Riser design and layout are of critical importance in steel casting production because they directly influence both casting quality and manufacturing cost. In lost foam steel casting, the presence of large shrinkage cavities and porosity demands a significant amount of liquid metal for feeding. Additionally, most risers employed in lost foam processes are blind risers, which tend to form an outer solidified shell during cooling. This shell restricts the internal molten metal to feeding the casting only by its own weight, thus severely reducing the feeding efficiency of the riser. This problem is further aggravated by the fact that many foundries still rely on empirical rules rather than systematic theoretical guidance for riser design, resulting in oversized and towering risers, low casting yield, and high production costs.
The present work is motivated by the need to provide a practical and economical solution to increase the feeding efficiency of blind risers in lost foam steel casting. Inspired by the Williams core patented concept and combining the characteristics of exothermic risers, three different sizes of exothermic cones were designed. These cones, similar to conventional exothermic riser sleeves but much smaller in volume, are intended to be placed at the top of blind risers. When molten steel comes into contact with the cone, an exothermic chemical reaction releases a large amount of heat, thereby prolonging the solidification time of the molten metal inside the blind riser. As a result, the formation of a solid outer shell at the top surface is delayed or prevented, and feeding efficiency is improved. In this study, differential scanning calorimetry (DSC) was used to confirm that the exothermic cone can function under conditions typical of lost foam blind risers. Several pouring trials were carried out on production-scale castings, and the results showed measurable improvement in riser feeding efficiency. Metallographic examinations indicated that the exothermic cone material does not adversely affect the cast steel microstructure.
In addition to the exothermic cone, this paper reviews the classification, shape, and calculation methods for riser systems in steel casting. It also discusses the application of insulating and exothermic riser sleeves to lost foam production of crankshafts and large hollow steel balls used in E-type coal mills. Pouring experiments were performed to compare the feeding efficiency between ordinary risers and those fitted with insulating/exothermic sleeves. Numerical simulation using the commercial software Huazhu CAE was carried out to visualize filling and solidification behavior, and to compare the effectiveness of ordinary versus insulated risers. The simulation also examined the influence of hot-side risers (risers fed through their own in-gate) and cold-top risers (risers located away from the in-gate). Both experimental and simulation results consistently showed that insulating/exothermic sleeves and hot-side riser arrangements significantly improve the feeding efficiency of blind risers in lost foam steel casting.
1. Introduction to Lost Foam Steel Casting and Riser Challenges
Lost foam casting (also known as evaporative pattern casting) has grown rapidly due to its advantages of near-net-shape production, design flexibility, and environmental friendliness. It has been widely applied to aluminum, cast iron, and copper alloys. However, application to steel castings has been relatively slow because of problems such as carbon pick-up, hydrogen pickup, gas porosity, and low process yield. Recent successful examples of lost foam steel casting are mostly limited to high-manganese steel and wear-resistant components. Table 1 presents a summary of the major lost foam steel casting producers in China, based on the author’s survey of dozens of foundries from 2009 to 2011.
| Company | Product types | Annual output (t/yr) |
|---|---|---|
| Anhui Tongyu Power Equipment Co., Ltd. | Steel and iron castings | – |
| Ma’anshan Haitian Heavy Industry Technology Development Co., Ltd. | Heat and wear resistant steels | 3,000 |
| Hengshui Zhongtiejian Steel Casting Co., Ltd. | Various steel castings up to 2 t | – |
| Sany Heavy Industry (Loudi) Zhongyuan New Material Co., Ltd. | Mn13 alloy steel bends | 1,000 |
| Wuhan Hengchang Special Steel Foundry | Wear-and heat-resistant parts | 1,000 |
| Jiangxi Fengyuan Steel Casting Co., Ltd. | Large steel castings | 5,000 |
| Hubei Genglian Wear-resistant Material Technology Co., Ltd. | Hammer heads, jaw plates | – |
| Zibo Tongpu Vacuum Pump Co., Ltd. | Medium steel castings | – |
From this survey, it was found that most lost foam steel foundries produce wear-resistant, heat-resistant, and erosion-resistant parts, accounting for nearly half of the total producing units. The typical yield (casting weight divided by total poured weight) ranges from 50% to 60%, which is significantly lower than the 80% figures reported in developed countries using insulating or exothermic risers. Therefore, improving riser feeding efficiency is a fundamental step toward reducing production costs and energy consumption.
