CA1137337A - Tough, high-strength steels, articles made therefrom and process for their production - Google Patents
Tough, high-strength steels, articles made therefrom and process for their productionInfo
- Publication number
- CA1137337A CA1137337A CA000325474A CA325474A CA1137337A CA 1137337 A CA1137337 A CA 1137337A CA 000325474 A CA000325474 A CA 000325474A CA 325474 A CA325474 A CA 325474A CA 1137337 A CA1137337 A CA 1137337A
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- Canada
- Prior art keywords
- steel
- range
- martensite point
- transformation
- carried out
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 68
- 239000010959 steel Substances 0.000 title claims abstract description 68
- 238000000034 method Methods 0.000 title claims description 15
- 230000008569 process Effects 0.000 title claims description 14
- 238000004519 manufacturing process Methods 0.000 title claims description 5
- 229910000734 martensite Inorganic materials 0.000 claims abstract description 44
- 230000009466 transformation Effects 0.000 claims abstract description 31
- 238000005279 austempering Methods 0.000 claims abstract description 20
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 16
- 239000000203 mixture Substances 0.000 claims abstract description 15
- 229910052748 manganese Inorganic materials 0.000 claims abstract description 10
- 229910052750 molybdenum Inorganic materials 0.000 claims abstract description 10
- 229910052804 chromium Inorganic materials 0.000 claims abstract description 9
- 239000012535 impurity Substances 0.000 claims abstract description 8
- 229910052742 iron Inorganic materials 0.000 claims abstract description 8
- 238000010438 heat treatment Methods 0.000 claims description 10
- 230000000694 effects Effects 0.000 claims description 3
- 229910052751 metal Inorganic materials 0.000 abstract description 3
- 239000002184 metal Substances 0.000 abstract description 3
- 241000251468 Actinopterygii Species 0.000 abstract 1
- 229910045601 alloy Inorganic materials 0.000 description 25
- 239000000956 alloy Substances 0.000 description 25
- 239000011651 chromium Substances 0.000 description 10
- 238000005275 alloying Methods 0.000 description 5
- 230000015572 biosynthetic process Effects 0.000 description 5
- 239000000463 material Substances 0.000 description 4
- 230000008859 change Effects 0.000 description 2
- 239000000470 constituent Substances 0.000 description 2
- 238000000844 transformation Methods 0.000 description 2
- 229910052720 vanadium Inorganic materials 0.000 description 2
- 229910000851 Alloy steel Inorganic materials 0.000 description 1
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 1
- 229910017709 Ni Co Inorganic materials 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 229910052796 boron Inorganic materials 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 230000008878 coupling Effects 0.000 description 1
- 238000010168 coupling process Methods 0.000 description 1
- 238000005859 coupling reaction Methods 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 229910052721 tungsten Inorganic materials 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/18—Hardening; Quenching with or without subsequent tempering
- C21D1/19—Hardening; Quenching with or without subsequent tempering by interrupted quenching
- C21D1/20—Isothermal quenching, e.g. bainitic hardening
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
-
- 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
-
- 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
- C22C38/22—Ferrous alloys, e.g. steel alloys containing chromium with molybdenum or tungsten
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Heat Treatment Of Steel (AREA)
- Heat Treatment Of Articles (AREA)
- Control Of Heat Treatment Processes (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A steel composition possessing both high toughness and strength, having the composition 0.50 - 1.00 % C, 0.10 - 1.50 % Si, 0.25 - 1.50 % Mn, max. 0.045 % P, max. 0.045 % S, en element selected from the group consisting of 0.20 - 0.90 % Mo and 0.20 - 2.00 % Cr, with the remainder being iron and normal impurities and which is formed by subjecting the composition to austempering in the temperature range of the martensite point or in the temperature range immediately above the martensite point to obtain a degree of transformation up to 85% Articles made from the composition are also disclosed, which include fastening devices such as screws, nails, bolts, rivets and the like, and machine parts and elements such as drills, shafts, dics, sprinas, and weapons and armour plate and marine and sporting articles such as chain, fish hooks, ski edges, and semi-manufactured articles such as wire, sheet metal, metal bar and tubes.
A steel composition possessing both high toughness and strength, having the composition 0.50 - 1.00 % C, 0.10 - 1.50 % Si, 0.25 - 1.50 % Mn, max. 0.045 % P, max. 0.045 % S, en element selected from the group consisting of 0.20 - 0.90 % Mo and 0.20 - 2.00 % Cr, with the remainder being iron and normal impurities and which is formed by subjecting the composition to austempering in the temperature range of the martensite point or in the temperature range immediately above the martensite point to obtain a degree of transformation up to 85% Articles made from the composition are also disclosed, which include fastening devices such as screws, nails, bolts, rivets and the like, and machine parts and elements such as drills, shafts, dics, sprinas, and weapons and armour plate and marine and sporting articles such as chain, fish hooks, ski edges, and semi-manufactured articles such as wire, sheet metal, metal bar and tubes.
