JPS6369948A - Tool material for manufacturing seamless steel pipe - Google Patents

Abstract

PURPOSE:To manufacture the titled tool material having a long service life, by adding specified amounts of Nb and one or more among W, Co and V to an Ni-Cr steel, casting the steel and heat treating the resulting casting under specified conditions. CONSTITUTION:A steel consisting of, by weight, 0.26-0.35% C, 0.10-1.00% Si, 0.20-2.00% Mn, 2.00-4.00% Cr, 0.50-2.00% Ni, 0.10-0.50% Nb, one or more among 0.50-2.00% W, 0.50-2.00% Co and 0.10-0.50% V and the balance Fe is cast into a prescribed shape. The resulting casting is heated to 850-1,100 deg.C in an oxidizing atmosphere, held and cooled to 450 deg.C at <=30 deg.C/hr cooling rate. A material for a piercing or elongator plug having superior wear resistance at high temp. and a long service life can be manufactured.

Description

[Detailed description of the invention] <Industrial application field> The present invention relates to a tool material for manufacturing seamless pipes.

The present invention relates to a long-life drilling or elongator plug that has excellent wear resistance especially at high temperatures.

<Prior art> As a method of manufacturing seamless steel pipes, a hollow or square steel piece is perforated using the Mannesmann method or a press method to form a hollow cable material, and this hollow material is elongated using an elongator, plug mill, mandrel mill, etc. The method is common.

In each step of manufacturing this seamed original pipe, the forming plug and guide shoe are exposed to severe wear conditions at high temperatures. Therefore, producing tools with excellent wear resistance at high temperatures and extending the tool life is one of the important issues in the production of seamless steel pipes using the above method. Its importance is becoming even greater when high alloy steel pipes are desired.

Prior art related to drilling and manufacturing of elongator plugs includes, for example, JP-A-60-159156.

As shown in Japanese Patent Application Laid-Open No. 60-208458, 1 weight of C
:0.1~0.25%, Cr:1~3%, Ni:1~9
%.

The total of one or two of Mo and W is 0.3~
With 3% as an essential component, the value of N i / Cr ratio is 1
-3 alloy materials for core metals have been proposed.

Also, in Japanese Patent Application Laid-Open No. 59-9154 filed by the same applicant.

Chemical composition C- contained in a normal drilling plug
In addition to 5i-Mn-Ni-Cr, an appropriate amount of Mo
, Nb plus A1. One or two of Zr, V, Co, and W are added.

<Problems to be solved by the invention> However, the former two patent publications 159156/1983
, JP-A-60-208458 both have a C content of 0.
This is because the amount of carbide produced is limited to 25% or less.

The service life is not sufficient when drilling chili alloy steels, such as stainless steel, for example.

Furthermore, in the case of JP-A-59-9154, an improvement in service life is observed compared to conventional materials, but the amount of surface oxide scale generated during heat treatment is reduced due to the addition of Mo. This decrease in the amount of surface oxide scale generated is due to the small amount of Mo and 1. When drilling 311'F4 with that plug, it does not have much of an adverse effect, but when drilling high alloy steel, such as 13Cr stainless steel, a small amount of Mo is added. A small reduction in the amount of scale produced by this process also has an adverse effect on plaque life. Furthermore, in the case of this invention.

Since the cooling rate after oxide scale adhesion heat treatment is not particularly limited, there was a problem that when a material cooled at a relatively fast cooling rate was used for drilling high alloy steel, it did not have a sufficient lifespan. .

The present invention was made in view of the above-mentioned problems, and has a long service life with excellent wear resistance at high temperatures.
The purpose is to provide plugs for Elongator.

Means to solve problems〉 In the present invention, C: 0.26 to 0.35% at a weight ratio of 1.

Si: 0.10-1.00%, Mn:
0.20-2.00%.

Cr: 2.00-4.00%, Ni:
0.50-2.00%.

Nb: o, io ~ 0.50%, further W: 0.50
~2.00%.

