Background
Cold-rolled hot-dip galvanized products are divided into two categories, one is a hot-dip pure zinc product, the other is a hot-dip alloyed product, and the mechanisms of the formation of the zinc coating layer of the two products are different. The surface of the zinc layer of the hot-dip pure zinc strip steel product is softer, and surface defects are easily caused.
During production, the sink roll is the main equipment for producing hot galvanizing products, and the sink roll is immersed in a molten zinc pot and rotates by the friction force between strip steel and the roll surface. The pure zinc liquid generally contains about 0.2 percent of aluminum according to the requirement of a hot galvanizing process, the aluminum, the zinc and iron dissolved on the strip steel form tiny zinc dross, and the zinc dross is rolled between the strip steel and the roller surface to form zinc dross defects on the surface of the strip steel.
In order to reduce the surface defects of strip steel caused by tiny zinc dross in zinc liquid, the prior art is to process a spiral groove structure on the surface of a roller, the tiny zinc dross can fall into a groove on the surface of the roller, and the zinc dross with small particles is discharged out of the roller along the groove under the action of the rotation of a sink roller. Therefore, the groove is a main means for solving the problem of the zinc dross at present.
The groove shape of the sink roll used in the production of the current hot galvanizing pure zinc product is shown in figure 1. As can be seen from fig. 1, the gap P1 between the grooves in the prior art is too large, and the rounding between the notch and the groove bottom is too small, thereby affecting the discharging effect of the zinc liquid in the grooves.
Based on the above, it is desirable to obtain a sink roll, which properly reduces the distance between the grooves and increases the size of the fillets at the notch and the bottom of the groove, thereby improving the fluidity of the zinc liquid on the roll surface of the sink roll, avoiding the deposition of zinc slag in the grooves and improving the surface quality of the strip steel.
Disclosure of Invention
The invention aims to provide a sink roll for producing cold-rolled hot-dip pure zinc strip steel, which improves the groove of the sink roll, improves the fluidity of zinc liquid on the roll surface of the sink roll, not only avoids the problem of deposition of zinc slag in the groove, but also ensures that aluminum in the zinc liquid fully reacts with the surface of the strip steel, thereby avoiding the occurrence of groove marks.
In order to achieve the aim of the invention, the invention provides a sink roll for producing cold-rolled hot-dip pure zinc strip steel, which is provided with a plurality of grooves, wherein the grooves are sequentially arranged in the axial direction of the sink roll, and each groove extends along the circumferential direction of the sink roll; the plurality of grooves are arranged to: each groove forms a wave trough portion on the sink roll, and a wave crest portion on the sink roll is formed between two adjacent grooves.
The inventor of the present invention finds that the groove print interval on the surface of the strip steel is almost consistent with the groove interval of the roll surface interval by researching the groove print existing in the prior art, and carries out chemical component analysis on the zinc layer at the groove print position to further find that the aluminum content in the zinc layer is not uniform. Through a great deal of research, the inventor analyzes that the reason of the groove mark is that the distance between the grooves of the sink roll is too long, the contact part of the strip steel and the flat section between the two grooves causes insufficient reaction between aluminum in zinc liquid and the surface of the strip steel due to poor zinc liquid fluidity, and accordingly dark-color difference mark is caused.
Based on the research, the inventor designs a sink roll for producing cold-rolled hot-dip galvanized pure zinc strip steel, and solves the problem of groove mark by arranging the structure of the groove.
Further, in the sink roll of the present invention, the top of the cross section of the crest portion is in a first circular arc shape, the bottom of the cross section of the trough portion is in a second circular arc shape, and the area between the top of the crest portion and the bottom of the trough portion is a linear plane, and the linear plane is represented by a tangent line connecting a circle in which the first circular arc shape is located and a circle in which the second circular arc shape is located on the cross section of the sink roll.
Further, in the sink roll of the present invention, a ratio of the radius R of the second circular arc to the radius R of the first circular arc is 0.7 to 0.8. This is because: when the ratio of the radius R of the second circular arc to the radius R of the first circular arc is greater than 0.8, the contact area of the top end and the strip steel is too small, and fine-line-shaped stripes are generated; when the ratio is less than 0.7, too much area of the top end of the sink roll and the strip steel causes a situation of low local aluminum content, and thus fine dark stripes are formed.
Further, in the sink roll of the present invention, the depth t of the groove satisfies:
t=(R+r)+K×r/R
wherein r represents the radius of the second arc; r represents the radius of the first arc; k is an adjusting coefficient, the value range of K is 0.35-0.45, and the unit parameter of K is the same as R and R. When the depth t is less than 0.35, the slag discharge capacity of the sink roll is obviously reduced, and a zinc slag bright spot is easily caused on the surface of the strip steel.
Further, in the sink roll of the present invention, the radius R of the first arc ranges from 0.4mm to 0.5 mm.
Further, in the sink roll of the present invention, the radius r of the second arc ranges from 0.3 mm to 0.4 mm.
Further, in the sink roll of the present invention, a distance δ between center lines of two adjacent crest portions satisfies:
δ=3×(r/R)
wherein r represents the radius of the second arc; r represents the radius of the first circular arc.
