WO2014015823A1

WO2014015823A1 - Ceramic-enameling steel and manufacturing method therefor

Info

Publication number: WO2014015823A1
Application number: PCT/CN2013/080157
Authority: WO
Inventors: 孙全社; 郑建忠; 居发亮; 张志超; 刘玉章
Original assignee: 宝山钢铁股份有限公司
Priority date: 2012-07-27
Filing date: 2013-07-26
Publication date: 2014-01-30
Also published as: CN102747309A

Abstract

A ceramic-enameling steel. The chemical element contents thereof in mass percentage are: C ≤ 0.020%, Si ≤ 0.05%, Mn: between 0.10% and 0.50%, P ≤ 0.03%, S: between 0.003% and 0.050%, Al: between 0.001% and 0.03%, N: between 0.001% and 0.015%, O: between 0.005% and 0.050%, Ca ≤ 0.005%, Mg ≤ 0.005%, Cu ≤ 0.10%, Cr ≤ 0.10%, Ni ≤ 0.10%, Mo ≤ 0.10%; any one among B: between 0.0005% and 0.003%, Nb ≤ 0.01%, V ≤ 0.02%, and Ti: between 0.001% and 0.05% is added; the remainder is Fe and other unavoidable impurities, where N(%) × Ti(%) ≤ 3 × 10^-4. Also disclosed is a method for manufacturing the ceramic-enameling steel. The ceramic-enameling steel has excellent overall properties.

Description

Enamel steel and manufacturing method thereof

Technical field

The present invention relates to steel grades and a method of manufacturing the same, and more particularly to a steel for enamel and a method of manufacturing the same. Background technique

An enamel process is a coating process in which the glaze is directly applied without glazing and the glaze is fired on the steel plate. The difference between an enamel process and a two-coating process is as follows: Two coatings first need to coat a bottom glaze on a bottom plate such as a steel plate, and then a layer of glaze on the bottom glaze, bottom glaze and steel plate bottom. And the bonding strength between the bottom glaze and the surface glaze is good, and is beneficial to improve the anti-scale explosion performance. Therefore, in comparison, the application of one coat to the adhesion between the steel plate bottom and the porcelain layer, the anti-scale explosion, and the prevention of defects such as bubbles and black spots are higher because of the scale explosion generated by the steel plate during the enamel process. Defects such as poor adhesion and air bubbles can seriously affect the quality of enamel products.

The scale explosion is caused by the water or crystal water in the porcelain slurry reacting with iron and carbon on the surface of the steel sheet to form atomic hydrogen. During the cooling process, the solubility of hydrogen in the steel drops sharply. There is not enough hydrogen absorption place, that is, the hydrogen storage trap, the hydrogen atoms will escape in a large amount, and the area of the steel plate and the porcelain layer will gather, and to a certain extent, the surface of the porcelain layer will be broken with a large pressure, and the scale will be peeled off.

Adhesion is an indicator used to measure the firmness of the bond between a steel plate and a porcelain layer. If the adhesion is poor, the porcelain layer is easily peeled off from the surface of the steel sheet.

The pinhole is a defect caused by the reaction of the crystal water in the porcelain slurry with the carbon in the steel at a high temperature to form a bubble, and the bubble escapes through the porcelain layer to form a pinhole shape.

In addition to the requirements for adhesion, anti-scale explosion, pinhole defects, etc., the enamel is easy to produce bubbles and black spots during the firing process. Therefore, the enamel is also required to be produced during the firing process. There are fewer bubbles to avoid similar defects.

In order to avoid the occurrence of scale explosion defects, the prior art generally forms a sufficient amount of hydrogen storage traps in steel, such as microvoids, inclusions, dislocations, grain boundaries, etc., or by adding a sufficient amount of titanium to make titanium in steel. Inclusions are formed in the middle.

Chinese patent document with the publication number CN 101535517A, published on September 16, 2009 A steel sheet for enamel which is excellent in scale resistance and a method for producing the same is disclosed. In this embodiment, Nb: 0.055 to 0.25% is added, and V: 0.003 to 0.15% is preferably added. In the continuous casting, it is necessary to control the cooling rate at the time of solidification of the slab, that is, the cooling rate at the time of solidification of 1/4 of the thickness of the slab is 10 ° C / s, and the cooling of the slab is highly demanded.

