se in abrasion resistance, i.e., a reversal of the desired effect~ However, in accoxdance with the present invention, addition of silicon in amounts grea~er than 1.7%
results in progressive increases in abrasion resistance with progressive increases in titanium content. The combined silicon and titanium additions, within the limits defined herein, must thus be reqarded as synergistic, i.e., better abrasion resistance is achieved th~n with addi~ion of an equal amount of either silicon or titanium alone.
In accordance with the invention, a stain-less steel having good coxrosion resistance andexcellent abrasion resistance in a heat hardened state consists essentially of, in weight percent, from about 1.8%
to about 10~ carbon, up to ~bout 1~0~ mangane~e, greater than l.t~ to about 4~5~ silicon, ab~ut 11.5% to about 18%
chromium, up to about 1~ nickel, from about 1% to a~out 10% tltanium, up to about 1.5% molybde~um, up to 0.1%
phosphorus, up to 0.05~ sul~ur, and balance iron except for incidental impurities.
Reference is made to the accompany~drawing wherein;
Fig~ 1 is a graphic illustration of the effects of varying titanium ~nd silicon addition~ on abrasion xesis-tance in a chromium-iron alloy conta~ng about 1% carbon, and Fig. 2 i5 a graphic illustration of the effects of varying titanium and silicon additions on abrasion resis-tance in a chromium-iron alloy containing about 2~ carbon.
While not wishing to be bound by theary, it i5 believed that the function of silicon in impro~ing abrasion or wear resistance is the de~elopment of greater oxidation .
10~91 resistance during wear testing. This results in decrease in ~ -the loss of matrix metal by an oxidation process and provides extended holding o~ the small titanium-enriched carbide particles in place within the matrix. Thus, silicon additions lower the rate of loss of matrix me~al which, in turn, lowers the rate of loss of carbide particles by mechanical erosion.
The stabilizing influence of silicon in retaining or improving abrasion resistance at higher titanium levels is believed to be due to the formation of silicon-titanium intermetallic compounds which apparently pr~ovide continued abrasion resistance.
The reason for the decrease in abrasion resistanc observed for high titanium addit~ons (withou~ compensating increases in silicon content) is unknown but may be due to depletion of the carbon contant of the matrix metal, or lowering of the martensitic transformation temperature thus r sulting in retained austenite in the heat treated product.
Heat treatment of a steel of ~he broad and preferred composition ranges set forth above produces a mar-tensitic stainless steel matrix, containing uniformly dispersedextremely hard abrasion resistant particles of titanium carbide.
These titanium carbide particles are micrsscopic in size and roughly sperical in shape. The creation of a martensitic matrix of high hardness and high compressive yield strength has been found to be necessary to provide the desired high abrasion resistance. In this condition the hard particles of titanium carbide are not forced into the matrix under applied heauy service loads.
Since titanium combines with carbon in a 1 1 atomic ratio, and since titanium carbide is o~ extreme hardness, a .
.
~086~a~L
highly efective resistance against abrasion can be achieved at a relatively low alloying level. Moreover, the degree of abrasion or wear resi~tance can be preselected for any given application by varying the carbon and titanium contents and by the heat treatment to which the steel is subjected, there-by controlling the hardness of the martensitic steel matrix and the relative volume of small titanium carbides di~persed in`the ~atrix.
While the presence of iron and chromium make it difficult to develop "pure" -titanium carbides as the bearing-particle or a~rasion-resistance phase, nevertheless this condition can be approached to the extent that only very small pro-portions of iron and chromium exist in the carbide phase. As is well known, the weight ratio of titanium to carbon in titanium carbide is about 4:1. In order to harden and strengthen the matrix a selected carbon level associated with iron and chromium needs to be taken into solution at the hardening temperature. Thus the titanium content will be less than 4 times the total carbon content. The solubility of Z carbon in iron increases with an increase in hardening temp-erature, and this provides the mechanism for controlling the proportion of carbon combined with titanium and hence the relative volume o~ the titanium carbide or bearing- ~
particle phase. At a selected temperature level of soluble ;
carbon, tha undissolved or insoluble carbon is combined with the titanium in the form of titanium carbide or titanium-enriched carbides. It should also be understood that any nitrogen present as an impurity will also react with titanium to produce some titanium cyanonitrides and/or titanium nitxides under ordinary commercial melting practice.
