CN112856477B - A water-cooled wall inner thread tube panel and its processing method - Google Patents

Abstract

The invention relates to a water-cooled wall inner thread tube panel and a processing method thereof, and belongs to the technical field of boiler water-cooled walls. In order to solve the problems that the thread of the existing internal threaded pipe panel is prone to stress concentration and the thermal stress between the internal threaded pipe and the flat steel is too large, the pipe panel bursts and the tube fails. The processing method is as follows: the water-cooled wall inner threaded pipe screen is welded by the inner threaded pipe and the flat steel, the section of the inner thread is a trapezoidal concave curved surface, the two sides of the inner threaded pipe are respectively processed with arc-shaped grooves, and the flat steel passes through the arc-shaped grooves. Welded with internally threaded pipe, flat steel is machined with a honeycomb core. The processing method is as follows: thread additive manufacturing is performed on the internal thread, and the two sides of the internal threaded pipe are processed by additive manufacturing to produce an arc groove, and a milling cutter is used to perform subtractive processing on the two sides of the arc groove, and additive manufacturing is used. The manufacturing method processes flat steel, and welds flat steel and internally threaded pipe. The invention can reduce the stress concentration phenomenon inside the inner thread tube panel and improve its service life.

Description

A water-cooled wall inner thread tube panel and its processing method

technical field

The invention belongs to the technical field of boiler water cooling walls, and in particular relates to a water cooling wall inner thread tube panel and a processing method thereof.

Background technique

The conventional boiler water wall inner threaded tube panel is formed by welding the inner threaded tube and the flat steel, and the welding method is longitudinal seam welding of the flat steel with groove and the outer wall of the threaded tube.

The internal thread pipe panel manufactured in this traditional way has the following problems in structure:

1. The thread section of the traditional internal threaded pipe is trapezoidal, and the top angle and the root are sharp angles. During the operation of the boiler, the sharp angles of the top angle and the root are subjected to thermal stress and residual stress, which is easy to produce stress concentration. As a result, the inner wall thread fails, and eventually the tube screen burst accident occurs.

2. The traditional flat steel is made of solid metal. At the same time, the weight of solid metal is large, which increases the overall weight of the heating surface, which leads to an increase in the number of suspension pipes in the upper part of the furnace, which increases the total weight of the boiler and increases the cost. In addition, the heat transfer efficiency of traditional solid metal flat steel is extremely high, so that the heat generated by the combustion of pulverized coal inside the furnace is dissipated to the outside of the furnace through the heat transfer of the flat steel. The heat conduction rate of metal flat steel is fast, and during operation, the flat steel is in a dry burning state without working fluid heat exchange, and the heat is transferred from the flat steel to the pipe wall, resulting in a high temperature at the junction of the flat steel and the pipe, and Due to the low temperature of the heat transfer of the working medium at the non-contact part, a large thermal stress is generated in the circumferential direction of the tube.

And it also has the following problems during processing:

The traditional welding method of pipe and flat steel is to weld the flat steel with groove and the curved surface without groove on the outer wall of the pipe, and the flat steel thickness at the root of the weld is reduced after the groove is processed on the side of the flat steel. It is prone to tearing at the flat steel weld, and eventually the crack extends to the tube body, resulting in the failure of the tube screen bursting.

SUMMARY OF THE INVENTION

In order to solve the problem that the thread of the existing internal threaded pipe panel is prone to stress concentration, the thermal stress between the internal threaded pipe and the flat steel is too large, and the tube panel bursts the failure of the tube, the present invention provides a water-cooled wall internally threaded pipe panel. .

Technical scheme of the present invention:

A water-cooled wall inner threaded pipe panel, comprising an inner threaded pipe and a flat steel, each two of the inner threaded pipes is connected by a flat steel to form a water-cooled wall inner threaded pipe panel, and the inner thread section of the inner threaded pipe is The inner concave curved surface is trapezoidal, the root of which is an arc transition, and its apex is a circular arc blade. The outer wall of the inner threaded pipe is respectively machined with arc grooves, and the flat steel passes through the arc groove and the inner thread. Tube connections, the flat steel is machined with a honeycomb core.