Description
The invention relates to alloy steels of high tough-ness and strength, or having extremely high strength, to articles which contain such alloy steels, and to processes for producing such alloy steels and arti~les.
It is known that by the addition of large amounts of valuable alloys to steel, it is possible to produce alloy steels which possess both high toughness as well as high strength. However, due to the high production costs and tech-nical problems encountered, alloys of this type can only be used for special purposes in practice. Frequent attempts to produce alloy steels of high toughness and strength by more economical mehods have been made. However, a really satisfactory solution has not yet been found.
For example, high alloy steels of high strength and toughness are known, for example, those having material numbers 1.6357 x 2 Ni Co Mo 18 8 3, 1.6358 and 1.6359. However, these steels have poor deformation and cutting properties and they are not very economical due to the high cost of the alloy constituents.
We have discovered alloy steels and articles there-from which posses high toughness and strength in the absence of significant amounts of valuable alloy constituents and which may reach extremely high strength values. Articles made from the alloy steels of the present invention include bolts or drive-in bolts of conventional shape suitahle for direct fast-ening and it is possible to drive these articles into high-strength constructional steel.
The steel of the present invention comprises unalloyed or low-alloyed steels which are austemperable, slow to transform and have a low martensite point, and articles containing such '~L
alloys. The composition of the steel is:
0.50 - 1.00 ~ C, 0.10 - 1.50 % Si, 0.25 - 1.50 ~ Mn, max. 0.045 ~ P, max. 0.045 % S, and Mo and/or Cr in amounts of 0.20 - 0.90 % Mo, and 0.20 - 2.00 % Cr, all percentages being % by weight, with the remainder being iron and, possibly, insignificant amounts of alloying elements and normal impurities.
The steel of the invention is obtained by subjecting this composition to austempering at temperatures in the range of the martensite formation temperature, or in the temperature range immediately above the former, to a degree of transforma-tion of about 85%. In this case, one part Mo can be substituted by, for example, one part Cr. Generally, molydenum is preferred over chromium. In special cases, the lower limit of the Mn content may be 0.25%.
The invention is based on the general finding that alloy steels and articles made therefrom possess both high toughness and strength when they have been subjected to an incomplete austempering ~heat treatment) in the temperature range of the martensite point, or in the temperature range slightly above the martensite point, until they are transformed in the order of magnitude of, at most, about 85~. Usually, both of these properties are not present simultaneously in any given steel.
In most cases, the martensite point is in the range .~
from about 180 to 280C and particularly is in the range from about 180 to 230C, and is most often in the range from about 185 to 210C. The expression temperature range of the mar-tensite point as used herein means temperatures in the range from about 10 above to 10C below the martensite formation temperature.
The expression temperature range above the martensite point, in which the incomplete austempering is carried out, as used herein, generally means 0 to about 100C, preferably 0 to about 50C and most preferably, about 5 to 50C above the actual martensite formation temperature. It has been generally found that, within the scope of the invention, the higher or lower the martensite point, the narrow~r or broad~r, respectively, the temperature range above the martensite point in which the inventive incomplete austempering can be carried out.
Preferably, the temperature for the incomplete austempering is below about 270 to 280C and preferably 260C
and lower. Especially advantageous effects occur when steels are used which have martensite points in the lower portion of the above-discussed range.
Of course, when the primary steels do not yet have the structure which is necessary for incomplete austempering, they must be pretreated accordingly, for example,by heat treatment with the formation of an austenitic base structure.
Small amounts of alloying elements may also be present, for example V, W, Ni, B, etc., in amounts in the order of magnitude of about 0.2% each. In this manner, it is possible to influence certain properties of the steels.
However, the presence or absence of such alloying elements is not important for the invention.
Usually, the transformation is carried out at an extent at most of about 85%, relative to the maximum or complete trans-formation. In most cases, the degree of transformation is in the range of about 55 to 85%, the ranges of 75 to 85~ and, particularly, of about 80~ being preferred. The degree of transformation can be observed by means of simple measuring techniques, using the fact that the austempering causes a positive change in length. Accordingly, the transformation kinetics and, finally, the degree of transformation at the respective temperatures can be observed in a simple manner by dilatometric measurement of samples of the steel. Accordingly, a degree of transformation of 80~ corresponds to 80% of the maximum change in length which can be achieved by complete bainitic transformation at the respective temperature.
According to a preferred embodiment of the invention, the alloy steel has the following composition:
0.57 - 0.75 ~ C, 0.15 - 0.35 % Si, 0.70 - 0.85 % Mn, max. 0.035 % P, max. 0.035 % S, 0.20 - 0.50 % Mo and/or 0.20 - 1.00 ~ Cr, the remainder being iron and, possibly, insiginficant amounts of alloying elements and normal impurities.
The above-mentioned transformation characteristics apply also to these alloys. These alloys have the optimum advantageous properties of the present invention when the transformation takes place in the temperature range of the martensite formation or in the temperature range of 0 to 50C
i~37337 above the martensite point and to a degree of transformation of about 75 to 85~ measured according to the dilatometrically determined transformation kinetics.