Co-: 0.50-2.00%, V: o, t
o Contains one or more selected from 1 to 0.50%, and the remainder consists of Fe and unavoidable impurities, and after being cast into a predetermined shape, it is heated at 850 to 1100°C in an oxidizing atmosphere. After heating and holding in the temperature range of 450℃
This is a tool material for manufacturing seamless pipes, which is characterized by being heat-treated to cool down at a rate of 30° C./h or less.

Function> The present inventors have repeatedly conducted experimental studies focusing on prolonging the life of the plug for perforation or elongator.

The most common means of improving the wear resistance of materials at high temperatures is to increase the high temperature strength of the materials. For that purpose, C, Cr.

Although it is necessary to add a considerable amount of alloying elements such as Mo, W, Co, Nb, and V, increasing the content of these alloying elements generally deteriorates the thermal conductivity and lowers the melting point.

If the plug has poor thermal conductivity when it is in constant contact with the object to be deformed, such as a plug used in the manufacture of seamless steel pipes, the heat input from the material to be deformed will concentrate on the surface, causing the temperature of one surface to decrease. The increase becomes significant. moreover.

If the melting point is lowered by the addition of alloying elements, the surface tends to become molten, causing significant wear on the plug surface.

Therefore, the amount of one alloying element added is limited, and there is also a limit to the increase in high temperature strength.

In drilling or elongator, the applied load is smaller than in distraction in a plug mill, but the deformation temperature of the raw tube is higher, and the ratio of the thickness of the material to be deformed in the part that comes into contact with the plug during drilling or distraction to the diameter of the plug is higher. Since it is large, the amount of heat transferred to the plug is large. Therefore, current plug materials for perforators or elongators have low alloy compositions, with emphasis placed on maintaining good thermal conductivity rather than high-temperature strength. It is becoming impossible to cope with the increase in alloying of steel.

The present inventors added Nb as an essential component to Ni-Cr addition steel, which is conventionally known as a plug material for drilling or elongator, and further added one or more of W, Co, and V, and oxidized this. Heat treatment for scale adhesion, that is, heating to a temperature range of 850 to 1100°C in an oxidizing atmosphere, cooling at a rate of 30°C/h or less to 450°C after holding, has higher high-temperature strength than conventional materials. Excellent.

In addition, a small oxide scale was formed on the surface. They succeeded in developing and manufacturing a plug for drilling high-alloy steel with a longer lifespan.

In particular, in the 1-surface oxidation scale generation process, in order to obtain a dense and well-adhered scale, a temperature of 850 to 1100℃ is required.
The cooling rate after heating and holding in the temperature range of 4 is important.
If the cooling rate to 50°C is higher than 30°C/h, a scale with good adhesion cannot be obtained;
It has been newly discovered that the life of the plug can be further improved by repeatedly performing heat treatment in which the plug is heated and maintained at 1100°C and then cooled down to 450°C at a rate of 30°C/h or less.

The reasons for limiting the alloy components in the present invention will be explained below.

C: C is an element that improves high-temperature wear resistance by forming carbides such as Cr, Nb, W, and V, and is added in a range of 0.26 to 0.35% as shown in Figure 1. Since it is effective in improving the life of the plug, it is limited to a range of 0.26 to 0.35%.

J Figure 1 shows Si: 0.32%, M
n: 0.55%.

Cr: 3.10%, Ni: 1. ．． 05%,
Nb: o, 2o%.

W: 0.98%, Co: 1.07%,
V: Made from materials with varying amounts of C in tlii containing 0.18%.

A hole plug with a diameter of 58N and a length of 400mm heated to 1200°C was heated to 950°C, held for 4 hours, and then cooled at 25°C/h.
Tsuru, and C: 0.20%, Si: 0.52
%.

The lifespan when a stainless steel billet containing Mn: 0.45% and Cr: 13.12% is continuously drilled.

C: 0.30%, Si: 0.35%, M
n: 0.80%.

Cr: 3.10%, Ni: 1.40%,
Mo: 3.0%.

The lifespan of the above billet when the above billet is drilled under the same conditions as above using a plug made from a material containing Nb: o, so% with the remainder substantially consisting of Fe and subjected to the same scale adhesion heat treatment as above. The divided value.

