A composite steel pipe with internal epoxy coating and external PE and a processing method thereof

Abstract

The application provides a composite steel pipe with epoxy inner coating and PE outer coating, which comprises a composite steel pipe body, one end of the composite steel pipe body is provided with a clamping joint, and the other end of the composite steel pipe body is provided with a clamping-in joint; the composite steel pipe body comprises an outer protective layer, the inner side of the outer protective layer is sequentially provided with a first polyethylene layer, a steel layer, a second polyethylene layer and a hot melt joint epoxy coating; a processing method of the composite steel pipe with epoxy inner coating and PE outer coating comprises the following steps: S1, treating the steel layer; S2, covering the outer surface of the steel layer with the first polyethylene layer; S3, preparing the second polyethylene layer by winding; S4, spraying the hot melt joint epoxy coating on the inner side; and S5, performing outer protective treatment on the composite steel pipe; the application is convenient to connect and install, the multilayer structure increases the protection, the covering modes of the layers are different, and the working efficiency and benefits are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of composite steel pipes, in particular, to an inner epoxy coating and outer PE composite steel pipe and a processing method. BACKGROUND

[0002] Composite steel pipes are high-performance and cost-effective products in steel-plastic composite pipe products, and are widely used in various fields such as water supply and drainage systems, fire sprinkler systems, gas and oil transportation pipe network systems, and cable threading protection pipe systems.

[0003] In simple terms, a composite steel pipe is a composite of steel and plastic, which has the advantages of both. For example, the composite steel pipe has excellent compression and tensile strength. In addition, it is excellent in corrosion resistance, acid and alkali resistance, and wear resistance. This type of pipe also has a rich color appearance and can satisfy different field merchants in terms of conveying efficiency.

[0004] Moreover, most composite steel pipes are more excellent in sanitary standards than other pipes. They do not accumulate dirt after long-term use, and do not breed microorganisms, thereby ensuring the original nature of the fluid. Such pipes have excellent insulating properties and can be used in many special environments to protect electrical wiring devices and other items. This can help us reduce the risk of electrical leakage.

[0005] In addition, the smooth inner wall of such pipes makes the overall construction precision more smooth and simple. Such composite pipes not only improve the overall construction precision, but also ensure the final construction effect.

[0006] However, the existing composite steel pipes still have some problems during use and preparation, as follows: the existing composite steel pipes generally need an external connecting ring for combination and connection during use, and such connection method cannot achieve a certain sealing, which will cause the composite steel pipe to bear less pressure during use, and is prone to rupture or leakage, and the material of the composite steel pipe relies on single protection of the composite plastic during use, the anti-corrosion effect is single, and is prone to damage and rupture after long-term use, and has low protection strength, and during preparation and processing, the multi-layer structure cannot be treated separately, and different processing techniques cannot be improved according to different use environments. SUMMARY

[0007] In order to make up for the above shortcomings, the application provides a composite steel pipe coated with epoxy inside and PE outside and a processing method, which effectively improves the existing composite steel pipe, which generally needs an external connecting ring for combination connection when in use, and such a connection mode cannot achieve a certain sealing performance, so that the composite steel pipe bears less pressure when in use, is prone to rupture or leakage and other problems, and the material of the composite steel pipe relies on a single protection of the composite plastic when in use, the anti-corrosion effect is relatively single, and is prone to damage and rupture after long-term use, and has low protection strength and other problems, and cannot realize separate treatment of the multi-layer structure during preparation and processing, improve different processing technology treatment according to different use environments and other problems.

[0008] The application is implemented as follows:

[0009] A composite steel pipe coated with epoxy inside and PE outside comprises a composite steel pipe body, one end of the composite steel pipe body is provided with a clamping joint, the other end of the composite steel pipe body is provided with a clamping-in head, and the composite steel pipe body is clamped and connected in the inside of the clamping joint through the clamping-in head when connected.

[0010] A first clamping ring is fixedly arranged at the inner side of the clamping joint, a first clamping groove is formed in the end face of the first clamping ring, a second clamping ring is fixedly arranged at the middle of the inner side of the clamping joint, a second clamping groove is formed in the end face of the second clamping ring, and a first clamping ring is fixedly arranged at the end of the clamping joint.

