CN107142364A - A production process of ultra-pure ferritic stainless steel twin-roll strip casting and rolling - Google Patents

Abstract

The invention relates to a casting-rolling production process of an ultrapure ferrite stainless steel strip, which comprises the following steps: (1) hoisting the molten steel with qualified components to a ladle turret; (2) pouring molten steel into a tundish; (3) double-roller casting and rolling; (4) hot rolling the strip blank; (5) cooling the strip steel and cutting off the head and the tail; (6) and (5) coiling the strip steel. The invention directly produces the ultra-pure ferrite stainless steel thin strip by the twin-roll casting and rolling, obtains the tiny and homogeneous cast and rolled thin strip by utilizing the characteristic that molten steel is rapidly solidified in the casting and rolling process, and obtains the finished plate with good formability and surface wrinkle resistance after rolling and annealing. After the double-roller casting rolling, the hot rolling only needs one pass of rolling to realize the production with the thickness specification of 0.8-3.0mm, and the technical problem of hot rolling roller sticking is solved.

Description

A production process of ultra-pure ferritic stainless steel twin-roll strip casting and rolling

technical field

The invention belongs to the technical field of metallurgical engineering of stainless steel strips, and in particular relates to a casting and rolling production process of ultra-pure ferritic stainless steel strips.

Background technique

While ultra-pure ferritic stainless steel has the advantages of traditional ferritic stainless steel, the extremely low carbon and nitrogen content in the steel also greatly improves its weldability, toughness and reduces the plastic-brittle transition temperature below room temperature. Excellent corrosion resistance and good processing performance and other advantages. Ultra-pure ferritic stainless steel has strong competitiveness in the market due to its excellent performance and high cost performance, and has great application prospects in various industries.

In the production process of ultra-pure ferritic stainless steel cast by traditional technology, ferritic stainless steel has good thermal conductivity. When it is produced by traditional thickness slab casting machine (220mm thick), the grains are easy to grow rapidly along the thickness direction, forming well-developed columnar crystals. , the proportion of columnar crystals is sometimes as high as 70%-80%. The columnar grain structure will deteriorate the formability of the finished plate and aggravate the degree of surface wrinkling. Therefore, refining the microstructure of the continuous casting slab and expanding the equiaxed grain ratio have become the main means to improve the formability and surface quality of ferritic stainless steel. At present, some stainless steel plants have adopted various methods, such as adding microalloying elements such as niobium and titanium, using electromagnetic stirring in the continuous casting process, and properly controlling the cooling water flow in the secondary cooling section of continuous casting, etc., but the effect is not satisfactory.

In addition, in the traditional process of rolling ultra-pure ferritic stainless steel, in order to realize the thickness specification of 2.5-3.5mm rolled from a 220mm thick billet, multi-pass and high-pressure rolling are adopted. Due to the ultra-pure ferritic stainless steel The strength of the machine body is low, and there is a prominent problem of hot rolling sticking in production. After hot rolling sticking, the surface of the ferritic stainless steel hot rolled annealed pickling plate will form linear surface defects along the rolling direction. After cold rolling, there will be weakened, but there are still some linear defects left on the finished board. However, the surface of the work rolls where hot roll sticking occurs becomes rough and uneven, and rolling cannot be continued. The occurrence of hot roll sticking deteriorates the surface quality of the rolled material, increases the cost of strip steel grinding, shortens the service life of the roll, and reduces the production efficiency.

Contents of the invention

The technical problem to be solved by the present invention is to provide an ultra-pure ferritic stainless steel strip casting and rolling production process in view of the existing problems in the prior art. The present invention utilizes twin-roll thin strip casting and rolling technology to prepare ultra-pure ferritic stainless steel thin ribbon.