Preferably, th~ inventive alloy steels and articles have a toughness, measured on unnotched round samples of 4.5 mm diameter, of more than 70 J, and preferably of 85 J to 90 J, and a hardness of at least 57 HRC, preferably 58 ~RC and higher, for example up to 60 and 61 HRC.
The invention further relates to a,process for the production of improved materials and articles of alloy steels which are slow to transform and are austemperable, and parti-cularly, low alloy or unalloy steels with low martensite transformation temperatures. For this purpose, austempering is performed in the temperature range of the martensite point, or in the temperature range immediately above this range, particularly in the ,ange of 0 to 100C, preferably up to 50C
and, for example 5 to 50C above the martensite point. The austempering is stopped when the transformation reaches no more than about 85%, is preferably from 55 to 85~, and most preferably from about 75 to 85~, relative to the dilatometrically measured maximum transformation. Advantageously, alloys of the above-mentioned compositions are used. Also in this case the possible presence of small amounts of alloying elements is not critical to obtain the results of the present invention.
Alloy steels according to the invention which can also be used in the present process are steels which are sufficiently slow to transform, which have the prerequisites for an isothermal bainitic transformation, and which have, if possible, low martensite points. In the autocatalytic diagram or system of Austin and Rickett, these steels usually show a bend in the transformation kinetics which otherwise is a straight line. At this point, obviously, a separation occurs which negatively influences the toughness. While obtaining alloys of high toughness and strength, by means of the present invention, it is possible to intentionally avoid such sequences which pO5-sibly negatively influence the toughness.
Articles having the advantageous properties of the present invention can be produced in a conventional manner, particularly by cold forming, from the alloy,steels according to the invention. Of course, it is also possible to pr~duce articles from alloy steels which are not pre-treated, particu-larly, steels having the above-mentioned compositions, and to subsequently convert the steels in these articles to the present invention by means of an appropriate treatment.
~ n essential advantage of the present invention resides in the fact that, contrary to the high-alloy steels which were re~uired heretofore, it is possible in accordance with the invention to economically produce products for mass use. Belonging to the articles of the present invention are particularly fastening means, e.g., screws, nails, bolts, particularly set bolts for direct fastening, rivets, dowels, dowel parts, tools, such as drills, drill shafts, screwdrivers, saws, dies, punches, machine elements, such as, locking pins, springs, cup springs valves, va~ve guides, piston rings, shafts, axles, split pins, couplings, disks, laminae, articles for the military, such as parts of weapons, armor plates, fixtures or fittings used in construction, ship building, sporting goods, and furniture, such as, chains, fishing hooks, edges for skis, parts of optical and measuring devices, semi-manufactured goods, such as belts, wires, sheet metal, bars, tubes and the like.
li37337 Proven as particularly suitable within the purpose of the invention are steels from the group of the spring steels, for example, those having the composition of Table 1 T~3LE 1 C% Si~ Mn~ Cr~ V%
62 SiMnCr 4 0.62 1.0 1.0 0.6 58 CrV 40.58 0.3 1.0 1.1 0.1 50 CrV 40.50 0.3 1.0 1.1 0.1 62 SiCr 50.62/0.72 1.3 0.5 0.5 Also suitable for steels from the group of cold work steels, for example, the steels having the composition of Table 2.
C% Si% Mn% Cr% V~
100 Cr 61.0 0.3 0.3 1.5 A steel with 0.73% C, 0.85% Mn, 0.2% Si and 0.29% Mo, in the form of a wire material which has been cold drawn, ~ - 7 -soft-annealed, and weakly redrawn, with a strength of about 800 N/mm2 was used as initial material after a heat treatment at 860C. This steel, in sections having a length of 50 mm and a diameter (0) of 4.5 mm, was subjected to a heat treatment at 240TC for 20 minutes followed by air cooling for 40 minutes.
The thus treated sections had a hardness of 58 HRC and an impact strength or toughness of 81 to 84 J.
After performing the same treatment as set forth in Example 1 on finished direct-fastening elements (nails, bolts), the articles were found to have good toughness with a hardness of 58 HRC and it was possible to bend them up to angles of 90 degrees.
Tension springs of high hardness and toughness and having a diameter of 80 mm made from a wire with d = 4.5 mm were obtained by subjecting the springs in the wound state to the treatment of Example 1.
Having described what is believed to be the best mode by which the invention may be performed, it will be seen that the invention may be particularly defined as follows:
A steel composition comprising in percent by weight about 0.50 - 1.00 ~ C, 0.10 - 1.50 % S, 0.25 - 1.50 % Mn, max. 0.045 % P, max. 0.045 % S, an element selected from the group consisting of 0.20 - 0.90 % Mo and 0.20 - 2.00 % Cr 1~ 37337 with the remainder being iron and normal impurities, said steel having a low martensite point and having been prepared by subjecting an austenitic steel to austempering in the temperature range of the martensite point, or in the tempera-ture range above the range of the martensite point to achieve a degree of transformation of from about 55 to 85% of the maximum expansion in length that can be achieved during bainitic transformation.
