A bimetallic composite wear resistant pipe

Abstract

This utility model discloses a bimetallic composite wear-resistant pipe, comprising an outer steel pipe and an inner high-chromium cast iron wear-resistant layer with a thickness greater than 3 mm. A 0.6–2 mm thick self-propagating layer is disposed between the inner and outer layers. The outer layer and the self-propagating layer are not metallurgically bonded, and there are no visible gaps at their interface. The self-propagating layer and the inner layer are also not metallurgically bonded, and the gap at their interface is ≤0.3 mm. A retaining ring is provided at one or both ends of the wear-resistant pipe, with the inner hole of the retaining ring flush with the inner surface of the wear-resistant layer. The shrinkage gap between the retaining ring and the end face of the wear-resistant layer is filled with a wear-resistant adhesive. The self-propagating layer of this utility model has the functions of heat insulation and preventing crack propagation, preventing the heat from welding the steel pipe from being transferred to the wear-resistant layer, and preventing cracks in the wear-resistant layer from propagating into the steel pipe.

Description

Technical Field

[0001] This utility model applies to the field of wear-resistant pipes, and relates to a bimetallic composite wear-resistant pipe, specifically a bimetallic composite wear-resistant pipe with a steel pipe as the outer layer, a high-chromium cast iron as the inner layer, and a self-propagating layer between the inner and outer layers. Background Technology

[0002] The most common composite wear-resistant pipe on the market is a composite layer of high-chromium cast iron or ceramic on the inner surface of a steel pipe. Ceramic composite wear-resistant pipes are often produced using self-propagating or ceramic patch manufacturing methods. There are several production processes for bimetallic pipes with a composite high-chromium cast iron wear-resistant layer, including centrifugal casting and nesting processes. Centrifugal casting is further divided into single-liquid casting and double-liquid casting. Single-liquid casting involves pouring molten high-chromium cast iron into a high-speed rotating steel pipe, while double-liquid casting involves pouring the outer layer of molten steel first, followed by the inner layer of high-chromium cast iron. The nesting process involves nesting the high-chromium cast iron wear-resistant pipe inside an outer steel pipe, filling the space between the inner and outer layers with nesting material. Double-liquid casting offers superior interface quality and can achieve a seamless bond, but it requires more equipment and has more complex process requirements; therefore, few manufacturers currently use this process. For example, the bimetallic composite pipe manufactured using the process described in CN101927327A, which involves metallurgically bonding the inner and outer layers, has the potential for cracks in the inner layer to propagate to the outer layer. Furthermore, when welding flanges or pipe clamps to the outer layer, cracks can form in the inner layer, affecting the safe operation of the pipeline. Single-liquid cast composite wear-resistant pipes have the following defects: 1) The wear-resistant layer is relatively thick, typically over 18mm. The steel pipe acts as an external chill, and the high-chromium cast iron molten metal experiences a large temperature drop, making filling difficult. 2) With a wear-resistant layer thickness of 12-16mm, even if molding is possible, the high cooling rate of high-chromium cast iron often leads to thermal stress cracks. 3) Gaps exist between the inner and outer layers. If the gaps are large, the wear-resistant layer lacks the support of the steel pipe, making it prone to cracking and spalling under impact conditions, severely affecting the pipeline's service life and safe operation. If the gaps are small, heat can be transferred to the inner layer during welding of the outer steel pipe, causing thermal stress cracks in the wear-resistant layer.

[0003] The applicant's patent application for a bimetallic wear-resistant pipe product (application number 2025202472053) utilizes a two-liquid centrifugal casting process. A slag layer exists between the inner and outer layers at both ends of the wear-resistant pipe. The outer layer and slag layer are cast using a mixture of steel and slag, resulting in no visible gaps at the interlayer interface, thus supporting the high-chromium cast iron pipe. The slag layer at both ends acts as thermal resistance, preventing cracks from forming in the inner layer during high-current welding of carbon steel pipes. The slag layer also prevents cracks in the inner layer from propagating to the outer layer. A drawback of this wear-resistant pipe is that the slag layer only exists at both ends, not in the middle. For short-length pipes, there is still a tendency for cracks to form in the inner layer when welding flanges or pipe clamps. Therefore, the applicant developed this utility model to address the defect that the slag layer does not penetrate the entire length of the wear-resistant pipe. Utility Model Content

[0004] The technical problem solved by this utility model is to provide a bimetallic composite wear-resistant tube, in which a self-propagating layer is provided between the inner and outer layers along the entire length of the wear-resistant tube. This self-propagating layer has the functions of thermal resistance and preventing the expansion of cracks in the inner layer, and can meet the quality requirements of short-length tubes.

