CN108048735B - Steel plate for cold rolling enamel and production method thereof - Google Patents

Abstract

The invention discloses a steel plate for cold rolling enamel, which comprises the following chemical components in percentage by mass: c: not more than 0.008 percent, not more than 0.03 percent of Si, Mn: 1.0-5.0%, S: 0.05-0.10%, P is less than or equal to 0.012%, Alt: less than or equal to 0.02 percent, Mn/S more than or equal to 20 percent, and the balance of iron and inevitable impurities. The invention also discloses a production method of the cold-rolled enamel steel plate. According to the cold-rolled steel plate for enamel and the production method thereof, the content of each element is controlled, and the hot rolling, cold rolling, annealing and leveling processes are controlled, so that the produced steel plate for cold-rolled enamel has stable scale explosion resistance and enamel adhesion, and the product quality is improved.

Description

Steel plate for cold rolling enamel and production method thereof

Technical Field

The invention relates to the technical field of steel smelting, in particular to a steel plate for cold-rolled enamel and a production method thereof.

Background

The enameled pressed steel plays an important role in national economy, has a close relationship with people in industrial production and daily life, is widely applied to industries such as light industry, household appliances, chemical industry, buildings and the like, and is used for manufacturing kitchen utensils, sanitary wares, barbecue ovens, water heater liners, chemical reaction tanks and the like. The scale explosion is the most terrible defect of the enameled steel sheet, and is generally considered to be the reaction of crystal water in the enamel slurry with iron and carbon on the surface of the steel sheet to generate atomic hydrogen during high-temperature enameling. When the steel plate is cooled, the solubility of hydrogen in the steel is reduced sharply, and if the steel plate does not have enough hydrogen storage places, a large amount of hydrogen atoms can escape, and gather on the surface area of the steel plate, so that the surface of the enamel is broken by a large pressure to a certain extent, and the enamel is flaked. The hydrogen storage location of the steel sheet determines the fishscale resistance of the steel sheet, i.e., the hydrogen trap. Grain boundaries, dislocations, vacancies, inclusions, second phase particles, etc. in steel are all good hydrogen traps, wherein inclusions and second phases are irreversible hydrogen traps, often used as technical starting points for the production of enamelled steel.

In the related patents/patent applications related to the cold-rolled enameled steel sheet and the manufacturing method thereof, most of the enameled steels include an alloy-element-containing enameled steel or a high-oxygen enameled steel, the alloy-element-containing enameled steel uses precipitates or inclusions as hydrogen traps, and the high-oxygen enameled steel uses oxides or precipitates as hydrogen traps.

In the prior art, most of enamel steels take precipitated carbonitride as a hydrogen trap to ensure the fish scaling resistance, and are mainly carbides, but the applicant researches show that the following problems still exist: as the enameling firing process is a high-temperature firing process, which is about between 800 and 950 ℃, and most of carbide second phases are easy to reversely dissolve at the high temperature of above 700 ℃, the scale-explosion resistance after enameling firing is reduced, and the TH value is reflected in the measurement index to be far lower than that before enameling firing. In addition, although the oxides are not dissolved reversely in the design method of the high-oxygen enamel steel, the quantity and distribution of the oxides need to be controlled, the process control difficulty is increased, and the corrosion of refractory materials is easily caused in the pouring process due to the excessively high oxygen content, so that the service life of equipment is influenced. Therefore, the enameled steel industry needs an enameled steel sheet with stable enamel performance, easy control of production process and good fish scaling resistance.

Disclosure of Invention

The embodiment of the application provides the cold-rolled steel plate for enamel and the production method thereof, so that the technical problem that the scale explosion resistance of the cold-rolled steel plate for enamel is reduced after enamel firing in the prior art is solved, and the TH value of a finished product reaches 50min/mm²The above.

In order to solve the technical problems, the invention provides a steel plate for cold rolling enamel on one hand, which comprises the following chemical components in percentage by mass:

c: not more than 0.008 percent, not more than 0.03 percent of Si, Mn: 1.0-5.0%, S: 0.05-0.10%, P is less than or equal to 0.012%, Alt: less than or equal to 0.02 percent, Mn/S more than or equal to 20 percent, and the balance of iron and inevitable impurities.