2. Riser Classification and Design Principles
2.1 Types of Risers
Risers can be classified based on position, exposure to atmosphere, and the method used to enhance feeding. A comprehensive classification is shown in Table 2. For steel castings, risers are necessary because the volumetric solidification shrinkage of steel is large, often around 5% to 7%. In lost foam steel casting, the majority of risers are blind (internal) because open risers are difficult to construct with a foam pattern and because the vacuum system is more easily maintained with closed moulds.
| Position | Atmospheric condition | Feeding method |
|---|---|---|
| Top riser | Open (atmospheric) | Self-feeding under atmospheric pressure |
| Side riser | Blind (sealed) | Atmospheric pressure is not applied unless vented |
| Hot-side riser | Open or blind | In-gate enters through the riser |
| Cold-top riser | Blind | Located away from the in-gate, receives cooler metal |
| Insulating riser | Open or blind | Uses insulating sleeve to slow heat loss |
| Exothermic riser | Open or blind | Uses exothermic material to generate heat |
| Atmospheric-pressure riser | Blind with vent core | Atmospheric pressure is transmitted through a core |
| Gas-sand riser | Blind with gas-generating core | Internal gas pressure enhances feeding |
2.2 Effect of Riser Shape on Feeding
Riser shape directly affects the solidification time and feeding efficiency. For a given volume, a smaller surface area reduces heat loss and prolongs the liquid state. Table 3 shows the solidification times for three shapes of 14.5 kg steel risers. The spherical riser has the longest solidification time, followed by the cylinder and the rectangular prism. Although spherical risers are theoretically the most efficient, they are difficult to form in foam patterns and are rarely used in production. Cylindrical and tapered cylindrical risers are more common. A conical riser (larger at the top) reduces the depth of shrinkage pipe and improves yield.
| Shape | Dimension (mm) | Surface area (m2) | Solidification time (min) |
|---|---|---|---|
| Sphere | Φ=152 | 2.54 | 7.2 |
| Cylinder | Φ=108, H=203 | 3.05 | 4.7 |
| Rectangular prism | 79 × 92 × 219 | 3.43 | 3.6 |
2.3 Riser Size Calculation Methods
Several methods are used for calculating riser dimensions. Among them, the modulus method (also known as Chvorinov’s method) is the most widely used for steel castings. The modulus \(M\) is defined as the ratio of volume \(V\) to cooling surface area \(S\).
\[
M = \frac{V}{S} \ (\text{cm})
\]
According to Chvorinov’s rule, the solidification time \(t_s\) is proportional to the square of the modulus:
\[
t_s = k M^2
\]
where \(k\) is the solidification constant for the given mould material. To ensure that the riser solidifies after the casting section it feeds, the following condition must hold:
\[
M_r = f \cdot M_c
\]
where \(M_r\) is the riser modulus, \(M_c\) is the casting modulus at the feeding zone, and \(f\) is a safety factor (typically 1.1–1.2 for side risers, 1.2–1.3 for top risers). In addition, the riser must contain sufficient liquid metal to compensate for volumetric contraction. The feeding condition is:
\[
\varepsilon V_c \le \eta V_r
\]
where \(\varepsilon\) is the volumetric solidification shrinkage of the alloy, \(V_c\) is the volume of the casting section to be fed, \(\eta\) is the riser feeding efficiency, and \(V_r\) is the riser volume. Table 4 lists typical feeding efficiencies for different riser types.
| Riser type | Feeding efficiency η (%) |
|---|---|
| Cylindrical or oblong ordinary riser | 12–15 |
| Spherical riser | 15–20 |
| Riser with teeming (hot topping) | 15–20 |
| Exothermic or insulating riser | 25–30 |
| Atmospheric-pressure riser | 15–20 |
| Compressed-air riser | 35–40 |
| Gas-pillow riser | 30–35 |
2.4 Calculation of Insulating and Exothermic Riser Sleeves
Insulating and exothermic riser sleeves increase the effective modulus of the riser. The modulus increase factor \(E\) is defined as:
\[
M’ = E \cdot M_r
\]
where \(M’\) is the enhanced modulus. For commercial insulating sleeves, \(E\) typically ranges from 1.3 to 1.45. For exothermic sleeves, \(E\) can be as high as 1.6. The actual value depends on the sleeve thickness \(\delta\) and the original riser modulus. Figure 1 shows a typical curve of \(E\) versus sleeve thickness for a given riser modulus. The curve indicates that beyond a certain thickness, further increase in sleeve thickness yields negligible benefit.
\[
E \approx 1 + a\left( \frac{\delta}{M_r} \right)^n
\]
where \(a\) and \(n\) are empirical coefficients determined by the sleeve material. In production, a practical choice is \(\delta / M_r \approx 0.3\)–0.5 to maximize efficiency without excessive cost.