[0011] A third clamping ring is fixedly arranged at the inner end of the clamping-in head, a third clamping groove is formed in the end face of the third clamping ring, an extension plate is fixedly arranged at the middle of the clamping-in head, a second clamping ring is fixedly arranged on the extension plate, and a third clamping ring is fixedly arranged at the end of the clamping-in head.

[0012] The third clamping ring is clamped and connected in the inside of the first clamping groove, the second clamping ring is clamped and connected in the inside of the second clamping groove, and the first clamping ring is clamped and connected in the inside of the third clamping groove.

[0013] The composite steel pipe body comprises an outer protective layer, a first polyethylene layer is fixedly arranged at the inner side of the outer protective layer, a steel layer is fixedly arranged at the inner side of the first polyethylene layer, a second polyethylene layer is fixedly arranged at the inner side of the steel layer, and a hot melt epoxy coating is sprayed on the inner side of the second polyethylene layer.

[0014] In an embodiment of the present application, the clamping head is provided in a trumpet shape that is outwardly flared, and the clamping-in head is provided in a V-shaped shape that is inwardly tapered, so that the first clamping ring is conveniently clamped and connected inside the third clamping groove, and the excessively tight fit is prevented to cause the clamping connection.

[0015] In an embodiment of the present application, the V-shaped design of the clamping-in head facilitates the clamping connection of the second clamping ring and the third clamping ring at the front end inside the first clamping groove and the second clamping groove, and the sealing connection is achieved through the curvature of the fit, and the second clamping ring is clamped and connected inside the second clamping groove, and the third clamping ring is clamped and connected inside the first clamping groove, so that multi-stage clamping connection is achieved, the sealing is improved, and the falling off is prevented.

[0016] In an embodiment of the present application, the outer protective layer is epoxy coal tar pitch, the thickness of the epoxy coal tar pitch is 300-500 um, and the epoxy coal tar pitch is sprayed on the outer side of the first polyethylene layer in a spraying manner.

[0017] In an embodiment of the present application, the first polyethylene layer and the second polyethylene layer each include epoxy powder, adhesive and polyethylene, that is, the epoxy powder, the adhesive and the polyethylene are mixed and stirred, and then are adhered on both sides of the steel layer through winding and round mold coating.

[0018] In an embodiment of the present application, the second polyethylene layer is adhered by winding, that is, after the mixed epoxy powder, adhesive and polyethylene solution are impregnated with resin glue, the solution is directly wound on a core mold or lining to form a reinforced plastic product, and then a solidification molding method is used to set the solution on the inner side of the steel layer.

[0019] In an embodiment of the present application, the first polyethylene layer is adhered on the outer side of the steel layer in a round mold coating manner, that is, the mixed epoxy powder, adhesive and polyethylene solution are extruded on the outer side surface of the steel layer, and then are cooled to achieve cold adhesion molding.

[0020] In an embodiment of the present application, the steel layer uses a steel pipe or a steel wire mesh, a single-layer steel pipe is used to support the pipe body strength when the steel pipe is used, the first polyethylene layer is extruded when the steel pipe is used, multiple layers of steel wire meshes are used when the steel wire mesh is used, and the multiple layers of steel wire meshes are adhered into one body through polyethylene mold casting molding, and the first polyethylene layer is coated when the steel wire mesh is used.

[0021] A processing method of an inner epoxy outer PE composite steel pipe, comprising the following steps:

[0022] S1, treating the steel layer: rust removal treatment is performed on the steel pipe or steel wire mesh of the steel layer, then the inner and outer surfaces of the steel pipe are treated by a shot blasting machine host, and then the steel layer is cleaned of dust by a dust removal machine;

[0023] The steel layer comprises a steel pipe or a steel wire mesh as a support pipe body; when the steel wire mesh is used as the support pipe body, a model casting method is used, and the multiple steel wire meshes are integrally cast by polyethylene to realize integral molding;

[0024] S2, covering the outer surface of the steel layer with a first polyethylene layer: after the steel layer is cleaned, the outer surface of the steel layer is covered with a first polyethylene layer by an extrusion method or a coating method, and then cooling is realized by air cooling to enable the first polyethylene layer to be quickly adhered to the surface of the steel layer by cold shrinking;

