CN115612941A

CN115612941A - High-strength enamel steel and cold rolling manufacturing method thereof by using low-temperature annealing process

Info

Publication number: CN115612941A
Application number: CN202211334743.3A
Authority: CN
Inventors: 杨宏武; 徐希义; 李军; 杜蓉; 谢芬; 雷泽红
Original assignee: Wuhan Iron and Steel Co Ltd
Current assignee: Wuhan Iron and Steel Co Ltd
Priority date: 2022-10-28
Filing date: 2022-10-28
Publication date: 2023-01-17

Abstract

The invention relates to the technical field of hot-rolled high-strength steel, and discloses a 1180 MPa-grade hot-rolled DH steel plate which comprises the following chemical components in percentage by mass: c:0.186 to 0.223%, si:1.74 to 1.92%, mn:1.91 to 2.14%, al:0.102 to 0.145 percent, less than or equal to 0.015 percent of P, less than or equal to 0.002 percent of S, and the balance of Fe and inevitable impurities. The invention also discloses a method for producing the 1180MPa hot-rolled DH steel plate by using the sheet billet. According to the 1180 MPa-grade hot-rolled DH steel plate and the production method thereof by using the thin slab, the tensile strength of the hot-rolled steel plate is more than or equal to 1180MPa, the elongation is more than or equal to 12%, the grain size is small, the grain size is more than or equal to 10 grade, and the hot-rolled DH steel plate has excellent matching of strength, plasticity and toughness.

Description

High-strength enamel steel and cold rolling manufacturing method thereof by using low-temperature annealing process

Technical Field

The invention relates to the technical field of metal material manufacturing, in particular to high-strength enamel steel and a cold rolling manufacturing method thereof by using a low-temperature annealing process.

Background

Along with the continuous development of scientific technology, the application range of enamel products is also expanded continuously, the enamel products are developed from the common single enamel washbasin, water cup and other products to the current various kitchen utensils, barbecue ovens, water heater liners for household appliances, building decoration panels, industrial heat exchanger products and the like, meanwhile, the requirements on the fish scaling resistance, the adherence and the pinhole control quality of the enamel steel are stricter, and particularly, higher requirements are provided for the fish scaling resistance and the mechanical property of the enamel steel. Meanwhile, market homogenization competition is more intense, lower price and higher quality are further demands of the market for products, the household appliance market is taken as an example, the household appliance market puts forward the demands of high strength, thinning and cost reduction on the enameled steel plate, and the high strength cold rolling enameled steel can meet the development demands of light weight of the enameled products such as water heater liners and the like in the household appliance market. The enameling performance is required to be ensured on the premise of meeting the high strength, and the main problem of enameling is the problem of scale explosion which is generated when the enamels are coated, and the reason for generating the scale explosion is that no enough trap is available for storing hydrogen produced in the enameling process. The hydrogen traps in steel include grain boundaries, dislocations, microscopic voids, inclusions, second-phase particles, and the like, and thus the hydrogen traps in the material are increased as much as possible while satisfying the strength. It is required to develop a cold-rolled enamel steel product satisfying high strength, low cost and good enameling property at the same time.

In the existing enamel steel technology, high-oxygen steel is frequently involved, the high-oxygen content is favorable for decarburization on one hand, and on the other hand, oxygen forms a large amount of oxide inclusions in steel, and the inclusions are favorable for improving the fishscaling resistance and the adherence of a steel plate.

Chinese patent publication No. CN101535517A, 2009, no. 16.09, 2009, discloses a steel sheet for enamel having remarkably excellent fishscaling resistance and a method for manufacturing the same, wherein the steel sheet comprises, by weight, 0.003 to 0.010% of C, 0.03 to 1.30% of Mn, 0.001 to 0.100% of Si, 0.035% or less of P, 0.08% or less of S, 0.0002 to 0.010% of Als, 0.055 to 0.250% of Nb, 0.005 to 0.0085% of O, 0.0055% or less of N, 0.0003 to 0.0030% of B, 0.003 to 0.15% of V, 0.0001 to 0.05% of Ni, 0.0001 to 0.05% of Ti, 1 or more of Ta, W, la, ce, ca, and Mg, and 1 or more of a, se, sn, and Sb. The alloy of the patent is added too much, and the loss of the high-oxygen smelting alloy is larger, so that the relative cost is much higher.

