JP2021084121A - Mandrel for ring roll and method for manufacture thereof - Google Patents

Abstract

To provide a mandrel for ring roll which is used for a ring roll molding machine which can provide improved yield strength when used under high temperature and high pressure.SOLUTION: A mandrel is located on an inner peripheral side of an annular work-piece, sandwiches a part of the annular work-piece together with a molding roll located on an outer peripheral side, and performs hot pressing of the same while mutually rotating. A diameter reduction part with a reduced diameter is provided in a prescribed section along a lengthwise direction of a substantially rod-like shaft body part comprising chromium-molybdenum steel or nickel-chrome-molybdenum steel. An abrasion resistant layer comprising a Co-based alloy is provided on the diameter reduction part by overlay welding with a thickness of 2 mm or less.SELECTED DRAWING: Figure 2

Description

The present invention relates to a ring roll mandrel used in a ring roll forming machine for hot working an annular workpiece and a method for manufacturing the same.

In a ring roll forming machine for hot-working an annular metal work, a mandrel and a forming roll are arranged on the inner peripheral side and the outer peripheral side of the annular work, respectively, and the annular work is sandwiched and rotated between them to rotate the annular work. This is a machining device that rolls a workpiece to make it thinner and expands its annular diameter.

For example, Patent Document 1 discloses the structure of such a ring roll molding machine and its operation. A groove is formed in the circumferential direction on the outer circumference of the large-diameter forming roll rotating around the central axis, and an annular workpiece having a diameter smaller than that of the forming roll presses the outer periphery of the groove to press the outer circumference of the forming roll. It is rotating with. The outer peripheral surface of the mandrel penetrating the inner space of the annular work is pressed against the inner peripheral surface side of the annular work corresponding to the pressure contact portion to the forming roll, and the forming roll and the mandrel form a circle. A part of the peripheral wall of the annular work is sandwiched from the outer peripheral side and the inner peripheral side, respectively. By moving the forming roll toward the mandrel in this state, the wall thickness of the sandwiched annular work is thinned, and the diameter of the work is increased by that amount.

In the ring roll mandrel as described above, generally, the rod-shaped shaft body made of tool steel such as chrome molybdenum steel or nickel chrome molybdenum steel is provided with wear resistance at the contact portion with the work. Manufactured with processing.

For example, in Patent Document 2, an outer ring member made of high-hardness die steel or heat-resistant steel that imparts wear resistance to a region of contact with an annular work on the outer peripheral surface of the core member is provided by "shrink-fitting". The mandrel for ring rolls is disclosed. On the inner circumference of the outer ring member, an outer ring inclined portion that gradually increases the inner diameter is provided at one end in the length direction. Further, on the outer periphery of the core member, a core inclined portion that gradually increases the outer diameter is provided corresponding to the outer ring inclined portion at the arrangement position of the outer ring member. Then, when the outer ring member is fitted from one end of the core member, the core inclined portion and the outer ring inclined portion come into contact with each other, and the arrangement position of the outer ring member can be positioned.

Japanese Unexamined Patent Publication No. 2015-24420 Japanese Unexamined Patent Publication No. 2017-21358

In the mandrel of a ring roll forming machine, various proposals have been made for processing that imparts wear resistance to a portion in contact with a work in order to further improve the proof stress when used under high temperature and high pressure. However, as for the method of shrink-fitting the outer ring member made of a hard material to the core portion (shaft body portion) as described above, the shape of the core portion, particularly the outer shape, is designed for the construction. It was pointed out that it was restricted and cracks were likely to occur from the discontinuous interface of hardness between the outer ring member and the core portion.

The present invention has been made in view of the above circumstances, and an object of the present invention is a mandrel for a ring roll used in a ring roll molding machine which can provide an improved proof stress in use under high temperature and high pressure. And its manufacturing method.

The mandrel according to the present invention is a ring roll forming machine which is arranged on the inner peripheral side of the annular work, sandwiches a part of the annular work together with the forming roll arranged on the outer peripheral side, and hot-processes the mandrel while rotating each other. In the mandrel of the above, a reduced diameter portion having a reduced diameter is provided in a predetermined section along the length direction of a substantially rod-shaped shaft main body made of chrome molybdenum steel or nickel chrome molybdenum steel, and Co It is characterized in that an abrasion-resistant layer made of a base alloy is provided by overlay welding to a thickness of 2 mm or less.

According to such an invention, cracking in the vicinity of the joint interface between the wear-resistant layer and the shaft main body can be suppressed, and the proof stress in use under high temperature and high pressure can be improved.

