CN109333369B - Method for reducing surface roughness after hot plate shot blasting treatment - Google Patents

Abstract

The invention provides a method for reducing surface roughness after shot blasting treatment of a hot plate, which comprises the following steps: selecting a shot blasting medium, wherein the shot blasting medium is selected to be steel shots; optimizing the granularity of the steel shots, wherein the total amount of the steel shots with the granularity of 0.5mm or more is less than 2 percent, and the total amount of the steel shots with the granularity of 0.3 mm-0.425 mm reaches about 90 percent; the grain size mixing ratio of the bin is controlled, the grain size mixing ratio of steel shots in the bin of the shot blasting machine is controlled to be more than 50 percent of steel shots with the grain size of 0.3 mm-0.355 mm, and the grain size of the steel shots with the grain size of 0.5mm or more is less than 5 percent. By using the method for reducing the surface roughness of the hot plate after shot blasting, the problems of deeper steel plate surface shot blasting, unsatisfactory surface appearance, high surface roughness and the like can be effectively solved, the highest cleaning efficiency can be obtained, and the surface roughness of the cold plate after shot blasting can be obviously reduced.

Description

Method for reducing surface roughness after hot plate shot blasting treatment

Technical Field

The invention belongs to the technical field of stainless steel rolling, and particularly relates to a method for reducing surface roughness after hot plate shot blasting treatment.

Background

With the development of the stainless steel industry, the customer demands are diversified, and in order to meet the requirements of high-grade decorative materials, the surface performance of the strip steel needs to be improved urgently, particularly the surface quality of the strip steel is improved, and the surface roughness of the strip steel is reduced.

In the prior art, pickling is needed before subsequent processes are carried out after stainless steel is hot rolled and annealed, namely stainless steel hot wire pickling, and the aim is to remove scale formed on the surface of a steel strip in the hot rolling and annealing processes. The chromium oxide which is more tightly combined with the matrix is contained in the iron scale of the stainless steel, so that the pickling is difficult. Therefore, in order to improve the pickling effect, pretreatment before pickling is necessary. For cold rolled steel coils, chemical descaling is generally used for pre-pickling pretreatment, while for hot rolled stainless steel (i.e., hot plate), mechanical descaling, such as shot blasting or roller descaling, is generally used for pre-pickling pretreatment.

The shot blasting treatment is to make very small steel shots sprayed on the surface of running strip steel at a high speed by utilizing centrifugal force, convert the kinetic energy of the steel shots into impact force on the surface of the strip steel, and make the oxide skin of the strip steel separate from a matrix, thereby achieving the effect of removing the iron scale on the surface of the strip steel. The quality of shot blasting treatment depends on the quality, the quantity, the injection speed, the impact direction and the granularity mixing ratio of steel shots in a shot blasting machine bin. Under the condition that the quality, the injection speed and the impact direction can be effectively controlled, the grain size mixing ratio of the steel shots and the quantity of the steel shots are particularly important to control in the shot blasting process.

In the prior art, due to the lack of an effective shot blasting treatment process, the surface roughness of a hot plate after shot blasting treatment is high, and the market demand cannot be met. Therefore, how to improve the shot blasting process to reduce the surface roughness after the hot plate shot blasting process becomes a technical problem to be solved by the technical staff in the field.

Disclosure of Invention

The invention aims to provide a method for reducing the surface roughness after shot blasting treatment of a hot plate, which can effectively reduce the surface roughness after shot blasting treatment of the hot plate by reasonably selecting shot blasting media, optimizing the granularity of steel shots and controlling the granularity mixing ratio of a storage bin, so that the surface roughness after shot blasting treatment of the hot plate is kept at the level of Ra being less than or equal to 3.2 mu m.

Therefore, the method for reducing the surface roughness after shot blasting treatment by the hot plate comprises the following steps:

selecting a shot blasting medium, wherein the shot blasting medium is selected to be steel shots;

optimizing the granularity of the steel shots, wherein the total amount of the steel shots with the granularity of 0.5mm or more is less than 2 percent, and the total amount of the steel shots with the granularity of 0.3 mm-0.425 mm reaches about 90 percent;

the grain size mixing ratio of the bin is controlled, the grain size mixing ratio of steel shots in the bin of the shot blasting machine is controlled to be more than 50 percent of steel shots with the grain size of 0.3 mm-0.355 mm, and the grain size of the steel shots with the grain size of 0.5mm or more is less than 5 percent.