Preferably, the arc-shaped groove is a root arc transition groove.

In order to solve the above-mentioned problem that the internally threaded pipe panel processed by the existing processing method is easy to crack and fail during operation, the present invention provides a processing method for the water-cooled wall internal thread pipe panel.

A method for processing a water-cooled wall inner threaded pipe panel, comprising the steps of:

Step 1. Use additive manufacturing to perform thread additive manufacturing on the internal thread of the internally threaded pipe;

In step 2, the two sides of the outer wall of the inner threaded pipe are processed by means of additive manufacturing to produce an arc-shaped groove, and a milling cutter is used to perform material reduction processing on the two sides of the arc-shaped groove;

Step 3, processing the flat steel with the honeycomb core by means of additive manufacturing;

Step 4: Weld the arc groove of the flat steel and the inner threaded pipe.

Preferably, the first step is as follows: using tungsten-containing Stellite6 powder with wear resistance and erosion resistance to perform thread additive manufacturing on the internal thread of the internally threaded pipe.

Preferably, the additive manufacturing method in the second step is double-sided laser additive manufacturing.

Preferably, the material-reduction manufacturing method in the second step is grinding, polishing, and material-reduction processing.

Preferably, the second step is as follows: using a double-sided rotatable and telescopic material-increasing/decreasing coupling manipulator arm, performing symmetrical additive manufacturing on the flat steel on both sides of the pipe by using the rotating powder feeding laser heads on both sides, and adding the two After the retractable mechanical arm on the side rotates 180°, the rotary shearing tool is used to grind, polish, and reduce the grooves on both sides.

Beneficial effects of the present invention:

1. The cross section of the internal thread of the water-cooled wall internal thread tube screen of the present invention is a trapezoid with a concave curved surface, its root is a circular arc transition, and its apex is a circular arc blade shape, and the stress concentration is eliminated by the curved surface transition. The stress concentration at the root and top corner of the thread is greatly reduced, and the fluid channel that cuts off the film boiling is increased through the circular arc edge, and the amount of powder used for the internal thread additive is reduced through the concave curved surface to reduce the manufacturing cost. The solution of the invention can greatly reduce the weight of the furnace, reduce the thermal stress of the tube screen, increase the heat exchange efficiency of the boiler, and generate more hot water rich working medium while improving the service life of the inner thread and the flat steel of the inner threaded tube panel. Do more than one thing.

2. The invention adopts the double-sided additive manufacturing method for both sides of the pipe to process the stress-relieving arc groove shape, so that the curved surface welding of the flat steel and the pipe is transformed into the butt welding between the grooves, and at the same time, the thickness is increased. The arc transition replaces the sharp angle at the root of the flat steel, which greatly enhances the strength of the flat steel root and reduces the stress concentration and the risk of tearing at the root. At the same time, the low-speed water working medium is passed into the core of the honeycomb flat steel through the low-parameter header, which greatly increases the heat exchange efficiency of the furnace, generates more hot water-rich working medium, and reduces the heat dissipation of the furnace through the solid metal flat steel. At the same time, this method can greatly reduce the risk of tube panel failure caused by thermal stress caused by the huge temperature difference between the flat steel and the tube.

3. The present invention adopts a double-sided rotatable and telescopic material-increasing-decreasing coupling manipulator arm, and performs symmetrical additive manufacturing on the flat steel on both sides of the tube through double-sided laser additive manufacturing. Grinding and polishing of side grooves for subtractive material processing, and the arm is loaded on an industrial robot. Greatly increase the production efficiency and the symmetry of the tube screen products.

