Technical Information

D-1 Large-Sized and High-Performance Cast Metal Manufacturing Technologies Supporting Large-Sized Machine Products

D-1 Large-Sized and High-Performance Cast Metal Manufacturing Technologies Supporting Large-Sized Machine Products

We manufacture cast iron and cast parts weighing about 200kg to 57000kg, which range from small- and medium-sized to large-sized. Primarily, we are specialized in manufacturing large-sized cast parts which fully utilize our large-sized cast part manufacturing technology for cast that are 10m or over in length (the largest in Japan), cast parts weighing 50 ton or more, and our complex casting technology for the internal chilling of pipelines. Now, we will introduce the large-sized part casting technology and high-performance cast blank that is used for internal chilling of pipelines.

[Platform]
D. Material technology
[Applications]
Large-sized machines such a machine tool, injection molding machine and die casting machine. large-sized and high-performance castings.

[Technical points]

  • Manufacture of large-sized long castings. Maximum dimensions (W × L × H): 5 × 10 × 2m or 2 × 15 × 2m
    Maximum product weight: 57000kg
  • Manufacture of large-sized, thick-walled spheroidal graphite iron castings. Maximum dimensions (W × L × H): 4 × 4 × 2m
    Maximum product weight: 57000kg
  • High-performance casting technology for internal chilling of pipelines. Improvement of functions of cast parts and reduction in hole machining labor or man hour.

1. Introduction

For large-sized long castings, the key technology lies in the elimination of a faulty profile caused by thermal deformation. Likewise, for large-sized thick spheroidal graphite iron castings, fabrication of castings with sound spheroidal graphite structure without use of feeder is the key point, and for the high-performance castings, casting of a pipe without causing deformation is very important.

2. Long castings manufacturing technology

2.1 Mechanism causing warpage

Fig. 1 Generation of warpage

Fig. 1 Generation of warpage

In the long castings, stress P is caused by the difference in wall thickness and the difference in temperature drop conditions of the top and bottom surfaces, as shown in Fig. 1, which may result in generation of arc warpage. The extent of warpage is affected by the length, height, sectional profile, etc. of the casting.

2.2 Reverse warpage of long casting

Generally, a die or mold is manufactured by warping it in the reverse direction to warpage of a long casting and fully considering the size of warping.
From the sectional profile of the relevant product and past records of warpage of similar products, larger (plus tendency) or smaller (minus tendency) warpage of the product as compared with that of the similar products should be judged, referring to the items given in Table 1 below. Actually, there are many complex profiles, and a die or mold is manufactured based on years of experience and data accumulated so far.

Table 1 Estimation of warpage of long castings
Items for comparison(-) <- Warpage tendency -> (+)
Product heightHigh <- -> Low
Wall thickness of bottom plateThin <- -> Thick
Ratio of wall thickness of bottom and top platesSmall <- -> Large
Ratio of area of bottom and top platesSmall <- -> Large
Ratio of cored hole area of top plateSmall <- -> Large
Total wall thickness of vertical ribLarge <- -> Small

From Table 1 above, the range of warpage can be estimated, then "reverse warpage" which is added to the opposite side is to be determined, fully considering the finishing allowance and machining technique.

2.3 Long size that can be produced

Fig. 2 Long cast product (bed)

Fig. 2 Long cast product (bed)

By adding the appropriate reverse warpage to the mold or die, the finishing allowance can be minimized and the man-hours can be reduced. For castings whose length is about 10m, we supply long cast products with warpage of 10mm or less. (Fig. 2)

Large-sized product that can be manufactured

  • Maximum dimensions (W × L × H):
    5m × 10m × 2m
    2m × 15m × 2m
  • Maximum product weight:
    57000kg

3. Large-sized thick spheroidal graphite cast iron manufacturing technology

Fig. 3 Die plate of a large-sized die casting machine with the die clamping force of 2500 ton

Fig. 3 Die plate of a large-sized die casting machine with the die clamping force of 2500 ton

By controlling the components, mold or die strength, shot temperature, spheroidizing rate and tensile strength without the use of a feeder, we manufacture spheroidal graphite iron castings whose interior is sound even if thick-walled to supply the die plate, etc. for the injection molding machine and die casting machine (Fig. 3). Additionally, cost reduction can be achieved with improvement of efficiency percentage.

Large-sized product that can be manufactured:

  • Maximum dimensions (W × L × H):
    4m × 4m × 2m
  • Maximum product weight:
    57000kg

In the large-sized thick spheroidal graphite iron castings, dross (Note 1) is likely to occur generally, and we minimize generation of dross by adjusting the components and improving the runner design.

Note 1: Dross: A mass of solid impurities which is a defect of oxide which will generate on the casting surface layer characteristic of the spheroidal graphite iron casting.

4. High-performance casting material manufacturing technology

Fig. 4 Steel pipe unit for internal chilling

Fig. 4 Steel pipe unit for internal chilling

Among the castings, there are parts on which versatile holes are to be machined. Machining of long holes or complicated holes is labor intensive and time consuming. Toshiba Machine supplies the parts where holes are formed (Fig. 5) by chilling a steel pipe unit (Fig. 4) in the casting, thus contributing to improve the functions of cast parts and to reduce the labor required for hole machining.

Fig. 5 Cast product internally chilled

Fig. 5 Cast product internally chilled

The following technologies are important for the fabrication:

  • Positional shift or deformation of pipe is not the cause.
  • Pipe weld is good without erosion.
  • Gas hole elimination.
  • No erosion is caused from the pipe welded area.

5. Conclusion

The improvement of machine performance and the reduction in labor become possible as a result of the provision of large-sized casting materials which are superior in machine performance and inexpensive; and tied in with the technology of high-performance casting material fabrication (i.e., internal chilling of pipe) by utilizing the hybrid casting technology. We supply such castings widely to not only our customers, but for in-house use also.