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Castings of Stainless Steel, Alloy & Carbon Steel, Cast Iron, etc.

Grey Cast Iron Magnetic Properties

Gray Iron Comparison Microstructure(Volume Fractions)(%)
China(GB/T 9439) ISO 185 ASTM A48/A48M EN 1561 Matrix Structure
HT100 (HT10-26) 100 No.20 F11401 EN-GJL-100 Pearlite: 30-70%, coarse flakes; Ferrite: 30-70%; Binary Phosphorus Eutectic: <7%
HT150 (HT15-33) 150 No.25A F11701 EN-GJL-150 Pearlite: 40-90%, medium coarse flakes; Ferrite: 10-60%; Binary Phosphorus Eutectic:<7%
HT200 (HT20-40) 200 No.30A F12101 EN-GJL-200 Pearlite: >95%, medium flakes; Ferrite<5%; Binary Phosphorus Eutectic<4%
HT250 (HT25-47) 250 No.35A F12401 No.40A F12801 EN-GJL-250 Pearlite: >98% medium thin flakes; Binary Phosphorus Eutectic:<2%
HT300   (HT30-54) 300 No.45A F13301 EN-GJL-300 Pearlite: >98% medium thin flakes; Binary Phosphorus Eutectic:<2%
HT350   (HT35-61) 350 No.50A F13501 EN-GJL-350 Pearlite: >98% medium thin flakes; Binary Phosphorus Eutectic:<1%

 

The magnetic properties of gray cast iron vary widely, from low permeability and high coercive force to high permeability and low coercive force. These changes mainly depend on the mictrostructure of gray cast iron. Adding alloying elements to obtain the required magnetic properties is achieved by changing the structure of gray cast iron.

Ferrite has high magnetic permeability and low hysteresis loss; pearlite is just the opposite, it has low magnetic permeability and large hysteresis loss. Pearlite is formed into ferrite by annealing heat treatment, which can increase the magnetic permeability by four times. Enlarging ferrite grains can reduce hysteresis loss. The presence of cementite will reduce the magnetic flux density, permeability and remanence, while increasing the permeability and hysteresis loss. The presence of coarse graphite will reduce the remanence. The change from A-type graphite (a flake-shaped graphite that is uniformly distributed without a direction) to a D-type graphite (a finely curled graphite with a non-directional distribution between dendrites) can significantly increase the magnetic induction and coercive force.

Before reaching the non-magnetic critical temperature, the temperature rise significantly increases the magnetic permeability of gray cast iron. The Curie point of pure iron is the α-γ transition temperature of 770°C. When the mass percentage of silicon is 5%, the Curie point will reach 730°C. The Curie point temperature of cementite without silicon is 205-220°C.

The matrix structure of commonly used grades of gray cast iron is mainly pearlite, and their maximum permeability is between 309-400 μH/m.

 

Magnetic Properties of Grey Cast Iron

Code of Grey Iron Chemical Composition (%)
C Si Mn S P Ni Cr
A 3.12  2.22  0.67  0.067  0.13  <0.03 0.04 
B 3.30  2.04  0.52  0.065  1.03  0.34  0.25 
C 3.34  0.83 - 0.91 0.20 - 0.33 0.021 - 0.038 0.025 - 0.048 0.04  <0.02
Magnetic Properties A B C
Pearlite Ferrite Pearlite Ferrite Pearlite Ferrite
Carbide Carbon w(%) 0.70  0.06  0.77  0.11  0.88  /
Remanence / T 0.413 0.435 0.492 0.439 0.5215 0.6185
Coercive Force / A•m-1 557 199 716 279 637 199
Hysteresis Loss / J•m-3•Hz-1 (B=1T) 2696 -696 2729 1193 2645 938
Magnetic Field Strength / kA•m-1 (B=1T) 15.9 -5.9 8.7 8.0  6.2 4.4
Max. Magnetic Permeability / μH•m-1 396 1960 353 955 400 1703
Magnetic Field Strength when Max. Magnetic Permeability / A•m-1  637 199 1035 318 1114 239
Resistivity / μΩ•m 0.73 0.71 0.77 0.75 0.42 0.37

 

Here in the following are the mechanical properties of grey cast iron:

Mechanical Properties of Gray Cast Iron

Item according to DIN EN 1561 Measure Unit EN-GJL-150 EN-GJL-200 EN-GJL-250 EN-GJL-300 EN-GJL-350
EN-JL 1020 EN-JL 1030 EN-JL 1040 EN-JL 1050 EN-JL 1060
Tensile Strength Rm MPA 150-250 200-300 250-350 300-400 350-450
0.1% Yield Strength Rp0,1 MPA 98-165 130-195 165-228 195-260 228-285
Elongation Strength A % 0,3 – 0,8 0,3 – 0,8 0,3 – 0,8 0,3 – 0,8 0,3 – 0,8
Compressive Strength σdB MPa 600 720 840 960 1080
0,1% Compressive Strength σd0,1 MPa 195 260 325 390 455
Flexural Strength σbB MPa 250 290 340 390 490
Schuifspanning σaB MPa 170 230 290 345 400
Shear Stress TtB MPa 170 230 290 345 400
Modules of elasticity E GPa 78 – 103 88 – 113 103 – 118 108 – 137 123 – 143
Poisson number v 0,26 0,26 0,26 0,26 0,26
Brinell hardness   HB 160 – 190 180 – 220 190 – 230 200 – 240 210 – 250
Ductility σbW MPa 70 90 120 140 145
Tension and pressure change σzdW MPa 40 50 60 75 85
Breaking Strength Klc N/mm3/2 320 400 480 560 650
Density   g/cm3 7,10 7,15 7,20 7,25 7,30

 

 


Post time: May-12-2021