icon

A New Method of Controlling the Casting Speed of Steel Billet Continuous Casting Machine

steel billet continuous casting machine

In order to solve the defects that the surface of continuous casting billets, especially large round billets of medium and high alloy steels, is easy to crack, and the surface of rolled finished steel products is easy to produce cracks of different shapes and lengths, a new method is provided to control the casting speed of continuous casting round billets reasonably, which is convenient for effectively improving or basically solving the widespread surface cracks of arc continuous casting billets. The overall growth efficiency of the steel billet continuous casting machine is greatly improved, the billet yield is further improved, and the surface quality of the continuous casting billet is better improved.

A new method to control the casting speed of a round steel billet continuous casting machine is to transfer the qualified molten steel into the continuous casting tundish through the ladle turret and then enter the continuous casting mold through the submerged nozzle and then enter the tension leveler after cooling.

The Characteristics of the Steel Billet Continuous Casting Machine

The control method of steel billet continuous casting speed is divided into two stages. In the first stage, the actual casting speed is controlled according to the traditional method before the continuous casting slab is separated from the dummy bar head, that is, the actual temperature or superheat of molten steel in the tundish is used to control the casting speed. In the first stage, the actual operation time of the slab is 10-30 minutes, and the actual casting speed is 0.30 m/min – 0.75 m/min;

In the second stage, after the slab is separated from the dummy bar head, the slab drawing speed is adjusted according to the slab surface temperature data at the first straightener, so that the slab can be separated from the theoretical brittle temperature zone as early as possible, i.e. 723°C – 912°C temperature range, taking into account the temperature of molten steel in the tundish. The slab surface temperature at the first straightener is 915 °C – 1000°C, In the second stage, the casting speed range is 0.40 m/min to 0.85 m/min.

When the billet is GCrl5 bearing steel, the surface temperature of the billet at the first leveler is 915 ° C – 9240°C.

When the billet is a 27SiMn coal mine special hydraulic prop, the surface temperature of the billet at the first straightening machine is 920°C – 930°C.

When the casting blank is 20CrMoA, a special oil field sucker rod, the surface temperature of the casting blank at the first straightening machine is 931°C – 949°C.

When the slab is GCrl5 bearing steel, the casting speed range of the slab in the second stage is 0.40 m/min – 0.45 m/min.

When the casting billet is a 27SiMn coal mine special hydraulic prop, the casting speed range in the second stage is 0.43 m/min – 0.48 m/min.

When the casting blank is 20CrMoA, the casting speed range of the casting blank in the second stage is

0.80 m/min – 0.85 m/min.

When the casting billet is GCrl5 bearing steel, the casting speed in the first stage is 0.30 m/min to 0.35 m/min.

When the casting billet is a round billet with a diameter of 500mm used for 27SiMn coal mine special hydraulic prop, the first stage of casting speed is 0.30m/min to 0.35m/min.

When the casting billet is a round billet with a diameter of 310mm for 20CrMoA, a special oil field sucker rod, the first stage of the casting speed is 0.70m/min to 0.75m/min.

The crystallizer is provided with a self-vibrating device, that is, the crystallizer is a vibrating crystallizer.

The principle of the invention is just opposite to the thinking mode of the traditional continuous casting process to formulate casting speed.

The traditional way of thinking about drawing speed is that the casting speed is determined by the only factor of the temperature of molten steel in the tundish, with little consideration given to the slab straightening temperature.

The thinking mode of the process formulation of the invention is to divide the control method of casting billet casting speed into two stages. In the first stage, the casting speed control of the continuous casting slab is formulated according to the traditional method before the slab is separated from the dummy bar head (about 10-30 minutes). In the second stage, after the slab is separated from the dummy bar head, the casting speed of the slab shall be determined according to the actual temperature of the slab surface in the straightening section, and the casting speed shall be gradually adjusted to make the slab leave the theoretical brittle temperature range of 723V – 912°C as early as possible, followed by the temperature of the tundish steel.