Description of drawings

Fig. 1 is the structural schematic diagram of internal thread pipe and flat steel;

Figure 2 is a partial schematic view of the internal thread of the internally threaded pipe;

Figure 3 is a schematic diagram of the structure of a double-sided rotatable and telescopic material-increasing-decreasing coupling manipulator;

Fig. 4 is the macroscopic appearance of the inner thread of the water-cooled wall inner thread tube screen obtained in Example 1 (enlarged by a stereo microscope 30 times);

5 is a SEM image (500 μm) of the inner thread wall of the water-cooled wall inner thread tube panel obtained in Example 1;

Fig. 6 is the thread topography schematic diagram of the thread section of the water-cooled wall inner thread pipe panel obtained in Example 1;

Fig. 7 is the structural representation of the internally threaded pipe and flat steel obtained in Comparative Example 1;

8 is a partial schematic view of the internal thread of the internally threaded pipe obtained in Comparative Example 1;

Fig. 9 is the macroscopic appearance of the inner thread of the water-cooled wall inner thread tube screen obtained in Comparative Example 1 (30 times magnification by a stereo microscope);

Figure 10 is the SEM image (500 μm) of the inner thread wall of the water-cooled wall inner thread tube panel obtained in Comparative Example 1;

11 is a schematic diagram of the original appearance of the thread described in Comparative Example 1;

FIG. 12 is a schematic diagram of the failure morphology of thread scouring and thinning described in Comparative Example 1;

Figure 13 is a cloud diagram of thermal stress distribution of the solid flat steel water-cooled wall tube shield described in Comparative Example 1;

In the picture: 1. Internal threaded pipe; 1-1, Internal thread; 1-2, Arc-shaped groove; 2. Flat steel; 2-1, Honeycomb core; Material coupling robot arm; 3-1, retractable robot arm, 3-2, rotary material cutting tool; 3-3, rotary powder feeding laser head.

Detailed ways

The technical solutions of the present invention will be further described below in conjunction with the embodiments, but are not limited thereto. Any modification or equivalent replacement of the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention should be included in the present invention. within the scope of protection.

Example 1

A water-cooled wall inner threaded pipe panel, comprising an inner threaded pipe 1 and a flat steel 2, each two of the inner threaded pipes 1 is connected by a flat steel 2 to form a water-cooled wall inner threaded pipe panel, the inner threaded pipe 1 The cross section of the internal thread 1-1 is a trapezoid with a concave curved surface, its root is a circular arc transition, and its top angle is a circular arc blade shape, and the two sides of the outer wall of the internal thread pipe 1 are respectively processed with a bevel arc with a circular arc transition at the root. Shape groove 1-2, the flat steel 2 is connected with the inner threaded pipe 1 through the arc groove 1-2, the flat steel 2 is processed with a honeycomb core 2-1, and its structural diagram is shown in Figure 1, Figure 1 2 shown.

The specific steps of its processing method are:

Step 1, using the wear-resistant Stellite6 powder containing tungsten element to perform thread additive manufacturing on the inner thread 1-1 of the inner threaded pipe 1;

Step 2: Using the double-sided rotatable and telescopic material increase and decrease coupling manipulator arm 3, through the rotary powder feeding laser heads 3-3 on both sides, the flat steel 2 on both sides of the pipe is symmetrically additively processed to produce an arc-shaped groove 1-2. After rotating the retractable mechanical arms 3-1 on both sides by 180°, use the rotary shearing tool 3-2 to perform subtractive processing on the arc groove 1-2;

Step 3, processing the flat steel 2 with the honeycomb core 2-1 by means of additive manufacturing;

Step 4: Weld the flat steel 2 and the arc groove 1-2 of the internally threaded pipe 1.

The surface morphology of the inner threaded wall of the obtained water-cooled wall inner threaded tube screen was observed by electronic scanning electron microscope. At this time, most of the horizontal lines and cracks are caused by the internal thread pipe wall material of the original matrix, which is caused by the expansion of the pipe wall to the internal thread, which is inevitable.

The thread profile of the obtained water-cooled wall inner threaded tube screen was observed by an optical microscope. The observation results are shown in Figure 6. From the figure, it can be observed that the thread is almost kept as it is, without deformation and cracks.

To sum up, the water-cooled wall inner threaded pipe panel obtained by the processing method of this embodiment is not easy to deform and crack.