The invention further comprises steel having the foregoing features and wherein the heat treatment is carried out in the temperature range from 10C above to 10C below the martensite point.
The invention further comprises steel having the foregoing features and wherein the heat treatment is carried out in the temperature range from about 0C to 50C above the martensite point.
The invention further comprises steel having the foregoing features and wherein the martensite point is in the range from about 180 to 280C.
The invention further comprises a process for the production of steel having both high toughness and strength comprising subjecting a steel having a low martensite point and which is slow to transform and having the composition 0.50 - 1.00 % C, 0.10 - 1.50 % Si, 0.25 - 1.50 % Mn, max~ 0.045 % P, ma~. 0.045 ~ S, an elèment selected from the group consisting of 0.20 - 0.90 % Mo and 0.20 - 2.00 % Cr, g with the remainder being iron and normal impurities, to austempering in the temperature range from about 10C
below at about 100C above the martensite point for the time period to achieve a transformation degree of from about 55 to 85% of the maximum expansion in length that can be achieved during bainitic transformation.
The invention further comprises a process having the foregoing features and wherein the temperature of the martensite point is in the range from about 180C to 280C.
The invention further comprises articles made from steel in accordance with the invention.
The foregoing is a description of a preferred embodiment of the invention which is given here by way of example only. The invention is not to be taken as limited to any of the specific features as described, but comprehends all such variations thereof as come within the scope of the appended claims.
' - 10 -
It is known that by the addition of large amounts of valuable alloys to steel, it is possible to produce alloy steels which possess both high toughness as well as high strength. However, due to the high production costs and tech-nical problems encountered, alloys of this type can only be used for special purposes in practice. Frequent attempts to produce alloy steels of high toughness and strength by more economical mehods have been made. However, a really satisfactory solution has not yet been found.
For example, high alloy steels of high strength and toughness are known, for example, those having material numbers 1.6357 x 2 Ni Co Mo 18 8 3, 1.6358 and 1.6359. However, these steels have poor deformation and cutting properties and they are not very economical due to the high cost of the alloy constituents.
We have discovered alloy steels and articles there-from which posses high toughness and strength in the absence of significant amounts of valuable alloy constituents and which may reach extremely high strength values. Articles made from the alloy steels of the present invention include bolts or drive-in bolts of conventional shape suitahle for direct fast-ening and it is possible to drive these articles into high-strength constructional steel.
The steel of the present invention comprises unalloyed or low-alloyed steels which are austemperable, slow to transform and have a low martensite point, and articles containing such '~L
alloys. The composition of the steel is:
0.50 - 1.00 ~ C, 0.10 - 1.50 % Si, 0.25 - 1.50 ~ Mn, max. 0.045 ~ P, max. 0.045 % S, and Mo and/or Cr in amounts of 0.20 - 0.90 % Mo, and 0.20 - 2.00 % Cr, all percentages being % by weight, with the remainder being iron and, possibly, insignificant amounts of alloying elements and normal impurities.
The steel of the invention is obtained by subjecting this composition to austempering at temperatures in the range of the martensite formation temperature, or in the temperature range immediately above the former, to a degree of transforma-tion of about 85%. In this case, one part Mo can be substituted by, for example, one part Cr. Generally, molydenum is preferred over chromium. In special cases, the lower limit of the Mn content may be 0.25%.
The invention is based on the general finding that alloy steels and articles made therefrom possess both high toughness and strength when they have been subjected to an incomplete austempering ~heat treatment) in the temperature range of the martensite point, or in the temperature range slightly above the martensite point, until they are transformed in the order of magnitude of, at most, about 85~. Usually, both of these properties are not present simultaneously in any given steel.
In most cases, the martensite point is in the range .~
from about 180 to 280C and particularly is in the range from about 180 to 230C, and is most often in the range from about 185 to 210C. The expression temperature range of the mar-tensite point as used herein means temperatures in the range from about 10 above to 10C below the martensite formation temperature.
The expression temperature range above the martensite point, in which the incomplete austempering is carried out, as used herein, generally means 0 to about 100C, preferably 0 to about 50C and most preferably, about 5 to 50C above the actual martensite formation temperature. It has been generally found that, within the scope of the invention, the higher or lower the martensite point, the narrow~r or broad~r, respectively, the temperature range above the martensite point in which the inventive incomplete austempering can be carried out.
Preferably, the temperature for the incomplete austempering is below about 270 to 280C and preferably 260C
and lower. Especially advantageous effects occur when steels are used which have martensite points in the lower portion of the above-discussed range.
Of course, when the primary steels do not yet have the structure which is necessary for incomplete austempering, they must be pretreated accordingly, for example,by heat treatment with the formation of an austenitic base structure.
Small amounts of alloying elements may also be present, for example V, W, Ni, B, etc., in amounts in the order of magnitude of about 0.2% each. In this manner, it is possible to influence certain properties of the steels.