[0005] The technical solution adopted in this utility model is as follows: the outer layer of the bimetallic composite wear-resistant pipe is a steel pipe, the inner layer is a high-chromium cast iron wear-resistant layer, and a self-propagating intermediate layer is set between the inner and outer layers. The outer layer and the self-propagating layer are not metallurgically bonded, and there are no visible gaps at their interface. The self-propagating layer and the inner layer are not metallurgically bonded, and the gap at their interface is ≤0.3mm.

[0006] Furthermore, the thickness of the self-propagating layer is 0.6–2 mm.

[0007] Furthermore, the thickness of the inner layer is 3 mm or more.

[0008] Furthermore, one or both ends of the bimetallic composite wear-resistant tube are provided with retaining rings, the inner hole of which is flush with the inner surface of the wear-resistant layer. Wear-resistant adhesive is filled between the retaining rings and the inner layer end face.

[0009] The beneficial effects of this utility model are: This utility model adds a self-propagating layer between the inner and outer layers. This self-propagating layer has the functions of heat insulation and preventing crack propagation. It can prevent the heat from welding the steel pipe from being transferred to the wear-resistant layer, and the cracks in the wear-resistant layer will not extend to the steel pipe. Attached Figure Description

[0010] Figure 1 This is a schematic diagram of the main structure of Example 1;

[0011] Figure 2 for Figure 1 A schematic diagram of the AA cross-section;

[0012] Figure 3 This is a schematic diagram of the main structure of Example 2;

[0013] Figure 4 This is a schematic diagram of the main structure of Example 3;

[0014] Among them: 1-steel pipe, 2-self-propagating layer, 3-wear-resistant layer, 4-retaining ring, 5-wear-resistant adhesive. Detailed Implementation

[0015] The "steel pipe" mentioned in this utility model refers to a non-cast steel pipe, such as a hot-rolled seamless steel pipe, a straight seam welded pipe, or a spiral welded pipe. The "self-propagating layer" is a heat insulation layer prepared using a self-propagating process. Example

[0016] The structure of the bimetallic composite wear-resistant tube in this embodiment is shown in the attached figure. Figure 1As shown, it has a three-layer structure consisting of an outer layer, a middle layer, and an inner layer. The outer layer is a purchased steel pipe 1, the middle layer is a self-propagating layer 2 of non-metallic material, and the inner layer is a wear-resistant layer 3 of high-chromium cast iron. Retaining rings 4 are welded to both ends of the pipe mold. These retaining rings 4 are process retaining rings.

[0017] The self-propagating layer 2 is prepared using a self-propagating process, and the wear-resistant layer 3 is prepared using centrifugal casting. The retaining ring 4 at one end of the wear-resistant tube has a small inner hole, serving as the casting end for centrifugal casting to prevent steel spillage during the process. In other words, the retaining ring at the casting end is a steel spillage prevention retaining ring, which is machined to be flush with the inner layer after casting. The retaining ring at the other end is a steel spillage prevention ring, with its inner diameter flush with the wear-resistant layer. Steel spillage can be used to control the thickness of the wear-resistant layer. Alternatively, the inner holes of the retaining rings at both ends can be the same, and the thickness of the wear-resistant layer can be controlled by the casting weight.

[0018] The self-propagating layer 2 provides thermal insulation and acts as a thermal barrier. During welding on the steel pipe, the welding heat from the outer layer is not transferred to the inner layer due to the thermal resistance of the self-propagating layer 2, preventing thermal stress cracking in the high-chromium cast iron of the wear-resistant layer 3. Simultaneously, the self-propagating layer 2 also prevents cracking. When conveying granular materials, the high-chromium cast iron wear-resistant layer may develop impact cracks. Under continuous impact, the crack penetrates the inner wear-resistant layer and extends to the interface with the self-propagating layer, where it stops. Therefore, the self-propagating layer prevents cracks from extending to the outer steel pipe, ensuring the safe operation of the pipeline.

[0019] In this embodiment, after welding retaining rings to both ends of the steel pipe, the steel pipe is inserted into the pipe mold, and the center of the steel pipe and the pipe mold is aligned using evenly distributed bolts on the pipe mold. Self-propagating powder is sprinkled inside the steel pipe, and a self-propagating layer is formed on the inner surface of the steel pipe using a self-propagating process. When the temperature of the self-propagating layer drops to 300℃~700℃, high-chromium cast iron molten metal is poured in, and after cooling and solidification, a bimetallic composite wear-resistant pipe is formed. The bimetallic composite wear-resistant pipe prepared by this method shrinks simultaneously across all three layers. The steel pipe 1 and the self-propagating layer 2 are not metallurgically bonded, and there are no visible gaps at the interface. The interface between the self-propagating layer 2 and the wear-resistant layer 3 is also non-metallurgically bonded. Thus, the self-propagating layer 2 and the steel pipe 1 can completely support the wear-resistant layer 3. Even if the wear-resistant layer 3 develops penetrating cracks, the inner high-chromium cast iron layer will not peel off due to the constraint of the outer layer and the self-propagating layer, ensuring the wear-resistant service life of the wear-resistant layer and the safe operation of the pipeline. This method is suitable for wear-resistant layer thicknesses in the range of 3mm~12mm. Example

