WO2020169077A1

WO2020169077A1 - Low-cost weathering steel and production method thereof

Info

Publication number: WO2020169077A1
Application number: PCT/CN2020/076118
Authority: WO
Inventors: 李化龙; 陈爱华; 冯庆晓; 施一新; 刘俭; 马毅; 周东升; 朱以海; 刘新院; 李婷婷; 李霞
Original assignee: 江苏沙钢集团有限公司; 江苏省沙钢钢铁研究院有限公司; 张家港中美超薄带科技有限公司
Priority date: 2019-02-21
Filing date: 2020-02-21
Publication date: 2020-08-27
Also published as: CN109881090A

Abstract

Low-cost weathering steel and a production method thereof. The weathering steel comprises components of: less than or equal to 0.03 of C, 0.10-0.50 of Si, 0.50-1.50 of Mn, 0.07-1.50 of P, less than or equal to 0.008 of N, less than or equal to 0.003 of S, less than 0.40 of Cu, less than 0.45 of Cr, and the balance being Fe and inevitable impurities; The protection method comprises the following steps: smelting; carrying out thin-strip continuous casting; continuously casting smelting qualified molten steel into a cast strip having the thickness of 1.4-2.5mm by means of a pair of casting rolls which oppositely rotate, and controlling the casting temperature of the molten steel at 1580-1650°C; carrying out online hot rolling on the cast strip, wherein the cast strip is rolled into a hot rolled thin strip with the thickness of 0.7 to 2.0 mm by means of one-pass hot rolling, the hot rolling reduction is 10-70%, and the temperature of the cast strip entering into a hot rolling mill is greater than 900°C; and after rolling, cooling and reeling, the hot rolled strip steel being cooled to 400 to 500°C by aerosol to obtain a uniform acicular ferrite structure, and soon afterwards reeling into a roll. The yield strength of the low-cost weathering steel is above 345 MPa, and the elongation of the low-cost weathering steel is above 23%. The production control has the characteristics of short production process, low production cost and alloy cost, and excellent surface quality and shape of the hot-rolled strip steel.

Description

Low-cost weathering steel and production method thereof

Technical field

The invention belongs to the field of low-alloy steel manufacturing, and specifically relates to a weathering steel strip with short process flow, low production cost, low alloy cost and excellent surface quality and a production method thereof.

Background technique

Weathering steel has high strength, high toughness, weldability, fire resistance, wear resistance and other properties, and has high atmospheric corrosion resistance in a variety of climatic environments. It is a green and environmentally friendly steel material and is widely used Production of tanks, vehicles, construction, bridges, pipelines, machinery and other industries.

At present, the main process of producing weathering steel is: converter or electric furnace-refining-thick or thin slab continuous casting-heating furnace heating-rolling-coiling, the production process is long, resource consumption is large, and waste The waste water discharge is large and the production cost is high. Weathering steel contains a high content of Cu. During the heating of the cast slab and the subsequent multi-pass rolling process, the Cu element is prone to segregate in the grain boundary due to its low melting point, causing the steel plate to "hot embrittlement", which seriously affects the performance of the steel plate. Surface Quality. In addition, due to the high content of P element in weathering steel, it is easy to cause continuous casting cracks during the continuous casting process, which affects the subsequent rolling and the final mechanical properties of the steel plate. In order to make weathering steel have higher strength, many steel plants add Nb, Ti, V and other microalloying elements in the composition design of weathering steel, which makes the cost of weathering steel higher. Therefore, it is of great significance to carry out research on low-cost, high-quality thin gauge weathering steel and its production technology.