However, the presence or absence of such alloying elements is not important for the invention.
Usually, the transformation is carried out at an extent at most of about 85%, relative to the maximum or complete trans-formation. In most cases, the degree of transformation is in the range of about 55 to 85%, the ranges of 75 to 85~ and, particularly, of about 80~ being preferred. The degree of transformation can be observed by means of simple measuring techniques, using the fact that the austempering causes a positive change in length. Accordingly, the transformation kinetics and, finally, the degree of transformation at the respective temperatures can be observed in a simple manner by dilatometric measurement of samples of the steel. Accordingly, a degree of transformation of 80~ corresponds to 80% of the maximum change in length which can be achieved by complete bainitic transformation at the respective temperature.
According to a preferred embodiment of the invention, the alloy steel has the following composition:
0.57 - 0.75 ~ C, 0.15 - 0.35 % Si, 0.70 - 0.85 % Mn, max. 0.035 % P, max. 0.035 % S, 0.20 - 0.50 % Mo and/or 0.20 - 1.00 ~ Cr, the remainder being iron and, possibly, insiginficant amounts of alloying elements and normal impurities.
The above-mentioned transformation characteristics apply also to these alloys. These alloys have the optimum advantageous properties of the present invention when the transformation takes place in the temperature range of the martensite formation or in the temperature range of 0 to 50C
i~37337 above the martensite point and to a degree of transformation of about 75 to 85~ measured according to the dilatometrically determined transformation kinetics.
Preferably, th~ inventive alloy steels and articles have a toughness, measured on unnotched round samples of 4.5 mm diameter, of more than 70 J, and preferably of 85 J to 90 J, and a hardness of at least 57 HRC, preferably 58 ~RC and higher, for example up to 60 and 61 HRC.
The invention further relates to a,process for the production of improved materials and articles of alloy steels which are slow to transform and are austemperable, and parti-cularly, low alloy or unalloy steels with low martensite transformation temperatures. For this purpose, austempering is performed in the temperature range of the martensite point, or in the temperature range immediately above this range, particularly in the ,ange of 0 to 100C, preferably up to 50C
and, for example 5 to 50C above the martensite point. The austempering is stopped when the transformation reaches no more than about 85%, is preferably from 55 to 85~, and most preferably from about 75 to 85~, relative to the dilatometrically measured maximum transformation. Advantageously, alloys of the above-mentioned compositions are used. Also in this case the possible presence of small amounts of alloying elements is not critical to obtain the results of the present invention.
Alloy steels according to the invention which can also be used in the present process are steels which are sufficiently slow to transform, which have the prerequisites for an isothermal bainitic transformation, and which have, if possible, low martensite points. In the autocatalytic diagram or system of Austin and Rickett, these steels usually show a bend in the transformation kinetics which otherwise is a straight line. At this point, obviously, a separation occurs which negatively influences the toughness. While obtaining alloys of high toughness and strength, by means of the present invention, it is possible to intentionally avoid such sequences which pO5-sibly negatively influence the toughness.
Articles having the advantageous properties of the present invention can be produced in a conventional manner, particularly by cold forming, from the alloy,steels according to the invention. Of course, it is also possible to pr~duce articles from alloy steels which are not pre-treated, particu-larly, steels having the above-mentioned compositions, and to subsequently convert the steels in these articles to the present invention by means of an appropriate treatment.
~ n essential advantage of the present invention resides in the fact that, contrary to the high-alloy steels which were re~uired heretofore, it is possible in accordance with the invention to economically produce products for mass use. Belonging to the articles of the present invention are particularly fastening means, e.g., screws, nails, bolts, particularly set bolts for direct fastening, rivets, dowels, dowel parts, tools, such as drills, drill shafts, screwdrivers, saws, dies, punches, machine elements, such as, locking pins, springs, cup springs valves, va~ve guides, piston rings, shafts, axles, split pins, couplings, disks, laminae, articles for the military, such as parts of weapons, armor plates, fixtures or fittings used in construction, ship building, sporting goods, and furniture, such as, chains, fishing hooks, edges for skis, parts of optical and measuring devices, semi-manufactured goods, such as belts, wires, sheet metal, bars, tubes and the like.
li37337 Proven as particularly suitable within the purpose of the invention are steels from the group of the spring steels, for example, those having the composition of Table 1 T~3LE 1 C% Si~ Mn~ Cr~ V%
62 SiMnCr 4 0.62 1.0 1.0 0.6 58 CrV 40.58 0.3 1.0 1.1 0.1 50 CrV 40.50 0.3 1.0 1.1 0.1 62 SiCr 50.62/0.72 1.3 0.5 0.5 Also suitable for steels from the group of cold work steels, for example, the steels having the composition of Table 2.
