Valve casting molten steel melting and pouring

See Table 1 and table 2 for the technical requirements and measured chemical composition of castings.

NameCSiMnPSCrNiMoN
Ingredients≤ 0.030.40-0.800.7-1.2≤ 0.03≤ 0.0224-266-83-50.24-0.32

The liquid steel of this steel has poor fluidity, easy to produce cold shut, easy to oxidize at high temperature and easy to form oxidized inclusions. Therefore, we regard the melting of liquid steel as the top priority of the whole process. The melting is divided into the following steps.

NameCSiMnPSCrNiMoN
Ingredients0.0250.690.530.0360.01424.866.603.480.26

(1) Dry the alloy before melting the molten steel. All alloy charge and slag collector are placed in the furnace at 200 ~ 300 ℃ for 2 ~ 3 hours.

(2) Molten steel is melted in a 3T medium frequency furnace. The main material is industrial pure iron, and the auxiliary materials are V3 Cr iron, Ni plate, Mo iron, electrolytic Mn and industrial Si. First, pure iron is added, and Ni, Cr, Mo and other alloy elements are added in the middle of power transmission and melting. Key points: control the content of C, Cr, Mo and Ni, and detect the composition spectrum according to the above production control chemical composition table.

(3) AOD furnace is used to refine steelmaking liquid. The function of this furnace is to remove C, P and s, eliminate non-metallic slag inclusion, increase the content of N and stably control the tapping temperature. The key point here is to ensure the content of N, control the content of C, P and s off the line, and adjust the content of Cr off the line.

(4) Pouring out of furnace; After the chemical composition is qualified through spectral inspection, the material is easy to oxidize and absorb air. During pouring, special attention shall be paid to large flow at the beginning to speed up the pouring speed. The upper part of the ladle and gate shall be protected with argon. When pouring to the riser root, the flow shall be reduced to half. While pouring, the flow shall be reduced, and thermal insulation agent shall be added.

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