JPS60148689A - Production of composite seamless guide shoe - Google Patents

Abstract

PURPOSE:To build-up a high carbon-contg. metal without cracking on the surface of the low carbon-contg. base metal in a casting mold by pouring the metal of a high carbon content melted in another melting furnace into the mold while melting an electrode in the mold by electroslag welding. CONSTITUTION:A base metal 5 which constitutes the inside material of a guide shoe and consists of an ordinary steel contg. <=0.3wt% carbon or austenite stainless steel contg., by weight, <=0.3% C, 8-25% Ni and 18-30% Cr is perpendicularly fixed and a welding wire 11 which is a consumable electrode is supplied to the spacing between water-cooled molds 6 and 7. The base metal 5 is melted by the Joule heat of molten slag 15 and when the material melts to a prescribed amt., a molten metal 13 prepared in another melting furnace is poured continuously or intermittently into the mold to form a build-up metal 14. The build- up metal 14 is formed by the molten metal 13, the wire 11 and the metal 5 which are melted and mingled with each other.

Description

[Detailed Description of the Invention] [Field of Technology] The present invention relates to a guide shoe for an inclined roll drawing machine used for manufacturing seamless steel pipes, and has particularly excellent wear resistance and seizure resistance, as well as cracking resistance. The present invention relates to a method of manufacturing a composite guide shoe.

[Prior art]

Generally, in the manufacturing process of seamless steel pipes, first, a round steel piece is heated to an appropriate temperature and formed into a hollow shell using a drilling machine. In the drawing machine located in the post-process, as shown in FIG. 1, the thickness of the hollow shell tube 2 is reduced while rotating the hollow shell tube 2 and making it elliptical with a plug 3. The drawing machine is equipped with a guide shoe 1 for adjusting the outer diameter and thickness of the hollow tube 2.
is installed. Since the hollow tube, which is a rolled material, is rotated forward in a spiral manner by the rolls 4, the hollow tube, which is a rolled material, is rotated forward in a spiral manner.
A friction phenomenon Z accompanied by rolling and sliding occurs between the guide shoe 1 and the guide shoe 1. Further, at this time, the guide shoe is used under severe conditions due to repeated rapid heating due to heat transfer from the hollow tube, which is a rolled material, and rapid cooling using cooling water.

Guide shoes used under such conditions have conventionally been made of monolithic cast steel having compositions as exemplified in Table 1.

Especially 01. O~1.4%, Ni35%, O
r 35%, Mo 1.5%, Wl, 5%.

High-alloy cast steel product with Ou5.0% (Special Publication No. 55-13806
No. 2) has been widely used to extend the service life.

However, it is difficult to satisfy the contradictory characteristics of wear resistance and crack resistance with a single component system7. In fact, in actual machines, cracks occur after about 20 rolls are rolled, and the rolls are usually scrapped after around 700 rolls, and in some cases, they are scrapped after 20 rolls. Therefore, the basic unit of the guide shoe is low and its improvement is desired.

In general, the components of guide shoes are developed with a focus on wear resistance, heat resistance, and cracking resistance, so specific examples include high-carbon, high-alloy steel as shown in Table 1 above. . Therefore, the microscopic structure exhibits a structure in which many carbides are dispersed, as shown in FIG. Therefore, there is a limit to the cracking resistance within this range of component systems, and it is preferable to use a low carbon type with less carbides in terms of cracking resistance. However, if it is made from a low carbon type material, it cannot be used as a guide shoe because it cannot obtain properties such as wear resistance, seizure resistance, and heat resistance.

Therefore, the optimal guide shoe is made of high-carbon, high-alloy steel with a large amount of carbide dispersed on the surface side that contacts the rolled material.
Ideally, the composite guide shoe should have wear resistance, seizure resistance, and heat resistance, while its inner side is made of low carbon steel with low carbide and excellent crack resistance.

The present invention relates to a method for manufacturing this composite guide shoe.

[Purpose of the invention]

The purpose of the present invention is to reduce cracking of the guide shoe and extend its service life. The object of the present invention is to provide a composite guide shoe that is significantly extended.

[Structure of the invention]

The first feature of the present invention is its combination.

