JPH0452026A - Manufacture of electric resistance welded pipe with excellent wear resistant property - Google Patents

Abstract

PURPOSE:To manufacture the electric resistance welded pipe with the high wear resistance of the inner surface of steel pipe by heating so as to make the laminated layer side of the steel blank material of plural layers which is laminated plurally with the jetted material of excellent hardenability more than the base material to be the inner side of the steel pipe after formed, and rapidly cooling from the inner side of steel pipe. CONSTITUTION:The melted alloy (material to be laminated) 2 of excellent hardenability more than the base slab 1 composed of the low alloy steel is atomized in the inert gas 3 at the nozzle 8 and laminated, made to the composite slab, it is hot rolled, formed so as to make the laminated side to be the inner side of steel pipe and made to the electric resistance welded pipe. Next, total pipe is heated to 800 deg.C-1,000 deg.C, after than, it is cooled only from the inner surface side of the steel pipe. In such a way, the elected resistance welded pipe with the low cost, having the good productivity and the excellent wear resistant property can be manufactured.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for manufacturing an electric resistance welded steel pipe with excellent wear resistance.

(Prior Art) In recent years of demand for steel pipes, there has been an increasing demand for wear resistance on the inner surface of the steel pipes. In the field of oil drilling, the development of offshore inclined (horizontal) oil wells is becoming more popular.In such inclined (horizontal) oil wells, the casing is Since it comes into contact with the inner surface of the pipe, there is a problem that the inner surface of the pipe may wear out. Furthermore, it is also required to improve the wear resistance of the inner surface of slurry pipes and the like.

Is it effective to increase strength (hardness) in order to improve wear resistance? When considering corrosion resistance, toughness, etc., it is not possible to increase the strength unnecessarily. Further, in order to increase the strength, it is possible to add expensive elements such as Nj and V, but this is not preferable because it increases the manufacturing cost.

Furthermore, in recent years, surface treatments and the like have been sometimes applied to harden only the vicinity of the surface of steel pipes, but this cannot be said to be a good idea from the viewpoint of manufacturing costs and productivity.

As a prior art related to multilayer steel pipes, Japanese Patent Application Laid-open No. 11i3-
There is No. 213633 (highly corrosion-resistant clad steel pipe for line pipe). In this technology, in order to obtain high corrosion resistance, Ni:
It is characterized by the use of very expensive elements such as 30-60% Cr and 18-25% Cr.

In addition, as a manufacturing technology for multilayer materials, Japanese Patent Application Laid-Open No. 632138
There is No. 077 (method for manufacturing composite metal material).

A key point in this technology is the thermal spraying and plating of Ni or a Ni-based alloy to improve the adhesion of the steel materials being joined.

(Problems to be Solved by the Invention) The present invention provides the following advantages when manufacturing an electric resistance welded steel pipe with excellent wear resistance.
The present invention provides a method for manufacturing an electric resistance welded steel pipe with excellent wear resistance, which advantageously eliminates conventional drawbacks such as high manufacturing cost and poor productivity.

(Means for Solving the Problems) The gist of the present invention is to form a multilayer slab by laminating a molten alloy having better hardenability than the base slab on a base slab made of low alloy steel. It is characterized by hot rolling, forming and welding so that the laminated side becomes the inner surface of the steel pipe to create an ERW steel pipe, then heating the entire pipe to 800°C to 1000°C, and then cooling only from the inner surface of the steel pipe. This is a method for manufacturing ERW steel pipes with excellent wear resistance.

That is, the present invention manufactures an electric resistance welded steel pipe using a hot coil manufactured by hot rolling using a multilayer slab made by laminating two types of low alloy steel with different hardenability by spraying one side. Or, at this time, after forming and welding so that the side with excellent hardenability becomes the inner surface of the steel pipe, the entire pipe is heated from 800°C to 100°C.
The product is heated to 0°C and then rapidly cooled and quenched only from the inner surface of the steel pipe, thereby quenching and hardening only the inner surface of the steel pipe, producing an ERW steel pipe with excellent abrasion resistance on the inner surface of the steel pipe. .

In the present invention, by using a slab made of multiple layers of low alloy steel, material costs can be kept low because high alloys (including Ti, Ni steel, etc.) are not used as in the prior art. Also, the adhesive strength of the bonding surfaces is very good because they are made of low alloy steel.

The present invention will be explained in detail below.

The key point of the present invention is to utilize a multilayer slab in which low alloy steel, which has better hardenability, is injected onto a base material made of low alloy steel and then laminated thereon.

In order to effectively bond low-alloy steels with different hardenability to each other, it is very effective to spray one steel from a molten state and laminate it with the other steel, as in the present invention. Thus, by spraying molten steel onto another steel, the interface between the two forms a complete metallic bond, resulting in very good adhesion.

Next, this multilayer slab is hot rolled, but there are no particular restrictions on the cooling conditions or cooling stop temperature at that time. However, if the coil is cooled too quickly and the coil is wound at a low temperature, the side with better hardenability will harden too much, making it difficult to wind the coil and causing problems in the subsequent manufacture of ERW steel pipes. It is also possible.

