Manufacturing process of high-strength spheroidal graphite cast iron sleeve pieces

A nodular cast iron, manufacturing process technology, applied in the field of casting, can solve problems such as functional failure and inability to guarantee strength

Inactive Publication Date: 2020-01-07

江苏万恒铸业有限公司

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AI-Extracted Technical Summary

Problems solved by technology

The conventional casting process cannot guarantee the strength and elonga...

Abstract

The invention relates to the casting industry, and provides a manufacturing process of high-strength spheroidal graphite cast iron sleeve pieces. The products manufactured by means of the process arehigh-strength spheroidal iron which mainly has the shop signs of the national standard QT700-3 and the national standard QT900-2. For the QT700-3 spheroidal iron, the tensile strength is larger than or equal to 800 Mpa, and the ductility is larger than or equal to 3%; and for the QT900-2 spheroidal iron, the tensile strength is larger than or equal to 900 Mpa, and the ductility is larger than or equal to 2%. The QT700-3 spheroidal iron reaches the advanced international standard-American standard ASTM A536 Grade100-70-03, the QT900-2 spheroidal iron correspondingly reaches the advanced international standard-American standard ASTM A536 Grade120-90-02, the spheroidization rate reaches 85% or above, and the compactness of the metallographic structure is high. The oxide inclusion is not higher than level II. The high-strength spheroidal graphite cast iron sleeve pieces are resistant to corrosion, abrasion and high temperature, and capable of achieving a good shock absorption effect, are not liable to crack, and are high in strength and free of deformation. The high-strength spheroidal graphite cast iron sleeve pieces are widely applied to crankshafts, shaft sleeves, gears, tool tracksand other mechanical parts.

Technology Topic

DuctilityCrankshaft +6

Examples

Experimental program(1)

Example Embodiment

[0022] 1. Production preparation: use Q10 pig iron, ferrosilicon, ferromanganese, spheroidizing agent, inoculant, and pure metals for added elements. Centrifugal casting is used, and intermediate frequency furnace is used for melting equipment;

[0023] 2. Melting method: smelting in an intermediate frequency furnace, slagging, slagging, recarburization, deoxidation, desulfurization, dephosphorization, degassing, and debris removal, that is, adjusting composition and temperature;

[0024] Composition control: refers to the control of key elements of ductile iron castings during chemical composition testing

[0025] C=3.2~3.8﹪, Si=1.5~2.5﹪, Mn=0.5~1.0﹪, Ni=0.5~1.5﹪, Cu=0.02~0.05﹪, Mg=0.035~0.06﹪, the control of harmful elements S≤0.02﹪ , P≤0.06﹪, other components shall be implemented according to relevant standards;

[0026] 3. Purification of molten iron: adding covering agent to the furnace, slagging and slagging repeatedly;

[0027] 4. Regulating temperature: keep the molten iron in the furnace at a temperature of 1460-1500℃;

[0028] 5. Spheroidizing treatment: add proper amount of magnesium alloy spheroidizing agent after calculation into the spheroidizing bag to make the graphite shape approximate to a spherical shape;

[0029] 6. Inoculation treatment: add proper amount of ferrosilicon powder after calculation into the spheroidizing bag;

[0030] 7. Measuring molten iron: weighing molten iron is 1.05~1.1 times the weight of the sleeve;

[0031] 8. Centrifugal pouring; select the centrifuge speed, start the centrifuge, turn on the water cooling system, and pour into the mold cavity at a temperature of 1420 to 1460°C;

[0032] 9. Mold opening cleaning: the mold opening temperature is the surface temperature of the thickest part of the casting <500℃ before the casting can be taken out;

[0033] 10. Heat treatment: adopt the quenching + tempering treatment method, the castings are put into the furnace at room temperature, the test bars of the same furnace number, the same batch, and the same furnace are treated, the quenching heating rate is ≤220℃/h, the holding temperature is 920-940℃, and the heat preservation More than 3h, tempering heating rate ≤220℃/h, heat preservation temperature 680℃, heat preservation more than 4h, castings ≤500℃, air cooling; 11. Shot blasting: clean up with steel shot blasting, and remove excess parts on the casting;

[0034] 12. Physical and chemical inspection:

[0035] Chemical composition: C=3.2~3.8﹪, Si=1.5~2.5﹪, Mn=0.5~1.0﹪, Ni=0.5~1.5﹪, Cu=0.02~0.05﹪, Mg=0.035~0.06﹪, control of harmful elements S ≤0.02﹪, P≤0.06﹪,

[0036] Mechanical properties: tensile strength> 835Mpa, yield strength> 630Mpa, elongation> 6%.

[0037] 13. Non-destructive testing: PT, VT, and RT three testing methods are used.

[0038] Defect welding repair: when eliminating surface defects, if the wall thickness is less than the minimum thickness or the surface crack depth is greater than 0.8mm, the casting is scrapped and welding repair is not allowed. For defects that can be repaired by welding, the principle of repair welding is: 2 repair welding is not allowed; repair welding area: not more than 3% of the total area.

[0039] 14. Inspection and warehousing: After the blank is qualified, the surface will be put into the warehouse after rust prevention treatment.

PUM

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