The beneficial effects that this embodiment can achieve:

1. The double-sided additive manufacturing method is adopted for both sides of the internal threaded pipe 1 to process the stress relief arc grooves 1-2, so that the curved surface welding of the flat steel 2 and the internal threaded pipe 1 is transformed into the butt between the grooves At the same time, the thickened arc transition replaces the sharp angle at the root of the flat steel, which greatly enhances the strength of the flat steel root and reduces the stress concentration and the risk of tearing at the root.

2. The flat steel 2 adopts the honeycomb shape of the core of additive manufacturing, which greatly reduces the weight of the flat steel 2 and the number of top suspensions. At the same time, the low-speed hydraulic fluid is passed through the low-parameter header into the honeycomb flat steel 2 core. , greatly increase the heat exchange efficiency of the furnace, generate more hot water rich working medium, and reduce the heat dissipation of the furnace through the solid metal flat steel 2. At the same time, this method can greatly reduce the risk of tube panel failure caused by thermal stress caused by the huge temperature difference between the flat steel 2 and the internally threaded tube 1 .

3. Using the additive manufacturing method, thread additive manufacturing is performed on the inner wall of the 15CrMoG rotating pipe. The wear-resistant and erosion-resistant stellite6 powder containing tungsten is used. The section 1-1 of the inner thread adopts a concave curved trapezoid, and the top corner adopts a circular arc edge. shape, and stress concentration is eliminated by surface transition. The stress concentration at the root and top corner of the thread is greatly reduced, and the fluid channel that cuts off the film boiling is increased through the circular arc edge, and the amount of powder used for the internal thread additive is reduced through the concave curved surface to reduce the manufacturing cost.

4. The double-sided rotatable and telescopic material addition and subtraction coupling manipulator 3 is used, and the flat steel 2 on both sides of the tube is symmetrically manufactured by double-sided laser additive. After rotating 180°, the double-end milling cutter is used for two Grinding, polishing, and subtractive machining of side grooves. All 4 arms are rotatable and retractable, and the arms are mounted on industrial robots. To greatly increase the production efficiency and the symmetry of the tube screen products, the schematic diagram of the structure of the double-sided rotatable and telescopic material-increasing/decreasing coupling mechanical arm 3 is shown in Figure 3.

5. The invention scheme can greatly reduce the furnace weight, reduce the thermal stress of the tube screen, increase the heat exchange efficiency of the boiler, and generate more hot water-rich working medium while improving the service life of the inner thread and flat steel of the inner threaded tube panel. Do more than one thing.

Embodiment 2

A water-cooled wall inner threaded pipe panel, comprising an inner threaded pipe 1 and a flat steel 2, each two of the inner threaded pipes 1 is connected by a flat steel 2 to form a water-cooled wall inner threaded pipe panel, the inner threaded pipe 1 The cross section of the internal thread 1-1 is a trapezoid with a concave curved surface, its root is a circular arc transition, and its top angle is a circular arc blade shape, and the two sides of the outer wall of the internal thread pipe 1 are respectively processed with a bevel arc with a circular arc transition at the root. Shape groove 1-2, the flat steel 2 is connected with the inner threaded pipe 1 through the arc groove 1-2, the flat steel 2 is processed with a honeycomb core 2-1, and its structural diagram is shown in Figure 1, Figure 1 2 shown.

The specific steps of its processing method are:

Step 1, using the wear-resistant Stellite6 powder containing tungsten element to perform thread additive manufacturing on the inner thread 1-1 of the inner threaded pipe 1;

Step 2: Using the double-sided rotatable and telescopic material increase and decrease coupling manipulator arm 3, through the rotary powder feeding laser heads 3-3 on both sides, the flat steel 2 on both sides of the pipe is symmetrically additively processed to produce an arc-shaped groove 1-2. After rotating the retractable mechanical arms 3-1 on both sides by 180°, use the rotary shearing tool 3-2 to perform subtractive processing on the arc groove 1-2;

Step 3, processing the flat steel 2 with the honeycomb core 2-1 by means of additive manufacturing;

Step 4: Weld the flat steel 2 and the arc groove 1-2 of the internally threaded pipe 1.