C% Si% Mn% Cr% V~
100 Cr 61.0 0.3 0.3 1.5 A steel with 0.73% C, 0.85% Mn, 0.2% Si and 0.29% Mo, in the form of a wire material which has been cold drawn, ~ - 7 -soft-annealed, and weakly redrawn, with a strength of about 800 N/mm2 was used as initial material after a heat treatment at 860C. This steel, in sections having a length of 50 mm and a diameter (0) of 4.5 mm, was subjected to a heat treatment at 240TC for 20 minutes followed by air cooling for 40 minutes.
The thus treated sections had a hardness of 58 HRC and an impact strength or toughness of 81 to 84 J.
After performing the same treatment as set forth in Example 1 on finished direct-fastening elements (nails, bolts), the articles were found to have good toughness with a hardness of 58 HRC and it was possible to bend them up to angles of 90 degrees.
Tension springs of high hardness and toughness and having a diameter of 80 mm made from a wire with d = 4.5 mm were obtained by subjecting the springs in the wound state to the treatment of Example 1.
Having described what is believed to be the best mode by which the invention may be performed, it will be seen that the invention may be particularly defined as follows:
A steel composition comprising in percent by weight about 0.50 - 1.00 ~ C, 0.10 - 1.50 % S, 0.25 - 1.50 % Mn, max. 0.045 % P, max. 0.045 % S, an element selected from the group consisting of 0.20 - 0.90 % Mo and 0.20 - 2.00 % Cr 1~ 37337 with the remainder being iron and normal impurities, said steel having a low martensite point and having been prepared by subjecting an austenitic steel to austempering in the temperature range of the martensite point, or in the tempera-ture range above the range of the martensite point to achieve a degree of transformation of from about 55 to 85% of the maximum expansion in length that can be achieved during bainitic transformation.
The invention further comprises steel having the foregoing features and wherein the heat treatment is carried out in the temperature range from 10C above to 10C below the martensite point.
The invention further comprises steel having the foregoing features and wherein the heat treatment is carried out in the temperature range from about 0C to 50C above the martensite point.
The invention further comprises steel having the foregoing features and wherein the martensite point is in the range from about 180 to 280C.
The invention further comprises a process for the production of steel having both high toughness and strength comprising subjecting a steel having a low martensite point and which is slow to transform and having the composition 0.50 - 1.00 % C, 0.10 - 1.50 % Si, 0.25 - 1.50 % Mn, max~ 0.045 % P, ma~. 0.045 ~ S, an elèment selected from the group consisting of 0.20 - 0.90 % Mo and 0.20 - 2.00 % Cr, g with the remainder being iron and normal impurities, to austempering in the temperature range from about 10C
below at about 100C above the martensite point for the time period to achieve a transformation degree of from about 55 to 85% of the maximum expansion in length that can be achieved during bainitic transformation.
The invention further comprises a process having the foregoing features and wherein the temperature of the martensite point is in the range from about 180C to 280C.
The invention further comprises articles made from steel in accordance with the invention.
The foregoing is a description of a preferred embodiment of the invention which is given here by way of example only. The invention is not to be taken as limited to any of the specific features as described, but comprehends all such variations thereof as come within the scope of the appended claims.
' - 10 -
Claims (22)
1. A steel composition comprising in percent by weight about 0.50 - 1.00 % C, 0.10 - 1.50 % Si, 0.25 - 1.50 % Mn, max. 0.045 % P, max. 0.045 % S, an element selected from the group consisting of 0.20 - 0.90 % Mo and 0.20 - 2.00 % Cr, with the remainder being iron and normal impurities, said steel having a low martensite point and having been prepared by subjecting an austenitic steel to austempering in the tempera-ture range of the martensite point, or in the temperature range above the range of the martensite point to achieve a degree of transformation of from about 55 to 85% of the maximum expansion in length that can be achieved during bainitic transformation.
2. The steel of Claim 1 comprising about:
0.57 - 0.75 % C, 0.15 - 0.35 % Si, 0.70 - 0.85 % Mn, max. 0.035 % P, max. 0.035 % S, an element selected from the group consisting of 0.20 - 0.50 % Mo and 0.20 - 1.00 % Cr, with the remainder being iron and normal impurities.
0.57 - 0.75 % C, 0.15 - 0.35 % Si, 0.70 - 0.85 % Mn, max. 0.035 % P, max. 0.035 % S, an element selected from the group consisting of 0.20 - 0.50 % Mo and 0.20 - 1.00 % Cr, with the remainder being iron and normal impurities.
3. The steel of Claim 1 wherein 0.50 to 1.50% Mn is present.
4. The steel of Claims 1 or 2 having a toughness as measured on unnotched round samples of 4.5 mm diameter of more than about 70 J and a hardness of at least about 57 HRC.
5. The steel of Claims 1 or 2 having a toughness as measured on unnotched round of samples of 4.5 mm diameter of more than about 85 J and a hardness of at least about 58 HRC.
6. The steel of Claims 1 or 2 having a hardness of 60 HRC.
7. The steel of Claims 1 or 2 wherein the heat treatment is carried out in the temperature range from 10°C above to 10°C below the martensite point.