The C content of the perforation plug is plotted against the amount.

Si: Si is added for deoxidation, but if it is less than 0.10%, its effect is small, and if it exceeds 1.00%, it reduces the amount of high-temperature oxide scale generated and has a negative impact on the life of the plug, so it is 0. It was limited to a range of .10 to 1.00%.

Mn: Mn is added to increase high temperature strength.

If it is less than 0.20%, the effect is small and 2.00%
If it exceeds this amount, the thermal conductivity will deteriorate and the high-temperature wear resistance will deteriorate, so the content was limited to a range of 0.20 to 2.00%.

Cr: Cr produces a scale on the surface that has good adhesion to the base metal alloy and has good heat insulation properties, and also increases high temperature strength by producing carbon carbides, but if it is less than 2.0%, the The effect is small, and if it exceeds 4.0%, it will reduce the amount of scale generated and deteriorate thermal conductivity, which will have a negative impact on the life of the plug.

It was limited to a range of 2.0 to 4.0%.

Ni: Ni is added to produce scale that has good adhesion to the base metal alloy, but if it is less than 0.50%, the effect is small, and if it exceeds 2.00%, it reduces the amount of scale produced. Moreover, since it deteriorates thermal conductivity and adversely affects plug life, it is limited to a range of 0.50 to 2.00%.

Nb: Nb significantly increases high-temperature strength through carbide formation, but
If it is less than 0.10%, the effect will be small, and if it exceeds 0.50%, cracks will easily occur during rapid heating and cooling of the plug, so it is limited to a range of 0.10 to 0.50%.

The above-mentioned limited amounts of C, Si, Mn, Cr, Ni, and Nb are essential components of the plug material for drilling of the present invention, and W
, Co 2 , and V within the following limited amounts, the objects of the present invention can be achieved.

W: W has the effect of increasing high-temperature strength through solid solution hardening and carbide formation, but if it is less than 0.50%, the effect is small, and if it exceeds 2.00%, it deteriorates thermal conductivity and causes scale formation. The content was limited to a range of 0.50 to 2.00% since it would reduce the amount and adversely affect the life of the plug.

CO: Co has high i! due to solid solution hardening. It has the effect of increasing strength and scale density.

If it is less than 0.50%, the effect will be small, and if it exceeds 2.00%, the amount of scale generated will be reduced and the life of the plug will be adversely affected, so it is limited to a range of 0.50 to 2.00%.

V: V has the effect of reducing the corrosion temperature by forming tricarbide, but its effect is small below 0.10'a.

If it exceeds 0.50%, cracks tend to occur when the plug is rapidly heated or cooled, so it is limited to a range of 0.10 to 0.50%.

Next, a description will be given of heat treatment of a material molded from a cast alloy having the above-mentioned limited components. The heat treatment after molding is not oxidizing; if it is carried out in an ambient atmosphere, the necessary oxidized scale will of course not be obtained. The heating temperature range is 850℃~1
The reason for limiting the heating temperature to 100"C is that if the heating temperature is less than 850°C, it will not be possible to obtain a scale thickness that is effective in improving plug life, and if it exceeds 1100t, the scale will become too large and the Ei property will deteriorate. Because it does.

Furthermore, after holding the heating temperature for a predetermined time, 4. ]O'C
The reason why the cooling rate was set to 30° C./h or less will be explained based on FIG. In this figure, the horizontal axis is 1.

The cooling rate when the heating temperature is lowered from 850°C to 450°C is shown, and the vertical axis shows the plug life ratio.

As is clear from the figure, the cooling rate at which the plug life ratio is significantly improved is 30° C./h, and if it exceeds this, a scale with good adhesion cannot be obtained and the plug life decreases.

Further, FIG. 3 shows the effect of the number of repetitions of heat treatment.

This is an evaluation of the effect on the plug life when the same material is subjected to heating-holding-cooling cycles multiple times.

If the above cycle is repeated twice or more, the life of the plug will be improved, but
The effect reaches saturation after 4 cycles, and beyond that, the cost increase due to repeated processing becomes greater than the cost reduction due to improved lifespan, so it is desirable to set the upper limit of the number of repeated cycles to 4 times.