Therefore, the temperature is preferably such that the coil is tempered (self-tempered) by self-sensible heat after being wound.
This temperature is preferably about 600°C to 700°C.

The cooling rate is preferably less than 10° C./second, and it is necessary to uniformly cool the upper and lower surfaces of the coil.

As described above, by slow cooling and winding at a relatively high temperature,
Base material side of multilayer coil, multilayer side (steel side with excellent hardenability)
The difference in strength is not large, and therefore there is no particular problem in the subsequent manufacture (forming, welding) of the electric resistance welded tube.

Next, a method for manufacturing ERW steel pipes will be described.

Using the multi-layer steel plate manufactured by the method described above,
l! 4 tubes are manufactured, but at this time, the multi-layered side, that is, the alloy side with excellent hardenability, is formed so that it becomes the inner side of the steel tube.
It is necessary to weld. In addition, in this multilayer coil, there is not much difference in strength between the base material side and the multilayer side at the time of manufacturing the steel pipe, and therefore there is no particular problem in forming and welding the steel pipe.

There are no other restrictions regarding the forming and welding of ERW steel pipes.

Subsequently, the entire tube is subjected to heat treatment, and the conditions at that time will be explained below.

Quenching is performed to improve the wear resistance of the inner surface of the tube, that is, to increase the hardness of the inner surface. After heating the entire back pipe formed into an ERW steel pipe from 800℃ to 1000℃,
Then, rapid cooling is performed only from the inner surface of the tube. In other words, by quenching from the inner surface of the tube, only the inner surface, which has multiple layers of alloys with excellent hardenability, is quenched and hardened, and the outer surface of the tube, that is, the base material side, has less hardenability, so it is hardened compared to the inner surface. do not.

By internal hardening as described above, it is possible to manufacture an electric resistance welded steel pipe with excellent wear resistance on the inside surface of the pipe. After further quenching, tempering the entire tube at a temperature below the AC3 transformation point is very effective in obtaining the desired strength and wear resistance, and can be done as necessary, but internal quenching It is possible to obtain the desired strength by selecting the component system.

The quenching conditions will be explained in more detail.

First, although the heating temperature varies depending on the components, it is desirable to uniformly heat the material to the austenite region, and from this point of view, the lower limit temperature was set at 800°C. Furthermore, since there is a possibility that quench cracking may occur if the material is rapidly cooled from a temperature exceeding 1000°C, the upper limit was set at 1000°C.

Next, there are no particular restrictions on cooling conditions, cooling rate, or cooling stop temperature, but in order to effectively harden the inner surface, a cooling rate of 10° C./sec or more is desirable. Further, the cooling stop temperature is preferably 400° C. or lower in order to suppress a decrease in strength due to reheating.

Next, we will discuss the component system.

There are no particular restrictions on the components of the base material and multilayer material (alloy to be sprayed) in the present invention. However, from the viewpoint of cost, it is preferable to use a component system that is as inexpensive as possible. As a result of the research conducted so far, it has been found that electric resistance welded steel pipes with excellent wear resistance can be manufactured very effectively using the following ingredients, and the details are introduced below.

First, we will discuss the ingredients of the alloy to be laminated.

Since it is necessary to harden the steel pipe by rapidly cooling the inner surface, it is important to use a composition system with excellent hardenability. Also, at this time, it is desirable to avoid adding expensive elements such as Ni as much as possible, so C and Si.

It is desirable to use Mn as a basic component and add relatively inexpensive elements such as B, Mo, and Cr as necessary.

First, regarding C, C is the most effective element for improving hardenability. Also, if the cooling conditions are the same,
It is said that the hardness of steel when hardened is controlled only by the C content of the steel. The wear-resistant steel pipe of the present invention aims to have a maximum hardness of 300 points or more on the Vickers hardness scale, and from this point of view, the C content is preferably 0.05% or more. Regarding the upper limit, C is an extremely effective element for improving hardenability, and by increasing its amount, the hardenability of the material improves, and as a result, the hardness increases. However, if unnecessarily hardened, cracks may occur on the coil surface, so the upper limit of the C content was set to 0.50%.

St is also a necessary element to increase strength and hardness,
From the viewpoint of weldability, 0.10 to 0.30% is desirable.

Like C, Mn is also an indispensable element for improving hardenability. However, if it is less than 0.50%*, it is not preferable in terms of a decrease in toughness, and if it exceeds 2%, the strength and hardness will become too high, so about 0.5% to 2.0% is preferable.

Furthermore, it is very effective to add one or more of B, Mo, Cr, etc. In particular, B is generally several ppm
It is said that the presence of the above solid solution B dramatically improves the hardenability of steel. On the other hand, adding more than necessary is not preferable because it embrittles grain boundaries. From the above, 0.0003
(3 ppm) to about 0.0030 (30 ppm) is the most preferable range. However, in order to ensure solid solution B, it is necessary to add Ti at the same time as B.