With the development of modern industrial technology, it has become a trend to replace cold rolling with hot rolling for enamel products in order to reduce manufacturing costs. For example, patents CN103589953A and CN103540845A both refer to a method for producing hot-rolled enamelled steel by using a short-flow CSP process, but the hot-rolled enamelled steel has poor surface quality and cannot meet the product with higher requirements on enamelling performance.

Disclosure of Invention

The invention aims to provide high-strength enamel steel and a cold rolling manufacturing method thereof by using a low-temperature annealing process aiming at the defects of the technology, so that the high strength, low cost and good enameling performance of the cold-rolled enamel steel are ensured.

In order to achieve the purpose, the high-strength enamel steel designed by the invention comprises the following chemical components in percentage by mass: c:0.02 to 0.07%, mn: 0.10-0.50%, si is less than or equal to 0.03%, P: 0.015-0.030 percent of Ti, less than or equal to 0.030 percent of S, less than or equal to 0.03 percent of Als: 0.01 to 0.03%, cu:0.02 to 0.05 percent, cr:0.02 to 0.05 percent, and the balance of Fe and other inevitable impurities.

The main components and the process of the invention have the following reasons for the action and control:

the content of C is selected to be 0.02-0.07%, C is a good solid solution strengthening element, but is unfavorable for the formability of the steel plate, and when the content of C is higher, CO bubbles are generated in the process of coating the steel plate, so that the defect of enamel pinholes is caused, and the surface quality of enamel is damaged, therefore, when the content of C is controlled to be 0.02-0.07%, the coating quality of the steel plate can be ensured, and the punching processing of the steel plate is facilitated.

The Mn content of the invention is selected to be 0.10-0.50%, mn is used as a solid solution strengthening element, mnO and MnS inclusion can be formed with O and S to be used as a trap for storing hydrogen, the fishscale resistance of the steel plate is improved, the Mn element content is too low to achieve proper yield strength, when the Mn element content is more than 0.50%, the plasticity of the steel plate is obviously reduced when the Mn element content is too high, the steel plate is not beneficial to processing and use, and simultaneously, the deformation of the steel plate during enameling firing is too large, so the Mn content is 0.10-0.50%.

Si is less than or equal to 0.03 percent, si element can improve the strength of the steel plate, but an oxide film is firstly produced in the enameling process to block the production of an adhesion layer between the steel plate and the enamel, and the enamel adhesion performance is influenced by too high content, so the Si content is controlled below 0.03 percent.

The P content of the invention is selected to be 0.015-0.030%, the P element has no adverse effect on enamel performance, but the welding performance of the steel can be reduced by excessively high content.

The S content of the steel plate is less than or equal to 0.030%, the S is a harmful element in the traditional steel plate, but a proper amount of S and Mn are combined to form MnS inclusions which serve as traps for hydrogen storage, and the scale explosion of the steel plate after being enameled is inhibited.

The Als content is less than or equal to 0.03%, al is strong deoxidizer, and Als is deoxidized product, so the content is controlled below 0.03%.

The Ti content of the invention is selected to be 0.01-0.03%, and the Ti element can form TiC and TiN compounds with C and N elements to form fine precipitated phases, thereby being beneficial to the manufacture of hydrogen traps and improving the enameling performance.

The Cu content of the invention is selected to be 0.02-0.05%, and the proper content of Cu element can improve the adherence of the enameled pressed steel.

The Cr content of the invention is selected to be 0.02-0.05%, and the Cr element is an element capable of improving the surface state of the rolled steel plate, adjusting the roughness of the surface of the steel plate and improving the enamel adhesion.

