Gray iron, or Grey Cast Iron, is a type of cast iron that has a graphite microstructure. It is named after the gray color of the fracture it forms. The gray cast iron is used for custom grey iron castings where the stiffness of the component is more important than its tensile strength, such as internal combustion engine cylinder blocks, pump housings, valve bodies, electrical boxes, counter weights and decorative castings. Grey cast iron's high thermal conductivity and specific head capacity are often exploited to make cast iron cookware and disc brake rotors. Grey cast iron (also called grey cast iron) is a group of cast iron including several kinds of grade according to different designation of diverse standards. Gray cast iron is a kind of iron-carbon alloy and it gets its name "grey" from the fact that their cutting sections looks grey. The metallographic structure of gray cast iron is mainly composed of flake graphite, metal matrix and grain boundary eutectic. During the grey iron, the Carbon is in the flake graphite. As one of the widely used casting metals, cast gray iron has many advangates in costs, castability and machinablity.
Mechanical Properties of Cast Gray Iron
Tensile Strength of Separately Cast Samples of Gray Cast Irons
Material Designation
HT100
HT150
HT200
HT250
HT300
HT350
Equivalent Materials
GG-10, EN-GJL-100
GG-15, EN-GJL-150
GG-20, EN-GJL-200
GG-25, EN-GJL-250
GG-30, EN-GJL-300
GG-35, EN-GJL-350
Tensile Strength (MPa)
≥100
≥150
≥200
≥250
≥300
≥350
Tensile Strength of Cast-on Samples of Gray Cast Irons
Material Designation
Wall Thickness of Casting (mm)
Tensile Strength (MPa) ≥
Sample Bar Dia. (mm)
Sample Block (mm)
Castings (Reference)
φ30
φ50
R15
R25
HT150, GG-15, EN-GJL-150
20-40
130
/
120
/
120
40-80
115
115
110
/
105
80-150
/
105
/
100
90
150-300
/
100
/
90
80
HT200, GG-20, EN-GJL-200
20-40
180
/
170
/
165
40-80
160
155
150
/
145
80-150
/
145
/
140
130
150-300
/
135
/
130
120
HT250, GG-25, EN-GJL-250
20-40
220
/
210
/
205
40-80
200
190
190
/
180
80-150
/
180
/
170
165
150-300
/
165
/
160
150
HT300, GG-30, EN-GJL-300
20-40
260
/
250
/
245
40-80
235
230
225
/
215
80-150
/
210
/
200
195
150-300
/
195
/
185
180
HT350, GG-35, EN-GJL-350
20-40
300
/
290
/
285
40-80
270
265
260
/
255
80-150
/
240
/
230
225
150-300
/
215
/
210
205
Note: When the thickness is over 300 mm, the exact mechanical properties are confirmed by the venders and buyers.
Tensile Strength of Gray Iron Casting in Different Wall Thickness
Cast Wall Thickness (mm)
Material Designation
HT100, GG-1, EN-GJL-100
HT150, GG-15, EN-GJL-150
HT200, GG-20, EN-GJL-200
HT250, GG-25, EN-GJL-250
HT300, GG-30, EN-GJL-300
HT350, GG-35, EN-GJL-350
Tensile Strength (MPa) ≥
2.5-4.0
130
175
220
/
/
/
4.0-10
270
10-20
100
145
195
240
290
340
20-30
90
130
170
220
250
290
30-50
80
120
160
200
230
260