[0025] S3, preparing the second polyethylene layer by winding: the mixed epoxy powder, adhesive and polyethylene solution impregnated resin glue are uniformly wound on the core mold or inner lining, and then the second polyethylene layer is adhered to the inner wall of the steel layer by a solidification thermal expansion adhesion method;

[0026] S4, spraying the inner hot melt epoxy coating: the inner hot melt epoxy coating is sprayed by a hot melt spraying method, that is, the hot melt epoxy is sprayed on the inner wall of the pipe by a centrifugal method, reacts with the 250 DEG C steel pipe substrate to form a steel-plastic alloy layer, and the sprayed thickness is 300-500 um;

[0027] S5, outer protection treatment of the PE composite steel pipe: an outer protective layer is arranged on the outer side of the PE composite pipe, that is, an epoxy coal tar pitch is sprayed by a spray gun, and the thickness of the epoxy coal tar pitch is 300-500 um.

[0028] The beneficial effects of the present application are:

[0029] The present application sets a clamping head and a clamping joint at two ends of the composite steel pipe, that is, the composite steel pipe is combined and connected through the setting of the clamping head and the clamping joint, and a plurality of clamping rings, clamping grooves and clamping rings are arranged on the clamping head and the clamping joint, respectively, and the connection strength and the sealing property are improved through the cooperation between them, so that the clamping head and the clamping joint can effectively improve the matching property, maintain the connection strength of the clamping connection at both ends, prevent falling off, and improve the sealing property and prevent leakage and other advantages;

[0030] And in the composite steel pipe preparation processing production, according to the different needs, adopt a variety of processing methods, improve the adaptability of composite steel pipe, namely the first polyethylene layer according to the convenience of covering the extrusion method or coating method, for the second polyethylene layer adopts winding type to stick production, then carries out the spraying treatment of hot melt epoxy coating, and the outside adopts the spray gun to realize the spraying of epoxy coal tar pitch, through the setting of multilayer structure, enhances the strength and protection of composite steel pipe. BRIEF DESCRIPTION OF DRAWINGS

[0031] In order to more clearly illustrate the technical scheme of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments, it should be understood that the following drawings only show some embodiments of the present application, therefore should not be regarded as a limitation on the scope, for those skilled in the art, without paying creative labor, can also obtain other related drawings according to these drawings.

[0032] Figure 1 is the structural schematic diagram of the present application;

[0033] Figure 2 is the structural schematic diagram of the present application Figure 1 is the enlarged schematic diagram of A in the figure;

[0034] Figure 3 is the step flow schematic diagram of the present application.

[0035] In the figure: 1, composite steel pipe body; 2, card joint; 3, card into head; 4, first clamping ring; 5, first clamping groove; 6, second clamping ring; 7, second clamping groove; 8, first clamping ring; 9, third clamping ring; 10, third clamping groove; 11, extension plate; 12, second clamping ring; 13, third clamping ring; 14, outer protective layer; 15, first polyethylene layer; 16, steel layer; 17, second polyethylene layer; 18, hot melt epoxy coating. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical scheme and advantages of the embodiments of the present application more clear, the following will combine the drawings in the embodiments of the present application, the technical scheme in the embodiments of the present application is described clearly and completely, obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor belong to the scope of protection of the present application.

[0037] Please refer to Figures 1-2The application provides a technical scheme: a composite steel pipe with internal epoxy coating and external PE, which comprises a composite steel pipe body 1, one end of the composite steel pipe body 1 is provided with a clamping joint 2, the other end of the composite steel pipe body 1 is provided with a clamping-in joint 3, and the composite steel pipe body 1 is clamped and connected in the inside of the clamping joint 2 through the clamping-in joint 3 when being connected;

[0038] A first clamping ring 4 is fixedly arranged at the inner side of the clamping joint 2, a first clamping groove 5 is formed in the end face of the first clamping ring 4, a second clamping ring 6 is fixedly arranged at the middle of the inner side of the clamping joint 2, a second clamping groove 7 is formed in the end face of the second clamping ring 6, and a first clamping ring 8 is fixedly arranged at the end of the clamping joint 2;

