GB2096171A

GB2096171A - Tool steel

Info

Publication number: GB2096171A
Application number: GB8131849A
Authority: GB
Original assignee: Teledyne Industries Inc
Current assignee: TDY Industries LLC
Priority date: 1980-11-10
Filing date: 1981-10-22
Publication date: 1982-10-13
Also published as: BR8107251A; FR2493877A1; IT1140479B; SE8106207L; DE3144476A1; IT8124916A0; JPS57110651A; AU7704281A

Abstract

A high speed and tool steel composition comprises: % By Weight Carbon 0.3 to 2.0 " Silicon 0.5 to 3.0 " Aluminum 0.5 to 3.0 " Chromium 0.5 to 10.0 " Molybdenum 0.5 to 10.0 " Tungsten 0.5 to 20.0 " Vanadium 0.5 to 6.0 " Cobalt 0.0 to 10.0 " Balance Iron. The combined silicon and aluminum should preferably be no more than about 3.5 percent by weight and vanadium can be partially or totally replaced by zirconium, niobium, hafnium, titanium and tantalum.

Description

SPECIFICATION High speed and other tool steels The present invention relates to a new composition for both high speed and other tool steels which partially or totally eliminates the need for cobalt.

Metals can be formed readily in either the hot or cold state by a variety of methods. In the cold state one of the most important forming methods is machining. Today virtually all the machining of metals is done either by hard metals, i.e. sintered grades of carbides, or by high speed steels. Almost all sintered carbides and most of the grades of high speed steels commonly used today contain cobalt as an essential element.

The first compositions of high speed steels did not include cobalt as an essential element. They derived their essential property, "hot hardness" (strength at elevated temperatures) by virtue of their high content of such refractory elements as tungsten, molybdenum and vanadium.

Although cobalt containing high speed steels were available by 1920, it was not until the late fifties and early sixties with the rise of the aerospace industry, both commercial and military, and its dependence on hard to machine alloys, that cobalt high speed steels were brought into prominence.

The most popular of these grades, then as now, have between five and ten percent cobalt as an essential alloying feature. Although the solid state chemistry of cobalt containing high speed steels is not entirely understood, its role is perfectly clear. The cobalt is responsible for the retention of hardness at the temperatures of cutting. These temperatures are estimated to be in the realm of 1 2000F (6500 C). The cobalt containing steels perform a particularly vital function in those machining operations where high temperatures are generated between the cutting tool and the workpiece. These include difficult to machine metals, stainless steels, and metals which rapidly work-harden during machining.This unique role of cobalt in providing "hot hardness" to high speed steels is reflected in the fact that about half of the grades of high speed steels produced today contain cobalt in appreciable amounts.

The price of cobalt has increased considerably over the last few years. In addition, limited availability has restricted the production of needed cobalt containing alloys. This increase in price and lack of availability has caused deep concern throughout the steel industry and has precipitated a search for substitutes for cobalt in high speed steels used in difficult machining operations.

Recently a non-cobalt high speed steel, manufactured by powder metallurgical methods, was introduced by Crucible Specialty Metals Division. In this instance existing alloy technology has been utilized to develop a high speed steel which is reported to contain no cobalt but which is reported to have performance characteristics competitive with high speed steels having 5 and 8 percent cobalt by increasing the levels of refractory elements to raise the hot hardness. It has been reported by Crucible Specialty Metals Division that these alloys can not be produced by conventional cast/hot work means, but must be manufactured by the more expensive powder atomization/consolidation route. Thus this approach is expensive and appropriate only to the rather restricted methods of powder metallurgy.The present invention, by discovering the ability to enhance hot hardness by adding silicon and aluminum in discrete amounts, is not dependent on the use of expensive powder technology, but can be properly applied to advantage through the use of conventional cast/hot work means.

