Usually by using alloy steel moulds, steel all carbon tool and high speed steel, the organization is the hardening of the crystal structure, the non-infarct-related have microcrack high carbon needle, flake martensite. Due to the high carbon, carbide in steel form elements, inevitably meshy, belt and chain carbide, often cause mould in use of brittle fracture. Due to the low carbon martensite structure is wrong, and has high intensity (hardness of 45hrc ~ factors, yield strength for 1000mpa ~ 1300mpa), good plastic (delta 5 p 10%, ψ experiment.it akv (40%) and toughness and good 59j p) cold processing, weldability and heat distortion etc. Therefore, how to make the steel quenching organization get more, even all the low carbon martensite, is to improve the mould tenacity and prolong the service life of die. Now is the development direction of low carbon steel quenching organization hopes to get all the plank martensite, to ensure the high tenacity, Drawing on reducing carbon content or tend to minimize quenching temperature to reduce the number of martensite non-infarct-related crystal, in order to ensure material tenacity, For carbon steel tend to get more high-temperature quenching, all or low carbon martensite organization, to improve the fracture toughness.
Low carbon martensite in plastic mould application

1 low carbon martensite carburizing steel type plastic

Low carbon steel, low alloy steel mold in forming after carbrization, quenching and tempering, make the mold surface get high carbon fine needle tempered martensite + granular carbide + small residual austenite, mainly for the heart of low carbon steel. Ensure mold surface with high hardness 58hrc (62hrc ~), wear resistance, and heart of high tenacity 30hrc (45hrc ~), used in the manufacture of complex shape, good abrasion resistance, high load of plastic forming mold.

2 ultra-low carbon cold extrusion plastic mold steels

Extensive application of ultra-low carbon steel cold extrusion technology and manufacturing plastic mould. Due to cold extrusion, except for low carbon content, the softening annealing, hardness, low (or 160hbs when 130hbs acuities extrusion complex cavity), particularly suitable for cold plastic deformation. This kind of steel in cold extrusion after carbrization, quenching and tempering. So has the high production efficiency and precision mould manufacturing cycle is short, the higher strengths. The typical American p series are the kinds of low carbon steel, Germany x6crmo4 steel (mass fraction, 0.07% acuities c, similarly hereinafter) and homebred lj - 08cr3nimov steel (0.08% acuities c).

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3 low carbon steel (martensite than 0.25% c) plastic steel type tenacity

Low carbon steel, low carbon martensite including carbon steel and low alloy steel by low carbon martensite after quenching process, strong toughness of high intensity, low carbon martensite replace medium-carbon steel treatment weeken or low permeability, nitrogen treatment, applicable to make various of plastic pattern, can significantly reduce manufacturing cycle, mould manufacturing cost and improve the service life of heat treatment in plastic mould, a wide range of applications.

4 low carbon limitation of martensite steel plastic sclerosis type

(1) low carbon steel martensite limitation

The steel with high QuJiang ratio, good cutting and welding performance and heat treatment process was simple, etc. Typical 18ni ultra-low carbon steel castings is 0.03% series (c), because more than 18ni steel expensive, in domestic rarely used. In recent years, the development 06ni6crmovtial (hereinafter referred to as 06 steel, 0.06% c), than low nickel, low carbon steel martensite limitation. This steel by 800 ~ 88 ° heating, cooling water or oil quenching, (5-540) degrees Celsius * (4-8) h after aging treatment of organization for low carbon martensite + precipitation strengthening phase ni3al ni3ti, tin, hardness, the tic and 42hrc for 45hrc ~ ~ ~ 1400mpa 1100mpa, yield strength. 06 steel is usually used to manufacture of tape box mould, its tape-recorder life expectancy > 1.1 million, is a promising material.

(2) homemade low carbon martensite steel separation (precipitation)

Typical for 25crni3moal castings and 10ni3mncual (pms-algebra), applicable to make request for deformation, mirror requirements or < 0.05% surface requirements of precision mirror lithography pattern process plastic mold. One 25crni3moal steel by 8.3 degrees solution, hardness, can reach 540 degrees Celsius (factors after aging treatment, hardness 4h 42hrc; for 39hrc - 870 degrees Celsius (PMS steel by 1h solution, 510 degrees Celsius (4h after aging treatment of microstructure for low carbon martensite distribution on a tiny dispersion matrix and its hardness intermetallic compound for 40hrc ~ 43hrc, tensile strength for 1000mpa 1300mpa ~.

5 low carbon martensite steel corrosion type plastic

(1) low carbon martensitic stainless steel

Main material for 2cr13 steel (c) (by 0.16% 0.25% ~ ~ ~ 1cr17ni2 and steel (c), 0.17% 0.11 per cent in corrosive medium applies to manufacture of plastic mold, transparent plastic mould.

(2) low carbon martensite precipitation (precipitation) sclerosis type of stainless steel

Typical for domestic steel castings 07cr16ni4cu3nb (0.07% c, than the steel, cr) referred by 10.5 degrees quenching after single low carbon martensite organization, hardness is 32hrc ~ 35hrc, can direct cutting, 46 ° ~ 480 degrees by after aging treatment, hardness is 42hrc ~ 44hrc, good mechanical properties and corrosion. Such as vinyl fluoride clustering valve cover three original USES 45 steel mold, chromium plating processing mould, service life for 10 ~ 4,000 pieces, convert low carbon steel, martensite PCR life can reach 10000-20000.

