Classifications

• • 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
  • 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
  • C21D6/00—Heat treatment of ferrous alloys
  • C21D6/002—Heat treatment of ferrous alloys containing Cr
• • 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
• • 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
  • C22C38/24—Ferrous alloys, e.g. steel alloys containing chromium with vanadium
• • 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
• • 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
  • C21D2211/00—Microstructure comprising significant phases
  • C21D2211/003—Cementite
• • 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
  • C21D2211/00—Microstructure comprising significant phases
  • C21D2211/008—Martensite

Definitions

• the invention relates to a new cold work steel, i.e. a steel intended for the manufacture of tools for cold working. Typical applications are blanking knives, punching tools, deep drawing moulds etc.
• the steels of the table were examined or compared with reference to micro structure, including the type and character of inclusions, response to heat treatment, hardenability, hardness after austenitising and after tempering, dimensional stability, spark machinability, toughness in terms of impact strength and bending strength, abrasive wear resistance, compressive yield point, grindability, and cuttability.
• the steel that satisfies the raised requirements best in terms of the different features mentioned in the foregoing should have the following composition in weight- %: 0.82-0.97 C, 0.70-1.10 Si, 0.38-0.62 Mn, at least 7.6 but less than 8.0 Cr, max 0.40 Ni, 2.30-2.70 Mo, max 0.25 W, 0.35-0.55 V, balance iron, impurities and accessory elements in normal amounts. Further, the steel normally contains max 0.15 N, preferably max 0.03 N, max 0.30 Cu, and max 6 ppm H.
• the Al content must be max 0.1 %, preferably max 0.045 %, but typically it amounts to 0.010-0.045 % as a residual element from the desoxidation treatment of the steel.
• the steel should contain 0.92 C, 0.95 Si, 0.5 Mn, 7.8 Cr, 2.5 Mo, 0.45 V.
• the micro structure of the steel consists, after austenitising at 1000-1080°C, cooling to room temperature and tempering once or several times at 180- 650°C, of tempered martensite, containing a total carbide volume of 3-6 vol-%, preferably 3-5 vol-%, of which 0.25-0.45 vol-% consists of MC carbides and the rest essentially of M 7 C 3 carbides.
• the amount of primary carbides is about 4 vol-%.
• the steel of the invention can be manufactured in a conventional way through production of a melt, which is cast to ingots, which can be hot worked to the shape of bars, plates, etc., of which there can be made tools or other articles, which can be heat treated for the achievement of a final product having the desired combination of features.
• the conventional production of ingots can be complemented by any subsequent melt-metallurgical process step, such as e.g. Electro Slag Refining (ESR) or, as an alternative process, the building up of castings of solidifying drops of the melt, such as the process which is known by the name Osprey.
• ESR Electro Slag Refining
• the steel of the invention is intended to be used for the manufacture of tools for cold working.
• Cold work tools are used e.g. in the automotive industry for blanking, punching, pressing and bending thin steel plates.
• new, ultrahigh strength steels have been developed in recent years.
• One of these steels has been developed by SSAB Tunnplat AB and is known by its trade name DocolTM 1400 DP and contains, besides iron and unavoidable impurities, in weight-% typically: 0.18 C, 0.50 Si, 1.80 Mn, 0.015 P, 0.002 S, 0.040 A, and 0.030 Nb.
• This steel is manufactured in gauges between 0.50 and 2.00 mm, in its delivery condition it has the mechanical features stated in Table 3.
• Steel No. 19 is a steel of the invention.
• the steel was manufactured as a 35 tons production heat in an electric arc furnace. Of the steel there were cast ingots, which were forged and rolled to the shape of bars.
• the contents of nickel, niobium, titanium, and copper are residuals from used raw materials and are unintentional. Aluminium has been added for the desoxidation of the steel, and the stated content of aluminium is a residue from that process.
• Steel No. 20 is a steel according to the above mentioned US-A-5, 160,553, which has been manufactured by another producer.
• the steel, which is commercially available, has been analysed by the applicant with reference to its chemical composition.
• 21, 22, and 23 are commercial steels, which are manufactured by the applicant.
• the contents of steels Nos. 21-23 stated in Table 4 are nominal contents.
• Steel No. 21 is a conventionally manufactured steel, while steels Nos. 22 and 23 have been manufactured powder metallurgically. Besides the contents of the different elements stated in the tables, these steels also contain impurities in normal amounts eminating from the raw materials which were used for the manufacture of steel.
• Punches with the punch diameter 10 mm were manufactured of bars of steels Nos. 19- 23.
• the bar dimensions are listed in Table 5. All punches were taken out from the centre of the bars and cross- wise the bar direction, the longitudinal direction of the punch coinciding with the height direction of the bar.
• the working material consisted of said DocolTM 1400 DP with a thickness of 1.0 mm. The material was cold rolled and heat treated for the achievement of highest strength level and it therefore gave a good indication concerning abrasive wear resistance and ductility/toughness.
• the punching operatings were carried out in a 15 tons excenter press. The punching rate was 200 strokes/min; punching play 6 %; no lubrication.
• the measurement of the wear was made by means of a prism, the curve deviation being measured before and after the punching series. The difference was transformed to number of ⁇ m 2 , which represents the wear.
• Table 5 shows the testing parameters and the registered punch wear after 200,000 punching strokes.
• the table also shows the heat treatment of the tools. All the tools had been hardened from the stated austenitising temperature (T A as is shown in the table) and tempered twice after cooling, each time for two hours at the tempering temperature given in the table.

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• 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)
• Forging (AREA)
• Heat Treatment Of Sheet Steel (AREA)

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Publications (2)

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• 1998
  • 1998-03-27 SE SE9801045A patent/SE511747C2/sv not_active IP Right Cessation
• 1999
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  • 1999-03-08 CN CN99804471A patent/CN1098369C/zh not_active Expired - Lifetime
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  • 1999-03-08 WO PCT/SE1999/000346 patent/WO1999050469A1/en active IP Right Grant
  • 1999-03-08 JP JP2000541355A patent/JP2002509987A/ja active Pending
  • 1999-03-08 DE DE69907896A patent/DE69907896D1/de not_active Expired - Lifetime
  • 1999-08-12 TW TW088113776A patent/TW500810B/zh not_active IP Right Cessation
• 2001
  • 2001-06-27 HK HK01104421A patent/HK1033964A1/xx not_active IP Right Cessation

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