A cold rolling manufacturing method for producing the high-strength enamel steel by using a low-temperature annealing process comprises the following steps: blast furnace iron making → molten iron pretreatment → converter smelting → RH treatment → continuous casting → slab heating → rough rolling → finish rolling → laminar cooling → coiling → acid rolling → continuous annealing → finishing → inspection → packaging, in the continuous annealing step, a low temperature annealing process is adopted, so that on one hand, energy conservation and emission reduction can be realized, the strength can be increased, on the other hand, the hydrogen storage capacity of the steel plate can be enhanced, and the enameling performance of the steel plate can be improved.

Preferably, in the continuous annealing step, the low-temperature annealing process adopts a low-temperature continuous annealing process, and the annealing temperature is 780-800 ℃.

Preferably, in the continuous annealing step, the speed of the strip steel is controlled to be 160-220 m/min, the flattening elongation is set to be 0.5 +/-0.2%, and the good matching of the strength of the steel plate and the enameling performance can be ensured.

Preferably, in the slab heating step, the heating temperature is 1200-1250 ℃, and the heating time is 120-200 s, so that the steel slab is heated sufficiently, and complete austenitizing is prevented.

Preferably, in the finish rolling step, the finish rolling temperature is 910 to 930 ℃.

Preferably, in the coiling step, the coiling temperature is 600-650 ℃, and the phase is sufficiently precipitated to achieve the function of setting a hydrogen trap.

Preferably, in the acid rolling step, the cold rolling reduction is set to be 53-60%, the rolling force load of the rolling mill is 1900-2100 tons, the thickness precision of the steel plate is high, the plate shape is good, and a wave-shaped curve is not easy to appear.

Compared with the prior art, the invention has the following advantages:

1. the enamel steel has the advantages of convenient component design for large-scale production, low content of Mn, ti and Cr alloy elements, convenient smelting and low molten steel cost;

2. the invention adopts a low-temperature annealing process, so that on one hand, the strength can be increased by energy conservation and emission reduction, on the other hand, the hydrogen storage capacity of the steel plate can be enhanced, and the enameling performance of the steel plate can be improved;

3. the enamel steel produced by the invention has the following metallographic structure: the recrystallized ferrite, the pearlite and a small amount of deformation structure, the yield strength of the steel plate in production is more than 270MPa, the tensile strength is between 300 and 400MPa, the elongation is more than 30 percent, the TH value is more than or equal to 10min/mm on a Q-t curve of a hydrogen permeation test ² 。

Drawings

FIG. 1 is a metallographic structure chart of high-strength enamel steel obtained in example 1 of the present invention.

Detailed Description

The invention is described in further detail below with reference to the figures and the specific embodiments.

Table 1 is a list of chemical compositions for each example of the present invention and comparative example;

table 2 shows the results of the performance tests of the finished products of the examples and comparative examples of the present invention.

Example 1: the chemical components of the corresponding examples are shown in the table 1 according to the weight percentage, and the balance is Fe and other inevitable impurities; the cast blank with the thickness of 230mm is sent into a heating furnace, the heating temperature is 1200 ℃, the heating time is 120s, the finish rolling temperature is 910 ℃, the coiling temperature is 600 ℃, the rolling temperature is 3.5mm, the cold rolling reduction rate is set to be 55%, the rolling force load of a rolling mill is 2000 tons, the cast blank is rolled to a 1.5mm thin plate through cold rolling and acid rolling, the cold rolling enamel steel of the embodiment 1 is prepared after continuous annealing, the annealing temperature is 780 ℃, the leveling elongation is 0.5%, and the cold rolling enamel steel is shown in figure 1 and is a metallographic structure diagram of recrystallized ferrite, pearlite and a small amount of deformation structure.

Example 2: the chemical components of the corresponding examples are shown in the table 1 according to the weight percentage, and the balance is Fe and other inevitable impurities; the casting blank with the thickness of 230mm is sent into a heating furnace, the heating temperature is 1230 ℃, the heating time is 130s, the finish rolling temperature is 920 ℃, the coiling temperature is 620 ℃, the rolling temperature is 2.5mm, the cold rolling reduction rate is set to be 60%, the rolling load of a rolling machine is 2100 tons, the casting blank is rolled to a 1.0mm thin plate by cold rolling acid, and after continuous annealing, the annealing temperature is 790 ℃, the flat elongation is 0.4%, and the cold-rolled enamel steel of the embodiment 2 is prepared.