In the above invention, the reduced diameter portion may be a circumferential groove having a depth of 2 mm or less, and the corner portion of the circumferential groove may be processed into an R shape. According to such an invention, cracks in the vicinity of the junction interface between the wear-resistant layer and the shaft body portion, particularly cracks at the corners of the circumferential groove which is the reduced diameter portion can be suppressed, and the use under high temperature and high pressure can be performed. The bearing capacity can be further improved.

In the above invention, the Co-based alloy may be characterized by containing at least chromium and tungsten. According to such an invention, the strength of the joint interface between the wear-resistant layer and the shaft body can be increased, cracks in the vicinity of the interface can be suppressed, and the proof stress in use under high temperature and high pressure can be further improved. It is.

Further, in the method for manufacturing a mandrel according to the present invention, a part of the annular work is sandwiched between the forming rolls arranged on the inner peripheral side of the annular work and arranged on the outer peripheral side, and the mandrel is hot-processed while rotating with each other. This is a method for manufacturing a mandrel in a ring roll forming machine, in which a reduced diameter portion having a reduced diameter is provided in a predetermined section along the length direction of a substantially rod-shaped shaft main body made of chrome molybdenum steel or nickel chrome molybdenum steel. A wear-resistant layer made of a Co-based alloy is built-up welded on the reduced diameter portion to a thickness of 2 mm or less.

According to such an invention, a mandrel for a ring roll which can make the joint interface between the wear-resistant layer and the shaft body portion sound, suppress cracking in the vicinity of the interface, and have improved proof stress in use under high temperature and high pressure can be obtained. It can be given.

In the above invention, the reduced diameter portion may be a circumferential groove having a depth of 2 mm or less, and the corner portion of the circumferential groove may be processed into an R shape. According to such a feature, cracks near the junction interface between the wear-resistant layer and the shaft body portion, particularly cracks at the corners of the circumferential groove which is the reduced diameter portion can be suppressed, and the use under high temperature and high pressure is performed. It is possible to provide a ring roll mandrel with further improved yield strength.

It is a block diagram of the ring roll molding machine using the mandrel in one Example by this invention. It is a side sectional view of the mandrel in one Example by this invention. It is a table of the component composition which shows the material of the wear-resistant layer of the mandrel used in the ring roll molding test. It is a list of the overlay thickness and the result of the wear-resistant layer in the ring roll forming test.

A mandrel for a ring roll and a method for producing the mandrel as one example according to the present invention will be described with reference to FIGS. 1 and 2.

As shown in FIG. 1, the ring roll forming machine 10 using the mandrel 1 is a processing device that heat-processes an annular work W to increase the annular diameter. The mandrel 1 is arranged on the inner peripheral side of the work W, and a part of the work W is sandwiched between the mandrel 1 and the forming roll 11 arranged on the outer peripheral side of the work W. Then, while rotating the forming roll 11 and the mandrel 1 with each other, the entire circumference of the work W can be rolled to reduce the thickness and increase the diameter. The ring roll forming machine 10 further includes a pair of backup rolls 12 and 13. The backup rolls 12 and 13 support the work W from two places on the outer circumference opposite to the forming roll 11 in order to maintain the annular shape of the work W in a well-balanced manner.

As shown in FIG. 2, the mandrel 1 has a substantially round bar shape, and chrome molybdenum steel or nickel provided with a reduced diameter portion 3 having a reduced diameter in a predetermined section including a central portion along the length direction thereof. It has a substantially rod-shaped shaft body 2 made of chrome molybdenum steel. A hard wear-resistant layer 4 made of a Co-based alloy is formed on the reduced-diameter portion 3 by overlay welding to improve the wear resistance of the mandrel 1. The wear-resistant layer 4 is formed to have a thickness of 2 mm or less, and the toughness is improved by arranging the wear-resistant layer 4 with a functionally graded material having a higher toughness than the wear-resistant layer 4.

In particular, since the wear-resistant layer 4 is formed by overlay welding, the heat input to the reduced diameter portion 3 of the shaft body portion 2 which is the base material can be reduced by making it thinner, and the heat-affected zone can be reduced. The formation can be suppressed and the joint interface between the shaft body 2 and the wear-resistant layer 4 can be made sound. That is, it is possible to suppress cracking in the vicinity of the joining interface in the reduced diameter portion 3, and it is possible to provide an improvement in proof stress in use under high temperature and high pressure. In this embodiment, the surface of the wear-resistant layer 4 has a stepped shape, and a stepped portion is formed on the inner peripheral surface of the work W.

By the way, the diameter-reduced portion 3 is a circumferential groove extending in the circumferential direction having a depth of 2 mm or less in order to form the wear-resistant layer 4 described above. Further, the corner portions 3a and 3b of the circumferential groove are processed into an R shape. As a result, it is possible to suppress the occurrence of cracks in the vicinity of the joint interface, particularly at the corners 3a and 3b, so that the joint interface between the wear-resistant layer 4 and the shaft body 2 has a continuous shape.