The invention effectively improves or basically solves the mechanism of the surface crack of the steel billet of the arc continuous casting machine. On the premise of ensuring the quality of the billet, the invention greatly improves the overall growth efficiency of the continuous casting machine, further improves the yield rate of cast products, and better improves the internal and external physical quality of the continuous casting billet. Compared with other continuous casting production technology ideas, the invention is more efficient, practical, simple, convenient, and easy to promote.

The continuous casting process of bearing steel, 27SiMn, 20CrMoA and other alloy steels developed according to this new thinking has been proved through repeated tests in practice that the physical quality of bearing steel, alloy steel, and other continuous casting billets, especially the surface quality of continuous casting billets, has been significantly improved, which has been widely praised by customers and the corporate product image has been greatly improved.

Example 1 GCrl5 Bearing Steel Large Round Billet Continuous Casting Technology

The qualified molten steel is transferred into the tundish through the ladle turntable, then enters the crystallizer through the submerged nozzle, and then enters the tension leveler after cooling. The control method of drawing speed is divided into two stages;

In the first stage, the time range is 20 minutes before the continuous casting slab is separated from the dummy bar head, and the casting speed control is established according to the traditional method, that is, through the temperature of the tundish, the casting speed is 0.30 m/min to 0.35 m/min.

In the second stage, the slab drawing speed is adjusted according to the slab surface temperature at the first straightening machine after the slab is detached from the dummy bar head, so that the slab can leave the theoretical brittle temperature area as early as possible. The slab surface temperature at the first straightening machine is 915°C – 924°C。 At the same time, the temperature of molten steel in tundish shall be considered. The temperature range of molten steel in the tundish is 1520°C – 1530°C. In the second stage, the casting speed range is 0.40 – 0.45m/min.

Before pouring, the tundish shall be filled with argon, and the baking effect of the tundish and the centering position between the stopper and the bowl mouth area shall be carefully checked to ensure that the centering position is accurate, and the baking temperature of the tundish is 1000°C.

The liquid level of molten steel in tundish is 600mm, and the liquid level of molten steel in tundish is more than 400mm before adding the tundish covering agent.

When the weighing system of the ladle turret shows 60t, 40t, 25t, and 10t, the turnkey workers must measure the temperature in time and compare it with the continuous temperature measurement value, so as to adjust the pulling speed in time.

The submerged nozzle must be vertically or vertically aligned. Bias flow casting is strictly prohibited.

Slag flow in tundish once every three heats.

The cutting length of the opening slab head is ≤ 1.2m, and the tail slab is ≤ 3m. The casting slab with significant defects due to a short interruption in the casting process or due to the replacement of the nozzle, etc., needs to be lifted out separately, stored separately with the head and tail slabs, and returned to the furnace for treatment.

Hot delivery is preferred for the first production of this steel, and when the continuous casting billet needs to enter the pit for slow cooling; The temperature of the billet out of the pit=150°C. When lifting out of the pit, the surface of the billet shall be strictly checked. If there are defects on the surface, the billet shall be completely polished before rolling.

Other unaccomplished matters shall follow the basic operating procedures.

Example 2 Continuous Casting Technology of 27SiMn Coal Mine Special Hydraulic Prop

The qualified molten steel is transferred into the tundish through the ladle turntable, and then enters the vibrating mold through the submerged nozzle, and then enters the tension leveler after cooling. The control method of the drawing speed is divided into two stages;

In the first stage, the time range is 30 minutes before the continuous casting slab is separated from the dummy bar head, and the casting speed control is established according to the traditional method, that is, through the temperature of the tundish, the casting speed is 0.30-0.35m/min.