Preferably, in the method for reducing the surface roughness after hot plate shot blasting treatment, the steel shot size distribution is as follows:

particle size

0.125mm

0.18mm

0.3mm

0.355mm

0.425mm

0.5mm

0.6mm

0.71mm

Steel shot

0.01％

7.42％

17.55％

39.56％

33.60％

1.85％

0.01％

0.00％

Preferably, in the method for reducing the surface roughness after hot plate blasting treatment of the invention, the mixing ratio of the bin particle sizes is controlled as follows:

particle size

0.125mm

0.18mm

0.3mm

0.355mm

0.425mm

0.5mm

0.6mm

0.71mm

Steel shot

0.79％

10.29％

18.53％

35.65％

31.14％

3.42％

0.18％

0.00％

Preferably, in the method for reducing surface roughness after hot plate blasting treatment of the present invention, the steel shot is a high carbon cast steel shot.

Preferably, in the method for reducing the surface roughness after hot plate blasting treatment of the present invention, the method for controlling the mixing ratio of the bin particle sizes comprises:

a) the adding mode is fixed, and 1.5 tons of supplementary grinding materials are uniformly and continuously added in 24 hours in each shot blasting machine;

b) controlling the shot blasting curtain separators to be uniformly distributed, wherein the air speed for winnowing reaches the normal range of 6-10 Km/h;

c) the proportion of effective particles with the size of more than or equal to 0.2mm in the dedusting ash is controlled to be less than or equal to 10 percent.

By using the method for reducing the surface roughness after shot blasting treatment of the hot plate, the steel shots are selected as shot blasting media, the use of mixed abrasive containing angular steel sand is avoided, and the problems of deeper steel plate surface polishing, unsatisfactory surface appearance, large surface roughness and the like in the prior art can be effectively solved; the highest cleaning efficiency can be obtained by optimizing the particle size distribution of the steel shots, and the surface roughness of the cold plate after shot blasting treatment can be obviously reduced; by optimizing the granularity mixing ratio of the steel shot bin, the situation that large particles throw and beat residual pits on the surface is avoided, the surface cleaning grade can be ensured to meet the expected requirement, in addition, the effective particle content of dedusting ash can be reduced, and shot blasting media can be saved.

Drawings

In order to more clearly illustrate embodiments of the present invention or technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without inventive efforts, wherein:

FIG. 1A is an enlarged view of shot-blasting mixed abrasives used in the prior art;

FIG. 1B is an enlarged view of a steel shot selected for use in the method of the present invention for reducing surface roughness after hot plate blasting;

FIG. 2 is a schematic view of the method of the present invention for reducing surface roughness after hot plate blasting;

FIG. 3 is a schematic diagram of an apparatus for controlling a grain size mixing ratio of bins in the method for reducing surface roughness after hot plate blasting according to the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be clearly and completely described below with reference to the specific embodiments of the present invention and the accompanying drawings. It is to be understood that the described embodiments are merely a few embodiments of the invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without making any creative effort, shall fall within the protection scope of the present invention.

As shown in fig. 2, the method for reducing the surface roughness after hot plate blasting treatment of the present invention comprises: the method optimizes and reasonably selects the shot blasting media, optimizes the steel shot granularity, and optimally controls the granularity mixing ratio of the storage bins.

In the prior art, the shot blasting media for iron scale treatment on the surface of the hot plate are generally high-carbon cast steel shots, high-carbon cast steel grits and mixed abrasive, wherein the mixed abrasive is shot blasting media formed by mixing the high-carbon cast steel shots and the high-carbon cast steel grits according to a certain proportion. Fig. 1A shows an enlarged view of a shot-blasting mixed abrasive used in the prior art, and under a 15-fold magnification, it can be seen that spherical particles account for less of the mixed abrasive, while the steel grit is irregularly shaped with edges and corners. Obviously, in the mixed abrasive used in the prior art, the steel grit accounts for a large amount, the steel grit has edges and corners, the edges and corners firstly contact with the strip steel during throwing, and because the contact area is small, the edges and corners can generate strong force on the contact surface of the steel plate, and under the effect of efficient descaling, the problems of deeper throwing and beating of the surface of the steel plate, unsatisfactory surface appearance, large surface roughness and the like are caused.

By comparing the components, hardness and appearance of the high-carbon cast steel shot and the mixed abrasive, the high-carbon cast steel shot is preferably used as the shot blasting medium in the method for reducing the surface roughness after the hot plate shot blasting treatment. Fig. 1B shows an enlarged view of the steel shot selected for use in the method of the invention for reducing surface roughness after hot plate blasting, which shows that the steel shot is substantially all spherical (few shapes < 15%) under 15 x magnification.

Compared with the mixed abrasive in the prior art, the steel shots selected in the method for reducing the surface roughness after hot plate shot blasting treatment have similar components, density and hardness, and theoretically have little influence on the consumption of the abrasive. The steel shot has better fluidity than the mixed abrasive due to the spherical shape, so that the shot blasting current is more stable. In addition, the steel shot is spherical, the contact surface area with the steel plate is large during throwing, the stress is relatively uniform, the local stress is not large, the throwing depth is shallow, and the surface roughness is not too large on the premise of ensuring the removal of the iron oxide scale.

