JPS6171148A - Hot working method of centrifugal casting pipe - Google Patents

Abstract

PURPOSE:To improve the quality and the yield of a pipe by hot-forging the whole or a part of a centrifugal pipe in a state that it remains a surface as forged, executing a pipe expansion, etc., and subsequently, performing heat treatment. CONSTITUTION:A round bar material 2 is inserted through a centrifugal casting pipe 1 and held so as to be rotatable, and press forging is executed through a die 3 by a roller 4. Or the centrifugal casting pipe 1 is placed in the axial direction on a base 8, and upsetting work for compressing it in the axial direction is executed by an anvil 7. Also, in accordance with the material quality of the pipe 1, heat treatment such as a water cooling solution treatment, etc. is executed. According to this method, the quality of the centrifugal casting pipe is improved, and also a waste material cut-off pipe of a long size one can be utilized. Accordingly, the quality and the yield of the pipe are improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a hot working method capable of improving the quality and yield of centrifugally cast pipes of various sizes manufactured by centrifugal force casting.

(Prior art) Centrifugal force casting is a casting method in which molten metal is injected while rotating a mold (mold), and is shaped and solidified while applying centrifugal force. In addition to this method, there is also the vertical centrifugal spinning method, in which the axis of rotation of the mold is vertical. The resulting centrifugal cast products can be produced in all steel types and in irregular shapes, have excellent mechanical properties, are sound products with no casting defects, and have accurate dimensions without uneven thickness. It has various advantages, such as being able to manufacture products in small batches.

In particular, in the case of pipe manufacturing, the horizontal centrifugal casting method is generally adopted, and the centrifugally cast pipes obtained are pressurized and solidified by centrifugal force, so they have a dense cast structure and have superior properties similar to those of rolled products. This results in improved mechanical properties. However, although the cast structure is dense, due to the solidification process, the structure becomes like a chill layer, Katsura crystal, and free crystal from the outside, and there is a problem that the mechanical properties in the horizontal and vertical directions are different. .

In addition, when manufacturing pipes using the centrifugal casting method, it is better to manufacture pipes that are as long as possible because the amount of cutting off of the Hot side and Co1d side at both ends can be reduced, and the yield can be improved. In order to use a small number of equipment (molds) for a wide variety of small lofts, it is often the case that pipes are manufactured that are longer than the product lot size. In this case, if the remaining cut-off pipes can be used effectively, molds of the same size can be used for lots of various sizes, and the yield can be improved by 1. can.

(Objective of the Invention) The present invention has been made to solve the above-mentioned problems and to meet the above-mentioned demands. The purpose of this invention is to provide a method that allows for expansion and further increases in yield.

(Structure of the Invention) In order to achieve the above object, the present invention hot-casts the entire pipe or a cut-out part of the pipe, which remains in a black crust state after centrifugal casting, and improves the casting structure and expands the pipe. It is intended to be used as a centrifugally cast pipe or as a ring by changing the shape of the pipe, such as shrinking or elongating, and also to improve the quality according to the material by applying the necessary heat treatment after hot casting. This is what we aim to do.

The present invention will be described below based on embodiments and with reference to the drawings.

Firstly, the centrifugally cast pipe to which the present invention is applied is made of materials (stainless steel, etc.) manufactured by normal centrifugal casting method.
However, from the viewpoint of high yield and reducing the initial cost of mold production, centrifugally cast pipes manufactured by the horizontal centrifugal casting method using relatively long molds of the same size are effective. and in this case,
In addition to being applicable to the entire length of the pipe, the present invention can also be applied to waste material cut into required dimensions or cut into lengths of required dimensions.

For centrifugally cast pipes, hot casting is carried out immediately after centrifugal casting or after the temperature is raised, and a product with the required dimensions is obtained by expanding, shrinking, elongating, etc.

The above-mentioned casting structure is improved to improve mechanical properties, correct internal defects, and other training effects.

For this reason, press forging is the hot casting method.

Various methods such as upsetting forging can be used as appropriate depending on the purpose. For example, in the case of press forging, as shown in FIG. 1, a round bar 2 is inserted into a centrifugally cast pipe 1 and held rotatably, and the centrifugally cast pipe 1 is rotated in the circumferential direction by rollers 4. At the same time, press forging is performed by reducing the thickness and elongating the material using a die 3 provided on the press ram. At this time, the end edge of the pipe can be heated by the burner 6 if necessary. Note that 5 is a base that supports the round bar 2.

In the case of upsetting forging, as shown in FIG. 2, the centrifugally cast pipe 1 is placed on the base 8 in the axial direction, and an upsetting operation is performed in which the pipe is compressed in the axial direction by the anvil 7.

Furthermore, in the present invention, depending on the material of the centrifugally cast pipe, it is also possible to effectively utilize residual ripeness after hot forging to perform necessary heat treatment. For example, 5US304,3
In the case of stainless steel such as No. 16, it is possible to carry out a water-cooling treatment immediately after hot forging.

Of course, when performing heat treatment, there is no problem in supplementary heating and cooling, if necessary, in order to ensure the heat treatment temperature.

(Example) A 5US304 centrifugally cast pipe (outer diameter 435 mm, inner diameter 344), length 3200n+l was made using the horizontal centrifugal casting method.
i) was produced and cut out as a product (length 5
After raising the temperature of the pipe (outer diameter 448 mm, inner diameter 3
64+nm, length 518mm) was obtained. Similarly, 5US304 centrifugally cast pipe (
(outer diameter 522nuo, inner diameter 348mm, length 360mm)
After the temperature is raised, the pipe is separately forged and shrunken (
An outer diameter of 418 mm, an inner diameter of 08 mm, and a length of 380 mm) were obtained.

The pipe was then immediately cooled with water from 1100'C and subjected to a compaction treatment.

Note that the pipe after hot forging has an improved cast structure due to centrifugal casting and has a uniform structure.

It was also confirmed that differences in mechanical properties in the horizontal and vertical directions were effectively eliminated.

(Effects of the Invention) As explained above, according to the present invention, it is possible not only to improve the quality of centrifugally cast pipes and expand their uses, but also to cut off long centrifugally cast pipes that were conventionally disposed of as waste. The present invention can be applied to a wide range of applications, and as a result, a high yield can be expected, and the initial cost can be significantly reduced by providing versatility to the same long mold without having to manufacture a centrifugal casting mold for each small lot as in the past. can be reduced, etc.
The effect is huge.

[Brief explanation of drawings]

The figure is a schematic explanatory diagram showing an example of a hot forging apparatus used in the method of the present invention, and FIG. 1 shows the case of press forging. FIG. 2 is a diagram showing each case of upsetting forging. 1...Centrifugal casting pipe, 2...Round bar material. 3...Dice, 7...Anvil. Figure 1

Claims (1)

[Claims] 1. Hot processing of a centrifugally cast pipe, characterized in that the entire centrifugally cast pipe or a cut out part thereof is subjected to hot forging in a black crust state to expand, contract or elongate the pipe. Processing method. 2. A hot processing method for a centrifugally cast pipe, which comprises hot casting the entire centrifugally cast pipe or a cut-out part of the centrifugally cast pipe in its black crust state to expand, thin, or elongate the pipe, and then subjecting it to heat treatment. .