In another aspect of the present invention, there is provided a method of producing the above-described cold-rolled steel sheet for enamel, comprising:

pretreating molten iron, and then carrying out converter smelting, LF refining and continuous casting to obtain a plate blank;

heating the plate blank, and then carrying out rough rolling and finish rolling to obtain a hot rolled plate, wherein the initial rolling temperature is controlled to be 1000-1070 ℃, and the final rolling temperature is controlled to be 900-980 ℃;

cooling the hot rolled plate by stages, and coiling the cooled hot rolled plate into a hot rolled coil;

pickling the hot rolled coil, and carrying out cold continuous rolling to obtain a cold hard coil;

and annealing and flattening the cold-hard coil to obtain a finished product.

Further, when the slab is heated, the heating temperature is controlled to be 1100-1290 ℃.

Further, the coiling temperature is controlled to be 500-780 ℃.

Further, when the hot-rolled coil is subjected to cold continuous rolling, the total reduction rate of the cold rolling is controlled to be 60-90%.

Further, continuous annealing is adopted when the cold-hard coil is annealed, the annealing temperature is controlled to be 700-850 ℃, and the annealing time is controlled to be 100-300 seconds.

Further, when the chilled coil is leveled, a double-rack leveling method is adopted, and the leveling elongation is controlled to be 2.0-5.0%.

Further, when the chilled coil is leveled, the leveling roll surface is subjected to texturing treatment, and the surface roughness Ra of the finished product reaches 2.5-4.0.

Further, the initial rolling temperature is controlled to be 1050 ℃ at 1000-.

One or more technical solutions provided in the embodiments of the present application have at least the following technical effects or advantages:

the invention adopts MnS to replace the traditional carbide as the second phase as the main hydrogen trap, has better anti-scaling performance, and the TH value can reach 50min/mm²And the MnS precipitation and dissolution temperature is over 1000 ℃, which is far higher than the dissolution temperature and the enameling temperature of carbide, and the MnS is relatively stable in the enameling process, so that the fishscaling resistance performance after enameling is not reduced.

Drawings

FIG. 1 is a TH value measurement curve of a cold-rolled enamel steel sheet provided in example two of the present invention;

FIG. 2 is a TH value measurement curve after simulated enameling in a muffle furnace according to a second embodiment of the invention;

FIG. 3 shows the adhesion test results of the cold-rolled enamel steel sheet according to the second embodiment of the present invention.

Detailed Description

The steel plate for cold-rolled enamel has stable fish scaling resistance and enamel adhesion, improves the product quality and can bring considerable economic benefit by controlling the content of each element and controlling the hot rolling, cold rolling, annealing and leveling processes.

In order to better understand the technical solution, the technical solution will be described in detail with reference to the drawings and the specific embodiments.

Example one

The embodiment of the invention provides a steel plate for cold rolling enamel, which comprises the following chemical components in percentage by mass:

c: not more than 0.008 percent, not more than 0.03 percent of Si, Mn: 1.0-5.0%, S: 0.05-0.10%, P is less than or equal to 0.012%, Alt: less than or equal to 0.02 percent, Mn/S more than or equal to 20 percent, and the balance of iron and inevitable impurities.

The lower the carbon content is, the better the formability of the steel sheet is, and carbon monoxide bubbles can be formed even if the carbon content is higher in the enameling firing process, and pinhole defects can be generated in serious cases to damage the surface quality of enamel, so that the carbon content is controlled to be less than or equal to 0.008% in the embodiment.

Si is used as a deoxidizer for removing oxygen in molten steel, Si is a harmful element in enamel steel, and the increase of Si content can obviously reduce the enamel adherence and damage the surface quality, so the Si content is selected to be controlled below 0.03% in the embodiment.

Generally, hot shortness is easily generated even when the sulfur content is high, and it is necessary to add MnS according to the Mn content to generate MnS to counteract the negative effect and eliminate brittleness of S, and MnS is a very stable hydrogen trap particle, and it is preferable to control Mn/S to be not less than 20 in order to ensure complete precipitation of S element and complete elimination of brittleness of S. Therefore, in this embodiment, Mn is controlled to be 1.0-5.0%, and S is controlled to be 0.05-0.10%.