Patent document CN101671797A discloses a high-phosphorus weathering steel cast-rolled strip with negative phosphorus segregation on the surface and a preparation method thereof. The strength is improved by adding 0.30-1.25wt% of Cr, and 0.12-0.65wt% of Ni is added to improve weathering resistance. Performance, the content of microalloying elements is higher, and the alloy cost is higher. Patent document CN104313491B discloses a weathering steel hot-rolled strip without P segregation and its manufacturing method. It adds 0.6-0.8wt% of Cr and trace B elements to improve strength, and adds 0.03-0.11wt% of Ni. Improve weather resistance and higher alloy cost. Patent document CN107881429A discloses a hot-rolled high-strength weathering steel and a manufacturing method thereof. The strength is improved by adding 0.09-0.11wt% of Ti element. Patent document CN107354391A discloses a weathering steel which is added with various microalloying elements, the Ti content is 0.06-0.79wt%, the Nb element is 0.035-0.052wt%, and the V element is 0.025-0.080wt%.

Summary of the invention

Aiming at the problems of existing weathering steels that are prone to continuous casting cracks, poor surface quality, high alloy costs, long production processes, and high production costs, the present invention provides a new low-cost weathering steel and its production method, which adopts thin strips Casting and rolling greatly shorten the production process; through the control of cooling temperature and cooling rate after strip rolling, the strength of weathering steel is improved on the basis of reducing alloy cost; through continuous casting temperature control and alloy content design guarantee Improve the surface quality and weather resistance of strip steel.

In order to achieve the above objective, on the one hand, the present invention discloses a low-cost weathering steel production method, which is carried out according to the following steps:

(1) Smelting

The chemical composition of molten steel is: C≤0.03wt%, Si: 0.10-0.50wt%, Mn: 0.50-1.50wt%, P: 0.07-1.50wt%, N≤0.008wt%, S≤0.003wt%, Cu<0.40 wt%, Cr<0.45wt%, the rest is Fe and unavoidable impurities;

(2) Thin strip continuous casting

The qualified molten steel is continuously cast into a casting belt with a thickness of 1.4-2.5mm through a pair of oppositely rotating casting rolls;

(3) On-line hot rolling of cast strip

The cast strip is hot-rolled into hot-rolled thin strip after one pass;

(4) Cooling and coiling after rolling

The hot-rolled steel strip is cooled by aerosol and coiled into coils.

According to the low-cost weathering steel production method of the present invention, preferably, the molten steel casting temperature is controlled at 1580°C-1650°C.

According to the low-cost weathering steel production method of the present invention, preferably, the cast strip is hot rolled into a thin strip steel after only one pass.

According to the low-cost weathering steel production method of the present invention, preferably, the reduction of the cast strip after hot rolling by the hot rolling mill is 10-70%.

According to the low-cost weathering steel production method of the present invention, preferably, the temperature of the cast strip before entering the hot rolling mill is above 900°C.

According to the low-cost weathering steel production method of the present invention, preferably, the cast strip is hot-rolled to form a hot-rolled thin strip with a thickness of 0.7-2.0 mm.

According to the low-cost weathering steel production method of the present invention, preferably, the hot-rolled thin strip is cooled to 400-500°C through aerosol, and the cooling rate is 30-100°C/s.

According to the low-cost weathering steel production method of the present invention, preferably, after the hot-rolled thin steel strip is cooled, the microstructure of the strip steel is a uniform acicular ferrite structure.

In order to achieve the above objective, on the other hand, the present invention also discloses a low-cost weathering steel, which is produced using the aforementioned low-cost weathering steel production method.

According to a low-cost weathering steel production method of the present invention, preferably, the yield strength of the hot-rolled thin strip steel is more than 345MPa, the elongation is more than 23%, and the microstructure of the strip steel is a uniform acicular ferrite structure .

In order to achieve the above objective, in another aspect, the present invention also discloses a low-cost weathering steel, the chemical composition of the steel includes: C≤0.03wt%, Si: 0.10-0.50wt%, Mn: 0.50-1.50wt%, P : 0.07-1.50wt%, N≤0.008wt%, S≤0.003wt%, Cu<0.40wt%, Cr<0.45wt%, the rest is Fe and unavoidable impurities.