3. Methods to Increase Riser Feeding Efficiency
Two primary physical mechanisms can be exploited to improve riser performance:
- Increasing the feeding pressure acting on the molten metal in the riser.
- Prolonging the time during which the riser metal remains liquid.
3.1 Insulating and Exothermic Sleeves
Insulating riser sleeves are made from lightweight refractory materials such as perlite, vermiculite, fly-ash cenospheres, ceramic fiber, and organic binders. They have low thermal conductivity, low density, and high heat storage capacity. Exothermic sleeves additionally contain aluminum powder, iron oxide, and magnesium sparks. When the molten steel contacts the sleeve, the aluminothermic reaction takes place:
\[
8\mathrm{Al} + 3\mathrm{Fe_3O_4} \rightarrow 4\mathrm{Al_2O_3} + 9\mathrm{Fe} + \Delta H
\]
\[
2\mathrm{Al} + \mathrm{Fe_2O_3} \rightarrow \mathrm{Al_2O_3} + 2\mathrm{Fe} + \Delta H
\]
These reactions release a significant amount of heat, increasing the temperature of the riser and effectively prolonging solidification. Compared to ordinary risers, insulating and exothermic sleeves can improve feeding efficiency by 10%–30% absolute, and the casting yield can increase from 50% to over 75%. Table 5 compares the shrinkage cavity characteristics and yield for different riser types.
| Riser type | Shrinkage cavity shape | Casting soundness | Process yield (%) |
|---|---|---|---|
| Ordinary sand riser | Inverted cone with secondary shrinkage | Internal porosity present | 50–55 |
| German exothermic sleeve | Shallow basin | Dense | 80 |
| Domestic exothermic sleeve | Basin | Dense | 80 |
| Insulating sleeve | Deep inverted cone | Dense | 70–76 |
3.2 Atmospheric Pressure Riser
An atmospheric-pressure blind riser is a blind riser with a small core or vent inserted through the top. The core is permeable to gas and extends into the hottest zone of the riser. When the riser top begins to solidify and a void forms, the vacuum is relieved by air entering through the core. Thus, atmospheric pressure acts on the liquid surface in addition to the metallostatic head. The maximum theoretical feeding height \(H\) can be estimated by equating atmospheric pressure to the metallostatic head:
\[
H = \frac{760 \times 13.6}{\rho_{\mathrm{steel}}}
\]
where 760 is the standard atmospheric pressure in mmHg, 13.6 is the density of mercury in g/cm3, and \(\rho_{\mathrm{steel}}\) is the density of liquid steel (about 7.8 g/cm3). Thus,
\[
H \approx \frac{760 \times 13.6}{7.8} = 1325\ \text{mm}
\]
In practice, due to inter-dendritic flow resistance, the effective feeding height is less than this theoretical value. Nevertheless, atmospheric pressure risers can substantially extend the effective feeding distance compared to ordinary blind risers. In lost foam casting, a ceramic tube may be placed above an exothermic cone to transmit atmospheric pressure and also to allow the vacuum below the mould to assist feeding—a “pressure above, suction below” effect.
3.3 Hot-Side Riser and Pouring System Considerations
Another efficient method is to design the pouring system so that the in-gate enters directly through the riser. This is known as a hot-side riser. The hot metal flowing through the riser during pouring heats the riser to a higher temperature than the casting, thus delaying its solidification. Conversely, a cold-top riser is a riser placed away from the gate; it is filled by metal that has already flowed through the mould and has lost superheat. Figure 2 illustrates the temperature distribution profiles of hot-side and cold-top risers during cooling.
For lost foam steel castings, a hot-side riser layout is generally preferred whenever the casting geometry permits. It not only improves feeding efficiency but also reduces the number and size of risers. The experimental results in Chapter 3 demonstrate that using a hot-side riser with an insulating sleeve can increase the yield by over 10% compared to a side-gated arrangement.
