To judge whether the performance of the overall stopper rod meets the requirements, the following aspects can be used:
1.Material difference
Erosion Resistance: Integral stoppers come into contact with high-temperature molten steel and slag during the continuous casting process, so they must exhibit excellent resistance to erosion and erosion from these substances. This can be assessed by observing the wear and corrosion of the stopper after use. Mild wear and corrosion indicate good erosion resistance. Severe pitting, flaking, and other signs of erosion resistance may indicate substandard erosion resistance. For example, some high-quality integral stoppers incorporate special refractory materials to enhance erosion resistance.
Thermal Shock Resistance: The continuous casting process experiences frequent and drastic temperature fluctuations, and the stopper must be able to withstand these thermal shocks without cracking or breaking. During testing, the stopper can be subjected to a cycle of rapid heating and cooling to observe for cracks and other damage. If the stopper remains intact after multiple thermal shock tests, it demonstrates good thermal shock resistance.
Spalling Resistance: During use, the stopper should exhibit excellent spalling resistance, with no signs of chipping or breakage. Check the surface and internal structure of the stopper rod. If there are signs of material peeling, or if material falls off during testing such as knocking before use, it indicates that its anti-peeling performance does not meet the requirements.
2.Size and shape
Dimensional Accuracy: The overall stopper rod dimensions, including length, diameter, and head shape, must meet design requirements. Use measuring tools such as calipers and micrometers to measure key stopper rod dimensions. Dimensional deviations must be within acceptable limits. For example, excessive diameter tolerances may result in a loose fit with the tundish nozzle, affecting molten steel flow control.
Shape Regularity: The stopper rod’s shape should be regular, with a smooth transition between the head and the stem, free of obvious deformation, bends, or other defects. The stopper rod’s shape can be inspected visually or using specialized testing tools such as a profilometer. Any bend in the stopper rod may impair its installation and operation within the tundish and even cause uneven molten steel flow.
3.Mechanical properties
Strength: The entire stopper rod must possess sufficient strength to withstand external forces during installation and use, such as insertion and removal, and the impact of molten steel. Mechanical property testing can be used to assess the rod’s strength. Simulation tests can also be conducted before actual use, such as compression and stretching tests under certain pressures, to determine whether the rod can withstand these forces without damage.
Toughness: Good toughness prevents the rod from breaking when subjected to external forces. Impact testing can be used to test the rod’s toughness, such as using an impact tester to observe the rod’s fracture behavior and energy absorption.
4.Functional performance
Flow Control Accuracy: Install the integral stopper rod on the tundish and conduct actual casting tests to observe whether the stopper rod accurately controls the molten steel flow rate. Adjusting the stopper rod’s position should ensure that the molten steel flow rate changes as expected, and the flow rate changes should be smooth and continuous, without sudden increases or decreases.
Sealing: A good seal must exist between the stopper rod and the tundish nozzle to prevent molten steel leakage. After installing the stopper rod, a sealing test can be performed. For example, a certain amount of water or simulated molten steel is injected into the tundish to observe whether there is any leakage between the stopper rod and the nozzle.
5.Other aspects
Appearance Quality: Inspect the stopper for defects such as cracks, pinholes, and air holes, which may affect its performance and service life. The surface should be smooth and flat, without obvious blemishes.
Manufacturer and Quality Certification: Choosing a reputable manufacturer and products with relevant quality certifications can increase confidence in the overall performance of the stopper. For example, check the manufacturer’s qualifications and the product’s quality inspection report.
More details about Monoblock Stopper
1.What is a monoblock stopper?
Monoblock Stopper (MBS) is an isostatically pressed refractory which is a critical element in the Continuous Casting of Steel where it is used to control the flow of steel from the “Tundish to Mould”.
2.What is the stopper rod mechanism?
The stopper rod mechanism is an integral part of the automatic stopper rod control system of a continuous casting machine which regulates the steel flow from the tundish to the mold. It is a mechanical device with a vertically moveable stopper rod to control the flow rate.
3.What is the use of monoblock stopper?
Monoblock Stopper is used mainly for flow control on Molten Steel poured from tundish to mould. Monolithic Stopper is installed in the Tundish above the Sub Entry Nozzle and the gap between stopper head and Nozzle decide the throughput requirement of Molten Steel inside the Mould.