,.: , . .
9~
More specifically, heat treatment temperatures ~or hardening the martensitic matrix range from about 1600 to about 2250F. A greater proportion of carbon is dissolved at the upper limit of this range, and some chromium is dissolved with the carbon, thereby improving the corrosion resistance and hardness of the matrix. On the other hand, titanium car-bides cannot dissolve in the matrix until temperatures higher than about 2050F are attained. While not wishing to be bound by theory, it is believed that about 0.10~ carbon is dissolved at 1600F, about 0.8% carbon is dissolved at 1900F, and about 1.5~ carbon is dissolved at 2200F. Any undissolved carbon remains in the form of titanium carbide. After the desired hardening temperature is reached the steel is cooled by any conventional system including air, a moving gas stream, oil and the like. Thereafter, stress-relieving heat treatment at about 550 to 700F may be applied to hardened sections, as needed for specific applications.
It is an essential feature of the invention that the heat treatment or ~ustenitizing temperature be ~ selected as to take enough carbon into solution that the martensite transformation temperature (Ms) will not be lowered, thus insuring the formation of a substantlally ~ully martensitic matrix on cooling. The cooling rate is not a limitation since the rate of martensite transformation is the governing factor, and thi~ is~dependent on the alloy content of the steel. In general, a cooling rate at least as rapid as air cooling is preferred.
Assuming a steel having a total carbon content of not greater than 5~, after melting and casting, it can be hot rolled, cold rolled, heat treated to dissolve a predetermined . 9 : ~ ' ' ' 9~
percentage or proportion of carbon in the matrix and to leave a selected proportion of the total carbon content in the form of titanium carbides. Alternatively, at relatively low carbon contents, all the carbon can be clissolved by hea~ treatment and a selected proportion can be precipitated as titanium carbide by a controlled cooling rate from the hardening temperature, or by a selected secondary heat treatment.
Exemplary hea~ treatments which may be applied are as follows:
A ~ heat to 1900F, hold 30 minuteS, air cool B - heat to l9Q0F, hold 30 minutes~ air cool, stress relieve at 600F
C - heat to 19009F, hold 30 minutest air cool to 1300QF, hold 1 hr., and air cool or oll ~uench to room temperature D - heat to l900~F, hold 30 minutes, air cool to 1300F, hold 1 hx., air cool or oil quench to room temperature, and stress-relieve at 600~F
As will be apparent from ~he above discussion, the titanium, silicon and carbon contents, and critical propor-tioning thereof, with conse~uent ~ormation of titanium oarbide particles and formation o~ a hard matrix, are responsible for the excellent abrasion re~istance of the steel of the invention.
However, in addition the titanium and carbon aontents are further responsible ~or the ease with which the steel can be hot and cold wor~ed. Parenthetically it should be noted at ~his point that: no prior art martensitic stainless steel con-taining more than about 2.5% carbon can be produced in wrought 9~
form. (The previously mentioned Fletchex patent, while allegingworkability up to 4.25% carbon, actually discloses carbon contents of only 2.35% and 2.7~ in the specific examples.) Accordingly, a permissible increase in carbon up to and including the S% level, while still retaining hot and cold workability, represents a significant contribution to the art~ In the practice of the present invention the tLtanium addition increases the workability o the steel by raising the temper-ature at which the alloy can be hot w~rked. By way of example, the previously mentioned AISI D-2 and D-4 tool steels are hot worked or forged from 1950F and ~rom l~OO~F~ respectively, whereas the steel of the present invention is hot worked from 2100F to 2250F. If the prior art D-2 and D-4 ~tool steels were hot worked from 2150 to 2250F, they would over- -heat and break up during working. Moreover, the titanium addition significantly increases the cold workability of the steel. For example, AISI Type 440C (containing about 1%
carbon) can accept only 15% cold reduction between anneals, whereas a steel of the present lnvention containing about 2%
carbon and about an equal amount o~ titanium can be cold reduced 40~ between anneals.