Since B has a strong affinity with N, which is inevitably present after refining, and forms nitrides (BN), solid solution B, which has an effect on hardenability, decreases or disappears. To prevent this and make effective use of the hardenability improvement effect of B, Tj
It is desirable to add

Ti has a stronger affinity with N than B, and Ti-based nitrides (T
i −N), it is possible to prevent the generation of BN.

The amount of Ti added is 0 to combine all solid solution N with Ti.
．． 010 to 0.035%. Preferably Tj-3.
4N, N≦1001)pll.

Also, for N, the upper limit is 100100pp, 0
100%) is preferable.

It is also effective to add appropriate amounts of Cr and Mo instead of B. Cr is an effective element for improving hardenability, but when added in large amounts, Cr-based oxides are generated in the weld and the quality of the weld deteriorates, so the upper limit is set at 1.00.
% is preferable.

If it is less than 0.10%, the effect will be small.

Mo is also an element effective in improving hardenability. Mo is effective in a range of 0.10% to 1.00%. If it is less than 0.10%, the effect is not expected, and 1
This is because the effect does not improve even if it is added in excess of 00%.

The above water components are based on necessity (steel thickness, required hardness)
You can choose accordingly.

Next, the base material components will be described.

The strength of a steel material depends on the strength of the base material, which is mostly the wall thickness, so it is only necessary to select a component system according to needs. However, B, Cr, Mo, such as those added to steel to effect
Hardenability improving elements such as C, Si, etc. are not added at all.
In terms of cost, it is preferable to use a low alloy steel consisting of Mn, Mn, and other elements that are unavoidably present.

Next, a method for laminating the molten alloy onto the base material will be briefly explained.

First, the base material used is a slab that has been refined in a converter and then continuously cast or cast in a mold. However [.

Continuously cast slabs are more advantageous in terms of productivity and cost.

A method of laminating molten alloy 2 on base slab 1 is shown in FIG.

There is no particular limit to the temperature of the base slab when laminating the molten alloy, and it may be in a hot state after casting or in a cold state after cooling the slab, or preferably above the A3 transformation point to further improve bonding properties. . Furthermore, from the viewpoint of productivity, it is most preferable to inject the molten alloy in a hot state immediately after continuous casting.

The molten alloy is atomized using the inert gas 3 through the nozzle 8, and the inert gas at this time is suitably Ar or N in consideration of cost and safety.

Further, the thickness of the molten alloy to be laminated may be selected by controlling the injection amount, time, and atomizing gas amount ratio as necessary.

Such multilayer slabs are hot rolled, then formed,
Weld and manufacture ERW steel pipes. This electric resistance welded steel pipe is cooled from the inner side as shown in FIG.

That is, the inner surface is made of a laminated material 4 with high hardenability, and is cooled with cooling water 6 from a water cooling nozzle 5, for example, to increase the hardness only on the inner surface side of the electric resistance welded steel pipe 7 and improve the wear resistance.

(Example) A, B, C, and D in Table 1 are examples of the present invention.

Electric resistance welded steel pipes are manufactured using multilayer steel materials with the composition system (laminate material, base material) shown in the table. At this time, the laminated steel (multilayer material side) is placed on the inner surface of the steel pipe, and then heated to 800℃. 1000℃
The graph shows the hardness of steel pipes according to their wall thickness when the pipes are heated and then water cooled from the inside.

In both cases, only the multilayer material side (inner surface side of the steel pipe) is hardened by water cooling from the multilayer material side (inner surface side of the steel pipe).

In addition, the base material side (outer surface side of the steel pipe) is not hardened as much because the hardenability is chemically inferior to that of the multilayer material side (inner surface side of the steel pipe), and the cooling acceleration is also small.

As described above, an electric resistance welded steel pipe with excellent wear resistance on the inner surface of the steel pipe was manufactured.

On the other hand, E and F in Table 1 are comparative materials for the present invention, or because they are both cooled from the outer surface of the steel pipe, a sufficient cooling rate cannot be obtained on the multilayer material side (inner surface of the steel pipe) and they cannot be hardened. .

From the above, a multilayer steel material made of multiple layers of injection material with better hardenability than the base material is used as the base material +4, and the laminated side is formed so as to become the inner surface of the steel pipe. By the method of the present invention in which quenching is performed only from the side, it is possible to manufacture an electric resistance welded steel pipe with excellent wear resistance on the inner surface of the steel pipe.

(Effects of the Invention) According to the present invention, it is possible to manufacture an electric resistance welded steel pipe with excellent abrasion resistance at low cost and with good productivity, and the effects thereof are extremely large.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing how laminated materials are laminated on a base slab, and FIG. 2 is an explanatory diagram showing a method of hardening an electric resistance welded steel pipe.

Claims (1)

[Claims] A base slab made of low-alloy steel is laminated with a molten alloy that has better hardenability than the base slab to form a multi-layer slab, and the multi-layer slab is hot rolled so that the laminated side becomes the inner surface of the steel pipe. Formed and welded into an ERW steel pipe, then the entire pipe was
A method for manufacturing an electric resistance welded steel pipe with excellent wear resistance, characterized by heating to 00°C to 1000°C and then cooling only from the inner surface of the steel pipe.