Japanese Patent Publication No. JP2006-37215A, published on Feb. 9, 2006, discloses an enamel steel sheet having a good adhesion enamel, a method for producing the same, and an enamel product thereof. The technical solution is low carbon or ultra low. To the carbon steel, a precious alloying element of at least one of Cu: 0.051 to 8.0%, Ni: 0.051 to 8.0%, Co: 0.051 to 8.0%, and Mo: 0.051 to 8.0% is added, and the alloying element is added in a relatively high amount. , but did not add Ca and Mg. Summary of the invention

An object of the present invention is to provide a steel for enamel and a method for producing the same, which should have good anti-scale and bubble resistance, and should also be able to overcome black spot defects, and the enamel steel should also have High strength, good formability and excellent coating properties.

In order to achieve the above object, the present invention provides a steel for enamel, wherein the chemical element mass percentage ratio control is: 0.020%; Si^O.05%; Μη: 0·10~0·50%; Ρ^ Ο.03%; S: 0·003~0·050%; Α1: 0·001~0·03%; Ν: 0.001~0.015%; 0: 0·005~0·050%; Ca^ 0.005%; Mg^ 0.005%; Cu^O.10%; Cr^O.10%; Ni^O.10%; Mo^0.10%; also contains B: 0.0005~3%, Nb 0.01%, V^O.02 %, Ti: at least one of 0·001 to 0·05%, and wherein Ν (%) X Ti (%) 3 X 10_ ⁴ ; the balance is Fe and other unavoidable impurities.

The design principle of the ratio of each chemical element in the technical solution is as follows:

Carbon: In general, the lower the carbon content, the better the formability. In addition, in the technical solution, the carbon content in the steel plays an important role on the surface quality of the enamel. When the carbon content in the steel is too high, more carbon monoxide is formed in the enamel process, and the number of bubbles formed is large and bulky. In severe cases, pinhole defects may occur on the surface of the enamel, which may damage the quality of the enamel. Therefore, the inventors have conducted extensive tests and verification to control the carbon content to 0.02%.

Silicon: Silicon is easy to form oxides. In the present invention, when the silicon content is high, a large amount of inclusions having poor ductility are easily formed in hot rolling, and the workability of the steel is deteriorated during the rolling, so that the silicon content is controlled to 0.05%. Manganese: Manganese is a deoxidizing element that controls the oxygen content of steel. In addition to manganese oxide, manganese can also react with sulfur to form manganese sulfide or manganese oxysulfide. The simple manganese sulfide inclusions are distributed in a slender strip after rolling, which affects the lateral properties of the steel sheet. In the present technical solution, manganese elements and a small amount of titanium elements in the steel form composite spherical inclusions such as manganese sulfide titanium, etc., and such inclusions can significantly improve the adverse effect of manganese sulfide on the processability. However, if the manganese content is too high, the adhesion property of the enamel is affected, and bubbles and black spots are easily generated, so the content of manganese is controlled to be 0.10 to 0.50%.

Phosphorus: Phosphorus is easily segregated at the grain boundaries in steel, and bubbles and black spots are easily generated during simmering, which affects the surface quality of enamel. Therefore, in the present technical solution, phosphorus is a harmful element, and the lower the content, the better.

Sulfur: Sulfur is generally a harmful element in steel, but in this technical solution, an appropriate amount of sulfur element plays a beneficial role. Sulfur can not only form manganese sulfide with manganese, but also form titanium sulfide with titanium or the like, which is advantageous for improving the anti-scale explosion performance, so the sulfur content is designed to be 0.003 to 0.050%.

Aluminium: Aluminum is a strong deoxidizing element. A high aluminum content leads to a decrease in the oxygen content of the steel. Due to the poor plasticity of alumina inclusions, and the large amount of alumina inclusions can seriously impair the processing properties of steel. In the steel of the present invention, since a certain amount of oxygen needs to be retained, the aluminum content should not be too high, and it is controlled to be 0.001 to 0.03%.

Nitrogen: In the present technical solution, after the titanium element is added to the steel, nitrogen preferentially forms a titanium nitride compound than carbon and sulfur, which is advantageous for improving the anti-scale resistance. At the same time, titanium nitride is also beneficial for suppressing the growth of ferrite grains, on the one hand suppressing ferrite grain growth during hot rolling and cold rolling annealing, and on the other hand preventing ferrite during high temperature firing. Abnormal growth of bulk crystallites. However, since titanium nitride is formed at a high temperature or even in a molten steel, when the contents of nitrogen and titanium are both high, the solubility product of nitrogen and titanium is large, and the formation temperature of titanium nitride is high, and nitrogen is formed. The particles of titanium will become larger. In order to avoid the formation of coarse titanium nitride, nitrogen and titanium should be controlled at Ν(%:>*Τ %) 3 Χ 1(Τ ⁴ . This not only makes the formed titanium nitride particles fine and evenly distributed, but also improves Anti-scale explosion performance and inhibition of ferrite grain growth. Considering the nitrogen content at 0.001~0.015%.