The beneficial effects that this embodiment can achieve:

1. The double-sided additive manufacturing method is adopted for both sides of the internal threaded pipe 1 to process the stress relief arc grooves 1-2, so that the curved surface welding of the flat steel 2 and the internal threaded pipe 1 is transformed into the butt between the grooves At the same time, the thickened arc transition replaces the sharp angle at the root of the flat steel, which greatly enhances the strength of the flat steel root and reduces the stress concentration and the risk of tearing at the root.

2. The flat steel 2 adopts the honeycomb shape of the core of additive manufacturing, which greatly reduces the weight of the flat steel 2 and the number of top suspensions. At the same time, the low-speed hydraulic fluid is passed through the low-parameter header into the honeycomb flat steel 2 core. , greatly increase the heat exchange efficiency of the furnace, generate more hot water rich working medium, and reduce the heat dissipation of the furnace through the solid metal flat steel 2. At the same time, this method can greatly reduce the risk of tube panel failure caused by thermal stress caused by the huge temperature difference between the flat steel 2 and the internally threaded tube 1 .

3. Using the additive manufacturing method, thread additive manufacturing is performed on the inner wall of the 15CrMoG rotating pipe. The wear-resistant and erosion-resistant stellite6 powder containing tungsten is used. The section 1-1 of the inner thread adopts a concave curved trapezoid, and the top corner adopts a circular arc edge. shape, and stress concentration is eliminated by surface transition. The stress concentration at the root and top corner of the thread is greatly reduced, and the fluid channel that cuts off the film boiling is increased through the circular arc edge, and the amount of powder used for the internal thread additive is reduced through the concave curved surface to reduce the manufacturing cost.

4. The invention scheme can greatly reduce the furnace weight, reduce the thermal stress of the tube screen, increase the heat exchange efficiency of the boiler, and generate more hot water rich working medium while improving the service life of the inner thread and flat steel of the inner threaded tube panel. Do more than one thing.

Comparative Example 1

The conventional boiler water wall inner threaded tube panel is formed by welding the inner threaded tube and the flat steel. The welding method is longitudinal seam welding between the flat steel with groove and the outer wall of the threaded tube. As shown in Figure 7, the inner threaded tube is welded. The cross-section of the internal thread is trapezoidal, as shown in Figure 8.

The internal thread tube panel manufactured in this traditional way has the following problems:

1. The traditional internal thread pipe is made by rotating and drawing the internal thread mandrel, the thread section is trapezoid, and the top angle and root are sharp angles. The drawing and forming causes a large residual stress inside the thread. At the same time, during the operation of the boiler, the sharp corners of the apex and the root are subjected to thermal stress and residual stress, which is easy to cause the failure of the inner wall thread caused by stress concentration, as shown in Figure 9 and As shown in Figure 10, the tube screen burst accident finally occurred.

2. The traditional internal thread pipe is produced by drawing after the mandrel is perforated. The thread and the pipe wall are inevitably made of the same material, but during the operation of the boiler, the internal thread is continuously washed by the water working medium. After long-term operation, the thread will be thinned and deformed, and the top angle will be ground into a circular arc, which cannot prevent the film boiling of the inner wall, which will eventually lead to overheating failure of the pipe. The original morphology of the thread is shown in Figure 11 and the failure morphology after flushing is shown in Figure 12.

The common problems of this traditional way of manufacturing water-cooled wall tube panels are:

1. The traditional welding method of pipe and flat steel is to weld the flat steel with groove and the curved surface without groove on the outer wall of the pipe, and the flat steel thickness at the root of the weld is reduced after the groove is processed on the side of the flat steel. During the operation of the boiler , it is more prone to tearing at the flat steel weld, and eventually the crack extends to the tube body, resulting in the failure of the tube screen bursting.

2. The traditional flat steel is made of solid metal. At the same time, the weight of solid metal is large, which increases the overall weight of the heating surface, which leads to an increase in the number of suspension pipes in the upper part of the furnace, which increases the total weight of the boiler and increases the cost.

3. The heat transfer efficiency of the traditional solid metal flat steel is extremely high, so that the heat generated by the combustion of pulverized coal inside the furnace is dissipated to the outside of the furnace through the heat transfer of the flat steel.

