I. Raw Material Requirements
Low Temperature High Toughness Ductile Iron (QT400-18AL/QT350-22AL)
Clean return material of the same kind that has been shot peened and cleaned without sticking sand.
Key words:
casting
requirements
Classification:
Low temperature high toughness ductile iron
Hotline:
Low Temperature High Toughness Ductile Iron (QT400-18AL/QT350-22AL)
Graphic Details
Medium frequency furnace melting process key points reference
1. pig iron: low silicon, low manganese and high purity pig iron, Si≤ 0.7%,Mn≤ 0.2%,P≤ 0.035%,S≤ 0.02%,Ti ≤ 0.035%,∑ interference element ≤ 0.1%.
2. Scrap steel: rust-free, low-carbon (C≤ 0.2%) and low-manganese (Mn≤ 0.2%) carbon steel without alloying elements.
3. Charging material: clean charging material of the same kind that has been shot peened and cleaned without sticky sand.
4. Accessories: spheroidizing agent ZT-1DF or ZT-1F, inoculant YJ-1, YJ-3, pretreatment agent YCJ-1, carburant C- 1.
II. Burden Proportion
High purity pig iron (65-85)%+ scrap steel (0-15)%+ return charge (remaining)%.
3. chemical composition control
|
Project Elements
|
C
|
Si
|
Mn
|
P
|
S
|
Mg residue
|
∑RE residual
|
∑ interference element
|
|
raw molten iron
|
3.75-3.85
|
0.5-0.7
|
<0.2
|
≤ 0.04
|
<0.02
|
-
|
-
|
<0.10
|
|
Finished products
|
3.50-3.75
|
1.85-2.20
|
<0.2
|
≤ 0.04
|
<0.02
|
0.035-0.06
|
0.008-0.020
|
<0.10
|
IV. Smelting Temperature
The smelting process is basically the same as the production of ordinary ductile iron. The smelting temperature is generally controlled at 1450-1520 ℃, the high temperature standing temperature is 1520-1550 ℃, and the standing time is 5-10 minutes.
Blow temperature: 1450-1480C (depending on how much the ladle size drops). Pouring temperature: 1360-1400 ℃.
V. Spherical and inoculated treatment
ZT-1DF or ZT-1F for spheroidizing agent, with an addition amount of 1.1-1.35%; YJ-3 inoculant for covering inoculation and iron trough inoculation, with an addition amount of 0.5-
1.2, half covered on the nodularizer, the other half rushed in with the flow when the second iron is discharged; The pretreatment agent is YCJ-1 with an addition amount of 0.3-0.4, and is placed opposite the alloy pit at the bottom of the bag (as shown in the figure for packing); YJ-1 for inoculation of gate basin, particle size 0.2-0.7mm, addition amount 0.15.
The 6. body is attached to the cast test block gold-phase tissue, mechanical performance requirements and part of the production example results comparison, respectively, see Table 1. Table 2. Table III.
Table 1: Metallographic structure of the body with cast test block
|
Project
|
spheroidization rate
|
Graphite size classification
|
matrix organization
|
cementite phosphorus eutectic
|
|
Requirements
|
≥85%
|
≥ Level 6
|
F>95%
|
None
|
|
Examples
|
≥ 90%
|
≥ Level 6
|
F≥ 98%
|
None
|
Table II: Mechanical Properties of Body-attached Cast Test Blocks
|
Project
|
wall thickness of casting
(Mm) |
Tensile Strength
(MP/mm2) |
Yield strength
(MP/mm2) |
Elongation
(%) |
Brinell hardness
(HB) |
|
Requirements
|
>30-60
|
≥ 390
|
≥250
|
≥ 18
|
130-180
|
|
>60-200
|
≥ 370
|
≥ 240
|
≥ 12
|
130-180
|
|
|
Examples
|
380-414.5
|
265-311.5
|
≥ 23
|
132-140
|
Table 3: Low temperature impact value of V-notch specimen of body attached casting block
|
Project
|
wall thickness of casting
(Mm) |
Temperature
(℃) |
Minimum impact value (J/cm3)
|
|
|
Average of three specimens
|
Individual value
|
|||
|
Requirements
|
>30-60
|
-20±2
|
≥ 12
|
≥ 9
|
|
>60-200
|
-20±2
|
≥10
|
≥ 7
|
|
|
Examples
|
-20±2
|
18.0 18.8 18.5
|
||
|
-30±2
|
16.5 17.0 15.0
|
|||
|
-40±2
|
13.0 14.0 12.5
|
|||
7. part of the wind power casting mold with casting test block metallographic structure, test bar fracture scanning electron mirror and processing toughness chip photos.
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