Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C33/00—Making ferrous alloys
  • C22C33/02—Making ferrous alloys by powder metallurgy
  • C22C33/0257—Making ferrous alloys by powder metallurgy characterised by the range of the alloying elements
  • C22C33/0278—Making ferrous alloys by powder metallurgy characterised by the range of the alloying elements with at least one alloying element having a minimum content above 5%

Definitions

• TECHNICAL FIELD This invention relates to a cold work steel, i.e. a tool steel intended for use near room temperature, in the first place for cutti and punching metallic materials but also for plastically forming col working operations, as for example for deep-drawing tools and for cold-rolling rollers.
• the invention also relates to a method of manufacturing the steel utilizing powder-metallurgy including the consolidation of metal powder to a dense body.
• the steel is inter al characterized by a very high impact strength in combination with an extremely good wear resistance, which makes the steel very useful fo punching and cutting tools.
• Cold work steels for cutting, punching or, forming metallic materials shall fulfil a number of demands which are difficult to combine. Particularly high demands are raised upon the impact strength, especially when the tool is intended for cutting or punching adhesiv materials (adhesive wear), as for example austenitic stainless steel Further, the tool material must not be too expensive, which limits t possibility of choosing high contents of expensive alloying components.
• the wear resistance of steels can also be improved by providing the steel object with a thin coating of a very wear resistant material.
• CVD-technique Chemical Vapour Deposition
• CVD Chemical Vapour Deposition
• the method also have some drawbacks which often render it impossible to " - use; it can be utilized only for the coating of comparatively small objects; the siz tolerances cannot be adjusted to any greater extent after the application of the CVD-coating; and it is very expensive.
• the steel shall, in order to achieve the above mentioned objects, contain 0.5-2.5 % C, 0.1-2 % Si, 0.1-2 % Mn, 0.5-1.5 % N, max 15 % Cr, preferably 6.5-11 % Cr, max 4 Mo, max 1 % W, 3-15 % V, wherein up to half the amount of vanadium c be replaced by 1.5 times as much niobium, and part of the vanadium c be replaced by titanium at a content up to four times the content of nitrogen and the double amount of zirconium at a content up to eight times the content of nitrogen, and wherein the ratio V/(C + N) shall amount to not- less than 2.5 and not more than 3.8, balance essential only iron, impurities and accessory elements in normal quantities.
• T total content of carbides, nitrides and carbonitrides amounts to between 5 and 20 volume-%, preferably between 5 and 12 volume-%. Carbon which is not bound in the form of carbides or other hard components, about 0.5-1 % C, is dissolved in the steel matrix.
• the steel according to the invention can be manufactured in the following way. A melt of molten metal is provided, the melt contain max 0.5 N and in other respects having the composition identified above. From this melt there is made a metal powder, suitably throug 5 conventional gas atomization, nitrogen being used as an atomizat'ion gas.
• This powder is heated to a temperature between 500° and 1000°C preferably to between 650° and 850°C, however not -above the A -temperature of the steel and is nitrided by means of nitrogen g in the ferritic state of the steel at the said temperature for so
• the above equations which define the contents of carbon and nitrogen in relation to the contents of vanadium are due to the following considerations.
• the carbon content in the matrix of the steel shall b so high that the desired hardness in the maxtrix is achieved after hardening and tempering, such that a high pressure strength is obtained in order to avoid problems because of blunting due to ? deformation of cutting edges in the case when the steel shall be use for punching or cutting tools.
• the steel shall contain as much vanadium-carbonitrides as is possibl without the toughness being reduced to an unacceptable level, i.e. i order to obtain as optimal mode of operation as is possible through low friction between tool and work piece and through sufficient toughness for avoiding flaking.
• Fig. 1 in the form of a diagram illustrates the wear of punches ma of tested material as a function of the number of cutting operations in the case of punching stainless steel (adhesiv wearing conditions) ,
• Fig. 2 in a corresponding mode illustrates the wear of the punches in the case of punching high strength steel strips (abrasiv wearing conditions)
• Fig. 3 in the form of bar charts illustrates the impact strength o a number of examined steels through testing un-notched test bars at room temperature.
• Steels Nos. 1-3 and 7-10 were made from gas atomized steel powder, which was consolidated in a manner known per se through hot isostat pressing to full density.
• Steels Nos. 4, 5 and 6 consisted of commerically available reference materials.
• Steels Nos. A and 5 consisted of powder-metallurgically manufactured high speed steels, while steel No. 6 was a conventionally manufactured cold work steel
• the compositions for steels Nos. 1-3 and 7-10 were analyzed composi tions, while the compositions for the reference materials Nos. 4, 5 and 6 are nominal compositions.
• the compacted billets of steels Nos. 1, 2, 3, and 7, 8, 9 and 10 were forged to appr 80 x 40 mm.
• the punches and the dies were hardened and temperered according to the following:
• the manufactured punches and dies were used for wear experiments.
• This figure also shows a typical appearance of a defect caused by wear on a punching tool.
• the tool made of the steel No. 7 of the invention did not show any noticeabl damage due to wear.
• the CVD-coated steel No. 10 exhibited a ve good resistance to this type of wear as well as the steels 8 and 9 the invention, which can be said to have a resistance comparable wi that of the CVD-coated steel.
• Steels Nos. 1-3 also demonstrated a g resistance to this type of wear while the other tested materials ha pronouncedly lower values.
• steel No. 7 had a combination of features which is the far best for cold work steels, particularly for punching and cutting tools, when the resistance to wear is the critical feature and moderately high demands are raised upon the impact strength.
• the steel of the invention containing 3-5 % vanadium and the carbon and nitroge contents mentioned in the claims provide an optimal combination of features for cold work steels for the most frequent applications of cold work steels, while steels with higher vanadium contents in combination with the carbon and nitrogen contents as mentioned in the claims may be advantageous when very high demands are raised with reference to low wear while only normal demands are raised upon the toughness of the material.

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Powder Metallurgy (AREA)
• Solid-Phase Diffusion Into Metallic Material Surfaces (AREA)

Priority Applications (3)

Applications Claiming Priority (3)

Publications (1)

Family

ID=25673082

Family Applications (1)

Country Status (8)

Cited By (8)

Families Citing this family (16)

Citations (4)

Family Cites Families (2)

• 1987
  • 1987-03-19 SE SE8701127A patent/SE456650C/sv not_active IP Right Cessation
• 1988
  • 1988-03-11 US US07/399,491 patent/US4936911A/en not_active Expired - Fee Related
  • 1988-03-11 JP JP63502853A patent/JPH02502736A/ja active Pending
  • 1988-03-11 WO PCT/SE1988/000123 patent/WO1988007093A1/en active IP Right Grant
  • 1988-03-11 EP EP88902966A patent/EP0417082B1/en not_active Expired - Lifetime
  • 1988-03-11 DE DE3889127T patent/DE3889127T2/de not_active Expired - Fee Related
  • 1988-03-11 AU AU14939/88A patent/AU1493988A/en not_active Abandoned
• 1989
  • 1989-09-25 CA CA000612784A patent/CA1339767C/en not_active Expired - Fee Related

Patent Citations (4)

Also Published As

Similar Documents

Legal Events