CN108998740A - A kind of hot-rolled pickling strip steel for water heater liner support and production method thereof - Google Patents

Abstract

The invention discloses a hot-rolled acid-washing strip steel for a high-strength water heater liner bracket and a production method thereof, wherein the hot-rolled acid-washing strip steel comprises the following raw materials in percentage by mass: 0.05-0.15% of C, less than or equal to 0.2% of Si, 0.6-1.0% of Mn, less than or equal to 0.02% of P, less than or equal to 0.006% of S, 0.01-0.05% of Nb, 0.10-0.50% of Mo, and the balance of Fe and inevitable impurities. The production method of the hot-rolled pickling strip steel for the high-strength water heater inner container support comprises the following steps: molten iron pretreatment, converter smelting, refining, continuous casting, hot rolling and acid washing. The hot-rolled pickled strip steel for the high-strength water heater liner support, which is produced by the invention, has the matrix structure of ferrite and bainite, the bainite content is more than or equal to 10 percent, the yield strength of a product is more than or equal to 430MPa, and the yield strength of the product is more than or equal to 400MPa after high-temperature short-time sintering at 840 ℃.

Description

A kind of hot-rolled pickling strip steel for water heater liner support and production method thereof

technical field

The invention relates to a hot-rolled pickling steel strip for a high-strength water heater liner support and a production method thereof, belonging to the technical field of hot-rolling pickling steel strip production technology.

Background technique

Hot-rolled pickled product is an intermediate product between cold-rolled and hot-rolled. It has a surface quality close to that of cold-rolled plate while maintaining the mechanical properties of hot-rolled product. It has a wide range of applications and has a good market prospect. Compared with ordinary hot-rolled sheets, hot-rolled pickled sheets remove the surface oxide scale and improve the surface quality of steel. Replacing cold-rolled sheets with pickled sheets can significantly reduce costs for enterprises. It has been widely used in compressors, Water heater liner, bracket and other parts.

After more than ten years of development, the technology of electric water heaters has been continuously improved. The safety, energy saving, heating speed and water output of electric water heaters have been continuously improved, and the market sales have continued to grow over the years. With the improvement of living standards in recent years, people's demand for water consumption is increasing. The best-selling volume of electric water heaters has increased from 40 liters around 2000 to about 60 liters today, and it has always been 80 liters in Hunan and Hubei. ~100-liter large-capacity water heaters are best-selling provinces, and there will be a broader market for 100-liter-capacity electric water heaters in the future.

As the capacity of electric water heaters increases, in addition to the tank of the water heater, its support also needs to be strengthened to meet its load-bearing requirements. The use of high-strength steel is an inevitable trend to adapt to the development of the home appliance industry.

According to investigations, 40-80 liter water heater tank supports are all made of 2-4mm hot-rolled pickled SPHC or cold-rolled SPCC/SPCD, which meet the load-bearing requirements of small-capacity tanks. For a water heater with a capacity of 100 liters, the strength of the product needs to be increased. The actual yield strength of the product is about 430MPa (the matrix structure is ferrite + pearlite). The liner bracket is easily deformed in the load-bearing test.

Contents of the invention

The present invention aims to provide a hot-rolled pickled steel strip for high-strength water heater inner tank support and its production method, which solves the technical problem that the yield strength of the material decreases significantly during the sintering process of the whole barrel and causes the inner tank support to be easily deformed in the load-bearing test . The hot-rolled pickling strip steel for the high-strength water heater inner tank support produced by the present invention has a matrix structure of ferrite + bainite, a bainite content of ≥ 10%, and a product yield strength of ≥ 430 MPa, which is sintered at a high temperature of 840°C for a short time Finally, the yield strength of the product is ≥400MPa.

The invention relates to a hot-rolled pickling strip steel for a water heater liner support, the chemical composition of which is: C 0.05-0.15%, Si≤0.2%, Mn 0.6-1.0%, P≤0.02%, S≤0.006%, Nb 0.01-0.05%, Mo 0.10-0.50%, and the rest are Fe and unavoidable impurities.

On the other hand, the present invention also relates to a production method of the above-mentioned hot-rolled pickled steel strip for the tank support of the water heater, comprising:

(1) After the molten iron is processed, the molten steel of the above-mentioned composition is obtained through converter smelting and LF refining, and then continuous casting is obtained to obtain a slab;

(2) After the slab is heated, rough rolling and finishing rolling are performed to obtain a hot-rolled plate;

The variation range of the thickness specification of the hot-rolled sheet is controlled within 1.6-6mm, the rolling speed is controlled within 5-12m/s due to thickness variation, and the finish rolling termination temperature is controlled at 820-880°C;

(3) The hot-rolled sheet is coiled into a hot-rolled coil by adopting a 30-80° C./S rapid water cooling process at a coiling temperature of 420-520° C., and the pickling process is completed.