Beneficial technical effect

Compared with the existing technology, the features and beneficial technical effects of the present invention include at least:

(1) The range of C content in weathering steel is controlled, so as to control the transformation process of solid phase transformation during continuous casting of thin strip and avoid the occurrence of surface cracks in continuous casting;

(2) By increasing the cooling rate after hot rolling of the strip, reducing the final cooling temperature of the strip, controlling the final structure of the strip, and improving the strength of the weathering steel;

(3) There is no need to add Nb, Ti, V and other microalloys, which reduces the alloy cost of weathering steel;

(4) By adding Mn element, the stability of austenite during continuous casting is improved, the cracks in the as-cast state are avoided, and the strength of weathering steel is also improved;

(5) Through strict control of the content of P and Cr, the weather resistance of weathering steel is ensured, and the occurrence of continuous casting cracks is avoided;

(6) The heating furnace and the multi-pass hot rolling process of traditional hot rolling and thin slab continuous casting and rolling are reduced, and the production cost of weathering steel is reduced.

Description of the drawings

In order to explain the technical solutions of the embodiments of the present invention more clearly, the drawings of the embodiments will be briefly introduced below. Obviously, the drawings in the following description only relate to some embodiments of the present invention, but do not limit the present invention.

Figure 1 is the metallographic structure of the low-cost weathering steel according to the present invention.

detailed description

In order to make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the described embodiments of the present invention, all other embodiments obtained by a person of ordinary skill in the art without creative work shall fall within the protection scope of the present invention.

Unless otherwise defined, the technical terms or scientific terms used in the present disclosure shall be the ordinary meanings understood by those with ordinary skills in the field to which the present invention belongs.

Example 1

This embodiment follows the following steps:

(1) Smelting

The chemical composition of molten steel is: C: 0.023wt%, Si: 0.20wt%, Mn: 1.20wt%, P: 0.075wt%, N: 0.005wt%, S: 0.002wt%, Cu: 0.30wt%, Cr: 0.40 wt%, the rest is Fe and unavoidable impurities.

(2) Thin strip continuous casting

The qualified molten steel is continuously cast into a cast strip with a thickness of 2.1mm through a pair of oppositely rotating casting rolls, and the continuous casting temperature is 1620°C.

(3) On-line hot rolling of cast strip

The hot rolling reduction is 50%, and the temperature of the strip before entering the rolling mill is 980°C.

(4) Cooling and coiling

The hot rolled steel strip is cooled to 420°C by aerosol at a cooling rate of 60°C/s, and then coiled into coils.

The weathering steel strip obtained through the above steps has a thickness of 1.05 mm. The mechanical properties of the strip are tested, and the yield strength is 378 MPa and the elongation is 28%. After surface inspection, the surface of the strip is good and no cracks appear.

Example 2

This embodiment follows the following steps:

(1) Smelting

The chemical composition of molten steel is: C: 0.021wt%, Si: 0.35wt%, Mn: 0.60wt%, P: 0.078wt%, N: 0.004wt%, S: 0.0025wt%, Cu: 0.35wt%, Cr: 0.30 wt%, the rest is Fe and unavoidable impurities.

(2) Thin strip continuous casting

The qualified molten steel is continuously cast into a casting strip with a thickness of 1.8mm through a pair of oppositely rotating casting rolls, and the continuous casting temperature is 1640°C.

(3) On-line hot rolling of cast strip

The hot rolling reduction is 20%, and the temperature of the strip before entering the rolling mill is 1010°C.

(4) Cooling and coiling

The hot rolled steel strip is cooled to 450°C by aerosol at a cooling rate of 45°C/s, and then coiled into coils.

The weathering steel strip obtained through the above steps has a thickness of 1.44 mm. The mechanical properties of the strip are tested, and the yield strength is 367 MPa and the elongation is 26%. After surface inspection, the surface of the strip is good and no cracks appear.