[0020] The structure of the bimetallic composite wear-resistant tube in this embodiment is shown in the attached figure. Figure 3 As shown. It is basically the same as Example 1, except that there is a shrinkage gap at the end of the retaining ring 4 and the wear-resistant layer 3, which is filled with wear-resistant adhesive 5. The wear-resistant adhesive 5 can be ceramic powder, or a mixture of high-chromium cast iron filings and adhesive.

[0021] The preparation of the self-propagating layer in this embodiment is the same as in Embodiment 1. The steel pipe with the self-propagating layer is kept as a ready-made product. When an order is received, or when production is scheduled in the medium-frequency furnace, the steel pipe and pipe mold are heated in a heating furnace, and then the pipe mold is hoisted onto a centrifuge to pour high-chromium cast iron molten metal. This method is suitable for composite wear-resistant pipes with a wear-resistant layer thickness of not less than 6 mm. The bimetallic composite wear-resistant pipe prepared using this method has the steel pipe and the self-propagating layer as a single unit, with a metallurgical bond between them and no visible gaps at the interface. Due to the large temperature difference between the self-propagating layer and the high-chromium cast iron molten metal, and the slightly greater shrinkage rate of the high-chromium cast iron compared to the steel pipe, a gap may exist between the self-propagating layer and the wear-resistant layer when the wear-resistant layer thickness is low. This gap is typically no larger than 0.3 mm and is directly related to the amount of high-chromium cast iron molten metal poured, i.e., the wear-resistant layer thickness. Because the gap size is very small (relative to the wear-resistant layer thickness), even if cracks appear in the wear-resistant layer, there will be no peeling or spalling. In addition, there will be a shrinkage gap between the retaining ring and the end face of the wear-resistant layer, which is filled with wear-resistant adhesive.

[0022] Although there is a small gap between the inner layer and the self-propagating layer, the high-chromium cast iron inner tube cannot be separated from the outer steel tube and the self-propagating layer due to friction, including when tension or thrust is applied to one end of the tube. Example

[0023] The structure of the bimetallic composite wear-resistant tube in this embodiment is shown in the attached figure. Figure 4 As shown, the retaining rings at both ends of the steel pipe are absent. In this embodiment, baffles installed at both ends of the pipe mold mate with the two end faces of the steel pipe, replacing the retaining rings. After the high-chromium cast iron molten metal is poured and solidified, an attached... Figure 4 Structure. Alternatively, after cutting off the retaining rings at both ends of the bimetallic composite wear-resistant tube in Examples 1 and 2, it becomes a short tube, which also forms an attached... Figure 4 The structure shown.

[0024] This invention adds an intermediate layer between the inner and outer layers along the entire length of the wear-resistant tube. This intermediate layer is prepared using a self-propagating process and has thermal insulation properties, effectively preventing heat transfer from the outer layer welding to the inner layer. The hard and brittle high-chromium cast iron wear-resistant layer will not develop thermal stress cracks. When impact cracks occur in the wear-resistant layer during use, the cracks will not penetrate through the self-propagating layer, thus preventing crack propagation to the outer layer. Even when laser-cut into short tubes, the self-propagating layer remains the intermediate layer, providing thermal resistance and preventing crack propagation.

Claims

1. A bimetallic composite wear-resistant pipe, comprising an outer steel pipe and an inner high-chromium cast iron wear-resistant layer, characterized in that: An intermediate layer exists between the inner layer and the outer layer; the intermediate layer is a self-propagating layer; the outer layer and the self-propagating layer are not metallurgically bonded, and there are no visible gaps at their interface; the self-propagating layer and the inner layer are not metallurgically bonded, and the gap at their interface is ≤0.3mm.

2. The bimetallic composite wear-resistant tube according to claim 1, characterized in that: The thickness of the self-propagating layer is 0.6 mm to 2 mm.

3. The bimetallic composite wear-resistant tube according to claim 1, characterized in that: The thickness of the inner layer is 3 mm or more.

4. The bimetallic composite wear-resistant tube according to claim 1, characterized in that: One or both ends of the bimetallic composite wear-resistant tube are provided with retaining rings, and the inner hole of the retaining ring is flush with the inner surface of the wear-resistant layer.

5. The bimetallic composite wear-resistant tube according to claim 4, characterized in that: The space between the retaining ring and the inner layer is filled with a wear-resistant adhesive.

Images