It is believed th~t the beneficial ef~ects of titanium on the hot and c~ld workabllity of the steel ari~e ; from the shape and size o~ the titanium carbides in the matrix.
Since these are small and spherical in shape the titanium carbides permit easy ~low of the matrix around them during hot and cold working~ Prior art cast alloys and so-called wrought Types ~40 A, B or C contain ledeburitic carbide structures, i.e., large platelets, which impede the ~low of metal around them, ~hereby causing craaking and breaking of the matrix during : , .
~L~86991 hot and cold working. Such ledeburitic caxbide st~uctures are common to hypereutectoid steels generally.
Chromium is also an essential element, a minimum of about 11.5% being necessary to impart good corrosion reqistance and haxdenability to the matrix. In this respect chromium lowers the eutectoid carbon level (from about 0.78% carbon in pure iron) to about 0.35% carbon at about 13~ chromium. More than 18% chro~ium is undesirable since it would ad~ssely affect the hot and cold working propert~es of the steel and unnec-essarily increase the cost of the alloy with no attendantbenefit.
Silicon functions in the same manner as chromium in lowering the eutectoid carbon level and appax~ntly is synergistic with chromium ~n ~his function.
Manganese, nickel, phosphorus and sulfux are non-essential elements in the steel of the invention. A maximum of about 1~ manganese can be tolerat~d and about 0~30% is preferred. Manganese in excess of 1% would he harmul because of its effect of stabilizing the high temperature phase austenite~ Up to a~out 1~ nickel may be present as an impurity without adverse effect/ and phosphorus and sulfur samilarly can be tolerated in amounts up to about 0.10% and 0.005~, respectively.
zirconium may be substituted in part for titanium.
Other carbide formers auch as vanadium and molybdenum may also be added br substituted in part for ~itanium, in amounts up to about 1.5% each, for ~pecial purposes such as increase in corrosion resistance. Columbium should not be added since it adversely affects the hot workability of the steel.
The critic~l proportioning of carbon, titanium and .~ .
.i . .
' ' ' : ., ~o~9~
silicon, and the synergistic e~ect of silicon additions together with titanium i~ improving abrasion resis~ance, are shown by a series of test heats of steels within and outside the ranges of the invention, the compositions and w~ar test results of which are set forth in Table I. For all samples, spea~s were hot for~ed to 1~2 inch diameter, annealed at 1450F, ma~hined, heat treated by austenitizing at 1850F, held for 30 minutes, and then oil quenched. The surfaces of the specimens were smoothed with 120 grit paper, and abrasion resistance tests were conducted on the Taber Met-Abrader Model 500.
A consideration of the data of Table I showS
that addition of increasing amounts of either silicon or titanium improves the abrasion resistance of a nominal 1~
carbon, chromium-bearing steel (comparison of Sample 1 with Samples 2-71, but that if the titanium addition exceeds about 1.5% and silicon is low ~less than 1.7%), abrasion resistance decreases Samples 8 and 9). However, if silicon is added in excess of 1.7~ when titanium exceeds 1.5%, then abraslon resis~ance is greatly imp~oved (compare Sample 8 and 9 with Sample 10), This efect is illustrated graphicall~ in Fig. 1 ~hich is plotted from the data of Table I. It will be noted therefrom that titanium con~ers a greater increase in abrasion resistance (in amounts up to about 1.5%) than silicon, but that silicon and titanium together, with silicon greater than 1.7% and titanium greater than 1.5%, exhibit a synergistic ef~ect (Samples 10-12).
Turning next to a consideration of a nominal 2%
carbon, chromium-bearing steel, it i~ evident that addition of increasing amounts of either silicon or titanium increases 99~
~b~asion resistance (again w~ith titaniu~ ha~ing a gxeater effect), but that when titanium exceeds about 4% and silicon iS 1QW (less than 1.7%) abrasion resistance decreases (compare Samples 13-15 with 16?. Thi~ is shown graphically in Fig. 2 which is plotted fxom Table I If silicon is added in excess of 1,7~o when titaniu~ exceeds about 4%, abrasion resistance is improved (compaxe Samples 15 and 16 with Samples ~O and 23~ The synergistic effect of silicon and - titanium at higher carbon levels is thus also evident. Figs.
