Bimetal wear-resistant pipe

Abstract

The utility model discloses a bimetallic wear-resistant pipe applied to the field of wear-resistant pipelines. The outer layer is a carbon steel pipe, the inner layer is a high-chromium cast iron pipe, a slag layer is arranged between the inner layer and the outer layer at two ends of the pipe, and no macroscopic gap exists in an interlayer interface. And melting pit type and shrinkage pit type interfaces are arranged between the slag layer and the inner and outer layers. The outer layer and the slag layer are formed by mixing and pouring steel slag, and the pouring speed to the launder ladle is larger than the flow speed of the flow nozzle. And the thickness of the slag layer is not more than 3mm due to the limitation of a slag layer forming process. The seamless interface can support the high-chromium cast iron pipe; the slag layers at the two ends play a role in heat resistance, the carbon steel pipe is subjected to high-current welding, and the inner layer cannot generate cracks; the slag layer and the interface can prevent inner layer cracks from expanding towards the outer layer.

Description

TECHNICAL FIELD

[0001] The utility model is applied to the field of wear -resistant pipeline, relates to double metal wear -resistant pipe, and specifically is a double metal wear -resistant pipe with slag layer in the middle layer. BACKGROUND

[0002] The wear -resistant pipe is usually carbon steel or low alloy steel in the outer layer, has good welding performance, guarantees pipeline connection, and is wear -resistant material such as ceramic, high chromium cast iron etc. in the inner layer, guarantees wear -resistant service life.For double metal wear -resistant pipe, double metal pouring centrifugal casting process is usually adopted. For example, the method for manufacturing double metal composite wear -resistant pipe by double liquid centrifugal pouring in CN1759956A pours A3 steel water in the centrifugal pipe mould first, pours high chromium cast iron molten iron after solidification, and produces double metal metallurgical composite wear -resistant pipe with outer sleeve steel pipe and inner lining wear -resistant alloy. The double metal wear -resistant composite pipe in CN101592265A adopts the same technological process to manufacture double metal wear -resistant composite straight pipe, but the timing of inner layer molten iron pouring is not disclosed. The production process of a kind of double metal composite pipe in CN101927327A pours carbon steel liquid first, pours high chromium cast iron liquid when the surface of steel liquid is liquid-solid mixed state, and two metals form intermelting transition layer. The double metal metallurgical composite wear -resistant pipe produced by using the above-mentioned technology has metallurgical combination of inner and outer layers, although the problem of inner layer high chromium cast iron fragmentation and peeling off and blocking pipeline is solved, but there are two main shortcomings: 1) once the crack of brittle high chromium cast iron layer occurs, the crack will expand to the outer layer, which causes hidden trouble to the safety of pipeline. 2) the welding of pipe end connecting parts is limited. If the flange or clamp groove is welded by using manual welding of large current at both ends of the wear -resistant pipe, the heat of large current welding will be transferred to the inner layer, and since the high chromium cast iron has poor thermal conductivity and is brittle, the inner layer high chromium cast iron will produce cracks, which will cause hidden trouble to the use of wear -resistant pipe. Only small current welding and rapid cooling can avoid the welding heat transfer to high chromium cast iron or avoid the large temperature difference of high chromium cast iron, and such welding process improves the welding cost and restricts the production efficiency. CONTENT OF UTILITY MODEL

[0003] The utility model solves the technical problem of providing a double metal wear -resistant pipe, and there is a slag layer at both ends of the pipe, which solves the problem of large current welding of the connecting flange or clamp groove of the double metal wear -resistant pipe, simplifies the welding process, improves the welding efficiency, and also solves the safety hidden trouble of crack expansion to the outer layer.

[0004] The technical scheme adopted by the utility model is that the outer layer of the double metal wear -resistant pipe is carbon steel pipe, the inner layer is high chromium cast iron pipe, and there is a slag layer between the outer layer and the inner layer at both ends of the pipe, and there is no gap visible to the naked eye between the layers. The slag layer and the outer layer are shrinkage pit type interfaces, and the slag layer and the inner layer are melting pit type interfaces.

[0005] Further, the outer layer and the slag layer are formed by pouring steel slag, and the pouring speed of the slag into the flow channel package is greater than the flow speed of the flow channel package nozzle.

[0006] Further, the melting point of the carbon steel is higher than the melting point of the slag layer, and the melting point of the slag layer is higher than the melting point of the high-chromium cast iron, which is a condition for forming the slag layer structure.

[0007] Further, the slag layer uses a CaO-Al2O3-SiO2 ternary system slag sub-substance for steelmaking reduction, and fluorite is used to adjust the melting point of the ternary system slag sub-substance. The slag layer raw material component allocation ratio is: lime: bauxite: sand: fluorite = 1.5: 0.8: 0.5: 0.4, and the melting point is preferably in the range of 1300-1500℃.