The use of silicon in steels is fraught with difficulty as silicon has been demonstrated to be embrittling in steel above about 1 or 2 percent. At the temperatures encountered in machining, these steels suffer from "temper embrittlement", a form of brittleness characterized by catastrophic failure through grain boundaries. Conventional wisdom has viewed silicon as a residue of the melting process in high speed steels. For example, in Hamaker et al U.S. Patent No. 3,259,489, sulfur, phosphorus, manganese and silicon may be omitted entirely from their cobalt containing premium performance high speed steel. Recently Haberling et al U.S. Patent No. 3,850,621 disclosed that silicon may be added to a high speed steel to control the composition and morphology of the carbides in the high speed steel, producing an improvement in wear resistance with a concomitant reduction in toughness.

Until now, no success has been achieved in finding an inexpensive and readily available substitution for cobalt that will perform this vital function of conferring hot hardness in high speed steels used in difficult machining operations.

It has been found that by incorporating combinations of silicon and aluminum in speed tool steels and other tool steels, the need for cobalt can be partially reduced or total eliminated without encountering the temper embrittlement characteristics of silicon alloyed steels. Further, the addition of silicon and aluminum can reduce the amounts of such refractory materials as tungsten, vanadium, and molybdenum used in high speed tool steels and other tool steels.

The present invention provides a new steel composition which is applicable to high speed steels and tool steels and is based on the discovery that cobalt can be partially or completely replaced by silicon and aluminum. It has further been discovered by the incorporation of silicon and aluminum in these steel compositions certain other refractory materials can also be reduced such as tungsten, vanadium and molybdenum.The new steel composition of the invention is set forth in the following Table I: High speed and other tool steels Table I Carbon 0.3 to 2.0 % By Weight Silicon 0.5 to 3.0 % By Weight Aluminum 0.5 to 3.0 % By Weight Chromium 0.5 to 10.0 % By Weight Molybdenum 0.5 to 10.0 % By Weight Tungsten 0.5 to 20.0 % By Weight Vanadium 0.5 to 6.0 % By Weight Cobalt 0.0 to 10.0 % By Weight Iron Balance % By Weight wherein the sum of the vanadium plus tungsten plus molybdenum is greater than or equal to 2 percent by weight.

Although it is possible to have as much as 3 percent silicon and 3 percent aluminum, it is preferred that the sum of silicon plus aluminum equal about 3.5 percent by weight. It is also possible that in some instances vanadium can be partially or totally replaced by one or more carbide formers such as zirconium, columbium, hafnium, titanium and tantalum.

The preferred range for producing high speed steel characterized by high hot hardness and good toughness and which is readily grindable is set forth in the following Table II: Table II Carbon 1.08 to 1.13 % By Weight Silicon 0.50 to 3.00 % By Weight Aluminum 0.50 to 3.00 % By Weight Chromium 3.60 to 3.90 % By Weight Molybdenum 9.50 to 10.000 % By Weight Tungsten 5.80 to 6.20 % By Weight Vanadium 1.40 to 1.60 % By Weight Cobalt 0.75 maximum Iron Balance % By Weight where the sum of the aluminum plus silicon is about 2 percent by weight.

Another example of a preferred range for high hot hardness high speed steels containing modest amounts of cobalt is set forth in Table ill: Table Ill Carbon 1.05 to 1.15 % By Weight Silicon 0.50 to 3.00 % By Weight Aluminum 0.50 to 3.00 % By Weight Chromium 3.60 to 3.90 % By Weight Molybdenum 9.50 to 10.00 % By Weight Tungsten 1.40 to 1.60 % By Weight Vanadium 0.90 to 1.10 % By Weight Cobalt 1.80 to 2.20 % By Weight Iron Balance % By Weight where the sum of the silicon plus aluminum content is about 2 percent by weight.

A preferred high speed steel composition having high wear resistance and good toughness and good hot hardness is set forth in the following Table IV: Table IV Carbon 1.40 to 1.60 % By Weight Silicon 0.50 to 3.00 % By Weight Aluminum 0.50 to 3.00 % By Weight Chromium 2.00 to 5.00 % By Weight Molybdenum 1.00 to 8.00 % By Weight Tungsten 5.00 to 15.00 % By Weight Vanadium 4.50 to 5.50 % By Weight Cobalt 0.75 maximum Iron Balance % By Weight where the sum of the silicon plus aluminum is preferably less than 3.5 percent.