Detailed Description of the Invention

The invention provides a hot-rolled pickling strip steel for a water heater liner support, the chemical composition of which is: C 0.05-0.15%, Si≤0.2%, Mn 0.6-1.0%, P≤0.02%, S≤0.006%, Nb 0.01-0.05%, Mo 0.10-0.50%, and the rest are Fe and unavoidable impurities.

The following are the effects of the main components involved in the present invention and their limitations:

Carbon: In the present invention, the content of C element is controlled at 0.05-0.15%. Carbon is an austenite-forming element. The level of carbon content determines the tensile strength level of the steel plate to a large extent, and is an important indicator affecting the carbon equivalent. .

Manganese: The present invention adopts 0.6-1.0% Mn content, uses manganese to delay pearlite transformation, improves the hardenability of steel and reduces bainite transformation temperature, and refines the structure substructure of steel.

Niobium: In the present invention, the content of Nb element is controlled at 0.01-0.05%. Promote fine-grain strengthening of ferrite grains and form a strengthening phase to increase the yield strength and tensile strength of the product.

Silicon: In the present invention, the content of Si is limited to less than 0.2%, which is used to promote the purity of the ferrite matrix and improve the formability of the product.

Phosphorus: Phosphorus in steel is generally dissolved in ferrite and has a strong solid solution strengthening effect. It is used to increase the strength of steel and reduce the toughness of steel. However, too high content of P is harmful to welding performance and is a harmful element. Therefore, the phosphorus content should be reduced as much as possible, and the content of P in the present invention is ≤0.02%.

Sulfur: S content in the present invention is ≤0.006%. The sulfur content and the form of sulfide are the main factors affecting the formability, and the formability of the product can be guaranteed through the control of the S content.

Molybdenum: The content of Mo in the present invention is 0.10-0.50%, which can strongly hinder the precipitation and growth process of pro-eutectoid ferrite, promote the formation of acicular ferrite with high-density dislocation substructure, and increase the Nb (C, N ) solubility product in austenite, so that a large amount of Nb is kept in solid solution, so that (Mo, Nb)C can be dispersed and precipitated in ferrite transformed at low temperature, so as to produce a higher precipitation strengthening effect and improve the product high temperature strength.

The internal microstructure of the hot-rolled pickled steel strip in the present invention is ferrite+bainite.

Further, in the internal microstructure of the hot-rolled pickled steel strip, the volume fraction of bainite is ≥ 10%.

Further, the yield strength of the hot-rolled pickling strip is ≥430MPa, and after short-time sintering at 840°C, the yield strength is ≥400Mpa.

In this patent application, the addition of Mo and Nb elements promotes the dispersion and precipitation of the strengthening phase (Mo, Nb)C in the ferrite transformed at low temperature, so as to produce a higher precipitation strengthening effect and improve the high temperature strength of the product. The above elements work together to ensure that the performance of the material meets the requirements of the standard.

The present invention also provides a method for producing the above-mentioned hot-rolled pickled steel strip for the tank support of the water heater, comprising:

(1) After the molten iron is processed, the molten steel of the above-mentioned composition is obtained through converter smelting and LF refining, and then continuous casting is obtained to obtain a slab;

(2) After heating the slab, rough rolling and finishing rolling are performed to obtain a hot-rolled plate;

(3) The hot-rolled sheet is coiled into a hot-rolled coil by adopting a 30-80° C./S rapid water cooling process at a coiling temperature of 420-520° C., and the pickling process is completed.

According to the production method of the hot-rolled pickled steel strip of the present invention, in step (2), the range of variation of the thickness specification of the hot-rolled sheet is controlled at 1.6-6 mm, and the rolling speed is controlled at 5-12 m/h due to thickness variation. s, the finish rolling finish temperature is controlled to be 820-880°C.

The invention provides a method for hot-rolled pickling strip steel for high-strength water heater liner support, through the control of the chemical composition and the control of the rolling process parameters, the microscopic metallographic structure of the produced strip steel is ferrite +Bainite, in which the bainite content is ≥10%, and the yield strength of the strip steel is ≥430MPa. After short-term sintering at 840°C, the yield strength is ≥400MPa, ensuring that the inner tank bracket does not undergo obvious deformation during the load-bearing test.

Detailed ways

The present invention will be described in detail below in conjunction with specific embodiments and examples, and the advantages and various effects of the present invention will be presented more clearly. Those skilled in the art should understand that these specific implementations and examples are used to illustrate the present invention, not to limit the present invention.

Throughout the specification, unless otherwise specified, terms used herein should be understood as commonly used in the art. Therefore, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In case of conflict, this specification shall take precedence.

Example 1

The embodiment of the present invention provides a hot-rolled pickling strip steel for the support of the inner tank of the water heater, the thickness specification is 4mm, and the chemical composition is: C 0.09%, Si 0.1%, Mn 0.8%, P 0.015%. , S 0.005%, Nb0.03%, Mo 0.2%, and the rest are Fe and unavoidable impurities.