In addition, the impact on the roughness of the surface of a product after shot blasting treatment is large due to the size of shot blasting, and the larger the steel shot granularity is, the larger the impact kinetic energy is, and the larger the impact force is. When the steel shot granularity is selected, on the premise of meeting the descaling efficiency, if the surface roughness is reduced, the steel shot with smaller size is selected as far as possible, and the steel shot with graded size is preferably used. The graded steel shots consist of more than 50 percent of steel shots with nominal size and gradually reduced steel shots, and the graded steel shots have both impact force and coverage rate, so that the highest cleaning efficiency and lower surface roughness can be obtained.

Therefore, in the method for reducing the surface roughness after the hot plate shot blasting treatment, the steel shot granularity is further optimized. Table 1 shows the particle size distribution of the steel shot used in the method for reducing the surface roughness after hot plate blasting treatment according to the present invention, as compared with the high carbon cast steel shot in shot blasting mixed abrasives used in the prior art.

TABLE 1 control of the particle size distribution of the mixed abrasives and the shot

Particle size

0.125mm

0.18mm

0.3mm

0.355mm

0.425mm

0.5mm

0.6mm

0.71mm

Mixed abrasive

0.01％

17.20％

8.79％

20.97％

25.99％

22.13％

4.72％

0.19％

Steel shot

0.01％

7.42％

17.55％

39.56％

33.60％

1.85％

0.01％

0.00％

Compared with the mixed abrasive used in the prior art, the method for reducing the surface roughness after hot plate shot blasting treatment has the advantages that the overall granularity of the steel shots is smaller, the proportion of the steel shots with the granularity of 0.5mm or more is reduced by about 25 percent, the total amount is less than 2 percent, and the total amount of the steel shots with the granularity of 0.5mm or more in the specific embodiment can be only 1.86 percent, so the granularity stability of a storage bin is easier to control; the steel shots with the nominal size of 0.3-0.425 mm and the granularity are increased by about 35 percent, the total amount reaches about 90 percent, in the specific embodiment, the total amount of the steel shots with the granularity of 0.3-0.425 mm can reach 90.71 percent, so that the impact force and the coverage rate are considered, the highest cleaning efficiency can be obtained, and meanwhile, the surface roughness of the cold plate after shot blasting treatment can be reduced by 0.4 percent.

Furthermore, experiments show that the particle size mixing ratio of the storage bin is controlled within a certain range, so that the surface roughness of the cold plate after shot blasting treatment can be effectively reduced. It should be noted that the bin grain size mixing ratio refers to the total content ratio of the steel shots actually replenished to the bin in the process of replenishing the abrasive material to the bin (i.e. adding sand) by using the steel shots prepared according to the grain size distribution ratio shown in the table 1 as the basic raw material under the control of the shot blasting curtain separator, and the bin grain size mixing ratio of the steel shots with various grain sizes is different from the grain size distribution ratio of the steel shots due to the influence of the sand adding amount, the sand adding frequency, the separator wind speed and the like.

Therefore, in the method for reducing the surface roughness after shot blasting treatment of the hot plate, the mixing ratio of the granularity of the storage bin is also optimally controlled. Table 2 shows the comparison of the grain size mixing ratio of the steel shot bins used in the method for reducing the surface roughness after hot plate blasting according to the present invention compared to the grain size mixing ratio of the shot blasting mixed abrasive bins used in the prior art.

TABLE 2 stock bin particle size mix ratio optimization control

It can be seen that in the method for reducing the surface roughness after hot plate shot blasting treatment of the invention, the bin grain size mixing ratio of the steel shots in the bin of the shot blasting machine is controlled to be more than 50% of the steel shots with the grain size of 0.3 mm-0.355 mm, and in a specific embodiment, the steel shots with the grain size of 0.3 mm-0.355 mm can be 54.18%; the steel shot content of 0.5mm or more may be less than 5%, and in specific examples, the steel shot content of 0.5mm or more may be only 3.6%, thereby reducing the surface roughness Ra of the cold plate after shot blasting from 3.5 μm to 3.1 μm.

In the method for reducing the surface roughness after shot blasting treatment of the hot plate, the method for optimally controlling the granularity mixing ratio of the storage bin comprises the following steps:

a) a fixed adding mode, namely 1.5 tons of supplementary grinding materials are uniformly and continuously added in 24 hours in each shot blasting machine;

b) controlling the shot blasting curtain separators to be uniformly distributed, wherein the air speed for winnowing reaches the normal range of 6-10 Km/h;

c) the proportion of effective particles with the size of more than or equal to 0.2mm in the dedusting ash is controlled to be less than or equal to 10 percent.