[0039] A third clamping ring 9 is fixedly arranged at the inner end of the clamping-in joint 3, a third clamping groove 10 is formed in the end face of the third clamping ring 9, an extension plate 11 is fixedly arranged at the middle of the clamping-in joint 3, a second clamping ring 12 is fixedly arranged on the extension plate 11, and a third clamping ring 13 is fixedly arranged at the end of the clamping-in joint 3;

[0040] The third clamping ring 13 is clamped and connected in the inside of the first clamping groove 5, the second clamping ring 12 is clamped and connected in the inside of the second clamping groove 7, and the first clamping ring 8 is clamped and connected in the inside of the third clamping groove 10;

[0041] The composite steel pipe body 1 comprises an outer protective layer 14, a first polyethylene layer 15 is fixedly arranged at the inner side of the outer protective layer 14, a steel material layer 16 is fixedly arranged at the inner side of the first polyethylene layer 15, a second polyethylene layer 17 is fixedly arranged at the inner side of the steel material layer 16, and a hot melt epoxy coating 18 is sprayed on the inner side of the second polyethylene layer 17.

[0042] In order to realize the combined connection of the composite steel pipe and improve the fitting property of the clamping connection, in an embodiment of the application, the clamping joint 2 is arranged in a trumpet shape which is opened outward, the clamping-in joint 3 is arranged in a cutting surface V shape which is contracted inward, the first clamping ring 8 is clamped and connected in the inside of the third clamping groove 10 through the setting of the V shape, and the clamping connection is prevented from being unable to be clamped and connected due to too tight fitting.

[0043] In order to realize the combination connection of the composite steel pipe, and improve the sealing and connection strength, in an embodiment of the present application, the V-shaped design of the snap-in head 3 facilitates the snap-in connection of the second snap-in ring 12 and the third snap-in ring 13 at the front end inside the first snap-in groove 5 and the second snap-in groove 7, realizes the sealing connection through the fitting arc, and realizes the multi-stage snap-in connection through the snap-in connection of the second snap-in ring 12 inside the second snap-in groove 7 and the snap-in connection of the third snap-in ring 13 inside the first snap-in groove 5, thereby preventing falling off while improving the sealing.

[0044] In order to realize the protection treatment of the surface of the composite steel pipe and improve the strength, in an embodiment of the present application, the outer protective layer 14 adopts epoxy coal tar pitch, the thickness of the epoxy coal tar pitch is 300-500um, and the epoxy coal tar pitch is sprayed on the outer side of the first polyethylene layer 15 in a spraying manner.

[0045] In order to realize the increase of the strength and adhesion of polyethylene, in an embodiment of the present application, the first polyethylene layer 15 and the second polyethylene layer 17 both include epoxy powder, adhesive and polyethylene, that is, the epoxy powder, the adhesive and the polyethylene are mixed and stirred, and then are adhered to both sides of the steel layer 16 through winding and round die coating.

[0046] In order to realize the adhesion of the inner second polyethylene layer 17, in an embodiment of the present application, the second polyethylene layer 17 adopts winding adhesion, that is, after the mixed epoxy powder, adhesive and polyethylene solution are impregnated with resin glue, they are directly wound on the core mold or inner lining to form reinforced plastic products, and then are set on the inner side of the steel layer 16 through the solidification forming method.

[0047] In order to realize the adhesion setting of the first polyethylene layer 15 and improve the connection strength through cold shrinking, in an embodiment of the present application, the first polyethylene layer 15 adopts round die coating adhesion on the outer side of the steel layer 16, that is, the mixed epoxy powder, adhesive and polyethylene solution are extruded on the outer side surface of the steel layer 16, and then are cooled to realize cold adhesion forming.

[0048] In order to realize the support pipe body of the composite steel pipe with different support pipe body, in an embodiment of the present application, the steel pipe or the steel wire mesh is used in the steel material layer 16, and the single layer steel pipe is used to support the pipe body when the steel pipe is used, and the first polyethylene layer 15 is used in the extrusion mode when the steel pipe is used, and the multiple layer steel wire mesh is used when the steel wire mesh is used, and the multiple layer steel wire mesh is adhered into a whole through the polyethylene mold casting forming, and the first polyethylene layer 15 is used in the coating mode when the steel wire mesh is used.