8. The steel of claims 1 or 2 wherein the heat treatment is carried out in the temperature range from about 0°C to 100°C
above the martensite point.
above the martensite point.
9. The steel of Claims 1 or 2 wherein the heat treatment is carried out in the temperature range from about 0°C to 50°C
above the martensite point.
above the martensite point.
10. The steel of Claims 1 or 2 wherein the heat treatment is carried out in the range from about 5°C to 50°C above the martensite point.
11. The steel of Claims 1 or 2 wherein the degree of transformation is from about 75 to 85%.
12. The steel of Claims 1 or 2 wherein the degree of transformation is about 80%.
13. The steel of Claims 1 or 2 wherein the martensite point is in the range from about 180 to 280°C.
14. Articles made from the steel of Claims 1 or 2.
15. A process for the production of steel having both high toughness and strength comprising subjecting a steel having a low martensite point and which is slow to transform and having the composition 0.50 - 1.00 % C, 0.10 - 1.50 % Si, 0.25 - 1.50 % Mn, max. 0.045 % P, max. 0.045 % S, an element selected from the group consisting of 0.20 - 0.90 % Mo and 0.20 - 2.00% Cr, with the remainder being iron and normal impurities, to austempering in the temperature range from about 10°C below to about 100°C above the martensite point for a time period to achieve a transformation degree of from about 55 to 85%
of the maximum expansion in length that can be achieved during bainitic transformation.
of the maximum expansion in length that can be achieved during bainitic transformation.
16. The process of Claim 15 wherein the austempering is carried out in the range from about 10°C below to 10°C above the martensite point.
17. The process of Claim 16 wherein the austempering is carried out in the range from 0°C to 100°C above the temperature of the martensite point.
18. The process of Claim 17 wherein the austempering is carried out in the range from 0°C to 50°C above the temperature of the martensite point.
19. The process of Claim 18 wherein the austempering is carried out in the range from about 5 to 50°C above the tempera-ture of the martensite point.
20. The process of Claims 15, 16 or 17 wherein the temperature of the martensite point is in the range from about 180 to 280°C.
21. The process of Claims 15 or 17 wherein the austem-pering is carried out for a period of time to effect a transformation between about 75 to 85%.
22. The process of Claims 15, 16 or 17 wherein the austempering is carried out for a period of time to effect a transformation of 80%.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DEP2817628.5 | 1978-04-21 | ||
| DE2817628A DE2817628C2 (en) | 1978-04-21 | 1978-04-21 | Tough, high-strength steel alloys and processes for making such workpieces |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1137337A true CA1137337A (en) | 1982-12-14 |
Family
ID=6037726
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000325474A Expired CA1137337A (en) | 1978-04-21 | 1979-04-12 | Tough, high-strength steels, articles made therefrom and process for their production |
Country Status (22)
| Country | Link |
|---|---|
| JP (1) | JPS54141313A (en) |
| AT (1) | AT393279B (en) |
| AU (1) | AU527551B2 (en) |
| BE (1) | BE875730A (en) |
| BR (1) | BR7902454A (en) |
| CA (1) | CA1137337A (en) |
| CH (1) | CH646199A5 (en) |
| CS (1) | CS211362B2 (en) |
| DE (1) | DE2817628C2 (en) |
| DK (1) | DK155053C (en) |
| ES (1) | ES479774A1 (en) |
| FI (1) | FI69121C (en) |
| FR (1) | FR2423549B1 (en) |
| GB (1) | GB2019436B (en) |
| IT (1) | IT1112992B (en) |
| NL (1) | NL191388C (en) |
| NO (1) | NO153933C (en) |
| PL (1) | PL136257B1 (en) |
| SE (1) | SE449229B (en) |
| SU (1) | SU1232147A3 (en) |
| YU (1) | YU40746B (en) |
| ZA (1) | ZA791422B (en) |
Families Citing this family (17)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2862430D1 (en) * | 1978-11-15 | 1984-08-23 | Caterpillar Tractor Co | Lower bainite alloy steel article |
| JPS5970724A (en) * | 1982-10-15 | 1984-04-21 | Seiko Instr & Electronics Ltd | Rolled hot-forged thread |
| JPS61130456A (en) * | 1984-11-29 | 1986-06-18 | Honda Motor Co Ltd | High-strength bolt and its production |
| JPH01268245A (en) * | 1988-04-19 | 1989-10-25 | Fujitsu Ltd | switching control circuit |
| US4960473A (en) * | 1989-10-02 | 1990-10-02 | The Goodyear Tire & Rubber Company | Process for manufacturing steel filament |