Oxygen: In this technical solution, oxygen directly affects the anti-scale and processing properties of steel. Controlling the oxygen content in the steel not only facilitates decarburization, but also oxygen and various elements are easily combined to form an oxide, which is favorable for forming a certain amount of oxide. Oxygen is an essential element in the present invention, but its content is also related to titanium. In order to prevent the formation of coarse oxide inclusions in the steel, it is necessary to control the oxygen content to be 0.05% or less, so that the oxygen content in the present invention is 0.005 to 0.05%.

Calcium and Magnesium: Both calcium and magnesium can improve the morphology of inclusions such as manganese sulfide in steel, avoiding the formation of long Strip-shaped inclusions help to improve the plasticity of the steel. Therefore, both calcium and magnesium were controlled to 0.005%. Copper: In the present technical solution, copper is a residual element. The copper content is too high and the formability is lowered.

Chromium: In the present technical solution, chromium is a residual element. Chromium is also prone to form oxides in steel, which makes the surface of the steel sheet resistant to pickling. When the content is too high, it not only affects the adhesion between the porcelain layer and the steel sheet but also increases the firing temperature of the steel sheet.

Nickel: In the present technical solution, nickel is a residual element. Nickel can form oxides in steel, and especially nickel oxide formed on the surface makes the surface of the steel sheet resistant to pickling. When the nickel content is too high, it is not only unfavorable for improving the adhesion performance of the steel sheet, but also increases the firing temperature of the steel sheet.

Molybdenum: In the present technical solution, molybdenum is also a residual element. Too high a molybdenum content increases the corrosion resistance of the steel sheet and affects the pickling speed of the steel sheet.

Boron: Boron is easily segregated at grain boundaries, and in the present technical solution, it can improve the resistance to scale and adhesion. Although boron has the above-mentioned beneficial effects, in the present embodiment, if the boron content is too high, cracks are generated on the cast slab during the continuous casting process. Therefore, the inventors controlled the boron content to 0.0005 to 0.003%.

铌: In the present technical solution, although it is advantageous for improving the anti-scale explosion, the niobium is a precious metal, and from the viewpoint of cost, a large amount of niobium is not particularly added. Residual ruthenium is allowed in the present invention.

Vanadium: In this technical solution, vanadium can combine with nitrogen and carbon to precipitate vanadium nitride and vanadium carbide. These second phase particles not only act as a strengthening matrix, but also effectively prevent the occurrence of scale explosion in the enamel process. trap. When the nitrogen content is high, vanadium is mainly combined with nitrogen at a high temperature to precipitate vanadium nitride, which has good strengthening effect and anti-scale effect. Considering comprehensively, the vanadium content is controlled to 0.02%.

Titanium: Titanium is a strong carbon and nitride forming element. Titanium can be combined with oxygen, carbon, nitrogen and sulfur to form a single compound or a composite compound. Titanium fixes carbon, nitrogen and sulfur to improve the plasticity and scale resistance of the steel sheet. Titanium is relatively stable with oxygen and nitrogen compounds, is not susceptible to thermal processing and process parameters during enamel, and is also very effective in improving pinhole defects and adhesion properties of steel sheets. However, titanium and oxygen are extremely easy to form compounds. If the titanium and oxygen content in the steel is too high, coarse oxide inclusions are formed, which seriously impairs the plasticity of the steel. Therefore, the technical solution controls the titanium content to be 0.001 to 0.05%.

Accordingly, the present invention also provides a method of manufacturing the steel for enamel, which comprises the following steps:

(1) smelting, vacuum degassing;

(2) casting;

(3) hot rolling of the slab: controlling the hot rolling heating temperature to 950~1200 °C, divided into two stages The first stage is rolled in the austenite zone, the final rolling temperature is 900~1100 °C, the second stage is rolled in the ferrite zone, and the finishing temperature (FT, °C) satisfies the formula 600 FT -9250xC + 900, where C is the mass percentage of the element;

(4) taking up;

(5) pickling to remove scale;

(6) cold rolling;

(7) Annealing.