- 10 1 and 2 contain curves in which titanium plus silicon are plotted against abrasion resistance, and progressive increases in the sum total of both cause a synergistic increased abrasion resistance throughout the range investigated.
In the preferred method of the present invention, the~step of proportioning the silicon and titanium additions relative to the carbon content thus comprises adding silicon, in excess of 1,7~O~in direct proportion to titanium when the titanium addition exceeds about 1.5% with a nominal 1% caxbon content, and adding silicon, in excess of 1.7%, in direct proportion to titanium when the titanium addition exceeds about 4% with a nominal 2% carbon c~ntent.
:, .
~. , . . , . , , : . ~ .. .
~69~1 TABLE I
Compositions - Weight Perc~nt and Abrasion Resistance Wear Number mg/100 cycle Taber Met-Abrader Sample C 9i Cr Ti Model 500 1 0.96 0.65 12.31 0.01 22,000
2 1.00 2.76 12.00 0.02 16,500
3 1.02 3.86 11.87 0.03 11,500
4 1.03 0.38 12.00 0.47 16,000 1.02 0.42 11.9~ 0.98 11,000 6 1~01 1.6~ 11.88 0.92 9,500 7 0.87 0.56 12.~0 1.43 10,800 8 1.02 ~.42 11.72 2.72 15,700 9 1.00 0.42 11.50 3~68 23,300 1.02 1.78 11.80 2.44 7-,560 11 0~95 3.11 11.99 1.72 6,500 12 0.81 4.41 11.9~ 1.54 5,500 13 2.14 0,55 11.54 1.26 4,090 14 2.34 0.50 12.03 2.14 3,400 2.35 0.51 12~00 3.84 3,000 16 2.06 0.75 12.55 5.20 4,100 17 2.30 0.46 11.87 2.28 3,150 18~ 2.05 0.67 13~]0 3.54 Mo 1.22 3,180 19* 2.28 1.75 12.01 2.31 2,~00 20* 2.12 1.83 11.97 4.18 2,550 21* 2.19 2.91 12.04 1.30 3,100 22* 2.22~ 2.8~ 12.01 2.31 2,450 23* 2.32 2.96 11.94 4.26 2,100 Residual elements in all above heats were 1% maximum Mn, 0~50~ maximum Ni, 0.030~ maximum P, 0.030~ maximum S.
*--Steels of the inve~tion.
' ~ ' .
~86g9~
The method of the invention is thus evident from the above description and tests. It is further apparent that articles and fabxicated products, such as materials processing equipment, having an abrasion resistance of less than 3,S00 milligrams per 1,000 cycles by the Taber Met-Ahrader Model 500 test can be produced in heat hardened aondition by the method of the invention fxom the steel of the invention, consisting essentially of, in weight percent fxom about 1.8% to about 10%
carbon, up to about 1.0~ manganese, greater than 1.7% to about 4.5% silicon, about 11.5% to about 18% chromium, up to about 1% nickel, rom about 1% to about 10% titanium, up to about 1.5~ molybdenum, up to about 0~1% phosphorus, up to about 0.05 sulfur, and balance ixon except for inaidental impurities.
B~th cast and ~rought articles of ultimate use may be involved having the above pxoperties, the steel composition being restricted to a maximum of abou 5% carbon ~or hot worked and cold worked articles prior to the heat treatment step.
If cold working is practiced, a stress relie treatment at about 550 to 700F is preferably conducted a~ter the heat hardening treatment. At carbon 1evels above 5~, cast articles of ultimate use, and partlculate materlal suitable for powder metallurgy processing such as compacting and sintering, may be produced and subjected to heat hardening.
Where ext~emely high abrasion resistance and hard-ness are desired and hot and~ar cold workability are not needed (as in commercial tungsten carbon tooling wherein carbide particles are bonded with nickel and/or cobalt, with the volume proportion of carbides being about 90%), high carbon and titanium embodiments of the steel of the invention can be sub-stituted with resultant lower cost for total alloy additions.
~019699~
.
For such applications the above compositlon is utilized witha carbon range of greater than 5% to about 10%, and a titanium range of greater than 5% to about 10%.