[0008] The beneficial effects of the utility model are that the slag layer at both ends of the bimetallic wear-resistant pipe plays a thermal resistance role, and the inner layer high-chromium cast iron pipe will not crack when the carbon steel pipe is subjected to large current welding. The slag layer and the interface can block the expansion of the high-chromium cast iron cracks to the outer layer, and ensure that the carbon steel pipe is in a safe state. The seamless interface can support the high-chromium cast iron pipe to avoid fragmentation and peeling of the high-chromium cast iron pipe. BRIEF DESCRIPTION OF DRAWINGS

[0009] Figure 1 It is an axial sectional view of the utility model;

[0010] Figure 2 It is Figure 1 It is a partial enlarged view;

[0011] Figure 3 It is an outer layer steel slag pouring illustration;

[0012] Wherein: 1-outer layer, 2-slag layer, 3-inner layer, 4-shrinkage pit, 5-melting pit, 6-flow channel package, 7-early molten steel, 8-pipe mold, 9-later molten steel. DETAILED DESCRIPTION

[0013] The following "carbon steel" refers to low-carbon steel or low-alloy steel with good welding performance, such as A3 steel or 16Mn, etc.

[0014] The bimetallic wear-resistant pipe of the utility model is a composite pipe of carbon steel and high-chromium cast iron, as shown in Figure 1 and shown in Figure 2 The outer layer 1 is a carbon steel layer, mainly to ensure the welding performance, and is used for pipe end welding connection, such as welding pipe ring connection, or welding flange connection, or welding clamp groove connection using a clamp. The inner layer 3 is a high-chromium cast iron layer, which ensures the wear resistance and is used to realize the expected service life of the wear-resistant pipe.

[0015] The welding position of the wear-resistant pipe is generally at the end of the pipe, and the slag layer 2 is between the inner and outer layers at both ends of the wear-resistant pipe, and the thickness of the slag layer is not more than 3 mm. There is no visible gap between the interface of the outer layer and the slag layer and the interface of the slag layer and the inner layer, forming a seamless gap contact. The role of the slag layer: 1) form a thermal resistance to avoid cracks in the inner layer. The slag layer has low thermal conductivity, which plays a role in thermal resistance, and can prevent heat transfer to the inner layer during high-current welding of the outer carbon steel pipe, preventing the high-chromium cast iron in the inner layer from cracking. 2) Block crack propagation. Even if the high-chromium cast iron in the inner layer produces cracks, the slag layer prevents them from spreading to the outer layer, ensuring the safety of the carbon steel pipe and the safety of the wear-resistant pipe. 3) Improve the service life of the wear-resistant pipe. The slag layer is similar to stone in composition, has high hardness and good wear resistance, and in use, even if the high-chromium cast iron pipe is worn, the slag layer can slow down the wear of the carbon steel pipe, thereby improving the service life of the wear-resistant pipe. 4) Support the high-chromium cast iron pipe. The high-chromium cast iron pipe is supported by the annular slag layer, and there is no gap between the two, so even if the high-chromium cast iron produces cracks, it will not break and fall off, and will not cause accidents such as pipe blockage.

[0016] The slag layer uses a CaO-Al2O3-SiO2 ternary system slag, and fluorite is used to adjust the melting point of the ternary system slag. The raw material component ratio is: lime: bauxite: sand: fluorite = 1.5:0.8:0.5:0.4, and the melting point of the slag should be in the range of 1300-1500°C. The reasons for choosing the CaO-Al2O3-SiO2 ternary slag system are: 1) The slag system can absorb other inclusions in the molten steel, and the molten steel and slag are mixed and poured, which can play a role in washing the outer layer of the molten steel, purifying the outer layer of the molten steel, and improving the mechanical properties of the outer layer; 2) The melting point temperature range of the slag system is small, and the softening point temperature is high, so when pouring the molten iron into the inner layer, the solid ring has already completely solidified, and there is no resistance to the molten iron; 3) The slag system has high hardness at room temperature and good wear resistance, which can assist in wear resistance.

[0017] The bimetallic wear-resistant pipe is a thin-walled pipe, and its production process is double-liquid centrifugal casting. First, the outer layer of molten steel and slag is mixed and poured, and then the inner layer of high-chromium cast iron liquid is poured. Figure 3To illustrate the steel slag mixed pouring and the slag layer formation at the pipe end, the left side is the flow condition when the pouring of the steel slag just starts, and the right side is the flow condition after the pouring of the steel slag, and the left and right sides respectively embody different stages of the pouring process. Since the slag specific gravity is far less than the molten steel, in the pouring ladle, the liquid slag floats on the surface of the molten steel. When the pouring of the ladle starts, the liquid slag on the surface of the molten steel in the ladle enters the runner ladle 6 together with the previous molten steel 7, and enters the pipe mold 8 through the flow nozzle together. The rapid ladle pouring makes a large amount of molten steel and slag enter the runner ladle, and since the inner diameter of the flow nozzle is small, the flow of the molten steel is limited, so that the molten steel entering the runner ladle is greater than the molten steel flowing out of the runner ladle, and the liquid slag floats up in the runner ladle. In the middle stage of the pouring, only the molten steel enters the pipe mold, and pushes the previous molten steel and the liquid slag to flow to the other end (non-pouring end) of the pipe mold. At this time, the later molten steel 9 and the slag in the ladle are all poured into the runner ladle. Finally, the remaining molten steel and the liquid slag in the runner ladle flow into the pipe mold, and fill the mold at the pouring end. Therefore, the slag layer is formed at both ends of the pipe mold, that is, the flow limitation of the flow nozzle and the rapid shaking of the ladle are necessary conditions for the slag layer to be formed at both ends of the wear-resistant pipe.