It is to be noted that with regard to the compositions of Tables II and IV above and with regard to all of the illustrative compositions in the present case, a cobalt content of 0.75 percent or less is considered zero, since cobalt can exist as an impurity at this level, particularly when incorporating steel scrap as raw material.

A preferred composition of high speed steels characterized by high toughness and good hot hardness and wear resistance is set forth in the following Table V: Table V Carbon 0.70 to 1.10 % By Weight Silicon 0.50 to 3.00 % By Weight Aluminum 0.50 to 3.00 % By Weight Chromium 2.00 to 6.00 % By Weight Molybdenum 1.50 to 6.00 % By Weight Tungsten 1.50 to 7.50 % By Weight Vanadium 1.00 to 2.00 % By Weight Iron Balance % By Weight where the sum of the silicon plus aluminum is preferably less than 3.5 percent.

A preferred composition of tool steels particularly hot work die steels is set forth in Table VI: Table VI Carbon 0.3 to .65 % By Weight Silicon 0.5 to 3.00 % By Weight Aluminum 0.5 to 3.00 % By Weight Chromium 0.5 to 10.00 % By Weight Molybdenum 0.5 to 10.00 % By Weight Tungsten 0.5 to 18.00 %ByWeight Vanadium 0.5 to 2.00 % By Weight Cobalt 0.0 to 10.00 % By Weight Iron Balance % By Weight where the sum of the vanadium plus molybdenum plus tungsten is greater than or equal to 2.0 percent and the sum of silicon plus aluminum is preferably less than 3.5 percent.

The invention is illustrated further by the following examples: Examples A series of heats were melted to show the effects of an addition of 1 percent silicon and 1 percent aluminum on high speed steel type compositions. The compositions of these heats are set forth in Table VII. The heats were melted as 30 Ib. (13.5 kg) induction ingots and subsequently hot worked to 1/2"x3" (1 .25x7.5 cm) cm) flats. After annealing, one-half inch (1.25 cm) cubes were cut as samples for heat treating and hot hardness studies. Table VIII presents the heat treating data for these experimental alloys. They show heat treat response typical of high speed steels and attain tempered hardnesses equivalent to conventional high speed steels.Microstructural studies have shown these steels to consist of residual primary carbides in a tempered martensitic matrix. Table IX presents the 12000F (6500C) hot hardness of these steels. Hot hardness is a measure of the resistance of a steel to deformation at the temperature in question. It gives an indication of the steel's potential in actual cutting since the frictional interaction between tool and work piece generates temperatures in the realm of 1 2000F (6500 C). These tests show that the hot hardness of the experimental analyses can be related to the addition of silicon and aluminum, as well as the addition of tungsten and vanadium.

Selected analyses were melted as 100 lb. (45 kg) induction heats, hot forged and rolled into bar stock for further evaluation. Table X presents the chemical analyses of these heats. Tables XI and XII present heat treating and hot hardness data for these heats confirming their potential as premium performance high speed steels.

Table XIII gives the composition of some well known high speed steels. Table XIV compares the hot hardness of three experimental alloys with values for some standard high speed steels. The addition of 1 percent aluminum plus 1 percent silicon has enhanced the hot hardness when compared to simiiar compositions without silicon and aluminum additions. In fact, the addition of silicon and aluminum to a composition containing only 2 percent cobalt produced hot hardness values higher than any standard high speed steel composition. Hence, for a given desired hot hardness level, one could reduce the tungsten, molybdenum and/or vanadium and add aluminum and silicon.

Table XV presents toughness data for three analyses showing that these steels are competitive with M-42 and T-1 5 high speed steels. Table XV also presents grindability data for the three analyses showing that the 1 percent vanadium steels are competitive to M-42 while the 2 percent vanadium composition is somewhat more difficult to grind. All are considerably easier than T-1 5 to grind.