Low carbon martensite in cold mould application

1 the mild cold mould hardened martensitic strong low carbon

Some countries have already in the cold steel standard on the low carbon steel (martensite than 0.25% c), for example iso4957.1999 in the cold steel alloy has the following kinds: "5crmo4 steel (0.07% c), more than 7crmoni2 steel (c), 20cr13 than 0.10% steel (c) (by 0.16% 0.25% ~, German tool steel castings 21mncr5: (c), before closing 0.16% up ~ 0.24% x6crmo4 steel (0.07% c), more than 15nicr18 steel (ds 0.17% ~ c).

China also has a lot of application of low carbon steel quenching process of martensite strong cold mould manufacturing. P# # # # e# title page

(1) 20 steel serrated lock washer for stamping die this cold stamping steel strip (65mn 179hbs ~ 217hbs). The original USES t10 steel (48hrc ~ factors), use life < 15 times, After cr12mov adopts steel (48hrc ~ factors), service life is 3000 times, With 20 steel (46hrc ~ 48hrc), the service life of 3 ~ 4 million times as its process for (9.1 ± 10) degrees, 10% nacl brine cooling heating, tempering, and cheaper to use directly.

(2) of q235 steel plate shears blade forgings tire mould punch bolts, 9sicr gcr15 selection had 45 steel, t8 and have bite because, mould casting mould phenomenon, forging die out of difficult from, punch, plastic deformation and fracture, short life, every 10 punch about 800-1200 pieces blunt bolts, And using of q235 steel material, the punch do 950 degrees c x 5min 10% nacl salt, salt water heating furnace quenching cooling after tempering directly use, hardness is 36hrc ~ 10 pieces, each 40hrc blunt bolts can punch 2,000 above, and failure form of plastic deformation, eliminating the use of fractured phenomenon, i. guarantee the safety of operators.

(3) 20crmnti steel suppression of aluminum extrusion die d16 d20 and cold pressing of aluminum wire type of cold extrusion die by the CRWMN after tempering steel quenching, hardness is 45hrc ~ factors, though hardness requirement in cold extrusion die because of low carbon steel, but CRWMN uniformity, hard to avoid mesh belt, and thus collapse carbide blade, craze and premature failure, service life is only 1000 pieces, and some even a few hundred thing only. Choose 20crmnti steel production d16 d20 and aluminum extrusion die of cold and heat brine by 950 degrees c, tempering directly after quenching, mould for 46hrc ~ 48hrc hardness, suppression of more than 2000 aluminum, continues to use.

(4) 20cr steel cold mould the steel by carburizing quench surface treatment, can make the mold surface fine needle tempered martensite, hardness is 62hrc; 58hrc - Heart of low carbon obtain martensitic organization, hardness, 35hrc ~ 40hrc matrix tenacity, can satisfy the cold die with high hardness and high strength and high toughness performance requirements. For example, the hose connector anise zinc alloy, hardness requirement 58hrc punch mould 62hrc ~. The cr12mov adopts steel manufacturing mode of life is short, octagon, often less than 2,000 will rupture, The punch materials into 20cr by carburizing steel and deep carbonitriding layer after treatment, 1.2 mm mm ~ 1.0, hardness is 60hrc ~ 62hrc, service life is increased to 3 million pieces.

2 carbon steel cold mould hardened martensitic high low carbon

For carbon steel mold, can make cold through improving the austenitic temperature, make the austenitic grain more evenly, tends to reduce carbon content, ms, thereby gaining more elevated point of low carbon martensite organizations, improving the tenacity, mould extended cold as the life of dies.

(1) 5crmnmo steel cold dui machine mould temperature of cold upsetting nut quenching will 5crmnmo steel quenching temperature to 900 degrees - 950 degrees c, can get almost single low carbon martensite organization. For example, using 5crmnmo steel production z41.24 type of multistage cold dui machine, cold dui nut by 900 degrees ~ 180 ° c heating, 930 grading quenching, 200 ° c * 2 times after treatment, low tempering longer than 2.6 times to improve cr12mov steel, can completely replace the t10a, 9crsi, cr12mov steel manufacture large cross-section of cold upsetting.

(2) 60si2mna steel cold-heading nuts and sequence of high temperature quenching 60si2mna stamping steel in high temperature quenching, organization of the growing number of martensite plate

And even can obtain martensitic batten, all have higher fracture toughness and impact toughness and good wear resistance. 60si2mna steel cooling forging die, the sequence of four nuts 92 degrees ~ 950 degrees c, life after quenching than normal temperature quenching mould raised about 2 times.

(3) 5crw2si steel cold temperature quenching 5crw2si shear modulus, the cold steel shear 950 degrees c quenching and tempering 250 ° c, attrib wattle martensite after adding a few evenly distributed in the carbide and wattle martensite boundary of tiny remains austenitic organization, can significantly improve the cold shear strength and toughness of shear blade, life 1.5 ~ 5 times.

3 high cold mould hardened martensitic low carbon temperature

High cold die quenching temperature, austenitic solid solubility of carbon content is low, ms hotter, low carbon martensite quantity. Therefore mould has high abrasion resistance and strong toughness, deformation and cracking.

(1) t10a steel mould temperature of cold upsetting short-term heating t10a steel quenching cold-heading mode (light), according to the original technology (780 c x 20min salt bath when heated quenching) processing chip non-infarct-related martensite organization, existing microcrack, under impactloading, due to poor, often produce collapse toughness. Now using 750 degrees Celsius (14min salt bath heating quenching, 200 ° c, can be tempered martensite small flakes and 50% (volume fraction) above the low carbon martensite, reduced microcrack, ensure high hardness, high toughness, thereby improving longevity nearly doubled.

(2) CRWMN steel small mould temperature quenching in CRWMN steel manufacturing watches with small protruding models, the conventional heat treatment of mould