As will be evident from Samp~e 18 in Table I
molybdenum may be added in amounts up to about 1.5~ without adverse effect on abrasiQn resistance, and such a modification can be used where improved corrosion resistance i9 desired.
-~';
,,:
'' .
.'`
:, . .
.: . .
*--Steels of the inve~tion.
' ~ ' .
~86g9~
The method of the invention is thus evident from the above description and tests. It is further apparent that articles and fabxicated products, such as materials processing equipment, having an abrasion resistance of less than 3,S00 milligrams per 1,000 cycles by the Taber Met-Ahrader Model 500 test can be produced in heat hardened aondition by the method of the invention fxom the steel of the invention, consisting essentially of, in weight percent fxom about 1.8% to about 10%
carbon, up to about 1.0~ manganese, greater than 1.7% to about 4.5% silicon, about 11.5% to about 18% chromium, up to about 1% nickel, rom about 1% to about 10% titanium, up to about 1.5~ molybdenum, up to about 0~1% phosphorus, up to about 0.05 sulfur, and balance ixon except for inaidental impurities.
B~th cast and ~rought articles of ultimate use may be involved having the above pxoperties, the steel composition being restricted to a maximum of abou 5% carbon ~or hot worked and cold worked articles prior to the heat treatment step.
If cold working is practiced, a stress relie treatment at about 550 to 700F is preferably conducted a~ter the heat hardening treatment. At carbon 1evels above 5~, cast articles of ultimate use, and partlculate materlal suitable for powder metallurgy processing such as compacting and sintering, may be produced and subjected to heat hardening.
Where ext~emely high abrasion resistance and hard-ness are desired and hot and~ar cold workability are not needed (as in commercial tungsten carbon tooling wherein carbide particles are bonded with nickel and/or cobalt, with the volume proportion of carbides being about 90%), high carbon and titanium embodiments of the steel of the invention can be sub-stituted with resultant lower cost for total alloy additions.
~019699~
.
For such applications the above compositlon is utilized witha carbon range of greater than 5% to about 10%, and a titanium range of greater than 5% to about 10%.
As will be evident from Samp~e 18 in Table I
molybdenum may be added in amounts up to about 1.5~ without adverse effect on abrasiQn resistance, and such a modification can be used where improved corrosion resistance i9 desired.
-~';
,,:
'' .
.'`
:, . .
.: . .
Claims (13)
1. A stainless steel having good corrosion resist-ance and excellent abrasion resistance in a heat hardened state, consisting essentially of, in weight percent, from about 1.8% to about 10% carbon, up to about 1.0% manganese, greater than 1.7% to about 4.5% silicon, about 11.5% to about 18% chromium up to about 1% nickel, about 1% to about 10% titanium, up to about 1.5% molybdenum, up to about 0.1%
phosphorus, up to about 0.05% sulfur, and balance iron except for incidental impurities.
phosphorus, up to about 0.05% sulfur, and balance iron except for incidental impurities.
2. Steel according to claim 1, wherein carbon is from about 1.8% to about 5% and titanium is from greater than 4% to about 10%.
3. Steel according to claim 1, wherein carbon is from about 5% to 10%.
4. Steel according to claim 1, wherein titanium is from greater than 4% to about 10%.
5. Steel according to claim 1, where carbon is from greater than about 5% to 10% and titanium is from greater than about 5% to about 10%.
6. A method of increasing the abrasion resistance of a heat hardenable stainless steel while retaining good corrosion resistance, which comprises the steps of providing a stainless steel melt containing, in weight percent, from about 0.75% to about 10% carbon, up to about 1.0% manganese, about 11.5% to about 18% chromium, up to about 1% nickel, up to about 1.5% molybdenum, up to about 0.1% phosphorus, up to about 0.05% sulfur, and balance iron except for incidental impurities, adding silicon within the range of greater than 1.7% to about 4.5% and adding titanium within the range of about 1% to about 10%, proportioning the silicon and titanium additions relative to the carbon content in such manner as to obtain a synergistic improvement in abrasion resistance, casting the steel, heat treating the steel by austenitizing within the temperature range of about 1600° to about 2250°F.
to dissolve sufficient carbon to prevent lowering the martensitic transformation point and to leave a predetermined proportion of undissolved carbon in the form of uniformly dispersed particles of titanium-rich carbides of microscopic size, and cooling at a rate sufficient to form a substantially fully martensitic matrix.
to dissolve sufficient carbon to prevent lowering the martensitic transformation point and to leave a predetermined proportion of undissolved carbon in the form of uniformly dispersed particles of titanium-rich carbides of microscopic size, and cooling at a rate sufficient to form a substantially fully martensitic matrix.