Table XVI presents the chemical compositions of three 2,000 Ib. (900 kg) experimental pilot scale heats selected to demonstrate the relative advantages of this invention in a heat size which reflects commercial practice. Table XVII summarizes the hot hardness, grindability (wear resistance) and toughness of these compositions confirming the fact that the combination of chemical control and processing control have produced super high speed steels which contain high contents of silicon and aluminum yet can be manufactured using conventional equipment and do not require the use of expensive technologies such as powder atomization and consolidation to attain premium properties without the use of cobalt.

Table XVIII presents a series of compositions which were melted to evaluate the effects of various levels of silicon and aluminum on the processability of high speed steels. Note that for silicon plus aluminum contents up to 3 percent that the alloys are easily hot worked into the required product form.

As the sum of the silicon and aluminum exceeds 3 percent the hot workability decreases as apparent ordering in the microstructural components reduces hot workability.

Table VII Steel compositions C Si Al Cr Mo W V Co Fe A 1.02 .75 .97 3.69 9.68 1.59 1.05 1.98 Balance B 1.19 1.18 1.07 4.06 9.40 1.55 2.05 .60* Balance C 1.03 1.05 .79 4.00 9.71 5.50 1.16 .34* Balance D 1.47 1.35 1.00 4.12 8.40 1.40 2.10 .50* Balance E 1.35 1.03 .79 3.59 8.41 5.03 2.12 .59* Balance F 1.17 .73 1.00 3.61 8.80 2.70 2.00 .50* Balance G .87 1.24 .93 3.54 8.40 1.60 2.10 .20* Balance All values given as weight percents.

*A cobalt content of 0.75 or less is considered zero and of an impurity level.

Table VIII Heat treat response of steel compositions *Hardness Tempering Indicated Hardening after at Temperatures Temperature 9750F (5250C) 10000F (5400C) 10250F (5500C) A 21750F(11900C) 67.2 67.0 65.8 B 22250F(12200C) 66.1 65.1 64.5 C 22000F(12000C) 66.4 66.5 65.5 D 22250F(12200C) 59.1 57.9 57.0 E 22250F(12200C) 65.8 64.7 64.3 F 22250F(12200C) 66.8 67.5 64.1 G 22250F(1220CC) 64.0 63.2 62.3 *All values Rockwell "C".

Table IX Hot hardness of steel compositions *Hardness at Indicated Temperature Room 8000F 10000F 1200 CF Prior Heat Treatment Temperature (425 C) (540 0C) (650 0C) A 2175 F+975 F (2+2+2 hr) 67.2 63.0 58.4 41.0 (1 1900C+5250C) B 22250F+9750F (2+2+2 hr) 66.1 60.0 58.0 39.0 (1 2200C+5250C) C 2200"F+9750F (2+2+2 hr) 66.4 61.0 58.4 43.3 (1 2000C+5250C) D 22250F+9750F (2+2+2 hr) 59.1 52.2 47.0 37.5 (12200C+5250C) E 2225"F+9750F (2+2+2 hr) 65.8 57.5 55.0 41.0 (12200C+5250C) F 22250F+9750F (2+2+2 hr) 66.8 58.0 56.0 46.0 (1 2200C+5250C) G 22250F+9750F(2+2+2hr) 64.0 57.0 53.0 41.0 (1 2200C+5250C) *All values Rockwell "C".

Table X Steel compositions C Si Al Cr Mo W V Co Fe H 1.40 1.06 1.04 3.46 8.85 5.64 2.07 .05* Balance 1.10 .94 1.10 3.67 9.30 1.48 1.15 1.70 Balance J 1.17 1.03 1.08 3.60 9.40 6.17 1.22 .02* Balance K 1.17 1.00 1.27 3.74 9.00 1.69 2.07 .12* Balance L 1.17 1.09 .98 3.76 9.17 4.69 2.08 .24* Balance All values given as weight percents.