Adopt following technical scheme for solving technical problem of the present invention:

A production process of ultra-pure ferritic stainless steel twin-roll strip casting and rolling, the specific steps are as follows:

(1) Hoist molten steel with qualified components to the ladle turret: hoist the ultra-pure ferritic stainless steel molten steel refined in the LF ladle refining furnace to the ladle turret, and calm it down for 15-25 minutes;

(2) Molten steel is injected into the tundish: the tundish is blown with argon for 10-20 minutes to drive out the air in the tundish, and then the molten steel is injected from the ladle into the tundish through the long nozzle, and the superheat is controlled at 20°C-40°C. Tundish covering agent for heat preservation and adsorption inclusions;

(3) Twin-roll casting: Molten steel is injected into the twin-roll casting machine through the submerged nozzle. The billet speed is 80-150 m/min. Argon or a mixed gas of argon and hydrogen is used for protection. During the solidification process of molten steel in the casting roll, the cooling rate control range is 500-950°C/s;

(4) Strip hot rolling: the cast-rolled strip is hot-rolled under the protection of argon or argon and hydrogen mixed gas, and the strip is sent to the hot rolling mill by pinch rollers for constant tension rolling. The rolling speed is 128-280 m/min, in which the strip hot rolling temperature is controlled at 1050-1150°C, and the strip thickness control range after hot rolling is 0.8-2.5mm;

(5) Cooling of strip steel and cutting head and tail

After hot-rolling, the strip steel is cooled and sent to the shearing machine through the pinch rollers to cut off the head and tail of the strip steel;

(6) Strip coiling

The strip after the head and tail are cut off is sent to the coiler for strip coiling through the pinch roller, and the finished thin strip coil is obtained.

The protective gas pressure in the step (3) is 0.3-0.5 MPa.

The volume ratio of argon to hydrogen in the step (3) is 3:1.

The protective gas pressure in the step (4) is 0.3-0.5 MPa.

The volume ratio of argon and hydrogen in the step (4) is 3:1.

The hot-rolled steel strip in the step (5) is cooled to 650-700° C. by a laminar flow cooling device.

The twin-roll strip casting and rolling technology is a cutting-edge technology in metallurgy, and it has been industrially applied in the production of carbon steel. According to the characteristics of the twin-roll thin strip casting and rolling process, we introduce it into the production of ultra-pure ferritic stainless steel. Through reasonable matching of key process parameters such as thickness, casting temperature, casting speed and cooling rate, we have achieved high quality and low cost. Cost-qualified production of ultra-pure ferritic stainless steel products. The beneficial effects of the present invention are as follows: (1) Using the feature of rapid solidification of molten steel in the casting and rolling process, a fine and homogeneous casting and rolling thin strip can be obtained. After rolling and annealing, a steel strip with good formability and surface wrinkle resistance Foldable finished board. (2) After twin-roll casting and rolling, due to the thin thickness of the original cast strip and rolling at high temperature, hot rolling only needs to be rolled once to realize the production of products with a thickness of 0.8-3.0mm, and effectively solve the problem Technical problems of sticking rolls in hot rolling. (3) The whole process of casting and hot rolling is protected by argon gas or a mixed gas of argon gas and hydrogen gas. The purity of molten steel is high, and the oxide scale on the surface is thin, which is conducive to improving the surface quality of products, reducing the cost of subsequent pickling, and improving production efficiency. improve.

Description of drawings

Fig. 1 is a schematic diagram of the production process of ultra-pure ferritic stainless steel thin strip casting and rolling in the present invention.

detailed description

The present invention will be further described in detail with reference to specific examples, but the implementation of the present invention is not limited thereto.