7. Method according to claim 6, wherein the carbon content is restricted to a maximum of about 5%, and including the step of reducing said casting to final thickness by hot working.
8. Method according to claim 7, wherein said heat treating includes austentizing the hot worked steel at a temperature of about 1850° to about 1900°F., holding at temperature for about 30 minutes, and cooling at a rate at least as rapid as air cooling.
9. Method according to claim 6, wherein the carbon content is restricted to a maximum of about 5%, and including the step of reducing said casting to final thickness by hot and cold working.
10. Method according to claim 9, wherein said heat treating includes austenitizing the cold worked steel at a temperature of about 1850° to about 1900°F, holding at temperature for about 30 minutes, cooling at a rate at least as rapid as air cooling, and stress relieving by heating at a temperature of about 550° to about 700°F.
11. Method according to claim 6, wherein silicon is added, excess of 1.7%, in direct proportion to titanium when titanium is added in excess of about 1,5% with a nominal 1% carbon content, and wherein silicon is added, in excess of 1.7%, in direct proportion to titanium when titanium is added in excess of about 4% with a nominal 2% carbon content.
12. A stainless steel having good corrosion resist-ance and excellent abrasion resistance in a heat hardened state, produced in accordance with the method of claim 6, consisting essentially of, in weight percent, from about 1.8%
to about 10% carbon, up to about 1.0% manganese, greater than 1.7% to about 4.5% silicon, about 11.5% to about 18% chromium, up to about 1% nickel, about 1% to about 10% titanium, up to about 1.5% molybdenum, up to about 0.1% phosphorus, up to about 0.05% sulfur, and balance iron except for incidental impurities.
to about 10% carbon, up to about 1.0% manganese, greater than 1.7% to about 4.5% silicon, about 11.5% to about 18% chromium, up to about 1% nickel, about 1% to about 10% titanium, up to about 1.5% molybdenum, up to about 0.1% phosphorus, up to about 0.05% sulfur, and balance iron except for incidental impurities.
13. A stainless steel according to claim 12, having an abrasion resistance of less than 3,500 milligrams per 1,000 cycles by the Taber Met-Abrader Model 500 test described herein, where carbon is from about 1.8% to about 5% and titanium is from greater than 4% to about 10%.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA285,202A CA1086991A (en) | 1977-08-22 | 1977-08-22 | Abrasion resistant stainless steel |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA285,202A CA1086991A (en) | 1977-08-22 | 1977-08-22 | Abrasion resistant stainless steel |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1086991A true CA1086991A (en) | 1980-10-07 |
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ID=4109380
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA285,202A Expired CA1086991A (en) | 1977-08-22 | 1977-08-22 | Abrasion resistant stainless steel |
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| Country | Link |
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| CA (1) | CA1086991A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2573440A1 (en) * | 1984-11-19 | 1986-05-23 | Cabot Corp | NUCLEAR QUALITY STEELS AND ALLOYS |
| CN100387747C (en) * | 2006-08-21 | 2008-05-14 | 苏州利德纺织机件有限公司 | Particle cutting knife material and its preparation method |
-
1977
- 1977-08-22 CA CA285,202A patent/CA1086991A/en not_active Expired
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2573440A1 (en) * | 1984-11-19 | 1986-05-23 | Cabot Corp | NUCLEAR QUALITY STEELS AND ALLOYS |
| US4643767A (en) * | 1984-11-19 | 1987-02-17 | Cabot Corporation | Nuclear grade steels |
| CN100387747C (en) * | 2006-08-21 | 2008-05-14 | 苏州利德纺织机件有限公司 | Particle cutting knife material and its preparation method |
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