JPS6250038A - Pipe end upset working die - Google Patents

Abstract

PURPOSE:To obtain a die having a long service life by bringing a specified alloy to buildup welding, by a powder buildup welding to the surface which contacts to as pipe of a die base material. CONSTITUTION:A Co base alloy or a layer which has dispersed and held a hard particle to the Co base alloy is brought to buildup welding by a powder buildup welding, to the surface which contacts to a pipe T of a base material of a die. As for the base material which is brought to a powder buildup welding, that which contains 0.35-0.60% C, 0.15-1.20% Si, 0.30-1.00% Mn, 1.00-5.50% Cr, 0.20-1.60% Mo, and 0.10-1.10% V, by wt% is desirable. Also, as necessary, that which contains furthermore 1.30-2.00% Ni and consists of inevitable impurities and Fe as the remainder is desirable. Moreover, as for a padding layer, that which contains 0.1-2.5% C, 18-32% Cr, and 3-20% W, by wt% is desirable. Or as necessary, said layer consists of the Co base alloy which contains furthermore <=15% Ni and consists of inevitable impurities and Co as the remainder, or that which has dispersed and held a hard particle to said alloy.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a pipe end upset processing die used for upsetting the end of a pipe.

[Conventional technology]

Screws are often used to connect pipes, but threading reduces the effective wall thickness of the pipe and weakens the strength of the connection, so for pipes where strength is important, such as oil country tubular goods, the ends of the pipe are upset-processed. Efforts are being made to increase the wall thickness.

This upset processing requires a die, gripping jaws,
This is done with a three-point tool on a mandrel.

The figure shows an example of this upset processing in which the outer diameter of the tube is expanded to increase the wall thickness. 1', and its inner surface extends a predetermined axial length from both end surfaces 1a and 1b to the diameter of the pipe to be processed before upsetting, T, corresponding to the diameter of the pipe to be processed after upsetting.
It is assumed that the diameter Du is larger than the outer diameter of. The top of the die is usually symmetrical in the axial direction as in this example, and if one side is damaged due to use, it is often possible to flip the front and back and make the other part usable again. is held by a die holder 4.4' attached to the processing machine,
The divided surfaces can be brought into close contact with each other and separated from each other.

Gripping Joe? The tube is provided immediately above the die, and is also divided into halves. By opening and closing each half with a holder, it is possible to hold and release the processed tube T at its outer diameter, and there is also a non-slip material on the inner diameter. Therefore, a large number of circumferentially continuous grooves are carved.

The mandrel 3 has a tip 3a with a diameter corresponding to the inner diameter of the tube to be processed T, and a shoulder surface 3b with an enlarged diameter behind the tip.
, and has a diameter portion 3c that can be fitted into the inlet diameter Du on the die.

Upset processing is performed by releasing the die and the main gripping jaws at their respective dividing surfaces, and inserting the heated pipe T into the tube for a predetermined length from the tip (from the tip surface 1a on the die to the central small diameter section). The leading end surface is supplied with the leading end surface substantially matching the leading end surface 1a of the die, and the gripping jaws are provided on the die and on the gripping jaws.
This is done by moving the mandrel 3 forward in the direction of arrow 5 after closing the housing. The tube to be processed T is held at the rear by the gripping jaws, and its inner diameter is held by the tip 3a of the mandrel 3 while the tip surface is held by the shoulder surface 3 of the mandrel 3.
By being compressed in the axial direction by b, upsetting processing, that is, upset processing is performed while the outer diameter is limited by the large diameter portion Du of the die.

After the upset processing is completed, after the mandrel 3 retreats,
The gripping jaw I on the die is opened, the tube to be processed is taken out, and the processing surface of each tool is cooled and lubricated by spraying water or oil containing a lubricant.

Conventionally, the die 1 used for this upset is JIS
5KD61 or its equivalent steel was heat treated to HRC (Rockwell hardness C scale, the same hereinafter) 45 (Hv Vickers hardness, hereinafter the same, converted to 446) and then nitrided. However, this die is 1
A heat check occurs because the pipe is rapidly heated to a high temperature by contacting it under high pressure and is then rapidly cooled by water spray, etc., which has been heated to a high temperature of 200-1300℃. A surface roughened by a heat check is likely to cause seizure, making it unusable relatively quickly, and also being prone to accidents that result in damage at an extremely early stage due to seizure.

[Problem that the invention seeks to solve]

It is an object of the present invention to provide an upset processing die with improved properties on one working surface and an excellent lifespan.

[Means to solve the problem]

The present invention is for pipe end upset processing, characterized in that a Co-based alloy or a layer of a Co-based alloy in which hard particles are dispersed and held is welded by powder build-up welding on the surface of the base material that contacts the pipe. It is a die, and preferably the base material is 1% by weight and C0.35-0.60%.

Si 0.15-1.20%, Mn 0.30-1.00%, Cr 1.00-5.50%, Mo 0.20-1.60% and V 0.10-1,10% Contains or further includes Ni1.30 to 2.00 if necessary
%, and the remainder consists of unavoidable impurities and Fe, and the overlay layer contains, in weight %, C001-2.5% Cr 18-32% and W3-20%, or if necessary, further contains 1 brocade or less of Ni. The alloy is characterized in that it is a Co-based alloy, the remainder of which consists of inevitable impurities and CO, or a Co-based alloy in which hard particles are dispersed and retained.

[Effect]

As mentioned above, conventional dies have been made of 5KD61 or equivalent steel that has been nitrided.