Preferably, the distance δ between the center lines is in a range of 2-2.5mm, and when the distance δ between the center lines is smaller than 2, that is, the radius R of the first arc is large, the contact area between the tops of the valleys and the strip steel is easily too large, so that a dark groove mark is generated.
When the sink roll for producing the cold-rolled hot-dip galvanized pure zinc strip steel is used for producing cold-rolled hot-dip galvanized products, the surface quality of the strip steel is good, the problem of groove printing in the prior art is solved, and the defect of zinc slag is avoided.
Detailed Description
The sink roll for cold rolling hot dip pure zinc strip production according to the present invention will be further explained with reference to the following specific examples and the attached drawings of the specification, but the explanation should not be construed as an undue limitation on the technical solution of the present invention.
FIG. 2 is a schematic structural diagram of a sink roll for cold rolling hot dip galvanized steel strip production according to an embodiment of the invention.
As shown in fig. 2, and optionally in conjunction with fig. 3, the sink roll 1 for cold rolling hot-dip galvanized pure zinc strip production in the present embodiment has a plurality of grooves 10 on the sink roll 1, and the grooves 10 are arranged as follows: each groove forms a wave trough 101 on the sink roll 1 and two adjacent grooves form a wave crest 102 on the sink roll between them.
Reference may be further made to fig. 3 with respect to the structure of the trench. Fig. 3 is a sectional view of the roll surface at a of fig. 2 in the axial direction.
As shown in fig. 3, in the present embodiment, the top of the cross section of the crest portion 102 is in a first circular arc shape, the radius of the first circular arc shape is R, the bottom of the cross section of the trough portion 101 is in a second circular arc shape, the radius of the second circular arc shape is R, and the area between the top of the crest portion 102 and the bottom of the trough portion 101 is a linear plane which is expressed as a tangent line of a circle in which the first circular arc shape is located and a circle in which the second circular arc shape is located on the cross section of the sink roll.
In addition, in order to better realize the quality of the produced strip surface, the structure of the sink roll 1 is further limited: the ratio of the radius R of the second circular arc to the radius R of the first circular arc is 0.7-0.8; the depth t of the groove satisfies: t ═ K × R/R, where R denotes the radius of the second circular arc; r represents the radius of the first arc; k is an adjusting coefficient, the value range of K is 0.35-0.45, and the unit parameter of K is the same as R and R; the radius R of the first arc ranges from 0.4mm to 0.5 mm; the radius r of the second arc ranges from 0.3 mm to 0.4 mm; the distance δ between the center lines of two adjacent peak portions satisfies: δ — 3 × (R/R), where R represents the radius of the second arc; r represents the radius of the first circular arc.
In the drawing, α represents an angle between a tangent line of a circle in which the first arc is positioned and a tangent line of a circle in which the second arc is positioned.
In addition, fig. 2 to 3 schematically show the structure of the sink roll for the production of cold-rolled hot-dip galvanized steel strip of the present case, and table 1 below lists the structural parameters and the implementation effects of the sink rolls for the production of cold-rolled hot-dip galvanized steel strip of examples 1 to 4 and the comparative sink rolls of comparative examples 1 to 4.
Table 1.
Note: "circa" in table 1 indicates that the groove mark inspection was passed, and "x" indicates that the groove mark inspection was failed.
As can be seen from table 1, in comparative example 1 and comparative example 2, the ratio of the radius R of the second circular arc to the radius R of the first circular arc is greater than 0.8, so that the contact area of the top end of the sink roll with the strip steel is too small, thereby generating groove marks on the surface of the strip steel. In the comparative example 3, the ratio of the radius R of the second arc to the radius R of the first arc is less than 0.7, so that too much contact area between the top end and the strip steel can generate local low aluminum concentration, and fine dark stripes are caused, and the slag discharge capacity of the sink roll is obviously reduced due to too low depth t of the groove, so that zinc slag bright spots are formed on the surface of the strip steel.
In addition, as can be seen from comparative examples 1 to 4, when the distance δ between the center lines of two adjacent peak portions is larger than 2.5 (for example, comparative example 1 and comparative example 2), the opening degree is too large, so that the flow velocity of the molten zinc in the groove becomes slow, which is not favorable for slag discharge. When delta is less than 2 (such as comparative example 3 and comparative example 4), R is larger, which causes the contact area between the top of the valley peak and the strip steel to be too large, and the groove marks with dark intervals are generated.
It should be noted that the prior art in the protection scope of the present invention is not limited to the examples given in the present application, and all the prior art which is not inconsistent with the technical scheme of the present invention, including but not limited to the prior patent documents, the prior publications and the like, can be included in the protection scope of the present invention.
In addition, the combination of the features in the present application is not limited to the combination described in the claims of the present application or the combination described in the embodiments, and all the features described in the present application may be freely combined or combined in any manner unless contradictory to each other.
It should also be noted that the above-mentioned embodiments are only specific embodiments of the present invention. It is apparent that the present invention is not limited to the above embodiments and similar changes or modifications can be easily made by those skilled in the art from the disclosure of the present invention and shall fall within the scope of the present invention.