After heat treatment and cold drawing hardening, the strength is relatively high, with certain flexibility and plasticity; Under the same surface condition and full quenching condition, the fatigue limit is comparable to that of multicolored alloy spring. But hardenability is very poor, mainly used for smaller size spring, such as pressure regulating speed spring, force spring, general mechanical round, square spiral spring or steel wire as a small mechanical spring.
● Chemical composition:
Carbon C: 0.62 ~ 0.70
Si: 0.17 ~ 0.37
Mn: 0.90 ~ 1.20
S: sulfur 0.035 or less
P P: 0.035 or less
Chromium Cr: 0.25 or less
Ni Ni: 0.25 or less
Copper Cu: 0.25 or less
Mechanical properties:
Tensile strength Rb(MPa) : 735
Yield strength Rs (MPa) : 430
Elongation δ10 (%) : 14~21.5
Section shrinkage ψ (%) : not less than 10
Gb_t699-1999 (High quality carbon structural steel)
Hardness
Hot rolling hardness: 240~270HB
Soft hardness of cold rolling: 190~220HB
Cold rolling hardness: 300~340HB
Hardness of heat treatment: 38~60HRC
Heat treatment
Heat treatment and specification
Quench 830℃±20℃, oil cold; Tempering 540℃±50℃(special needs,±30℃).
Critical point temperature (approximate value) Ac1=726℃, Ac3=765℃, Ar3=741℃, Ar1=689℃, Ms=270℃.
Normalizing specification: Temperature 810±10℃, air cooled.
Specification for quenching and tempering: quenching temperature 830±10℃, oil cooling; Tempering temperature 540℃±10℃, water, oil cooling.
The delivery status
Hot rolled steel is delivered under heat treatment or no heat treatment, cold drawn steel is delivered under heat treatment. (2.0-16) *1250*C Lai Steel/hot coil/hot plate
50Mn (2.0-16) *1250*C Lai Steel/hot coil/hot plate
65Mn (2.0-16) *1010/1250*C Lai Steel/hot coil/hot plate
weight
Sheet: length (M) * width (M) * thickness (mm) * density =KG
Bar: Radius * Radius *3.14* Height * density /1000000=KG
Annealing specification
Traditional periodic spheroidizing annealing process, annealing temperature 750℃, holding 2H, furnace cold to the temperature of (680±10) ℃, holding 3h, furnace cold to 550℃, furnace air cooling. Low production efficiency, oxidation decarbonization rate up to 22%-40%, surface hardness and elasticity can not meet the requirements. New incomplete annealing process, annealing temperature (740±10) ℃, holding for 4h, after the furnace is cooled to 550℃, the furnace is air-cooled. The tensile strength is 600-620mpa, the elongation is 53.5%-40%, the hardness is 209-214hbW, the microstructure is spheroidized pearlite + a small amount of dot pearlite, shorten the production cycle and save energy.
New annealing process
Traditional annealing process, annealing temperature 730℃, holding 13h, refurnace cooling to 650℃, furnace air cooling. New annealing process: annealing temperature (860±10) ℃, holding 45-60min, furnace cold to (750±10) ℃, holding 3-3.5h, after furnace cold to 650-660℃, furnace pile cold or into the holding pit slow cooling. The metallographic structure meets the requirements: the pearlite structure is 2.5-6 grade, and about 4 grade is the best. The process can improve the efficiency by 80%-100%.
Baj popilè: 65mnval structural steel, China, suppliers, manufacturers, factory, buy, price, pricelist, for sale, in stock, free sample