Example 3

This embodiment follows the following steps:

(1) Smelting

The chemical composition of molten steel is: C: 0.03wt%, Si: 0.40wt%, Mn: 0.80wt%, P: 0.085wt%, N: 0.003wt%, S: 0.0015wt%, Cu: 0.25wt%, Cr: 0.35 wt%, the rest is Fe and unavoidable impurities.

(2) Thin strip continuous casting

The qualified molten steel is continuously cast into a casting strip with a thickness of 2.4mm through a pair of oppositely rotating casting rolls, and the continuous casting temperature is 1590°C.

(3) On-line hot rolling of cast strip

The hot rolling reduction is 45%, and the temperature of the strip before entering the rolling mill is 1150°C.

(4) Cooling and coiling

The hot-rolled steel strip is cooled to 480°C by aerosol at a cooling rate of 30°C/s, and then coiled into coils.

The weathering steel strip obtained through the above steps has a thickness of 1.32 mm, and the mechanical properties of the strip are tested. The yield strength is 392 MPa and the elongation is 25%. After surface inspection, the surface of the strip is good and no cracks appear.

The foregoing descriptions are merely exemplary embodiments of the present invention, and are not used to limit the protection scope of the present invention, which is determined by the appended claims.

Claims

A production method of low-cost weathering steel, characterized in that the production method comprises the following steps:

(1) Smelting

Smelting to obtain molten steel with the following composition: C≤0.03wt%, Si: 0.10-0.50wt%, Mn: 0.50-1.50wt%, P: 0.07-1.50wt%, N≤0.008wt%, S≤0.003wt%, Cu ＜0.40wt%, Cr＜0.45wt%, the rest is Fe and unavoidable impurities;

(2) Thin strip continuous casting

The qualified molten steel is continuously cast into a casting belt with a thickness of 1.4-2.5mm through a pair of oppositely rotating casting rolls;

(3) On-line hot rolling of cast strip

The cast strip is hot-rolled into hot-rolled thin strip after one pass;

(4) Cooling and coiling after rolling

The hot-rolled steel strip is cooled by aerosol and coiled into coils.
The method for producing low-cost weathering steel according to claim 1, wherein in step 2), the molten steel casting temperature is controlled at 1580°C-1650°C.
The method for producing low-cost weathering steel according to claim 1 or claim 2, characterized in that, in step 3), the cast strip undergoes only one pass of hot rolling to produce thin strip steel.
The method for producing low-cost weathering steel according to any one of the preceding claims, characterized in that, in step 3), the reduction of the cast strip after hot rolling by the hot rolling mill is 10-70%.
The method for producing low-cost weathering steel according to any one of the preceding claims, characterized in that, in step 3), the temperature of the cast strip before entering the hot rolling mill is above 900°C.
The method for producing low-cost weathering steel according to any one of the preceding claims, characterized in that, in step 3), the cast strip is hot-rolled to form a hot-rolled thin strip with a thickness of 0.7-2.0 mm.
The production method of low-cost weathering steel according to any one of the preceding claims, characterized in that, in step 4), the hot-rolled thin strip is cooled to 400-500°C by aerosol, and the cooling rate is 30-100 ℃/s.
The production method of low-cost weathering steel according to any one of the preceding claims, characterized in that, in step 4), after the hot-rolled thin strip is cooled, the microstructure of the strip is uniform acicular ferrite Body tissue.
The production method of low-cost weathering steel according to any one of the preceding claims, characterized in that in step 4), the yield strength of the hot-rolled thin strip steel is above 345 MPa and the elongation is above 23%.
A low-cost weathering steel, characterized in that the chemical composition of the steel includes: C≤0.03wt%, Si: 0.10-0.50wt%, Mn: 0.50-1.50wt%, P: 0.07-1.50wt%, N≤0.008 wt%, S≤0.003wt%, Cu<0.40wt%, Cr<0.45wt%, the rest is Fe and unavoidable impurities.