*A cobalt content of 0.75 or less is considered zero and of an impurity level.

Table Xl Heat treat response of steel compositions *Hardness after Tempering at Indicated Temperatures Hardening Temperature 9 75 OF (525 C) 1000 F (540 C) 1025 F (550 C) H 21750F(11900C) 67.0 66.8 66.8 I 21750F(11900C) 67.1 67.0 67.0 J 2175 F (1190 C) 67.0 66.2 66.4 K 22000F(12000C) 67.0 67.0 66.0 L 22000F(12000C) 66.1 65.1 64.4 *All values Rockwell "C".

Table XII Hot hardness of steel compositions *Hardness at Indicated Temperature Room 8000F 10000F 12000F Prior Heat Treatment Temperature (4250C) (540 C) (6500C) H 21 750F+9750F (2+2+2 hr) 67.0 59.8 58.2 45.3 (1 1900C+5250C) 2175 F+975 F (2+2+2 hr) 67.1 64.0 59.5 49.3 (1 1900C+5250C) J 21750F+9750F(2+2+2hr) 67.0 60.4 56.8 44.5 (1190 C+525 C) K 22000F+10000F(2+2+2 hr) 67.0 60.0 56.4 44.4 (1220 C+540 C) L 2200 F+1000 F (2+2+2 hr) 65.1 59.4 55.3 43.2 (1 2200C+5400C) *All values Rockwell "C".

Table XIII Known high speed steels C W Cr V Mo Co Fe M-2 0.85 6.20 4.20 1.85 4.90 - Balance M-7 0.99 1.75 3.75 2.05 8.75 - Balance M-42 1.07 1.50 3.75 1.15 9.50 8.00 Balance T-15 1.57 12.50 4.75 5.00 - 5.00 Balance All values given as weight percents.

Table XIV Comparative hot hardness* Room Temperature 800 F (425 C) 1000 F (540 C) 1200 0F (650 0C) M-7 65.0 58.0 54.0 35.0 K 67.0 60.0 56.4 44.4 M-2 65.0 59.0 55.0 36.0 L 65.1 59.4 55.3 43.2 M-42 68.0 62.0 59.0 44.0 67.1 64.0 59.5 49.3 *All values Rockwell "C".

Table XV Impact data and grindability data PriorHeat Room Temp. Impact Strength Treatment *Hardness Gl Range Average H 21750 +9750F 67.0 1.1 14-19ft.-lb. 16.8ft.-lb.

(1190 C+525 C) (+10200F 66.8 14 14-20ft.-lb. 18.2 ft.-lb.

5500C) +1 1000 F 64.3 1.2 16-18ft.-lb. 17.4 ft.-lb.

6000C) 21750 +9750F 67.1 2.0 14-16ft.-lb. 15.0ft.-lb.

(1190 C+525 C) +10250F 67.0 - 13-19ft.-lb. 16.3 ft.-ib.

550 C) +11000F 64.8 1.9 16--18 ft.-lb. 17.0 ft.-lb.

600 C) J 21750 +9750F 67.0 2.5 14-18ft.-lb. 15.3ft.-lb.

(1 1900C+5250C) +10250F 66.4 - 14-18ft.-lb. 15.9 ft.-lb.

5500C) +1 1000F F 64.2 2.2 15-19ft.-lb. 16.8ft.-lb.

6000 C) M-42 21750 +9500F 68.0 1.5 16--20 ft.-lb. 18.5ft.-lb.

(1 1900C+5100C) T-15 22750 +9500F 67.0 .4 13-17ft.-lb. 15.5ft.-lb.

(1 2500C+51 00C) *All values Rockwell "C".

Table XVI Steel compositions C Si Al Cr Mo W V Co Fe M 1.09 1.03 .95 3.78 9.52 6.14 1.11 .34* Balance N 1.05 1.02 .98 3.67 9.45 6.16 1.50 .39* Balance 0 1.02 1.00 .95 3.56 9.43 1.49 1.10 2.25 Balance All values given as weight percents.