Fig. 3 is a schematic diagram showing an apparatus for controlling a grain size mixing ratio of a bin in the method for reducing surface roughness after hot plate blasting according to the present invention, wherein steel shots are added into a new material storage tank 1, and the opening degree of a pipeline opening controller 3 is remotely controlled, so that the steel shots are uniformly added into a shot blasting machine bin 4 through a feeding pipeline 2, thereby avoiding one-time centralized addition and effectively controlling the grain size mixing ratio of the bin.

Examples

In the method for reducing the surface roughness after hot plate shot blasting treatment, high-carbon cast steel shots are selected as shot blasting media, the granularity of the steel shots is shown in the table 1, and meanwhile, the granularity mixing ratio of the steel shots in a bin of a shot blasting machine is controlled to be about 17 percent of particles with the nominal size of 0.3 mm; particles above 0.5mm in size < 5%. By using the method for reducing the surface roughness after shot blasting treatment of the hot plate, the surface roughness Ra of the cold plate after shot blasting treatment can be reduced from 3.5 mu m to 3.1 mu m, meanwhile, the consumption of shot blasting media per ton of steel is reduced from 2.06 Kg/ton of steel to 1.88 Kg/ton of steel, and the amplitude reduction reaches 8.7%.

The method for reducing the surface roughness after shot blasting treatment of the hot plate has the beneficial effects that:

by selecting the steel shot as the shot blasting medium, the use of mixed abrasive containing angular steel grit is avoided, and the problems of deeper steel plate surface throwing, unsatisfactory surface appearance, large surface roughness and the like in the prior art can be effectively solved;

the highest cleaning efficiency can be obtained by optimizing the particle size distribution of the steel shots, and the surface roughness of the cold plate after shot blasting treatment can be obviously reduced;

by optimizing the granularity mixing ratio of the steel shot bin, the proportion of particles with the nominal size of 0.3mm is about 17%, the proportion of particles with the size of more than 0.5mm is less than 5%, residual pits caused by large particles on the surface can be avoided, the surface cleaning grade can meet the expected requirement, in addition, the effective particle content of dedusting ash can be reduced, shot blasting media can be saved, and the consumption of shot blasting media per ton of steel can be reduced by 8.7%.

It should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention, and not for limiting the same; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or alterations do not depart from the spirit of the invention.

Claims (1)

1. A method for reducing surface roughness after hot plate shot blasting treatment is characterized by comprising the following steps:

selecting a shot blasting medium, wherein the shot blasting medium is selected from high-carbon cast steel shots;

optimizing the granularity of the steel shots, wherein the total amount of the steel shots with the granularity of 0.5mm or more is 1.86 percent, and the total amount of the steel shots with the nominal size of 0.3 mm-0.425 mm is 90.71 percent;

controlling the granularity mixing ratio of a bin, wherein the granularity mixing ratio of steel shots in the bin of the shot blasting machine is controlled to be 54.18% for the steel shots with the granularity of 0.3-0.355 mm, and 3.6% for the steel shots with the granularity of 0.5mm or more;

wherein, the steel shot particle size distribution is as follows:

particle size 0.125mm 0.18mm 0.3mm 0.355mm 0.425mm 0.5mm 0.6mm 0.71mm Steel shot 0.01％ 7.42％ 17.55％ 39.56％ 33.60％ 1.85％ 0.01％ 0.00％

The grain size mixing ratio of the storage bin is controlled as follows:

particle size 0.125mm 0.18mm 0.3mm 0.355mm 0.425mm 0.5mm 0.6mm 0.71mm Steel shot 0.79％ 10.29％ 18.53％ 35.65％ 31.14％ 3.42％ 0.18％ 0.00％

The bin grain size mixing ratio refers to the total content ratio of the steel shots actually supplemented to the bin in the bin under the control of the shot blasting curtain separator in the process of supplementing the abrasive to the bin by taking the steel shots prepared according to the steel shot grain size distribution ratio shown in the table as the basic raw material, and the bin grain size mixing ratio of the steel shots with various grain sizes is different from the steel shot grain size distribution ratio due to the influences of the sand adding amount, the sand adding frequency and the wind speed of the separator;

the method for controlling the particle size mixing ratio of the storage bin comprises the following steps:

a) the adding mode is fixed, and 1.5 tons of supplementary grinding materials are uniformly and continuously added in 24 hours in each shot blasting machine;

b) controlling the shot blasting curtain separators to be uniformly distributed, wherein the air speed for winnowing reaches the normal range of 6-10 Km/h;

c) the proportion of effective particles with the size of more than or equal to 0.2mm in the dedusting ash is controlled to be less than or equal to 10 percent.

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