Phosphorus is an impurity element, tends to segregate at grain boundaries, increases brittleness of the steel sheet, impairs formability of the steel sheet, and tends to generate bubbles and black spots during the slush-firing to affect surface quality, so that phosphorus is controlled to 0.012% or less.

Aluminum is a strong deoxidizer, can inhibit the generation of other oxides, aluminum reacts with oxygen to generate aluminum oxide, the shaping of the aluminum oxide is poor, and a large amount of aluminum oxide inclusions can damage the processability of the steel plate, so that the Alt is controlled to be less than or equal to 0.02 percent in the embodiment.

The embodiment of the invention also provides a production method of the steel plate for cold rolling enamel, which comprises the following steps:

step S1: pretreating molten iron, and then carrying out converter smelting, LF refining and continuous casting to obtain a plate blank;

step S2: heating the plate blank, and then carrying out rough rolling and finish rolling to obtain a hot rolled plate, wherein the initial rolling temperature is controlled to be 1000-.

Step S3: cooling the hot rolled plate by stages, and coiling the cooled hot rolled plate into a hot rolled coil;

step S4: pickling the hot rolled coil, and carrying out cold continuous rolling to obtain a cold hard coil;

step S5: and annealing and flattening the cold-hard coil to obtain a finished product.

In the embodiment, when the slab is heated, the heating temperature is controlled to be 1100-1290 ℃, so that the full austenitization of the slab can be ensured, and the purpose of uniform structure is achieved. Then, when hot rolling is carried out, the initial rolling temperature is controlled to be 1000-. In the temperature range, Mn and S elements are fully combined to form enough MnS second-phase hydrogen traps, the scale explosion resistance of the enamel steel is improved, MnS formed at high temperature is very stable and cannot be decomposed in the enamel firing process, and the scale explosion resistance of the steel plate cannot be reduced after the enamel firing.

Then, the coiling temperature is controlled to be 500-780 ℃ in the embodiment so as to adjust the final grain size and performance of the steel plate. The total reduction rate of cold rolling is 60-90%, and the high cold rolling reduction rate can store enough distortion energy in the steel, thereby being beneficial to texture development, improving the forming performance of the steel plate, reducing the recrystallization temperature and being beneficial to recrystallization after annealing. The annealing process adopts continuous annealing, the annealing temperature is controlled to be 700-850 ℃, the annealing time is 100-300 seconds, and complete recrystallization and texture development are guaranteed.

Because the rough surface structure is very powerful to enamel adhesion, the embodiment finally adopts double-frame flattening, the flattening elongation is controlled to be 2.0-5.0%, the large flattening elongation increases the replication rate of the roughness of the roller surface, and the flattening roller surface adopts texturing treatment, so that the surface roughness Ra of a finished product reaches 2.5-4.0.

Example two

The chemical compositions and production processes of the experimental groups 1-4 provided in this example are shown in tables 1 and 2, respectively:

table 1 chemical composition of experimental groups, wt. -%)

Experimental group	C	Si	Mn	S	P	Alt
							1	0.003	0.01	1.2	0.056	0.012	0.016
2	0.004	0.01	2.8	0.074	0.011	0.012
							3	0.002	0.01	2.9	0.088	0.010	0.014
4	0.007	0.01	4.8	0.085	0.008	0.017
							5	0.002	0.03	1.0	0.052	0.009	0.020
6	0.008	0.02	5.0	0.098	0.012	0.018
							7	0.003	0.01	3.0	0.048	0.004	0.019
8	0.005	0.03	4.0	0.068	0.009	0.012

Table 2 process parameters of the experimental groups

Example steel sheet, a hydrogen permeation sample was cut at a sheet width of 1/4 and a TH value of the steel sheet was measured and calculated, and further, a sample was cut at the same position, after a muffle furnace simulation of 860 ℃ for a smoldering time of 5min, a hydrogen permeation test was performed, and a variation in the TH value of the calculated steel sheet was measured and calculated.