Example 1

A casting and rolling production process of 0.8mm thick, steel type 444 ultra-pure ferritic stainless steel strip product, comprising the following steps:

(1) Hoist the molten steel with qualified composition to the ladle turret: hoist the ultra-pure ferritic stainless steel molten steel refined in the LF ladle refining furnace to the ladle turret, and calm it down for 25 minutes;

(2) Molten steel is injected into the tundish: the tundish is blown with argon for 20 minutes to drive out the air in the tundish, and then the molten steel is injected from the ladle into the tundish through the long nozzle. tundish covering agent;

(3) Twin-roll casting: molten steel is injected into the twin-roll casting machine through the submerged nozzle, the billet speed is 150m/min, the preset roll gap of the casting rolls is 1.5mm, and the molten steel is flowed using argon mixed gas. Protection, the protective gas pressure is 0.5MPa, the strip thickness obtained after casting and rolling is 1.5mm, and the cooling rate is 950°C/s during the solidification process of molten steel in the casting roll;

(4) Strip hot rolling: the cast-rolled strip is hot-rolled under the protection of argon, and the protective gas pressure is 0.5MPa. The strip is sent to the hot rolling mill through pinch rollers for constant tension rolling, the rolling speed is 280 m/min, the hot rolling temperature of the strip is 1150°C, and the thickness of the strip after hot rolling is controlled to 0.8mm;

(5) Cooling of strip steel and cutting head and tail

After hot-rolling, the steel strip at a temperature of 950°C is cooled to 700°C by a laminar flow cooling device, and then sent to a shearing machine through pinch rollers to cut off the head and tail of the strip;

(6) Strip coiling

The strip after the head and tail are cut off is sent to the coiler for strip coiling through the pinch roller, and the finished thin strip coil is obtained.

Example 2

A casting and rolling production process of 1.5mm in thickness and steel type 445 ultra-pure ferritic stainless steel thin strip product, comprising the steps:

(1) Hoist the molten steel with qualified composition to the ladle turret: hoist the ultra-pure ferritic stainless steel molten steel refined in the LF ladle refining furnace to the ladle turret, and calm it down for 20 minutes;

(2) Molten steel is injected into the tundish: the tundish is blown with argon for 15 minutes to drive out the air in the tundish, and then the molten steel is injected from the ladle into the tundish through the long nozzle, and the superheat is controlled at 40°C; tundish covering agent;

(3) Twin-roll casting: Molten steel is injected into the twin-roll casting machine through the submerged nozzle, the billet speed is 100m/min, and the preset roll gap of the casting rolls is 2.5mm. A mixed gas of argon and hydrogen is used for protection during the flow of molten steel, wherein the volume ratio of argon and hydrogen is 3:1, the pressure of the protection gas is 0.5 MPa, and the thickness of the strip obtained after casting and rolling is 2.5 mm. During the solidification process of molten steel in the casting roll, the cooling rate is 750°C/s;

(4) Strip hot rolling: the cast-rolled strip is hot-rolled under the protection of a mixture of argon and hydrogen, wherein the volume ratio of argon and hydrogen is 3:1, the protective gas pressure is 0.5MPa, and the strip is pinched The rolls are sent to the hot rolling mill for constant tension rolling, the rolling speed is 167 m/min, the strip hot rolling temperature is 1100°C, and the strip thickness after hot rolling is 1.5mm;

(5) Cooling of strip steel and cutting head and tail

After hot-rolling, the steel strip at a temperature of 910°C is cooled to 680°C by a laminar flow cooling device, and then sent to a shearing machine through pinch rollers to cut off the head and tail of the strip;

(6) Strip coiling

The strip after the head and tail are cut off is sent to the coiler for strip coiling through the pinch roller, and the finished thin strip coil is obtained.

Example 3

A casting and rolling production process of 2.5mm in thickness and steel type 443 ultra-pure ferritic stainless steel thin strip product, comprising the steps:

(1) Hoist the molten steel with qualified composition to the ladle turret: hoist the ultra-pure ferritic stainless steel molten steel refined in the LF ladle refining furnace to the ladle turret, and calm it down for 15 minutes;

(2) Molten steel is injected into the tundish: the tundish is blown with argon for 10 minutes to drive out the air in the tundish, and then the molten steel is injected from the ladle into the tundish through the long nozzle, and the superheat is controlled at 20°C; tundish covering agent;