[0049] Reference Figure 3 A processing method of an inner epoxy outer PE composite steel pipe, comprising the following steps:

[0050] S1, treating the steel material layer 16: rust removal treatment is performed on the steel pipe or the steel wire mesh of the steel material layer 16, then the inner and outer surfaces of the steel pipe are treated by the shot blasting machine host, and then the steel material layer 16 is cleaned by the dust collector, the steel material layer 16 includes the steel pipe or the steel wire mesh as the support pipe body, the mold casting mode is used when the steel wire mesh is used as the support pipe body, and the multiple layer steel wire mesh is poured into a whole by the polyethylene to realize the integral molding;

[0051] S2, covering the first polyethylene layer 15 on the outer surface of the steel material layer 16: after the steel material layer 16 is cleaned, the first polyethylene layer 15 is covered on the outer surface of the steel material layer 16 by the extrusion mode or the coating mode, and then the cooling treatment is realized by the air cooling to enable the first polyethylene layer 15 to be quickly adhered on the surface of the steel material layer 16 by the cold shrinkage;

[0052] S3, preparing the second polyethylene layer 17 by the winding type: the mixed epoxy powder, the adhesive and the polyethylene solution impregnated resin glue are uniformly wound on the core mold or the inner lining, and then the second polyethylene layer 17 is adhered on the inner wall of the steel material layer 16 by the solidification thermal expansion adhesion mode;

[0053] S4, spraying the inner hot melt epoxy coating 18: the inner hot melt epoxy coating 18 is sprayed by the hot melt spraying, that is, the hot melt epoxy is sprayed on the inner wall of the pipe by the centrifugal mode, reacts with the 250 DEG C steel pipe base body to generate the steel plastic alloy layer, and the spraying thickness is 300-500 um;

[0054] S5, protecting the outer side of the PE composite steel pipe: the outer side protection layer 14 is arranged on the outer side of the PE composite pipe, that is, the epoxy coal tar pitch is sprayed by the spray gun, and the thickness of the epoxy coal tar pitch is 300-500 um.

[0055] The above merely describes the preferred embodiments of the present application and is not used to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A composite steel pipe having an inner coating of epoxy and an outer PE, characterized in that, The utility model provides a composite steel pipe body (1), one end of the composite steel pipe body (1) is equipped with the joint (2), the other end of the composite steel pipe body (1) is equipped with the head (3), when the composite steel pipe body (1) is connected, the head (3) is connected in the inside of the joint (2) through the joint, The inside end of the joint (2) is fixedly provided with a first clamping ring (4), the end face of the first clamping ring (4) is provided with a first clamping groove (5), the middle part of the inside of the joint (2) is fixedly provided with a second clamping ring (6), the end face of the second clamping ring (6) is provided with a second clamping groove (7), and the end part of the joint (2) is fixedly provided with a first joint ring (8). The inside end of the head (3) is fixedly provided with a third clamping ring (9), the end face of the third clamping ring (9) is provided with a third clamping groove (10), the middle part of the head (3) is fixedly provided with an extension plate (11), the extension plate (11) is fixedly provided with a second joint ring (12), and the end part of the head (3) is fixedly provided with a third joint ring (13). The third joint ring (13) is clamped and connected in the inside of the first clamping groove (5), the second joint ring (12) is clamped and connected in the inside of the second clamping groove (7), and the first joint ring (8) is clamped and connected in the inside of the third clamping groove (10). The composite steel pipe body (1) comprises an outside protective layer (14), the inside of the outside protective layer (14) is fixedly provided with a first polyethylene layer (15), the inside of the first polyethylene layer (15) is fixedly provided with a steel material layer (16), the inside of the steel material layer (16) is fixedly provided with a second polyethylene layer (17), and the inside of the second polyethylene layer (17) is sprayed with a hot melt epoxy coating (18).

2. The composite pipe according to claim 1, wherein The joint (2) is arranged in a trumpet shape that opens outward, the head (3) is arranged in a cutting surface V shape that contracts inward, the first joint ring (8) is clamped and connected in the inside of the third clamping groove (10) through the arrangement of the V shape, and the excessively sealed fit is prevented to prevent clamping and connection.