3.4 Numerical Simulation of Riser Feeding
Computational simulation tools such as Huazhu CAE, ProCAST, MAGMAsoft, and Flow-3D allow engineers to visualize filling, solidification, and defect formation. In this study, Huazhu CAE was used to simulate the lost foam casting of a large hollow steel ball for an E-type coal mill. The steel grade is ZG75Cr2MnNiMo, with a chemical composition given in Table 6. The simulation parameters are listed in Table 7.
| C | Si | Mn | Cr | Mo | Ni | P | S |
|---|---|---|---|---|---|---|---|
| 0.70–0.80 | 0.40–0.50 | 0.80–1.00 | 2.00–2.50 | 0.30–0.40 | 0.60–0.80 | ≤0.12 | ≤0.12 |
| Initial temperature | Density | Specific heat | Thermal conductivity | Latent heat | Liquidus | Solidus |
|---|---|---|---|---|---|---|
| 1560 °C | 7.08 g/cm3 | 0.3168 cal/g·°C | 0.082 cal/cm·s·°C | 53.9 cal/g | 1470 °C | 1368 °C |
Two different gating systems were compared. Scheme A used a bottom side gate feeding the lower half of the ball, while Scheme B used a top gate passing through the riser. The top-gated scheme produced significantly less shrinkage porosity in the casting, confirming the advantage of hot-side riser design. Figure 3 shows the simulated shrinkage distribution for both schemes; scheme B exhibited only a shallow riser pipe and no porosity in the casting body.
4. Exothermic Cone Design and Experiments
4.1 Design Rationale
Although insulating and exothermic sleeves are effective, their cost is relatively high for small and medium foundries. To provide a more economical solution, a small exothermic cone was designed to be placed at the top of a blind riser. The cone is made from a mixture of aluminum powder, iron oxide, coal powder, magnesium powder, and sodium silicate binder. Three sizes were fabricated: small, medium, and large, as listed in Table 8. The density of the cone material is approximately 0.75 g/cm3.
| Type | D1 (mm) | D2 (mm) | H1 (mm) | H2 (mm) | Density (g/cm3) | Unit cost (RMB) |
|---|---|---|---|---|---|---|
| Small | 50 | 30 | 20 | 8 | 0.75 | 0.9 |
| Medium | 60 | 40 | 40 | 12 | 0.75 | 1.4 |
| Large | 100 | 60 | 65 | 15 | 0.75 | 5.6 |
4.2 Differential Scanning Calorimetry (DSC) Analysis
Because lost foam casting is performed under vacuum, it was important to verify that the exothermic reaction can occur with limited access to atmospheric oxygen. DSC tests were conducted in air and under argon atmosphere. The DSC curves showed similar endothermic and exothermic peaks at approximately 130 °C, 320 °C, and 420 °C, with a major exothermic event occurring above 1000 °C due to the aluminothermic reaction. Even in the argon atmosphere, a distinct exothermic peak was observed, confirming that the cone can release heat inside a blind riser where oxygen is scarce.
4.3 Experimental Procedure
Pouring experiments were conducted at three foundries using actual production castings. The general procedure was as follows:
- The top of the foam pattern of the blind riser was machined to accept the exothermic cone.
- An exothermic cone was inserted into the recess and sealed with foam adhesive and a thin layer of coating.
- For the “cone + tube” variant, a ceramic tube was placed vertically above the cone, penetrating the mould and connected to the atmosphere. The outer end of the tube was plugged with foam during sand filling and pouring, and then the foam was burned off after pouring.
- Each experiment batch contained three identical castings: one with a plain blind riser, one with an exothermic cone, and one with an exothermic cone plus a ceramic vent tube.
- After cooling, the risers were cut open, and the shrinkage cavities were measured by carefully filling them with water using a burette. The density of each riser was also measured to detect very fine porosity.
4.4 Small Cone Applied to Alloy Hammer Heads
The first trial was performed on a small hammer head weighing 7 kg, made of ZG30CrMnSiBRE alloy steel. Three hammer heads were grouped in one mould in a series pouring arrangement with the in-gate entering through the riser. Thus, these were hot-side risers. However, the exothermic cone was installed on top of each riser. The results showed that the shrinkage volume in the cone riser was larger than in the ordinary riser, meaning that more liquid metal had been delivered to the casting. Table 9 gives the measured shrinkage volumes and riser densities.
| Riser type | Half A volume (cm3) | Half B volume (cm3) | Total volume (cm3) | Riser density (g/cm3) |
|---|---|---|---|---|
| Ordinary | 2.4 | 8.3 | 10.7 | 8.015 |
| With cone | 10.0 | 2.3 | 12.3 | 7.939 |
| With cone + tube | 4.6 | 8.6 | 13.2 | 8.055 |
The larger shrinkage volume in the cone risers corresponds to better feeding of the casting. The castings produced with the exothermic cone were free of visible shrinkage defects, whereas the plain-riser casting contained a small surface shrink hole. Metallographic samples taken from the base of each riser showed similar microstructures: pearlite matrix with acicular ferrite (Widmanstätten structure) and a few oxide inclusions. The inclusion content was comparable, indicating that the cone material did not contaminate the casting.