| SE510344C2 (en) * | 1997-08-01 | 1999-05-17 | Ovako Steel Ab | Way for complete bainite hardening of steel |
| NL1011806C2 (en) | 1999-04-15 | 2000-10-17 | Skf Engineering & Res Services | Ball bearing steel with a surface with an underbainitic structure and a method of manufacturing it. |
| RU2186859C2 (en) * | 2000-01-18 | 2002-08-10 | Комсомольское-на-Амуре авиационное производственное объединение | Method of hardening of articles from steels and alloys |
| RU2277593C1 (en) * | 2004-11-30 | 2006-06-10 | Открытое акционерное общество "ТРУБОДЕТАЛЬ" | Large-size article heat treatment process |
| DE202005015611U1 (en) * | 2005-09-30 | 2005-12-29 | Textron Verbindungstechnik Gmbh & Co. Ohg | Bolts or screws with high rigidity are made from steel wire by hot rolling and cooling glowing product by blowing on air, then rolling out and cold-forming to produce head and thread |
| FR2916371B1 (en) * | 2007-05-24 | 2010-02-26 | Fwu Kuang Entpr Co Ltd | PROCESS FOR PREPARING FORGED PARTS HAVING EXCELLENT TRACTION RESISTANCE AND ELONGATION FROM STEEL MAMINERY WIRES |
| RU2342571C1 (en) * | 2007-06-05 | 2008-12-27 | Открытое акционерное общество "Магнитогорский метизно-калибровочный завод "ММК-МЕТИЗ" | Dowel pin |
| DE102008041391A1 (en) * | 2008-08-20 | 2010-01-14 | Kamax-Werke Rudolf Kellermann Gmbh & Co. Kg | High strength bolt has bainite structure produced by austempering which extends across whole cross-section of the bolt and increases its tensile strength |
| GB2485107A (en) * | 2009-08-24 | 2012-05-02 | Secr Defence | Armour |
| DE102011054840A1 (en) | 2011-10-26 | 2013-05-02 | Rud Ketten Rieger & Dietz Gmbh U. Co. Kg | Hardening steel for grade 8 and higher hoisting, lifting, tensioning and / or lashing equipment, lifting, lifting, tensioning and / or lashing equipment, and method of making such a component |
| DE102011055497A1 (en) | 2011-11-18 | 2013-05-23 | Kamax Holding Gmbh & Co. Kg | Ultra-high-strength screw with high yield ratio |
| KR101751530B1 (en) * | 2015-12-28 | 2017-06-27 | 주식회사 포스코 | Steel sheet for tool and method of manufacturing for the same |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB517118A (en) * | 1938-07-13 | 1940-01-22 | Ver Oberschlesische Huttenwerk | Improvements in and relating to improved steels and the application thereof |
| DE973413C (en) * | 1944-05-31 | 1960-02-11 | Gussstahlwerk Witten Ag | Process to achieve a hardness of at least 54RC with high impact resistance |
| US2914401A (en) * | 1958-02-24 | 1959-11-24 | Crucible Steel Co America | Alloy steel |
| US3155550A (en) * | 1961-09-15 | 1964-11-03 | United States Steel Corp | Heat treatment of chromium-free steel bearings |
| DE1558505A1 (en) * | 1967-01-23 | 1970-04-16 | Hilti Ag | Anchoring means |
| SE342475B (en) * | 1969-03-31 | 1972-02-07 | Sandvikens Jernverks Ab |
-
1978
- 1978-04-21 DE DE2817628A patent/DE2817628C2/en not_active Expired
-
1979
- 1979-02-28 FI FI790666A patent/FI69121C/en not_active IP Right Cessation
- 1979-03-07 NL NL7901840A patent/NL191388C/en not_active IP Right Cessation
- 1979-03-15 CS CS791731A patent/CS211362B2/en unknown
- 1979-03-20 GB GB7909840A patent/GB2019436B/en not_active Expired
- 1979-03-26 ZA ZA791422A patent/ZA791422B/en unknown
- 1979-03-30 IT IT21467/79A patent/IT1112992B/en active
- 1979-03-30 AU AU45625/79A patent/AU527551B2/en not_active Expired
- 1979-04-02 CH CH305179A patent/CH646199A5/en not_active IP Right Cessation
- 1979-04-02 AT AT2419/79A patent/AT393279B/en not_active IP Right Cessation
- 1979-04-04 YU YU802/79A patent/YU40746B/en unknown
- 1979-04-12 CA CA000325474A patent/CA1137337A/en not_active Expired
- 1979-04-19 SE SE7903448A patent/SE449229B/en not_active IP Right Cessation
- 1979-04-19 NO NO791296A patent/NO153933C/en unknown
- 1979-04-19 FR FR7909853A patent/FR2423549B1/en not_active Expired
- 1979-04-20 BE BE0/194732A patent/BE875730A/en not_active IP Right Cessation
- 1979-04-20 SU SU792753403A patent/SU1232147A3/en active
- 1979-04-20 BR BR7902454A patent/BR7902454A/en unknown
- 1979-04-20 ES ES479774A patent/ES479774A1/en not_active Expired
- 1979-04-20 PL PL1979215033A patent/PL136257B1/en unknown
- 1979-04-20 DK DK162779A patent/DK155053C/en not_active IP Right Cessation
- 1979-04-20 JP JP4809679A patent/JPS54141313A/en active Granted
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