*A cobalt content of 0.75 or less is considered zero and of an impurity level.

Table XVII Summary of properties Hot Hardness Toughness Grindability 10000F (540 C) 1200 F (650 C) at 65/66 Rc At 65/66Rc M 53.3 Rc 40.6 Rc 16/17 ft.-lb. 2.5 N 54.8 Rc 44.7 Rc 15/16 2.2 0 56.7 Rc 47.9 Rc 16/17 1.8 Table XVIII Steel compositions C Si Al Cr Mo W V Co Fe P 1.12 .68 1.26 3.92 9.70 5.99 1.56 .03* Balance Q 1.13 1.11 1.82 3.83 9.98 6.19 1.56 .04* Balance R 1.13 2.20 2.26 3.83 9.80 6.00 1.55 .02* Balance S 1.13 1.25 2.96 3.73 9.81 6.05 1.49 .03* Balance T 1.11 1.14 3.65 3.85 9.90 6.20 1.40 .04* Balance U 1.13 2.15 2.80 3.80 9.88 6.07 1.50 .04* Balance V 1.13 .73 1.56 3.70 9.70 6.05 1.58 .04* Balance W 1.11 .77 1.30 3.68 9.66 6.01 1.52 .04* Balance X 1.10 .93 1.09 3.87 9.65 5.92 1.57 .02* Balance Y 1.11 1.21 .85 3.67 9.65 5.80 1.52 .02* Balance Z 1.10 1.31 .70 3.65 9.53 5.85 1.53 .03* Balance AA 1.12 .94 1.58 3.80 9.70 5.87 1.50 .02* Balance All values given as weight percents.

*A cobalt content of 0.75 or less is considered zero and of an impurity level.

P 1. Forged hot top end-slight cracking.

2. Worked bottoms-cracking.

3. Took bottom to 4" RCS.

4. Tops taken to 4" RCS-top cropped-billet corners hammered.

Q 1. Forged hot top end-cracking.

2. Bottom cracked badly.

3. Bottom didn't make it to 4" RCS-bad cracking.

4. Top to 4" RCS with only slight cracking.

R 1. Worked hot top end-cracking "billet sounds hard".

2. Lower third cracked badly.

3. Cracked in half-put in stress relief furnace.

4. N/A.

S 1. Worked hot topdeep crack on side and at hot top.

2. Lower half cracked badly.

3. Cracked at hot top-put into furnace for stress relief.

4. N/A.

T 1. Worked hot top end-cracked on side-hot top moved out.

2. Breaking in half.

3. Split in half. Put in stress relief furnace.

4. N/A.

U 1. Worked hot top end-lost hot top, 2/3's of ingot reheated.

2. Breaking up in half-material worked by hand.

3. Broke in half. Placed largest in stress relief furnace.

4. N/A.

V 1. Worked hot top end-very slight cracking-"worked best so far".

2. Worked bottomonly slight cracking.

3. Bottom to 4" RCS.

4. Top to 4" RCS-top cropped-corners hammered.

w 1. Worked hot top end--only slight cracking.

2. Slight surface tears.

3. Bottom to 4" RCS.

4. Top to 4" RCS-top cropped--corners hammered.

X 1. Worked hot top end-Ingot worked well.

2. Slight cracking on bottom half.

3. Cracked on bottom but appeared to look best at this stage.

4. Top to 4" RCS-top cropped-corners hammered.

y 1. Worked hot top end-slight cracking.

2. Slight cracking on bottom.

3. Crack on bottom-partial split near hot-top where hyster is holding ingot.

4. More cracking in going to 4" RCS-Top cropped-corners hammered.

z 1. Worked hot top end-slight cracking.

2. In working bottom-crack half way up billet.

3. Cracking on bottom--got to 4" RCS.

4. Top to 4" RCS-more cracking-top cropped-corners hammered.

AA 1. Worked hot top end-hot top separated.

