Abstract: Roof plate serves as a vital component in the rotating structure of a certain type of armored wheeled special vehicle, providing support and protection for the safety of security personnel. This steel casting boasts excellent material properties and stringent internal and external quality requirements, adhering to the specifications for steel castings used in special vehicles. This paper conducts a process analysis of the roof plate steel casting structure, selects a more reliable casting process method from two options, optimizes the casting process design based on visualization simulation results, and implements it in the production of model tooling and core box tooling. After trial and mass production verification, no issues arose, ultimately gaining customer recognition and affirmation for the product. This article summarizes the research and application of the visualization process for thin-walled steel casting of the roof plate, emphasizing the use of casting CAE visualization technology to improve casting quality and production efficiency.
Keywords: Roof plate; thin-walled steel casting; process analysis; visual simulation; optimize the process; excellent quality
1. Introduction
The roof plate is a crucial part of the rotating structure of a certain type of armored wheeled special vehicle, playing a role in support and protection. Due to its large size, complex shape, and demanding casting process, it is prone to casting deformation. Therefore, it is essential to carry out process analysis and optimization for the casting process of roof plate products. This paper introduces the research and application of a visualization process for thin-walled steel casting of the roof plate, aiming to improve casting quality and production efficiency.
2. Product Structure Characteristics
The roof plate is an important component of the rotating structure of a certain type of armored wheeled special vehicle, belonging to the typical category of curved thin-plate products. With a maximum contour size of 1,316 mm × 917 mm × 216 mm, its middle structure is designed as a “large flange + small flange”, and the four edges are irregular structures with angled curved thin plates. It features a complex shape, large size, poor casting process, and susceptibility to casting deformation.
3. Process Analysis
Based on the structural characteristics of the roof plate, which is a medium-to-large, thin-walled, ring-shaped product, combined with the company’s many years of practical experience in casting process design, the following process plan is proposed:
- Overall Layout: The entire plane is placed on the upper sand mold, which facilitates sequential solidification and the placement of risers.
- Gating System: Designed to be placed in the inner circle of the observation mirror plane, reducing heat loss of molten steel and aiding in preventing casting deformation. The number of ingates is set to 5, facilitating rapid and smooth mold filling.
- Riser Placement: Risers are placed above the junction of the ingate and casting, aiding in eliminating hot spots, venting, and slag collection.
- Crack-resistant Reinforcement: Designed at the junction of the observation mirror plane and the surrounding sidewalls, aiding in eliminating thermal and cold cracks.
- Sand Mold Design: The parting surface of the sand mold is designed 35 mm below the bottom of the roof casting, with a total of 2 sand cores. The observation mirror structure is formed by the sand core, and each sand core has 3 lifting rings pre-embedded for stable lifting and transportation.
4. Process Design
Based on the principles of casting process design analysis, the casting process for the roof plate is designed in detail, using a special steel grade for armored products and a green renewable ester-hardened sodium silicate sand process.
Table 1: Casting Process Design Parameters
| Parameter Name | Actual Parameter Settings |
|---|---|
| Material | Casting: Armor-specific steel; Mold: High-quality quartz sand |
| Interface Heat Transfer Coefficient | h = 500 W/(㎡•K) |
| Boundary Conditions | Pouring speed: 2 m/s; Cooling method: Air cooling |
| Initial Conditions | Pouring temperature: 1,570 ℃; Initial mold temperature: 25 ℃ |
| Pouring Method | Sand mold gravity pouring |
| Gravity Direction | Z direction |
| Operation Time | Mold filling flow: 32 s |
| Stop Condition | 1,000 ℃ |
4.1 Riser Design
Using empirical design formulas for risers, such as the “Hot Spot Circle Method,” “Volume Method,” and “Modulus Method,” combined with the feeding distance of the risers, 7 risers with dimensions of Ф89 mm × 104 mm are placed on the plane above the observation mirror, and 6 risers with dimensions of Ф58 mm × 79 mm are evenly distributed at the highest points of the overall ring. To increase the safety factor for riser feeding, the risers are designed as heat-generating and insulating riser sleeves.
4.2 Gating System Design
To reduce heat loss during the flow of molten steel in the ingate and assist in preventing casting deformation, the ingate is designed to be placed in the inner circle of the observation mirror plane. The number of ingates is designed to be 5, with a size of 45 mm/50 mm × 30 mm, ensuring rapid and smooth mold filling according to the design size ratio of the total cross-section of the open gating system. Hot spots are prone to form at the junction of the ingate and the roof casting, so riser sleeves are placed above these positions to eliminate hot spots and facilitate venting and slag collection.
4.3 Crack-resistant Reinforcement Design
Due to the small fillet at the junction of the observation mirror plane and the surrounding sidewalls of the roof plate product, and the large size and thickness of the risers designed above, combined with the small wall thickness of the product, thermal stress from riser solidification shrinkage can easily lead to thermal or cold cracks at the junction of the plane and the surrounding sidewalls. Therefore, crack-resistant reinforcement bars are designed at this location, with a quantity of 8 bars arranged in a “triangular” structure, with dimensions of 50 mm × 100 mm × 60 mm. After the quenching and tempering heat treatment process, they are removed by flame cutting and ground flush with the product body.
4.4 Sand Core Design
The parting surface of the sand mold is designed 35 mm below the bottom of the roof plate product, with a total of 2 sand cores. The mating surfaces of the two sand cores are designed without a taper, and the 4 observation mirror structures are formed by the sand cores. Each sand core has 3 lifting rings pre-embedded for stable lifting and transportation of the sand cores. The sand cores are made using high-collapse water glass new sand and placed on a drying board for natural drying for 24 hours before being uniformly coated with alcohol-based zirconium silicate powder composite coating on the use surface.
5. Visualization Process Simulation
Using the 3D modeling software Creo 4.0, the casting process scheme for the roof plate product is modeled. The ProCAST visualization casting simulation software is used to simulate the process, with the casting process model of the roof plate being meshed, with a mesh size of 8 mm and a total number of body meshes of 359,289. The roof plate product undergoes two stages from pouring to cooling: mold filling and solidification.
Using the Visual-Cast pre-processing module, parameters such as material properties, boundary conditions, and initial conditions are set for the finite element model, as shown in Table 1.
The simulation results show that the molten steel is above the alloy liquidus line during the mold filling process, and the filling of the casting is smooth and free of turbulence, indicating that the design of the gating system is reasonably distributed.
From the temperature field simulation results, the high-temperature areas of the roof plate casting are concentrated near the risers, and the cooling and solidification process achieves sequential solidification from bottom to top. The solidification rate is lowest near the risers of the roof plate casting, with no isolated liquid regions, ensuring that the roof plate casting solidifies first away from the risers and last at the risers.
From the simulation results of shrinkage porosity casting defects, the roof plate casting does not exhibit significant casting defects overall, with only a certain probability of casting defects occurring at the junctions of 3 observation mirror windows and sidewalls, ranging from 0 to 5%. This indicates that the casting process design scheme for the roof plate is reasonable and feasible.