In this case, 1st section 2nd section and 3rd section are c:o, 3o%.

SI: 0, 329i, Mn: 0.5
5%, Cr: 3.08%.

Ni: 1.0. )%, Nb: 0.20%,
Co: 1.10%.

v:O, made from a material containing 2o% with the remainder substantially consisting of Fe, heat treated to adhere surface oxide scale, i.e. heated to 950'C in oxidized '3' JM air, held for 4 hours and then cooled. C: 0.20%, Si: 0.52%, heated to 1200'C using a plug subjected to the above process once or 2 to 6 times.
Mn: 0.45%.

Containing Cr: 13.12% Diameter 58n1 Length 4
The life when continuously drilling a stainless steel billet at 00℃m is c: o, 3o%, Si: 0.35
%, Mn: 0.80%, Cr: 3.10%,
Ni: 1.40%, Mo: 3.0%, Nb
: 0.50% balance made from a material consisting essentially of Fe, heated to 950°C, held for 4 hours, then heated to 450°C - 50°C
The above billet is continuously perforated under the same conditions as above using a heat-treated plug that is cooled at 1/2 hour. The value divided by the life is plotted against the cooling rate or the number of drying cycles of heat treatment. be.

<Example> Table 1 shows the chemical composition of the present invention material and comparative material.

A heat treatment was performed under the conditions shown in Table 2 to form a surface circulating scale in an oxidizing atmosphere, and the chemical composition was C: 0.
20%, Si: 0.52910+Mn: 0
．． 45%.

Cr +13.12%1 Direction 175m, Length 2.2m
X stainless steel billet! ! Table 1 shows the chemical composition, and Table 2 shows the heat treatment conditions.The life of the comparative material is expressed as a multiple of 2, and is shown in Table 2, as well as the heat treatment conditions.

As is clear from the plug life ratio in Table 2: +.

All of the invented materials have excellent longevity.

Table 2〈Effects of the Invention〉 As is clear from the above-mentioned five can examples, the present invention is capable of fixing the components of a tool material for manufacturing a continuous round pipe at 850°C to 850°C in an oxidizing atmosphere. By performing a heat treatment in which the material is heated to a temperature range of 1100°C and then cooled down to 450°C at a rate of 30°C/h or less, it is possible to produce a tool material with excellent wear resistance at high temperatures and a long life. It is something.

As a result, it is possible to improve the perforation and the wear and tear of elongator plugs, which are the biggest problems when manufacturing high-alloy seamless pipes in Mannesmann mills, so oil wells in recent years,
In view of the increasing demand for high-alloy steel pipes in the field of seamless pipes for gas wells, their industrial value is significant.

[Brief explanation of the drawing]

Figure 1 shows Si -Mn -Cr -Ni -Nb
-W-Go - Figure 2 shows the characteristics of C content over the life of a drilling steel plug containing V.
-Mn -Cr -Ni -Nb -Co -V
1 is a diagram showing the relationship between the life of a drilling steel plug containing 1 and the appropriate cooling from 850'C to 450'C during surface oxide scale adhesion treatment. Figure 3 shows C-3i-C-3i-
It is a figure showing the relationship between the life of a steel material plug for drilling containing -Ni-Nb-Co-V and the number of repeated cycles of heat treatment for adhesion of oxidized scale on one surface. Figure 1 - C content fl (%) Figure 2

Claims (1)

[Claims] (1) C: 0.26-0.35%, Si: 0 in weight ratio
．． 10-1.00%, Mn: 0.20-2.00%, C
r: 2.00-4.00%, Ni: 0.50-2.00
%, Nb: 0.10-0.50%, further W: 0.50
~2.00%, Co:0.50~2.00%, V:0.
Contains one or more selected from 10 to 0.50%, the remainder consisting of Fe and unavoidable impurities,
85 in an oxidizing atmosphere after being cast into a predetermined shape.
1. A tool material for producing seamless steel pipes, characterized in that it has been subjected to a heat treatment of heating and holding in a temperature range of 0 to 1100°C and then cooling to 450°C at a rate of 30°C/h or less.