The TH value of the enameled pressed steel is measured and calculated according to the national standard GB/T29515-. (the thickness of the steel plate in this example is 1mm)

For each example, 5 samples at different positions of the steel plate are subjected to small sample enameling in a laboratory, the enameling method is wet enameling, and the scale explosion phenomenon is observed by adopting different enameling firing temperatures and times.

The enamel adherence measurement method is carried out by a drop hammer impact experiment, the weight of a hemisphere is 1.5kg, the drop hammer height is 1.0m, different temperatures and different times are adopted in the enamel process and are all 1 grade, and the test results are shown in a table 3:

TABLE 3 TH-value and enamel adhesion of the experimental groups

One or more technical solutions provided in the embodiments of the present application have at least the following technical effects or advantages:

1. the invention adopts MnS to replace the traditional carbide as the second phase as the main hydrogen trap, has better anti-scaling performance, and the TH value can reach 50min/mm²And the MnS precipitation and dissolution temperature is over 1000 ℃, which is far higher than the dissolution temperature and the enameling temperature of carbide, and the MnS is relatively stable in the enameling process, so that the fishscaling resistance performance after enameling is not reduced.

2. The steel plate for cold-rolled enamel manufactured by the invention has rough surface, forms more microcosmic contact interfaces with an enamel layer and improves the enamel adhesion.

Finally, it should be noted that the above embodiments are only for illustrating the technical solutions of the present invention and not for limiting, and although the present invention has been described in detail with reference to examples, it should be understood by those skilled in the art that modifications or equivalent substitutions may be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, which should be covered by the claims of the present invention.

Claims (2)

1. The steel plate for cold-rolled enamel is characterized by comprising the following chemical components in percentage by mass:

c: not more than 0.008 percent, not more than 0.03 percent of Si, Mn: 2.8-5.0%, S: 0.05-0.10%, P is less than or equal to 0.012%, Alt: not more than 0.02 percent, Mn/S not less than 20 percent, and the balance of iron and inevitable impurities;

the preparation method of the steel plate for cold rolling enamel comprises the following steps:

pretreating molten iron, and then carrying out converter smelting, LF refining and continuous casting to obtain a plate blank;

heating the plate blank, and then carrying out rough rolling and finish rolling to obtain a hot rolled plate, wherein the initial rolling temperature is controlled to be 1000-;

cooling the hot rolled plate in stages, and coiling the cooled hot rolled plate into a hot rolled coil, wherein the coiling temperature is controlled to be 500-780 ℃;

pickling and cold continuous rolling the hot rolled coil to obtain a cold hard coil, and controlling the total reduction rate of cold rolling to be 60-90% when the hot rolled coil is subjected to cold continuous rolling;

annealing and flattening the chilled coil to obtain a finished product, continuously annealing the chilled coil when the chilled coil is annealed, controlling the annealing temperature to be 700-850 ℃ and the annealing time to be 100-300 seconds, flattening the chilled coil by using a double-frame, controlling the flattening elongation to be 2.0-5.0%, roughening the surface of a flattening roller, and enabling the surface roughness Ra of the finished product to reach 2.5-4.0.

2. A method of producing the cold-rolled steel sheet for enamel according to claim 1, comprising:

pretreating molten iron, and then carrying out converter smelting, LF refining and continuous casting to obtain a plate blank;

heating the plate blank, and then carrying out rough rolling and finish rolling to obtain a hot rolled plate, wherein the initial rolling temperature is controlled to be 1000-;

cooling the hot rolled plate in stages, and coiling the cooled hot rolled plate into a hot rolled coil, wherein the coiling temperature is controlled to be 500-780 ℃;

pickling and cold continuous rolling the hot rolled coil to obtain a cold hard coil, and controlling the total reduction rate of cold rolling to be 60-90% when the hot rolled coil is subjected to cold continuous rolling;

annealing and flattening the chilled coil to obtain a finished product, continuously annealing the chilled coil when the chilled coil is annealed, controlling the annealing temperature to be 700-850 ℃ and the annealing time to be 100-300 seconds, flattening the chilled coil by using a double-frame, controlling the flattening elongation to be 2.0-5.0%, roughening the surface of a flattening roller, and enabling the surface roughness Ra of the finished product to reach 2.5-4.0.

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