Dephosphorization in the steelmaking process

The effect of phosphorus on the properties of steel

Phosphorus exists in the form of iron phosphide in steel, generally represented by [P]. Its specific effects on steel properties are:

Defects of Special-shaped Billet Continuous Casting and Prospect of Solutions

 Abstract: This article presents an in-depth review of the literature on the defects of special-shaped billets, mainly focusing on the formation mechanism of defects, proposes solutions to reduce defects, shows the techniques used to investigate defects, and measures to improve the quality of molten steel and mold design in the continuous casting process , Secondary cooling modification and instrument calibration, sector support, continuous casting arc calibration, etc.

The Causes and Control Measures of Four Major Surface Defects of Billets

 Surface defects of billets

1.Reconnect

1.1 Reasons for formation

a.Pouring is interrupted due to various operating failures, and reconnection defects are easily caused on the surface of the cast slab after re-pouring.

b.Slow drawing speed leads to too deep vibration marks on the surface of the cast slab, forming a reconnection.

1.2 Control measures

a.Fully do all the preparations for pouring steel to ensure the normality and stability of pouring steel, and avoid stop-flow accidents.

b.Ensure that the speed is normal and reasonable.

2.Inclusion and scarring

2.1 Reasons for formation

a.The liquid level of the mold fluctuates violently, so that the mold slag or other inclusions on the molten steel surface are involved in the casting slab, and inclusions are formed on the surface of the casting slab.

b.The molten steel overflows at the drawing leak, is cooled by the mold, and forms defects on the surface of the cast slab.c. The drawing speed fluctuates excessively and frequently.

2.2 Control measures

a.Improve the technical quality and work responsibility of the operators, and ensure the stability of the crystallizer liquid level.

b.Improve the performance of the mold powder, increase the thickness of the slag layer, and increase the absorption capacity of inclusions.c. Strict process operation procedures, stable pulling speed.

d. Improve the corrosion resistance of the tundish nozzle and plug.

3.scratches

3.1 Reasons for formation

a. There is scrap steel on the foot roll of the second cold section frame, causing scratches on the surface of the cast billet.

b. Uneven pulling and straightening rolls or uneven secondary cooling, causing the cast slab to deviate, and the casting slab and the pulling and straightening frame contact and scratch the surface of the cast slab.

3.2 Control measures

a.Strengthen the maintenance of the second cold section, and find that the steel breakout should be cleaned up in time.

b.Strengthen the maintenance of the tension-straightening system to ensure the levelness of the tension-straightening rollers, and install side guides to prevent the casting slab from deviating.

4.Vibration marks

4.1 Reasons for formation

a.Vibration marks are the inevitable result of mold vibration, and it is difficult to completely eliminate them. The greater the fluctuation of the mold liquid level, the deeper the vibration marks.

b.The slower the pulling speed, the lower the vibration frequency and the deeper the vibration marks.

c.The solidification characteristics of steel grades have a great influence on vibration marks. Shrinkage-sensitive steel has deep vibration marks, and crack-sensitive steel has shallow vibration marks.

4.2 Control measures

a.Use low-amplitude, high-frequency sinusoidal vibration.

b.Take measures to ensure the stability of the crystallizer liquid level.

Summary of Measures to Improve Tundish Life

 The life of the continuous casting tundish determines the index of the number of continuous casting furnaces in a single ladle, and the life of the tundish is unstable, which will directly affect the production, resulting in an increase in the cost of the production process.

About ladle breathable brick

Argon blowing is usually to build one or several breathable bricks at the bottom of the pouring ladle or brick ladle, and blow argon gas through the breathable bricks after tapping to cause agitation of the molten steel in the ladle. Argon blowing can promote the floating of emulsified slag droplets and inclusions in the steel, and can partially remove the dissolved gas and uniform components in the steel. In the case of continuous casting, the ladle blowing of argon can play a role in adjusting the temperature of the molten steel. Ladle argon blowing is an important steelmaking process, and breathable bricks are an important functional element of this process.

Aluminum strip billet continuous casting and rolling process application

 The aluminum strip continuous casting and rolling process is an advanced production process introduced from abroad in the 1980s. Its basic process is: aluminum ingot → melting furnace → standing furnace → degassing → filtering → casting nozzle → rolling mill → intermediate unit → Coiler.

The difference and characteristics of aluminum alloy continuous casting and rolling

 1.What is the continuous casting and rolling method

Continuous casting and rolling is a combination of continuous casting and rolling deformation to complete in one process, that is, the casting and rolling process is completed in the rotation of a pair of rolls. When molten aluminum is cooled and solidified, it receives a certain amount of pressure and produces a certain amount of plastic deformation.

Detailed explanation of the composition, type and lining structure of continuous casting tundish

 

The tundish is a transition device for molten steel between the ladle and the mold. After the tundish bears the molten steel flowing in from the continuous casting ladle, it plays the role of "connecting up and down". The installation position is shown in Figure 1.

What are the reasons for the porosity and shrinkage of continuous casting slabs

 

1.Introduction

A steel-making plant of a steel (group) company built a 1800mm slab continuous caster. The designed billet specifications are 200mm, 220mm, 250mm in thickness and 1400mm~1800mm in width. During the trial operation, Q235 and Q345 steel slabs with a cross-section of 250mm×1550mm were produced. The macrostructure inspection results showed that the center segregation and center porosity were serious. We excerpted the low power inspection reports of 13 furnace batch numbers and carried out comparative inspections, and found that the center segregation is generally B2.5 and the center porosity is about 2. After the cast slab is rolled into a product, when the two cross-sections are perpendicular to each other in the welding test, local delamination appears on the oxygen cutting or notch. According to the actual production situation of the plant, in order to reduce the center segregation and center porosity as much as possible and produce high-quality cast slabs, the reasons for the formation of center segregation and center porosity defects were analyzed, and specific preventive measures were put forward.

What are the types of continuous casting breakout accidents?

The so-called breakout refers to the phenomenon that the slab shell is not solidified in the initial stage of continuous casting or during the pouring process, or the slab shell is broken or leaked due to other external forces, causing the internal molten steel to flow out. Breakout is one of the vicious accidents in continuous casting production. Serious breakout accidents not only affect the normal production of the continuous casting machine, reduce the operating rate, but also damage the equipment of the casting machine and cause equipment damage. Breakout accidents can be divided into various forms due to the different time and location on the casting machine, and the causes are also different, mainly divided into the following points:

Selection of Continuous Casting Nozzle and Study on Spray Characteristics

Abstract: This article discusses the selection and spray characteristics of large-size square and round billet continuous casting nozzles, and proposes suggestions for improving the nozzle arrangement. Keywords: square and round billet; continuous casting nozzle; spray characteristics