(3) Twin-roll casting: Molten steel is injected into the twin-roll casting machine through the submerged nozzle, the billet speed is 80m/min, the preset roll gap of the casting roll is 4.0mm, and argon gas is used for protection during the flow of molten steel. Gas pressure 0.3MPa. The strip thickness after casting and rolling is 4.0mm, and the cooling rate is 500°C/s during the solidification process of molten steel in the casting roll;

(4) Strip hot rolling: the cast-rolled strip is hot-rolled under the protection of argon, and the protective gas pressure is 0.3MPa. The strip is sent to the hot rolling mill through pinch rollers for constant tension rolling, the rolling speed is 128 m/min, the strip hot rolling temperature is 1050°C, and the strip thickness after hot rolling is 2.5mm;

(5) Cooling of strip steel and cutting head and tail

After hot-rolling, the steel strip at a temperature of 900°C is cooled to 650°C by a laminar flow cooling device, and then sent to a shearing machine through pinch rollers to cut off the head and tail of the strip;

(6) Strip coiling

The strip after the head and tail are cut off is sent to the coiler for strip coiling through the pinch roller, and the finished thin strip coil is obtained.

Claims (6)

1. a kind of super-purity ferrite stainless steel double roll strip casting rolling production process, it is characterised in that comprise the following steps that：

（1）The qualified molten steel of composition is hoisted to bale panoramic tables：Super-purity ferrite stainless steel after LF ladle refining furnaces are refined Molten steel is hoisted to bale panoramic tables, calm 15-25min；

（2）Molten steel is injected into tundish：Tundish blowing argon gas 10-20min drive out of in bag after air by long nozzle by molten steel from Ladle is injected into tundish, and degree of superheat control is added on 20 DEG C -40 DEG C, molten steel for being incubated and adsorbing the centre being mingled with Covering agent；

（3）Double-roller rolling：Molten steel is injected in twin-roll cast-rolling mill by submersed nozzle, and strand speed is 80-150 m/min, casting Roller gap is adjustable between 1.5-4.0mm, is carried out during MOLTEN STEEL FLOW using the mixed gas of argon gas or argon gas and hydrogen Protection, molten steel is in Casting Roller in process of setting, and cooldown rate control range is 500-950 DEG C/s；

（4）Made-up belt hot rolling：Roll casting sheet is in the mixed gas protected lower carry out hot rolling of argon gas or argon gas and hydrogen, and made-up belt is through pinching Roller is sent to hot-rolling mill and carries out constant-tension rolling, and mill speed is 128-280 m/min, and wherein made-up belt hot-rolled temperature control is 1050-1150 DEG C, belt steel thickness control range is 0.8-2.5mm after made-up belt hot rolling；

（5）The cooling and excision of strip are end to end

Strip cooling after hot rolling, is sent to cutter through pinch roll and carries out the excision of strip end to end；

（6）Strip coiling

Strip after excision end to end is sent to coiling machine through pinch roll and carries out strip coiling, obtains finished product thin strip steel coil.

2. a kind of super-purity ferrite stainless steel double roll strip casting rolling production process according to claim 1, it is characterised in that： The step（3）Middle protective gas pressure is 0.3-0.5MPa.

3. a kind of super-purity ferrite stainless steel double roll strip casting rolling production process according to claim 2, it is characterised in that： The step（3）The volume ratio of middle argon gas and hydrogen is 3: 1.

4. a kind of super-purity ferrite stainless steel double roll strip casting rolling production process according to claim 1, it is characterised in that： The step（4）Middle protective gas pressure is 0.3-0.5MPa.

5. a kind of super-purity ferrite stainless steel double roll strip casting rolling production process according to claim 4, it is characterised in that： The step（4）The volume ratio of middle argon gas and hydrogen is 3: 1.

6. a kind of super-purity ferrite stainless steel double roll strip casting rolling production process according to claim 3 or 5, its feature exists In：The step（5）Strip after middle hot rolling is cooled to 650-700 DEG C through cooling facility for laminar flow.