Preferably, in the above method for manufacturing enamel steel, iron oxide powder is added during the smelting process of the step (1), and the iron oxide powder is added in an amount of 0.40 to 2.50 kg per ton of steel, and is sufficiently stirred after the addition, and the stirring time is not For more than 30 minutes, make O 010~0.050% in molten steel.

Preferably, in the method for producing enamel steel, after the vacuum degassing of the step (1), nitrogen is blown in the method for producing the enamel steel, and the casting method in the step (3) is continuous casting or molding. Cast. In the above method for producing enamel steel, the coiling temperature in the step (4) is 500 to 800 °C. In the above method for producing enamel steel, the total reduction ratio of cold rolling in the step (6) is controlled to be 60% or more.

In the above method for producing enamel steel, the annealing temperature in the step (7) is 650 to 900 ° C, and the annealing time is 2 minutes to 25 hours.

In the above technical solution, the smelting and vacuum degassing steps ensure that the basic chemical composition of the molten steel meets the requirements, decarburizes and removes harmful gases such as hydrogen in the steel, and controls H<2 ppm in the steel by stirring with argon blowing. Add the necessary alloying elements to adjust the composition, especially to control carbon, nitrogen, sulfur and oxygen, because they can form various compounds to improve the anti-scale resistance of steel, but excessive inclusions will damage steel. Formability. When the oxygen content in the steel sheet is required to be high, the total oxygen content in the steel can be stably controlled by blowing oxygen or adding iron oxide powder during the smelting process to achieve the desired target value. Among them, the addition of iron oxide powder is the preferred technical solution, because when the carbon content in the steel is high, the oxygen blowing method is used to increase the oxygen content, which is prone to boiling during the casting process, and excessive boiling easily leads to the connection. Casting problems such as steel leakage during casting, and the method of adding iron oxide powder can avoid excessive boiling of molten steel. In addition, the addition of iron oxide powder to supplement and increase the oxygen content in the steel can shorten the refining time and save costs. In addition, nitrogen can be increased in the steel by blowing nitrogen or adding ferromanganese nitride after vacuum degassing. Blowing nitrogen is the preferred technical side This is because the addition of ferromanganese iron increases carbon, so for steels with extremely low carbon requirements, nitrogen blowing can prevent carbon addition, and nitrogen blowing can save costs and stabilize nitrogen in steel.

When low carbon steel or very low carbon steel is used in the conventional hot rolling process, ferrite grains are generally large. Therefore, in the present technical solution, the hot rolling adopts two-stage rolling, the first stage is rolling in the austenite region, and the second stage is rolling in the ferrite region. Because the second stage is rolled in the ferrite body, more deformation energy can be stored, which is beneficial to refining the ferrite grains and significantly improving the strength of the steel plate, which overcomes the difficulty in refining the ultra-low carbon steel grains and the strength. Low problem. And the refined ferrite grains are more beneficial to improve the yield strength and steel ductility after cold rolling and annealing. The heating temperature of the slab rolled in the ferritic zone is lower than that of the conventional rolling, so that the heating energy consumption can be greatly reduced and the heating furnace output can be increased. Low-temperature rolling also reduces the production of secondary iron oxide scale, improves the surface quality of hot rolled products, and greatly reduces production costs. By rolling in the ferritic zone, the hot rolled structure of the steel sheet and the structure after cold rolling and annealing are both ferrite or ferrite + cementite. At the same time, both the first and second stages of rolling use lower temperatures to reduce energy consumption.

In the technical solution, as the cold rolling reduction rate is increased, the distortion inside the steel sheet can be increased to store sufficient distortion energy in the steel, so the use of a higher cold rolling reduction ratio is advantageous for the annealing after annealing. Crystallization and texture development.

In the technical solution, the annealing may be selected by continuous annealing or hood annealing. The annealing process involved in the present technical solution ensures the complete development of the ferrite structure in the steel to complete recrystallization, grain growth and recrystallization texture.