4.5 Small Cone Applied to Balance Shaft Housing
A second trial used a balance shaft housing weighing about 50 kg, made of ZG310-570. In this trial, the two castings were arranged symmetrically in the mould, but the riser was located away from the in-gate, making it a cold-top riser. This is the most severe condition for feeding. The measured shrinkage volumes for the three types are listed in Table 10. The plain riser had a total shrinkage of 52 cm3, while the cone riser had 144 cm3 and the cone+tube riser had 148 cm3. The dramatic increase of shrinkage cavity volume indicates that the exothermic cone was highly effective, even in a cold-top riser where the ordinary riser would quickly form a solid crust and stop feeding.
| Riser type | Shrinkage volume (ml) |
|---|---|
| Ordinary blind riser | 52 |
| With exothermic cone | 144 |
| With cone + vent tube | 148 |
The cross-sections of the risers showed that the ordinary riser had dispersed shrinkage through the entire height, while the cone risers had a concentrated pipe at the top third, leaving the lower part dense. This indicates that the cone delayed solidification of the upper riser region and allowed atmospheric pressure to push the liquid downward. The results clearly support the use of exothermic cones for cold-top blind risers in lost foam steel casting.
4.6 Large Cone Applied to a Medium Hammer Head
A third experiment was carried out with a medium hammer head weighing 186 kg, material 40Cr. The casting was produced in a single mould, with three risers: ordinary, cone, and cone+tube. The top surfaces of the risers are shown in Figure 4. The ordinary riser had a honeycomb-like top, indicating that some feeding had occurred, but the cone risers had large open pipes, which are characteristic of effective atmospheric feeding. The measured shrinkage volumes are given in Table 11.
| Riser type | Half A (cm3) | Half B (cm3) | Total (cm3) | Riser density (g/cm3) |
|---|---|---|---|---|
| Ordinary | 280 | 220 | 500 | 8.79 |
| With cone | 280 | 276 | 556 | 7.93 |
| With cone + tube | 300 | 262 | 562 | 8.74 |
Even in a hot-side riser where the ordinary riser has already performed reasonably well, the exothermic cone provides an additional increase in shrinkage cavity volume, i.e., better feeding. The effect is smaller than that observed in the cold-top riser, but it is still positive. In practice, exothermic cones are especially recommended when the riser is located away from the in-gate, buried deep in the mould, or when multiple risers are used and only one is near the gate.
4.7 Scope of Application for the Three Cone Sizes
Based on the experimental campaigns and engineering calculations, the recommended operating ranges for the three cone sizes are summarized in Table 12.
| Type | Riser diameter (mm) | Riser height (mm) | Riser weight (kg) | Maximum casting weight fed (kg) |
|---|---|---|---|---|
| Small | 80–130 | 100–200 | 5–20 | 100 |
| Medium | 120–210 | 180–350 | 15–30 | 300 |
| Large | 200–450 | 320–500 | 30–180 | 800 |
5. Application of Exothermic Sleeves to a Crankshaft
An industrial trial was performed in collaboration with a foundry producing a 45# steel crankshaft weighing 21 kg. Two identical castings were prepared. One riser was left as a conventional open riser; the other was fitted with a commercial exothermic sleeve. The sleeve exterior diameter was slightly smaller than the foam pattern, so the pattern was reduced by cutting away a ring of foam to accommodate the sleeve. After casting, the two risers were sectioned. The ordinary riser showed an evenly distributed shrink hole across the entire cross-section, while the sleeved riser produced a deep concentrated pipe at the top, indicating efficient feeding. The ordinary riser weighed 11.2 kg, giving a process yield of about 52%. The sleeved riser weighed only 4.8 kg, increasing the yield to 73%. No defects were observed in either casting, which demonstrates that exothermic sleeves can safely reduce the riser size and improve yield in lost foam steel casting.