2. Cracks on bottom half-sides and corners.

3. Bottom to 4" RCS.

4. Top to 4" RCS-more cracking-hot top cropped-corners hammered.

In summary of this disclosure, the present invention provides certain novel steel compositions containing silicon and aluminum. Modifications are possible within the scope of this invention.

Claims

1. A high speed and tool steel composition comprising: Carbon 0.3 to 2.0 % By Weight Silicon 0.5 to 3.0 % By Weight Aluminum 0.5 to 3.0 % By Weight Chromium 0.5 to 10.0 % By Weight Molybdenum 0.5 to 10.0 % By Weight Tungsten 0.5 to 20.0 % By Weight Vanadium 0.5 to 6.0 % By Weight Cobalt 0.0 to 10.0 % By Weight Iron Balance where the sum of vanadium plus tungsten plus molybdenum is greater than or equal to 2 percent.

2. A composition as claimed in Claim 1, in which the sum of silicon and aluminum is 3.5 percent by weight.

3. A composition as claimed in Claim 1 or 2 having high hot hardness and comprising: Carbon 1.08 to 1.13 % By Weight Silicon 0.50 to 3.00 % By Weight Aluminum 0.50 to 3.00 % By Weight Chromium 3.60 to 3.90 % By Weight Molybdenum 9.50 to 10.0 % By Weight Tungsten 5.80 to 6.20 % By Weight Vanadium 1.40 to 1.60 % By Weight Cobalt 0.75 maximum Balance Iron

4. A composition as claimed in Claim 1 or 2 having high hot hardness and comprising: Carbon 1.05 to 1.15 % By Weight Silicon 0.50 to 3.00 % By Weight Aluminum 0.50 to 3.00 % By Weight Chromium 3.60 to 3.90 % By Weight Molybdenum 9.50 to 10.00 % By Weight Tungsten 1.40 to 1.60 % By Weight Vanadium 0.90 to 1.10 %ByWeight Cobalt 1.80 to 2.20 % By Weight Balance Iron

5.A composition as claimed in Claim 1 or 2 having high wear resistance and comprising: Carbon 1.40 to 1.60 % By Weight Silicon 0.50 to 3.00 % By Weight Aluminum 0.50 to 3.00 % By Weight Chromium 2.00 to 5.00 % By Weight Molybdenum 1.00 to 8.00 % By Weight Tungsten 5.00 to 15.00 % By Weight Vanadium 4.50 to 5.50 % By Weight Cobalt 0.75 maximum Balance Iron

6. A composition as claimed in Claim 1 or 2, having high toughness and comprising: Carbon 0.70 to 1.10 % By Weight Silicon 0.50 to 3.00 % By Weight Aluminum 0.50 to 3.00 % By Weight Chromium 2.00 to 6.00 % By Weight Molybdenum 1.50 to 6.00 % By Weight Tungsten 1.50 to

7.50 % By Weight Vanadium 1.00 to 2.00 % By Weight Balance Iron 7.A composition as claimed in Claim 1 or 2, comprising: Carbon 0.3 to .65 % By Weight Silicon 0.5 to 3.00 % By Weight Aluminum 0.5 to 3.00 % By Weight Chromium 0.5 to 10.00 % By Weight Molybdenum 0.5 to 10.00 % By Weight Tungsten 0.5 to 18.00 % By Weight Vanadium 0.5 to 2.50 % By Weight Cobalt 0.0 to 10.00 % By Weight Iron Balance where the sum of vanadium plus molybdenum plus tungsten is greater than or equal to 2.0 percent by weight.

8. A composition as claimed in any one of Claims 3 to 7, in which the sum of silicon and aluminum is 2 percent by weight.

9. A composition as claimed in any one of Claims 1 to 8, in which Vanadium is partially or totally replaced by at least one refractory metal which is zirconium, columbium, hafnium, titanium and tantalum.

10. A high speed and tool steel composition substantially as hereinbefore described with reference to any one of the Examples.