The present inventors conducted various investigations on a large number of conventional dies before and after use. As a result, it was found that nitriding treatment was not appropriate for the upset processing conditions. That is, the nitride layer applied to these dies is typically 0. ll! Although the nitride layer has a thickness of approximately fi, the thermal conductivity of the nitride layer is lower than that of the base material, so rapid heating and cooling will cause rapid temperature changes over a wide temperature range, as can be seen from the processing conditions above. The nitrided layer or its underlying layer experiences large temperature gradients and therefore large thermal stresses, and due to its extremely brittle nature, easily undergoes heat checking.

Furthermore, although the nitrided layer has a low thermal conductivity, its thickness is as thin as approximately 0.1 m, so it cannot prevent the base material from rising in temperature, and the base material is subject to the tempering effect, which usually results in room temperature hardness. The hardness has decreased to about Hν300, which greatly reduces the backup effect on the brittle nitride layer. Although the nitride layer has high room temperature hardness,
Its temperature coefficient is large.

At high temperatures, hardness decreases and wear resistance decreases significantly.

Therefore, nitriding treatment is not appropriate considering the usage conditions. Note that the thickness of the nitride layer requires diffusion of nitrogen atoms, so significantly increasing the thickness
It's actually embarrassing.

The present invention has obtained the above knowledge, eliminated the nitriding treatment that does not match the working conditions, and investigated various alternative treatment methods. As a result, the present invention has developed a Co-based This is due to the prospect of obtaining a die with a long lifespan by applying an overlay layer in which hard particles are dispersed and retained in an alloy or the same.

The built-up layer of Co-based alloy has high temperature strength and oxidation resistance.

It has excellent corrosion and wear resistance, and of course has much higher toughness and thermal conductivity than nitrided layers, so it has been found that it can withstand rapid heating and cooling well and has high heat check resistance. Furthermore, since the thickness of the built-up layer can be made significantly larger than that of the nitrided layer, it is possible to prevent the hardness of the base material from decreasing due to overheating.

However, this Co-based alloy generally has low workability, and it is difficult or impossible to draw wire, especially those with high carbon content, so welding rods manufactured by casting etc. are very expensive, and It is almost impossible to obtain small diameter ones.

In the present invention, the Co-based alloy is built up using a powder built-up welding method. Since this welding method uses powder as a raw material, it does not affect the manufacturability of the welding rod, and it is possible to retain and contain a large amount of hard particles. In addition, with the powder build-up welding method, the thickness of the build-up layer can be adjusted over a wide range, and even when this thickness is reduced, the build-up layer is rarely diluted with the base metal, and the properties of the surface area deteriorate due to dilution. Less is.

In addition, at the boundary with the base metal, each alloy component changes gradually,
It is particularly effective in alleviating thermal stress.

Note that the component range of the base material that is particularly effective in the present invention is 5K.
The range of ingredients used for upset dies such as D61 is the same, and the range of ingredients for the build-up layer is generally C.
This is a component range of what is called an O-based surface hardening alloy, and in the present invention, hard particles are further dispersed and held as necessary.

〔Example〕

Using two types of materials A and B whose chemical compositions are shown in Table 1, three and two pairs of die base materials were manufactured, respectively, and after heat treatment by quenching and tempering to a HRC of 40 to 43,
Plasma powder overlay welding was performed using Co-based alloy powders and hard particle WC and VC powders having chemical components 1 to 4 shown in Table 2. The applicable base materials are shown in Table 2 with a 0 mark.

Table 1 (tzt%) Table 2 The build-up thickness is about 2 degrees, and after this build-up, the temperature is 20℃ higher than the tempering temperature of each base material to relieve stress.
After heating at a low temperature for 2 hours, it was slowly cooled and finished.

The finishing allowance of the built-up layer was about 0.5 mm. Work in each of these steps went smoothly, and after finishing, a dye penetrant test was conducted and no abnormalities were found.

These dies are currently operating smoothly with no reports of abnormalities, and are expected to have a significantly longer lifespan than conventional products.

As the hard particles, in addition to carbides as in the above embodiments, oxides, nitrides, etc. can be used.

〔Effect of the invention〕

As described above, the present invention is based on the fact that, as a result of investigating conventional dies, it was found that nitriding was not an appropriate treatment method in terms of longevity, and an alternative treatment method was found. Considering the usage conditions, the die of the present invention can be expected to have a significantly extended lifespan.

[Brief explanation of the drawing]

'fA/ is a diagram showing an example of tube end upset processing. 1: Die, 2 Nigelipping Jaw, 3: Mandrel

Claims (1)

[Scope of Claims] 1. In a half-split die for pipe end upset processing that compresses the heated end of a pipe in the axial direction to increase its wall thickness, the surface in contact with the pipe is welded with powder overlay, A die for pipe end upsetting, characterized in that a Co-based alloy or a layer in which hard particles are dispersed and held in a Co-based alloy is overlay-welded. 2 The base metal to be powder overlay welded has a C0.3 weight%.
5-0.60%, Si0.15-1.20%, Mn0.30-1.00%, Cr1.00-5.50%, Mo0.20-1.60% and V0.10-1.10 %, or if necessary further Ni1.30 to 2.00
%, and the remainder consists of unavoidable impurities and Fe, and the built-up layer contains, in weight %, 0.1 to 2.5% C, 18 to 32% Cr, and 3 to 20% W, or if necessary, further 15% or less. Co-based alloy containing Ni, the remainder consisting of inevitable impurities and Co,
The die for upsetting a tube end according to claim 1, wherein the die has hard particles dispersed therein. 3. The pipe end upsetting die according to claim 1 or 2, wherein the powder build-up welding method is a plasma powder build-up method.