In other words, the surface side that comes into contact with the rolled material is made of high-carbon, high-alloy steel with excellent wear resistance, seizure resistance, and heat resistance, and the inner side is made of low-carbon steel to prevent the propagation of cracks. Reduce waste by 1. Conventional one-piece high-alloy cast steel products have a large wall thickness, and relatively coarse carbides develop in a network, so once cracks occur due to thermal fatigue and stress during rolling, this network Since the crank develops along the carbide, it is often discarded due to cracking. The present invention aims to prevent this crack from occurring only on the surface side by making it composite, and uses low-carbon ordinary steel or stainless steel on the inner side, which has almost no grains.

The second feature is that electroslag welding is used as the welding method.

The reason for this is that when overlaying a metal with a high carbon content, such as a guide shoe, the cooling rate after overlaying is rapid, and the
'A POO welding and TIG welding cause cracks in the overlay metal. FIG. 3 shows the relationship between the amount of carbon in the overlay metal and the occurrence of cracks.It is impossible to overlay high carbon content fingers such as guide shoes using anything other than electroslag welding. In addition, since the guide shoe has a large wear loss, the build-up thickness must be at least a certain thickness. FIG. 4 shows a comparison of the build-up thicknesses, and the limit for methods other than electroslag welding is 2 to 3 μ or less. As mentioned above, due to (1) cracking of the overlay metal and (2) the thickness of the overlay, methods other than electroslag welding cannot be applied to the overlay of the guide shoe.

The third feature is the addition of molten metal.

The first reason is that the total amount of alloying elements (0+ Si+Mn+Ni+Or+Mo+O
Since it is technically impossible to secure a welding material (consumable wire) alone with a weight t% of 80% (u+W), molten metal is added as a method to secure the alloy components.

The second reason is that by adding molten metal, the amount of heat per unit length that enters the core material is reduced, and even thin (50 mm) base materials such as guide shoes can be melted uniformly. You can get dirt.

Figure 5 shows the experimental results of the relationship between the amount of molten metal added and the depth of penetration. From this result, it was found that an appropriate amount of penetration could be obtained by adding molten metal to 60 to 80% of the overlay metal and supplying the rest with welding wire.

Furthermore, by adding molten metal, the overlay efficiency was significantly improved, and the efficiency was improved to about five times that of electroslag welding alone.

The fourth feature is the component composition.

The component on the surface side of the guide shoe (overlay metal) may be conventional high-carbon high-alloy steel, but the base material on the inside is made of 0,3. wt
% or less, :0. r 18~30 w 1%, Ni8~2
8W 1% austenitic stainless steel or 00
．． 3 It is necessary to use ordinary steel with a w content of 1% or less.

Figure 6 shows the results of a thermal shock test conducted to select the base material. The test was performed using a test piece with a diameter of 100Xt50, and a
After heating at °C and cooling with water 10 times, the depth Z of cross-sectional cracks was measured to examine thermal shock properties. The test material used in the test was 25% Or -20% Ni; 18% Or
-8%Ni: Or.

0 content'& 0.05~1 in 3 component system without Ni
．． The relationship Z between the 0 content and the crack depth was determined by varying the content up to 0%. From the test results, the 0 content is Q, 3 w 1
% or less, there is almost no cracking in any of the falling component systems. (If it exceeds 0.5wL%, the amount of cracks will increase rapidly.From this test result, 0 content t is 0.3w1%)
Below, Or 18-30 wt%, Ni 8-25 wt%
austenitic stainless steel or 0-containing -i, Q,
3. Ordinary steel with a w content of 1% or less was selected as the inner material, that is, the overlay base material.

The guide shoe is manufactured as shown in FIG. 7 as follows.

The base material 5 of low carbon steel that will become the inner material of the guide shoe is fixed vertically, and the surface side that contacts the rolled material, that is, the overlay metal part, is formed by a water-cooled mold 6.7 placed around the base material 5. A welding wire 11'Y, which is a consumable electrode, is continuously supplied to the gap, and the Joule heat of the molten slag 15 causes the base metal 5' to 0
: When the base metal 5 has melted to a predetermined amount, molten metal 13 prepared in advance for melting in another melting furnace is added at a constant rate to form overlay metal 1.
4 will be formed. In this case, molten metal 13 and welding wire 1
1. The melted base material 5 is mixed with the molten base material 5 to form the overlay metal 14. Therefore, in order to ensure a predetermined composition of the overlay metal 14, the ratio of the molten metal 13 to the welding wire 11,
Uniform melting of the base material 5 is an important technical issue. Therefore, the ratio of welding wire 11 to molten metal 13 is 20 to 4.
It is necessary to keep it within the range of 0% to 80-60%. When overlaying, the base material may be fixed as described above and the overlay may be applied from the bottom to the top, or the overlay portion may be fixed and the base material may be lowered.