As described above, according to the mandrel 1, the joint interface between the shaft body 2 and the wear-resistant layer 4 provided by the thin build-up welding of 2 mm or less, which receives less heat from the Co-based alloy, can be made sound, and the temperature is high. It can provide improved proof stress when used under high pressure. Further, since the mandrel 1 uses build-up welding, the degree of freedom in designing the outer shape of the shaft main body 2 is relatively high, and for example, the shape can be made symmetrical with respect to the center in the length direction.

[Ring roll molding test]
Next, a mandrel using a different material at the position of the wear-resistant layer 4 was manufactured on the shaft body 2 similar to the mandrel 1 described above, and a ring roll forming test was performed using the mandrel. The results will be described below.

Using the material having the component composition shown in FIG. 3, overlay welding was performed on the reduced diameter portion 3 of the shaft main body portion 2 to obtain a mandrel. As shown in the table, "U520" is a Ni-based alloy and "Stellite # 12" is a Co-based alloy. The material and thickness of the overlay are shown in FIG. SCM440, which is chrome molybdenum steel, was used for the shaft body 2 of the mandrel.

No. 4 in FIG. As shown in 1, when a 0.5 mm thick overlay layer made of a Ni-based alloy was given, the wear rate was 5.6 × 10 ^-4 mm / Shot. However, at this wear rate, all the wear-resistant layers are lost within 1000 Shots by simple calculation. In order to cope with such a high wear rate, the thickness of the overlay layer was increased to 2.5 mm. In 2, the shaft body has cracked. It is considered that this is because the heat input to the shaft main body is increased by thick build-up welding exceeding 2 mm to form a thick heat-affected zone, which makes it easy to crack. Therefore, No. As shown in 3, a build-up layer having a thickness of 2.0 mm or less, specifically 0.5 mm, was formed by a Co-based alloy (Stellite (registered trademark) # 12), which is expected to have a low wear rate. .. As a result, the shaft body 2 was not cracked and the wear rate could be made very low.

In this way, the thickness of the build-up layer should be 2 mm or less in order to prevent cracks from occurring in the shaft body 2. On the other hand, it has been found that it is preferable to use a Co-based alloy having a low wear rate as the overlay layer in order to sufficiently function as the wear resistant layer 4 even with such a thin layer.

From the above, it was found that as the wear-resistant layer 4, overlay welding with a thickness of 2 mm or less using a Co-based alloy is suitable. In addition, No. It was speculated that containing at least chromium and tungsten, such as Stellite # 12 used in No. 4, is more suitable as such a Co-based alloy.

Although typical examples of the present invention have been described above, the present invention is not necessarily limited to this, and those skilled in the art will not deviate from the gist of the present invention or the appended claims. , Various alternative and modified examples will be found.

1 Mandrel 2 Shaft body 3 Reduced diameter 3a, 3b Square 4 Abrasion resistant layer 11 Molding roll W work

Claims (5)

A mandrel in a ring roll forming machine that is arranged on the inner peripheral side of an annular work, sandwiches a part of the annular work together with a forming roll arranged on the outer peripheral side, and heat-processes the annular work while rotating each other.
A reduced diameter portion with a reduced diameter is provided in a predetermined section along the length direction of a substantially rod-shaped shaft body made of chrome molybdenum steel or nickel chrome molybdenum steel, and wear resistance made of a Co-based alloy is provided on the reduced diameter portion. A mandrel for ring rolls, characterized in that the layers are provided by overlay welding to a thickness of 2 mm or less. The ring roll mandrel according to claim 1, wherein the reduced diameter portion is a circumferential groove having a depth of 2 mm or less, and the corner portion of the circumferential groove is processed into an R shape. The mandrel for a ring roll according to claim 2, wherein the Co-based alloy contains at least chromium and tungsten. A method for manufacturing a mandrel in a ring roll forming machine that is arranged on the inner peripheral side of an annular work, sandwiches a part of the annular work together with a forming roll arranged on the outer peripheral side, and heat-processes the annular work while rotating each other. There,
A reduced diameter portion with a reduced diameter is provided in a predetermined section along the length direction of a substantially rod-shaped shaft body made of chrome molybdenum steel or nickel chrome molybdenum steel, and wear resistance made of a Co-based alloy is provided on the reduced diameter portion. A method for manufacturing a ring roll mandrel, which comprises overlay welding a layer to a thickness of 2 mm or less. The method for manufacturing a ring roll mandrel according to claim 4, wherein the reduced diameter portion is a circumferential groove having a depth of 2 mm or less, and the corner portion of the circumferential groove is processed into an R shape. ..

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