Analysis and Improvement of Slag Hole Defects on the Surface of Heavy Section Machine Tool Tray Casting

1. Casting Basic Information and Technical Requirements

InformationDetails
Casting Outline SizeApproximately 800 mm×800 mm×200 mm
Product Weight700 kg
Product MaterialHT300
Surface Quality RequirementNo casting defects such as porosity, sand holes, slag holes allowed after machining
Existing ProblemSlag holes and inclusions on the upper surface of each casting, affecting appearance quality and customer installation effect

2. Casting Process Scheme Analysis

2.1 Pouring System Design

Pouring System ComponentSpecifications
Direct Pouring Channelϕ60 mm ceramic tube
Cross Pouring ChannelUpper 40 mm, lower 50 mm, height 50 mm trapezoidal
IngateWidth 60 mm, thickness 7 mm, quantity 6
Section Ratio of Pouring System∑s内:∑s损:∑s在=1:1.8;1.2
FilterTwo 100 mm×100 mm×22 mm 20 PPI filters placed upright on the cross pouring channel

2.2 Filling and Solidification Simulation Analysis

Simulation AspectObservation
Flow FieldTurbulence, air entrainment, and gas wrapping are obvious after molten iron enters the cavity, causing severe oxidation of molten iron
Temperature Field
Oxide InclusionsOxide film leads to the risk of secondary oxidation slag inclusion, and slag defects appear on the side wall and upper plane
Particle Tracking

3. Process Optimization and Improvement Results

3.1 Pouring System Optimization

Optimization ItemBefore OptimizationAfter Optimization
Pouring System TypeSemi-closedOpen
Ingate Size60 mm×7 mm100 mm×10 mm
Section Ratio of Pouring System∑s内:∑s损:∑s在=1:1.8;1.2∑s内:∑s损:∑s在=1:0.75;0.47
Molten Iron Filling StatusTurbulent, with slag and gas problemsStable, with reduced secondary slag

3.2 Reduction of Oxides and Sulfides

Improvement MeasureDetails
Selection of Curing AgentUse a low acidity curing agent with an addition amount of about 45% to reduce sulfur content in recycled sand
Adjustment of InoculantChange from silicon-calcium-barium inoculant to ferrosilicon inoculant
Selection of CoatingUse antioxidant, anti-seepage sulfur shielding coating to prevent sulfur infiltration and reduce iron oxidation

3.3 Effect Verification

Verification ResultDescription
Casting Defect StatusSlag hole defects are significantly reduced, the surface is clean, and no large slag holes appear
Production VerificationMultiple small-batch production verifications have been carried out in similar products, with a significant reduction in slag hole defects and a greatly reduced rejection rate

4. Conclusions

  1. The design of the pouring system is crucial. For different types of products, a suitable pouring system can effectively prevent slag and ensure stable molten iron flow during filling, reducing casting defects.
  2. Numerical simulation technology is used to analyze the feasibility of the casting process. By referring to the simulation results, the process rationality is evaluated and optimized to minimize potential problems and casting defects in production, thereby improving product quality.
  3. The selection of coatings is also important for different product structures and production processes. Appropriate coatings can help reduce casting defects, improve product quality, and lower the rejection rate.
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