In the second stage, the slab drawing speed is adjusted according to the slab surface temperature at the first straightening machine after the slab is detached from the dummy bar head, so that the slab can leave the theoretical brittle temperature area as early as possible. The slab surface temperature at the first straightening machine is 915°C – 921°C. At the same time, the temperature of molten steel in tundish shall be considered. The temperature range of molten steel in the tundish is 1575°C – 1585°C. In the second stage, the casting speed range is 0.43 – 0.48m/min.

Before pouring, the tundish shall be filled with argon, and the baking effect of the tundish and the centering position between the stopper and the bowl mouth area shall be carefully checked to ensure that the centering position is accurate, and the baking temperature of the tundish is 1000°C.

The liquid level of molten steel in tundish is 600mm, and the liquid level of molten steel in tundish is more than 400mm before adding the tundish covering agent.

When the weighing system of the ladle turret shows 60t, 40t, 25t, and 10t, the turnkey workers must measure the temperature in time and compare it with the continuous temperature measurement value, so as to adjust the pulling speed in time.

The submerged nozzle must be vertically or vertically aligned. Bias flow casting is strictly prohibited.

Slag flow in tundish once every three furnaces

The cutting length of the opening slab head is>1.2m, and the tail slab is>3m. The casting slab with obvious defects due to a short interruption in the casting process or due to the replacement of the nozzle, etc., needs to be lifted out separately, stored separately with the head and tail slabs, and then returned to the furnace for treatment.

Hot delivery is preferred for the first production of this steel, and when the continuous casting billet needs to enter the pit for slow cooling; The temperature of the billet out of the pit=150°C. When lifting out of the pit, the surface of the billet shall be strictly checked. If there are defects on the surface, the billet shall be completely polished before rolling.

Example 3 Continuous Casting Technology of 20CrMoA Special Sucker Rod for Oil Field

The qualified molten steel is transferred into the tundish through the ladle turntable, and then enters the vibrating mold through the submerged nozzle, and then enters the tension leveler after cooling. The control method of the drawing speed is divided into two stages;

In the first stage, the time range is 10 minutes before the continuous casting slab is separated from the dummy bar head, and the casting speed control is established according to the traditional method, that is, the casting speed is 0.70-0.75m/min by controlling the temperature of the tundish.

In the second stage, the slab drawing speed is adjusted according to the slab surface temperature at the first straightening machine after the slab is detached from the dummy bar head, so that the slab can leave the theoretical brittle temperature area as early as possible. The slab surface temperature at the first straightening machine is 931°C-949°C。 At the same time, the temperature of molten steel in tundish shall be considered. The temperature range of molten steel in the tundish is 1580°C – 1590°C. The casting speed range in the second stage is 0.80-0.85m/min.

Before pouring, the tundish shall be filled with argon, and the baking effect of the tundish and the centering position between the stopper and the bowl mouth area shall be carefully checked to ensure that the centering position is accurate, and the baking temperature of the tundish is 1000 ° C.

The liquid level of molten steel in tundish is 600mm (15t). Only when the liquid level of molten steel in tundish exceeds 400mm can the tundish covering agent be added to maintain a high liquid level to facilitate the floating and absorption of inclusions.

When the weighing system of the big bag turntable shows 60t, 40t, 25t and 10t, the big bag workers must measure the temperature in time.

The submerged nozzle must be vertically or vertically aligned. Bias flow casting is strictly prohibited.

The cutting length of the opening slab head is ≥ 0.8m, and the tail slab is ≥ 2m. The casting slab with significant defects due to a short interruption in the casting process or due to the replacement of the nozzle, etc., needs to be lifted out separately, stored separately with the head and tail slabs, and then returned to the furnace for treatment.

During the first production of this steel grade, the steel billet continuous casting machine needs to be slowly cooled in the pit, and in subsequent production, the billet is preferred to be hot delivered, followed by others; The billet exit temperature is S 2000C, and the billet surface shall be strictly checked when lifting out of the pit. If the surface has defects, the billet shall be fully grinded before rolling.

Leave a Reply

Your email address will not be published. Required fields are marked *