Compared with the prior art, the present invention has the following beneficial effects by adopting the above technical solutions:

(1) The enamel steel manufactured by the technical scheme can achieve the comprehensive performance requirements: yield strength: RpO.2^180 MPa, tensile strength: Rm 270 MPa; elongation: A ₈ . 36%, with good plasticity and high strength;

(2) The enamel steel according to the present invention has excellent coating properties, and has the advantages of resistance to scale explosion, and resistance to air bubbles and black spots;

(3) The enamel steel according to the present invention has excellent moldability and can be processed into various complicated enamel members, and has high strength and improved resistance to deformation at high temperature firing. DRAWINGS

Figure 1 shows the metallographic structure of an enamel steel sheet of Example A of the present invention. detailed description

Example A-H:

The enamel steel of the present invention was produced in accordance with the following procedure, and the chemical elements of the respective examples were controlled as shown in Table 1 (see Table 2 for specific process parameters of each example):

(1) Smelting, vacuum degassing: Add iron oxide powder during the smelting process. The amount of iron oxide powder added is 0.40~2.50kg per ton of steel. After mixing, stir well. The stirring time is no more than 30 minutes, so that the steel O 010~ 0.050%; argon gas agitation after vacuum degassing, control H<2ppm in steel, when N ^ (0.002~0.015wt%), blow nitrogen after vacuum degassing treatment;

(2) continuous casting;

(3) hot rolling of the slab: controlling the hot rolling heating temperature to 950~1200 °C, rolling in two stages, the first stage rolling in the austenite zone, the temperature is 900~1100 °C, the second stage Rolling in the ferritic zone, the finishing temperature (FT, °C) satisfies the formula 600 FT -9250xC +900, where C is the mass percentage of the element;

(4) Coiling: The coiling temperature is 500~800 °C;

(5) pickling to remove scale;

(6) Cold rolling: The total reduction ratio is controlled above 60%;

(7) Annealing: The annealing temperature is 650 to 900 ° C, and the annealing time is 2 minutes to 25 hours. Combined with Table 2 and Table 1, it can be seen that the above-mentioned composition design and process parameters are used for smelting and processing, and the yield strength of the finished steel sheet is 180^03⁄4, the tensile strength is 270^^&, and the elongation is A ₈ o ^36%. Has good plasticity and high strength. After double-sided enamel, there is no scale explosion phenomenon, and the adhesion between the steel plate and the enamel is excellent, and it has good properties such as resistance to bubbles and black spots.

As can be seen from Fig. 1, the microstructure in the embodiment A of the present invention is a ferrite structure, and a small amount of inclusions are distributed in the grains or grain boundaries of the ferrite. 134582

Table 1. Chemical composition ratio (% by mass, wt%) of various examples of the present invention

Table 2. Specific process parameters and performance of various embodiments of the present invention

Claims

Claim

An enamel steel characterized in that the chemical element mass percentage thereof is:

0.020%;

Si^O.05%;

Mm 0· 10~0·50%;

Ρ^Ο.03%;

S: 0·003~0·050%;

Α1: 0.001~0·03%;

Ν: 0·001~0·015%;

0: 0·005~0·050%;

Ca^ 0.005%;

Mg^ 0.005%;

Cu^O.10%;

Cr^O.10%;

Ni^O.10%;

Mo ^0.10%;

B: 0·0005~0·003%, Nb^O.01%, V^O.02%, Ti: at least one of 0.001 to 0.05%;

The balance is Fe and other unavoidable impurities;

Where N (%) X Ti ( %) 3 X 10-4.

The method of producing an enamel steel according to claim 1, comprising the following steps:

1) smelting, vacuum degassing;

2) casting;

3) hot rolling of the slab: controlling the hot rolling heating temperature to 950~1200 ° C, rolling in two stages, the first stage rolling in the austenite zone, the final rolling temperature is 900~1100 ° C, the second The stage is rolled in the ferritic zone, and the finishing temperature FT satisfies the formula: 600 FT -9250 XC +900, where C is the mass percentage of the element;

4) winding up;

5) pickling; 6) cold rolling;

7) Annealing.

The method for producing enamel steel according to claim 2, wherein iron oxide powder is added during the smelting process of the step (1), and the amount of the iron oxide powder is 0.40 to 2.50 per ton of steel. Kg, stir well after the addition, the stirring time is not more than 30 minutes, so that the molten steel O is 0.010~0.050%.

The method for producing an enamel steel according to claim 2, wherein the nitrogen gas is blown after the vacuum degassing of the step (1).

The method of producing an enamel steel according to claim 2, wherein the casting method in the step (3) is continuous casting or die casting.

The method of producing an enamel steel according to claim 2, wherein the coiling temperature in the step (4) is 500 to 800 °C.

The method of producing an enamel steel according to claim 2, wherein the total reduction ratio of the cold rolling in the step (6) is controlled to be 60% or more.

The method for producing an enamel steel according to claim 2, wherein the annealing temperature in the step (7) is 650 to 900 ° C, and the annealing time is 2 minutes to 25 hours.