Example 3: the chemical components of the corresponding examples are shown in the table 1 according to the weight percentage, and the balance is Fe and other inevitable impurities; the casting blank with the thickness of 230mm is sent into a heating furnace, the heating temperature is 1220 ℃, the heating time is 200s, the finish rolling temperature is 930 ℃, the coiling temperature is 610 ℃, the rolling temperature is 2.5mm, the cold rolling reduction rate is set to be 58%, the rolling force load of a rolling mill is 2000 tons, the casting blank is rolled to a 1.0mm thin plate through cold rolling and acid rolling, and the cold rolling enamel steel of the embodiment 3 is prepared after continuous annealing, the annealing temperature is 790 ℃, and the flat elongation is 0.5%.

Example 4: the chemical components of the corresponding examples are shown in the table 1 according to the weight percentage, and the balance is Fe and other inevitable impurities; the casting blank with the thickness of 230mm is sent into a heating furnace, the heating temperature is 1210 ℃, the cold rolling reduction rate is set to be 53%, the rolling force load of a rolling mill is 2000 tons, the heating time is 160s, the final rolling temperature is 920 ℃, the coiling temperature is 620 ℃, the rolling is carried out to 3.5mm, the rolling is carried out to 1.5mm thin plate through cold rolling and acid rolling, the continuous annealing is carried out, the annealing temperature is 800 ℃, the flat elongation is 0.6%, and the cold-rolled enamel steel of the embodiment 4 is prepared.

Example 5: the chemical components of the corresponding examples are shown in the table 1 according to the weight percentage, and the balance is Fe and other inevitable impurities; the casting blank with the thickness of 230mm is sent into a heating furnace, the heating temperature is 1200 ℃, the heating time is 140s, the finish rolling temperature is 920 ℃, the coiling temperature is 630 ℃, the rolling temperature is 4.5mm, the cold rolling reduction rate is set to be 55%, the rolling force load of a rolling machine is 1900 tons, the casting blank is rolled to a 2.0mm thin plate by cold rolling acid, and after continuous annealing, the annealing temperature is 790 ℃, the flat elongation is 0.7%, and the cold-rolled enamel steel of the embodiment 5 is prepared.

Example 6: the chemical components of the corresponding examples are shown in the table 1 according to the weight percentage, and the balance is Fe and other inevitable impurities; the cast blank with the thickness of 230mm is sent into a heating furnace, the heating temperature is 1250 ℃, the heating time is 130s, the finish rolling temperature is 910 ℃, the coiling temperature is 650 ℃, the rolling temperature is 3.8mm, the cold rolling reduction rate is set to be 55%, the rolling force load of a rolling mill is 2000 tons, the cast blank is rolled to a 1.75mm thin plate by cold rolling and acid rolling, and the cold rolling enamel steel of the embodiment 6 is prepared after continuous annealing, the annealing temperature is 780 ℃ and the flat elongation is 0.3%.

Comparative example 1: the chemical components of the corresponding examples are shown in the table 1 according to the weight percentage, and the balance is Fe and other inevitable impurities; and (2) feeding the casting blank with the thickness of 230mm into a heating furnace, heating the casting blank at 1250 ℃, heating the casting blank for 120s, rolling the casting blank to 2.5mm at the final rolling temperature of 950 ℃, rolling the casting blank to the coiling temperature of 700 ℃, setting the cold rolling reduction rate to be 65 percent, rolling the casting blank to a sheet with the rolling force load of 2100 tons, rolling the sheet to 1.0mm by cold rolling acid, continuously annealing the sheet at the annealing temperature of 830 ℃, and obtaining the cold-rolled enamel steel of the comparative example 1, wherein the flat elongation of the sheet is 0.5 percent.