6. Numerical Simulation of a Large Hollow Steel Ball
6.1 Casting description
The E-type mill grinding ball is a large hollow sphere with outer diameter 1150 mm and inner diameter 850 mm. Its weight is approximately 3,600 kg. The material is ZG75Cr2MnNiMo wear-resistant steel. The original production process used two large ordinary blind risers, each with diameter 482 mm and height 725 mm. The process yield was only 63%. By using insulating sleeves, the riser diameter could be reduced to 370 mm and height to 562 mm. Simulation and actual production confirmed that the reduced-size insulating risers were sufficient to feed the casting.
6.2 Simulation models
Two gating system designs were simulated: (A) bottom side gate feeding the lower hemisphere, with the riser placed on top but not aligned with the ingate; and (B) top gate passing through the riser (hot-side riser). Table 13 summarizes the mesh parameters and yield for each scheme.
| Scheme | Grid size (mm) | Number of grids | Riser weight (kg) | Gating weight (kg) | Yield (%) |
|---|---|---|---|---|---|
| Original (ordinary, side gate) | 12 | 2,276,880 | 1,933 | 182 | 63 |
| A (insulating sleeve, side gate) | 12 | 2,922,624 | 946 | 341 | 73.6 |
| B (insulating sleeve, top gate) | 12 | 2,368,485 | 946 | 176 | 76.2 |
The simulation results showed that scheme B produced the least shrinkage porosity. The hot-side riser arrangement provided a higher thermal gradient, promoting directional solidification toward the riser. The insulating sleeves also delayed riser solidification. Together, they increased the yield from 63% to 76.2% while maintaining casting soundness. Thus, a combination of hot-side riser design and insulating sleeves is highly effective for large lost foam steel castings.
7. Metallographic Verification
Samples were cut from the bottom of each riser (near the casting connection) in the hammer-head experiment. The samples were ground, polished, and etched with 8% nitric acid in alcohol. The microstructure was observed at 200× magnification. All three samples (ordinary riser, exothermic cone riser, and exothermic cone plus tube riser) exhibited a black pearlite matrix with white acicular or blocky ferrite, typical of a Widmanstätten structure in cast low-alloy steel. Some dark oxide inclusions were visible on the ferrite, but their distribution and quantity were similar in all samples. Therefore, the exothermic cone material does not introduce harmful inclusions into the casting. This is likely because the cone material is very low in density (0.75 g/cm3) and any loose particles float to the top of the riser rather than entering the casting body.
8. Conclusions and Outlook
Through a combination of field surveys, pouring experiments, and numerical simulations, the following conclusions are drawn for improving riser feeding efficiency in lost foam steel casting:
- Ordinary blind risers in lost foam steel casting often solidify from the surface, forming a crust that prevents atmospheric pressure from assisting feeding. This is the primary reason for low riser efficiency.
- Insulating and exothermic riser sleeves are effective and can increase process yield by 10–15%. However, their relatively high cost limits their widespread use.
- The newly developed exothermic cone, placed at the top of a blind riser, is a low-cost and practical solution. It works by releasing exothermic heat upon contact with molten steel, delaying the formation of a solid crust and allowing atmospheric pressure to push the liquid metal into the casting.
- When combined with a ceramic vent tube, the exothermic cone creates an atmospheric-pressure riser that also benefits from the vacuum-driven suction at the mould bottom. This “pressure above, suction below” action significantly enhances feeding, especially for cold-top risers.
- For hot-side risers (in-gates entering through the riser), the improvement due to the cone is positive but less pronounced, because the hot metal already improves feeding.
- Numerical simulation with Huazhu CAE correctly predicted the shrinkage distribution and confirmed the advantage of hot-side riser design. Simulation is a valuable tool for optimizing riser layout in lost foam steel casting.
- Metallographic analysis verified that the exothermic cone material does not affect the casting microstructure.
Future work should focus on optimizing the cone composition to reduce gas generation and potential carbon pick-up in steel castings. Additionally, the statistical database of experimental results should be expanded to refine the size-selection charts and establish a more precise empirical formula for the exothermic cone design.
In summary, the following improvements are recommended for lost foam steel casting foundries: use hot-side riser layouts whenever possible, apply insulating sleeves or exothermic cones to blind risers, provide atmospheric venting through ceramic tubes, and use computer simulation to verify and optimize the riser system before production.