3. The composite pipe according to claim 2, wherein the inner coating is an epoxy resin. The V shape design of the head (3) facilitates the clamping and connection of the second joint ring (12) and the third joint ring (13) at the front end in the inside of the first clamping groove (5) and the second clamping groove (7), the sealing connection is realized through the fit of the arc, the second joint ring (12) is clamped and connected in the inside of the second clamping groove (7), the third joint ring (13) is clamped and connected in the inside of the first clamping groove (5), multi-stage clamping and connection is realized, the sealing property is improved, and falling is prevented.

4. The composite steel pipe according to claim 1, wherein The outside protective layer (14) adopts epoxy coal tar pitch, the thickness of the epoxy coal tar pitch is 300-500 um, and the epoxy coal tar pitch is sprayed on the outside of the first polyethylene layer (15) in a spraying mode.

5. The composite steel pipe according to claim 1, wherein The first polyethylene layer (15) and the second polyethylene layer (17) each comprise epoxy powder, adhesive and polyethylene, i.e. the epoxy powder, the adhesive and the polyethylene are mixed and stirred, and then are adhered to the two sides of the steel layer (16) by winding and round die coating.

6. The composite pipe according to claim 5, wherein The second polyethylene layer (17) is adhered by winding, i.e. after the mixed epoxy powder, the adhesive and the polyethylene solution are impregnated with resin glue, they are directly wound on a core mold or a liner to form a reinforced plastic product, and then are set on the inner side of the steel layer (16) by a solidification forming method.

7. The composite pipe according to claim 5, wherein the inner coating is an epoxy resin. The first polyethylene layer (15) is adhered to the outer side of the steel layer (16) by round die coating, i.e. after the mixed epoxy powder, the adhesive and the polyethylene solution are extruded on the outer side surface of the steel layer (16), they are cooled to realize cold adhesion forming.

8. The composite steel pipe according to claim 1, wherein The steel layer (16) adopts a steel pipe or a steel wire mesh, when a steel pipe is used, a single-layer steel pipe is used to support the pipe body strength, and when a steel pipe is used, the first polyethylene layer (15) is used in an extrusion manner, and when a steel wire mesh is used, multiple layers of steel wire meshes are used, and the multiple layers of steel wire meshes are adhered into one body by polyethylene model casting forming, and when a steel wire mesh is used, the first polyethylene layer (15) is used in a coating manner.

9. A method of processing the inner epoxy-coated outer PE composite steel pipe according to claim 8, characterized in that, The method comprises the following steps: S1, treating the steel layer (16): rust removal treatment is performed on the steel pipe or the steel wire mesh of the steel layer (16), then the inner and outer surfaces of the steel pipe are treated by a shot blasting machine, and then the steel layer (16) is cleaned by a dust removal machine; The steel layer (16) comprises a steel pipe or a steel wire mesh as a support pipe body, when the steel wire mesh is used as a support pipe body, a model casting method is used, and multiple layers of steel wire meshes are poured into one body by polyethylene to realize one-piece forming; S2, covering the first polyethylene layer (15) on the outer side of the steel layer (16): after the steel layer (16) is cleaned, the first polyethylene layer (15) is covered on the outer surface of the steel layer (16) by an extrusion method or a coating method, and then cooling is performed by air cooling to realize cold shrinkage and rapid adhesion of the first polyethylene layer (15) on the surface of the steel layer (16); S3, preparing the second polyethylene layer (17) by winding: the mixed epoxy powder, the adhesive and the polyethylene solution are uniformly wound on a core mold or a liner by impregnating resin glue, and then the second polyethylene layer (17) is adhered to the inner wall of the steel layer (16) by a solidification thermal expansion adhesion method; S4, spraying the inner side hot melt epoxy coating (18): the inner side hot melt epoxy coating (18) is sprayed by a hot melt spraying method, i.e. the hot melt epoxy is sprayed on the inner wall of the pipe by a centrifugal method, reacts with a 250℃ steel pipe base body to form a steel-plastic alloy layer, and the spraying thickness is 300-500um; S5, the PE composite steel pipe is protected on the outside: the outer protective layer (14) is arranged on the outside of the PE composite pipe, that is, the epoxy coal tar is sprayed by using a spray gun, and the thickness of the epoxy coal tar is 300-500 um.

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