JPS6218269B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a cylinder in which the inner surface of the cylinder is required to have sufficient wear resistance, such as a cylinder for discharging cement in a concrete pump.

Conventionally, cylinders in concrete pumps, etc. are made of structural carbon steel material with hardening effect or structural alloy carbon steel which is hardened and tempered.
If necessary, the inner surface is further plated with chrome, but this poses a practical problem in terms of wear resistance. In other words, their useful life is short.

In order to improve wear resistance, a method of heat treating the inner surface of the above cylinder by induction heating is also being considered, but since this type of cylinder is generally formed with a flange, induction heating is applied to the flanged cylinder. When heat treatment is performed to harden the inner surface using Currently, there are variations in surface hardness, making it impossible to manufacture a wear-resistant cylinder whose entire surface is finished with uniform hardness.

In view of the current state of the manufacturing of wear-resistant cylinders, the present invention has been developed to apply an inner surface hardening treatment substantially uniformly to the inner surface of the cylinder by induction heating, and to apply the inner surface hardening treatment to the flange without impairing the effect of the inner surface hardening treatment at all. This was developed with the purpose of providing a method for manufacturing cylinders with attached parts, and its structure consists of a ring-shaped high-frequency After disposing an inductor and moving the inductor and the element cylinder relative to each other, the inner surface of the element cylinder is subjected to heat treatment by induction heating to harden the inner surface of the element cylinder. A separately formed member such as a flange is applied to a portion of the element cylinder where a flange or the like is to be provided, and a coolant is constantly injected and supplied to the inside of the element cylinder to which the flange or the like is applied. The outer side of the blank cylinder to which the flange, etc. is applied is cooled with a coolant, except for the part to be welded between the flange, etc. and the blank cylinder, and then the flange, etc. is welded to the blank cylinder. It is.

Next, an example of the method of the present invention will be described with reference to the drawings.

Reference numeral 1 denotes a cylinder body made by cutting a structural carbon steel pipe with a hardening effect to a predetermined length, and in the present invention, on the outer surface side of the cylinder body 1 whose length is adjusted,
Heating means by annular high frequency inductor (not shown)
Further, cooling means (not shown) for supplying a coolant such as water to the heated portion are provided on the inner surface side, and both of the means are arranged along the longitudinal direction of the blank cylinder 1. By moving it relative to the raw cylinder body 1, the inner surface of the raw cylinder body 1 is hardened to an appropriate depth (approximately 30% of the wall thickness) by quenching and tempering. Note that the heating by the high-frequency inductor may be applied from the inner surface of the element cylinder 1 depending on the shape and wall thickness of the element cylinder 1. Further, it is desirable that the tempering be performed at a temperature of 150 to 200°C for about 2 hours.

The flange 2 is then attached to a predetermined portion of the element cylinder 1, which has been subjected to the inner surface hardening treatment, by welding.Since the principle of this welding work is as shown in Fig. 1, the flange 2 is welded. This will be explained based on FIG.

Reference numeral 2 designates a flange, and before welding, a member having a hole formed in accordance with the outer shape of the cylinder body 1 is temporarily fixed to a temporary fixing step 1a formed in advance on the cylinder body 1. It has been positioned. Although the flange 2 is not shown in the drawings, an appropriate flange temporary fixing jig may of course be used to temporarily fix the flange 2. Reference numeral 3 denotes a coolant container containing a water-based coolant 4, and 5 a stand disposed within the container 3, which supports the blank cylinder 1 to which the flange 2 is temporarily fixed. 6
are gap materials provided at four locations in the circumferential direction between the upper end surface of the pedestal 5 and the lower surface of the flange 2, which ensure and promote the flow of the coolant 4 inside and outside of the pedestal 5 in the container 3. It is for the purpose of 7 is a coolant injection jacket disposed inside the blank cylinder 1, with its coolant jet nozzle 7a directed toward the inner part of the blank cylinder 1 corresponding to the part to which the flange 2 is applied; The coolant supply pipe 9 is connected to the jacket 7, and 9 is a weld bead for attaching the flange 2 to the blank cylinder 1. In this embodiment, this part is welded in four layers as shown in FIG. The welding was carried out by No. 91 to 94 welding, and an austenitic material with good weldability was used as the welding material.

That is, the cylindrical body 1 to which the flange 2 is temporarily attached is set on the pedestal 5 in the state shown in FIG. Then, the thickness of the gap material 6 and the height of the frame 5 are adjusted so that the part of the flange 2 to be welded does not sink into the coolant 4, and the coolant injection jacket 7 is placed inside the cylinder 1. , and the cylindrical body 1 and the flange 2 are welded by a conventional method while jetting coolant from the jacket 7 toward the inner surface of the cylindrical body 1.

Therefore, the above welding was performed indoors at a room temperature of 27.5°C.
Using tap water at around 20℃ as a coolant,
When the temperature of the portion of the inner surface corresponding to the welded portion was measured for each pass, the inner surface temperature was as shown in the graph of FIG.

That is, curve groups A to D represent three points on the inner surface of the cylindrical body 1 during the first to fourth passes.

Claims (1)

[Claims] 1. A ring-shaped high-frequency inductor is arranged on the outer surface of a hardened element cylinder that is not provided with attached members such as flanges, and by moving this inductor and the element cylinder relative to each other, the inner surface of the element cylinder is , after hardening the inner surface of the element cylinder by applying heat treatment by induction heating, applying a separately formed member such as a flange to a portion of the element cylinder where a flange or the like is to be provided;
While constantly injecting and supplying coolant to the inside of the element cylinder body to which the flange, etc. is applied, the outer surface of the element cylinder body to which the flange, etc. is applied, is welded between the flange, etc. and the element cylinder body. A method of manufacturing a wear-resistant cylinder for a concrete pump, etc., characterized in that the flange, etc. is welded to a blank cylinder body while cooling the cylinder with a coolant except for the parts where the flange is to be removed.