[0018] The baffles at both ends of the pipe mold have a cooling effect on the molten steel and the liquid slag, so at the pipe end, the slag layer is relatively thick, and generally does not exceed 3 mm. From the pipe end to the pipe body, under the joint action of the centrifugal force and the surface tension, the thickness of the slag layer gradually thins.

[0019] A bimetallic wear-resistant pipe of 20# steel / inner Cr26 high-chromium cast iron is taken as an example to illustrate the manufacturing method thereof. The outer layer thickness is 8 mm, the pouring weight is about 80 kg, the slag weight is 2-3 kg, the inner layer thickness is 5 mm, and the weight is about 45 kg. The outer layer carbon steel pipe is poured by mixing with the slag, the pouring temperature is 1600°C, the inner diameter of the flow nozzle is Φ28 mm, the outer layer ladle shaking speed is not more than 4 seconds, and the inner surface temperature is measured by an infrared high-temperature gun after the molten steel flows out of the runner ladle. The melting point of the outer layer carbon steel is higher than that of the slag, so in the later stage of the solidification of the carbon steel molten steel, the liquid slag fills the shrinkage space of the molten steel, and a shrinkage pit 4 is formed at the interface between the outer layer and the slag layer, as shown in the accompanying drawing. Figure 2 When it reaches about 1200°C, the inner layer high-chromium cast iron liquid metal is poured, and the pouring temperature is 1430°C. The inner layer pouring temperature is far lower than the melting point of the outer layer carbon steel, so the inner layer high-chromium cast iron in the middle pipe body of the wear-resistant pipe cannot be metallurgically fused with the outer steel layer. Although the inner layer pouring temperature is not much different from the melting point of the slag, since the pouring amount is insufficient, the slag cannot be remelted in a large amount, but a melting pit 5 can be formed on the surface of the slag, the molten liquid fills the melting pit, the remelted liquid slag floats up under the centrifugal force, and an interface as shown in the accompanying drawing is formed. Figure 2

[0020] ​The shrinkage rates of the high-chromium cast iron and the carbon steel are basically consistent, and there is no visible gap between the inner layer and the outer layer in the middle of the wear-resistant pipe through shrinkage and high-temperature atomic diffusion bonding. At the two ends of the wear-resistant pipe, there is a slag layer between the inner layer and the outer layer, the interface between the outer layer and the slag layer is a shrinkage pit type interface, and there is no visible gap. The interface between the inner layer and the slag layer is a melting pit type interface, and there is no visible gap.

[0021] The utility model discloses a bimetallic wear-resistant pipe, when the pipe end welding operation, the welding heat of outer layer is obstructed by slag layer, can not be transferred to the inner layer, and the high-chromium cast iron of inner layer can not produce crack because of thermal stress, can adopt large current welding, has simplified the welding process, improved the welding efficiency. In addition, even if the high-chromium cast iron of inner layer produces crack because of impact, crack extension reaches slag layer, and will not extend to the outer layer. If the high-chromium cast iron inner layer of no slag layer position in the middle of wear-resistant pipe produces crack, crack extension reaches the interface of inner layer and outer layer, and will not extend to the outer layer, because the inner layer and the outer layer are not fused or metallurgical bonding, just contact without visible gap. The seamless gap can support the high-chromium cast iron pipe, is tightly restricted by the outer ring, and will not produce peeling, influences the safe use of wear-resistant pipe.

Claims

1. A bimetallic wear tube, the outer layer being a carbon steel tube and the inner layer being a high chromium cast iron tube, characterized in that: The slag layer is between the outer layer and the inner layer at both ends of the tube, and there is no visible gap between the interfaces of the layers; the slag layer and the outer layer are connected by a shrinkage pit interface, and the slag layer and the inner layer are connected by a melting pit interface.

2. A bimetallic wear tube according to claim 1, wherein: The thickness of the slag layer is not more than 3 mm.

3. A bimetallic wear tube according to claim 1 wherein: The melting point of the carbon steel is higher than the melting point of the slag layer, and the melting point of the slag layer is higher than the melting point of the high-chromium cast iron.

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