Its production methods include: molten iron pretreatment, converter smelting, refining, continuous casting, hot rolling, tempering and pickling. Among them, the finish rolling termination temperature is controlled at 860°C, and the rolling speed is controlled at 7m/s; a 40°C/S rapid water cooling process is adopted, and the coiling temperature is 450°C, coiled into hot rolled coils, and the pickling process is completed. After pickling, the surface color of strip steel is off-white, and after drying, double-sided electrostatic spraying of anti-rust oil, coiling and packaging become finished products.

The microstructure of the steel strip finally produced in this example is ferrite + bainite, the volume of bainite is 25%, and the yield strength is 460MPa. After sintering at 840°C for a short time, the yield strength is 420MPa. The bracket did not undergo obvious deformation during the load-bearing test.

Example 2

The embodiment of the present invention provides a hot-rolled pickling strip steel for the support of the inner tank of the water heater, the thickness specification is 4mm, and the chemical composition is calculated in weight percentage (%): C 0.14%, Si 0.05%, Mn 0.6%, P 0.015% , S 0.005%, Nb 0.02%, Mo 0.15%, and the rest are Fe and unavoidable impurities.

Its production methods include: molten iron pretreatment, converter smelting, refining, continuous casting, hot rolling, tempering and pickling. Among them, the finish rolling termination temperature is controlled at 870°C, and the rolling speed is controlled at 7.5m/s; a 40°C/S rapid water cooling process is adopted, and the coiling temperature is 420°C, coiled into hot rolled coils, and the pickling process is completed. After pickling, the surface color of strip steel is off-white, and after drying, double-sided electrostatic spraying of anti-rust oil, coiling and packaging become finished products.

The microstructure of the steel strip finally produced in this example is ferrite + bainite, the volume of bainite is 30%, and the yield strength is 480MPa. After sintering at 840°C for a short time, the yield strength is 430MPa. The bracket did not undergo obvious deformation during the load-bearing test.

Example 3

The embodiment of the present invention provides a hot-rolled pickling steel strip for the support of the inner tank of the water heater, the thickness specification is 4mm, and the chemical composition is calculated in weight percentage (%): C 0.06%, Si 0.2%, Mn 0.9%, P 0.012% , S 0.003%, Nb 0.04%, Mo 0.45%, and the rest are Fe and unavoidable impurities.

Its production methods include: molten iron pretreatment, converter smelting, refining, continuous casting, hot rolling, tempering and pickling. Among them, the finish rolling termination temperature is controlled at 880°C, and the rolling speed is controlled at 8.5m/s; a 45°C/S rapid water cooling process is adopted, and the coiling temperature is 460°C, coiled into hot rolled coils, and the pickling process is completed. After pickling, the surface color of strip steel is off-white, and after drying, double-sided electrostatic spraying of anti-rust oil, coiling and packaging become finished products.

The microstructure of the steel strip finally produced in this example is ferrite + bainite, the volume of bainite is 20%, and the yield strength is 465MPa. After sintering at 840°C for a short time, the yield strength is 410MPa. The bracket did not undergo obvious deformation during the load-bearing test.

While preferred embodiments of the invention have been described, additional changes and modifications to these embodiments can be made by those skilled in the art once the basic inventive concept is appreciated. Therefore, it is intended that the appended claims be construed to cover the preferred embodiment as well as all changes and modifications which fall within the scope of the invention. Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention also intends to include these modifications and variations.

Claims (5)

1. a kind of water heater liner bracket hot rolling acid-cleaning strip, chemical component is according to percent by weight (%) are as follows: C 0.05 ~0.15%, Si≤0.2%, Mn 0.6~1.0%, P≤0.02%, S≤0.006%, Nb 0.01~0.05%, Mo 0.10 ~0.50%, remaining is Fe and inevitable impurity.

2. hot rolling acid-cleaning strip as described in claim 1, which is characterized in that the internal microstructure of the hot rolling acid-cleaning strip For ferrite+bainite, bainite volume >=10%.

3. hot rolling acid-cleaning strip as described in claim 1, which is characterized in that the yield strength of the hot rolling acid-cleaning strip >= 430MPa, after 840 DEG C of high temperature, short times are sintered, yield strength >=400MPa.

4. a kind of production method of water heater liner bracket hot rolling acid-cleaning strip as described in claim 1, comprising:

(1) by after molten iron and processing, continuous casting obtains slab after converter smelting, LF refining obtain the molten steel of mentioned component；

(2) after being heated the slab, hot rolled plate is obtained using roughing, finish rolling；

(3) hot rolled plate is used into the quick water-cooling process of 30~80 DEG C/S, coiling temperature is 420~520 DEG C, coils into hot rolling Volume, and complete pickling process.

5. hot rolling acid-cleaning strip production method as claimed in claim 4, which is characterized in that in step (2), the hot rolled plate The control of thickness specification variation range is terminated because of thickness change, control in 5~12m/s, the finish rolling in 1.6~6mm, mill speed Temperature control is 820~880 DEG C.