4. The heat conduction rate of the metal flat steel is fast, and during the operation, the flat steel is in a dry burning state without working fluid heat exchange, and the heat is transferred from the flat steel to the pipe wall, resulting in a higher temperature at the junction of the flat steel and the pipe. , because the temperature of the heat transfer of the working medium is lower at the non-connected part, a large thermal stress is generated in the circumferential direction of the tube, and the heat distribution cloud diagram is shown in Figure 13.

By comparing Fig. 9 with Fig. 4 and Fig. 10 with Fig. 5, it can be observed that the water-cooling wall inner threaded pipe panel obtained by the processing method of the present invention is more The resulting horizontal lines and tortoise cracks have been significantly reduced, the 3D printed threads have been able to significantly resist the impact of water flow and failure deformation, and the failure morphology of the tortoise cracks has been significantly reduced; it can be observed by comparing Figure 12 with Figure 7 that the Compared with the water-cooled wall inner threaded pipe screen obtained by the above processing method, the thread section of the water-cooled wall inner threaded pipe screen obtained by the existing processing method almost maintains the original appearance of the thread without deformation and cracks. To sum up, the water-cooled wall inner threaded pipe panel obtained by the processing method of the present invention has less stress concentration and thread failure than the water-cooled wall inner threaded pipe panel obtained by the existing processing method.

Claims (7)

1. The utility model provides a water-cooling wall internal thread tube panel, includes internal thread pipe (1) and band steel (2), per two internal thread pipe (1) is connected through band steel (2) within a definite time, forms one side water-cooling wall internal thread tube panel, its characterized in that, internal thread (1-1) cross-section of internal thread pipe (1) is the concave surface trapezium, and its root is the circular arc transition, and its apex angle is the circular arc sword form, arc groove (1-2) have been processed respectively to the outer wall both sides of internal thread pipe (1), band steel (2) are connected with internal thread pipe (1) through arc groove (1-2), band steel (2) processing has cellular core (2-1).

2. The tube panel with the internal threads on the water-cooled wall according to claim 1, wherein the arc-shaped groove (1-2) is a root arc transition groove.

3. A processing method of the water-cooled wall internal thread tube panel is characterized by comprising the following steps:

step one, using an additive manufacturing mode to perform thread additive manufacturing on internal threads (1-1) of an internal thread pipe (1);

step two, machining arc-shaped grooves (1-2) on two sides of the outer wall of the internally threaded pipe (1) in an additive manufacturing mode, and performing material reduction machining on the arc-shaped grooves (1-2) on the two sides by using a milling cutter;

step three, processing the flat steel (2) with the honeycomb core part (2-1) in an additive manufacturing mode;

and fourthly, welding the flat steel (2) and the arc-shaped groove (1-2) of the internal threaded pipe (1).

4. The processing method of the water-cooled wall internal thread tube panel according to claim 3, characterized in that the first step is specifically as follows: and (3) performing thread additive manufacturing on the internal thread (1-1) of the internal thread pipe (1) by using tungsten-containing wear-resistant and scouring-resistant Stellite6 powder.

5. The processing method of the water-cooled wall internal thread tube panel according to claim 4, characterized in that the additive manufacturing manner in the second step is double-sided laser additive manufacturing.

6. The processing method of the water-cooled wall internal thread tube panel according to claim 5, characterized in that the material reducing manufacturing mode in the second step is grinding and polishing material reducing processing.

7. The processing method of the water-cooled wall internal thread tube panel according to claim 5, characterized in that the second step is specifically: the material adding and reducing method is characterized in that double-side rotatable and telescopic material adding and reducing coupling mechanical arms (3) are adopted, symmetrical material adding and manufacturing are carried out on flat steel (2) on two sides of a pipe through rotary powder feeding type laser heads (3-3) on the two sides, and after the telescopic mechanical arms (3-1) on the two sides are rotated for 180 degrees, grinding, polishing and material reducing processing are carried out on grooves on the two sides through rotary material shearing cutters (3-2).

Images