〔Example〕

Next, an example will be given and explained.

Base material is 0.15w 1%0.18wt%Or, 8w
A stainless steel cast product with t%N1 was used. Overlaying was carried out under the conditions shown in Table 2. The electrical conditions at this time were such that appropriate penetration could be obtained from past experiments.

As a result, the penetration of the base material was approximately 1 to 3II11 thick, but substantially uniform penetration over the entire length was obtained. Therefore, the composition of the overlay metal is oH) ~ 1.3 in weight%.
%, 8i 0.7-1.0%, Mn 0.7-0.8
%, Ni34-36%, Orr33-35%, MoI,
l ~1.3%, Ou 45~5%, Wl, 0~13
%, we were able to secure the target component. In addition, it was possible to manufacture a good guide shoe using the overlaid metal without causing any cracks. Figure 8 shows the microscopic structure of the overlay metal.

The structure exhibits a structure in which eutectic chromium carbide is uniformly crystallized on an austenite base, and is finer than that of a monolithic cast steel product (Fig. 2). Table 3 shows the results of the upper tension test at the boundary, and the tensile strength is 55.9 K.
9/aa'' and elongation of 13.8%, which is superior to that of monolithic cast steel products, and good results were also obtained regarding the boundary properties that are a concern with cypress composite materials.

Table 3 Tensile test results of boundary parts As a result of applying the composite guide shoe manufactured in the above example to an actual drawing machine, cracks occurred in the guide shoe of the conventional monolithic cast steel product after about 20 pieces of rolled material started to be used. The average lifespan of the guide shoes was approximately 700, but with the composite guide shoes of the present invention, even after rolling the average life of 700 shoes, one of the guide shoes did not develop any cracks, and the remaining one had only one small clutter. Although it was occurring, it stopped at the overlay metal and did not reach the base metal.

〔Effect of the invention〕

From the above, the composite guide shoe manufactured by the method of the present invention is less prone to cracks than conventional cast steel products, and even if cracks occur, they remain within the overlay metal. The lifespan of the guide shoes has been significantly extended compared to conventional guide shoes.

2 In addition, since no cracks occur in the base material, it is possible to process and re-overlay when it wears out, making it possible to significantly lower the unit consumption of the guide shoe.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of an inclined roll drawing machine, Figure 2 is the microstructure of high-alloy cast steel used in conventional guide shoes, Figure 3 is the result of overlay metal cracking tests using various welding methods, Figure 4 is a comparison of the build-up thickness of various welding methods, Figure 5 is the test result of the relationship between the molten metal ratio and penetration depth of the present invention, and Figure 6 is the comparison of the build-up thickness of various welding methods.
The figure shows the thermal shock test results for base material selection, Figure 7 is a schematic diagram of the process of the present invention, lal is a side view, tb+ is a plan view, and Figure 8 is the meat of the guide shoe manufactured by the method of the present invention. The microstructure of the mound is shown. In the drawing, ■ is a guide shoe, 2 is a hollow tube, 3 is a plug, 4 is a roll, 5 is a base material, 6 is a side copper mold, 7 is a mobile water cooling mold, 8 is a start tab, 9 is a surface plate, 10
1 is a welding nozzle, 11 is a welding wire, 12 is a pouring ladle, 1
3 is molten metal, 14 is overlay metal, and 15 is molten slag. Agent Patent attorney Masamitsu Aki Sawa and 2 others [;:[::[::1Pl 11L Kanoguchi 41S11
-Starting To--Hei arc its, Ro S Haku (contains 1 quantity do alλ Shi 嫂 2 figure 4 circle 5 each hand [4 eyes I puffer fish diagonal 6 figure 0 /, θ C# beauty rga f% ) Shu7en

Claims (1)

[Claims] (1) Carbon content of 9.3w1% or less is achieved by melting an electrode in the mold using electroslag welding and simultaneously injecting molten steel produced in another melting furnace into the mold continuously or intermittently. Ordinary steel or 00
．． 3 wt% or less, Ni 8-25 w't%. Method for manufacturing a composite seamless guide shoe characterized by overlaying high carbon high alloy steel on the surface of 0r18-3Qwt% austenitic stainless steel0