Comparative example 2: the chemical components of the corresponding examples are shown in the table 1 according to the weight percentage, and the balance is Fe and other inevitable impurities; and (2) feeding the casting blank with the thickness of 230mm into a heating furnace, heating the casting blank at 1250 ℃, heating the casting blank for 120s, finishing the rolling at 960 ℃, coiling the casting blank at 720 ℃, rolling the casting blank to 3.5mm, setting the cold rolling reduction rate to 55 percent, rolling the casting blank to a 1.5mm thin plate by using a rolling machine with the rolling force load of 2000 tons, and continuously annealing the casting blank at 850 ℃ with the flat elongation of 0.5 percent to prepare the cold-rolled enamel steel of the comparative example 2.

Comparative example 3: the chemical components of the corresponding examples are shown in the table 1 according to the weight percentage, and the balance is Fe and other inevitable impurities; and (3) feeding the casting blank with the thickness of 230mm into a heating furnace, heating the casting blank at 1250 ℃, heating the casting blank for 120s, rolling the casting blank to 3.5mm at the final rolling temperature of 940 ℃, rolling the casting blank to a coiling temperature of 680 ℃, setting the cold rolling reduction rate to be 60 percent, rolling the casting blank to a sheet with the rolling force load of 2000 tons through cold rolling and acid rolling, continuously annealing the sheet at the annealing temperature of 850 ℃ and the flat elongation of 0.5 percent to prepare the cold-rolled enamel steel of the comparative example 3.

The cold-rolled enamel steels prepared in examples 1 to 6 and comparative examples 1 to 3 were examined, and as shown in table 2, product performance data of the cold-rolled enamel steels were obtained.

As can be seen from Table 2, the cold-rolled enamel steel produced by the method has good scale-explosion resistance and mechanical properties, and meets the performance requirements of most of the current industrial requirements on the enamel steel.

TABLE 1 list of chemical compositions of inventive examples and comparative examples (%)

TABLE 2 test results of the properties of the finished products of the examples of the present invention and the comparative examples

Claims

1. The high-strength enamel steel is characterized in that: the weight percentage of the chemical components is as follows: c:0.02 to 0.07%, mn: 0.10-0.50%, si is less than or equal to 0.03%, P: 0.015-0.030 percent of Ti, less than or equal to 0.030 percent of S, less than or equal to 0.03 percent of Als: 0.01 to 0.03%, cu:0.02 to 0.05 percent, cr:0.02 to 0.05 percent, and the balance of Fe and other inevitable impurities.

2. A cold rolling manufacturing method of the high strength enamel steel as claimed in claim 1 using a low temperature annealing process, characterized in that: the method comprises the following steps: blast furnace iron making → molten iron pretreatment → converter smelting → RH treatment → continuous casting → slab heating → rough rolling → finish rolling → laminar cooling → coiling → acid rolling → continuous annealing → finishing → inspection → packaging, and in the continuous annealing step, a low temperature annealing process is adopted.

3. The cold rolling manufacturing method of the high strength enamel steel using the low temperature annealing process according to claim 2, characterized in that: in the continuous annealing step, the low-temperature annealing process adopts a low-temperature continuous annealing process, and the annealing temperature is 780-800 ℃.

4. The cold rolling method for manufacturing high-strength enamel steel using a low temperature annealing process according to claim 3, wherein: in the continuous annealing step, the speed of the strip steel is controlled to be 160-220 m/min, and the flat elongation is set to be 0.5 +/-0.2%.

5. The cold rolling method for manufacturing high strength enamelled steel according to claim 2, characterised in that it comprises the following steps: in the slab heating step, the heating temperature is 1200-1250 ℃, and the heating time is 120-200 s.

6. The cold rolling method for manufacturing high strength enamelled steel according to claim 2, characterised in that it comprises the following steps: in the finish rolling step, the finish rolling temperature is 910 to 930 ℃.

7. The cold rolling manufacturing method of the high strength enamel steel using the low temperature annealing process according to claim 2, characterized in that: in the coiling step, the coiling temperature is 600-650 ℃.

8. The cold rolling manufacturing method of the high strength enamel steel using the low temperature annealing process according to claim 2, characterized in that: in the acid rolling step, the cold rolling reduction is set to be 53-60%, and the rolling force load of a rolling mill is 1900-2100 tons.