Dummy Bar Bolts Grade: 4.6, 8.8, Size: M30, M36
Introduction of Dummy Bar Bolt
A Dummy Bar Bolt’s main function is to support the dummy bar during the continuous casting process. Known as Reamer Bolt, it is a type of Half-Thread Hex Head Bolt. Features as a long, heat-resistant steel bar that guides the molten steel into the mold.
The dummy bar bolt is made of heat-resistant steel material, it belongs to the fit bolt type, AGICO supplies DIN 609 (M20-M50) hex Reamer bolts for dummy bar fastening, and it can be customized to meet customer requirements. if you are looking to buy high-performance dummy bar bolts, send us a message now for the details and price!
Dummy Bar Bolt for Sale
| Dimensions | Thread Type | Usage/Application | Material | Other Dimensions |
|---|---|---|---|---|
| M30 x 210mm | Half Thread | Continuous Casting Machine | Mild Steel | M20 To M50 |
| M30 x 220mm | ||||
| M30 x 230mm | ||||
| M30 x 240mm | ||||
| M30 x 250mm |
Common Steel Materials for Dummy Bar Reamer Bolt
| Material | Description | Tensile Strength | Yield Strength | Applications |
|---|---|---|---|---|
| ASTM A193 Grade B7 | High-strength alloy steel commonly used for high-temperature and high-pressure applications. | Minimum 860 MPa (125,000 psi) | Minimum 725 MPa (105,000 psi) | Suitable for use in high-temperature environments, making it a common choice for dummy bar hex bolts. |
| ASTM A320 Grade L7 | Low-temperature alloy steel with good toughness and strength. | Minimum 860 MPa (125,000 psi) | Minimum 725 MPa (105,000 psi) | Although designed for low temperatures, its mechanical properties also make it suitable for high-temperature applications in some cases. |
| ASTM A193 Grade B16 | High-strength alloy steel with improved heat resistance. | Minimum 965 MPa (140,000 psi) | Minimum 825 MPa (120,000 psi) | Used in environments requiring higher heat resistance compared to B7. |
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What is Dummy Bar and How Does it Work?
The dummy bar is an indispensable and important part of the steel-making process: in the continuous steel casting line, molten steel passes through the water-cooled crystallizer for preliminary cooling, it is pulled out with the help of a dummy bar. Then it is cooled and cut in the continuous casting machine.
Rigid Dummy Bar in Steel Mill
Rigid dummy bar is mostly used in the continuous casting of common carbon steel and low alloy steel billets. It is an arc-shaped dummy bar made of an entire steel bar.
After guiding the billet out of the crystallizer and the tensioning rolls, it is disengaged from the billet and parked above the billet discharge roller path. Because the billet does not have the problem of bulging, it does not require supporting and guiding devices in the secondary cooling section. Only simple guide plates are needed in the lower section of the secondary cooling area.
The rigid dummy bar system has stable pouring, which can prevent steel leakage accidents caused by the shaking of the dummy bar during the pouring of small cross-section billets. The simplification of the supporting mechanism in the secondary cooling section is conducive to quickly handling steel leakage accidents and improving the production capacity of the continuous casting machine.
Dummy Bar Structure and Fastening Method
The dummy bar structure is simple, it consists of a dummy head, a transition piece, and a shaft. Before molten steel is poured in the steel mill, the dummy head and part of the transition piece are placed into the mold to form a movable “inner bottom”.
Molten steel solidifies in the inner bottom and condenses with the dummy bar, so it can be pulled out continuously, and at last separated from the dummy bar. To ensure the working safety, it mainly uses large-size half-thread hex head bolts and pin bushes to connect the dummy bar body, which has to bear the high temperature in the molding process.
Rigid Type Dummy Bar Fastening
Dummy bars are mainly divided into 2 types: chain type and rigid type, here are the fastening method drawing for 2 types of rigid type dummy bar details :
- Flexible dummy bar: Usually used in continuous casting machines and rolling mills, it is composed of multiple chain links. Chain dummy bars are composed of arc segments and connected by Hex Head Reamer Bolts and Pin Brushes. This design is more convenient in manufacturing and transportation.
- Rigid dummy bar: When using a rigid dummy bar, the slab guide device of the continuous casting machine does not need to be equipped with many rollers for guidance, but it needs a group of hex bolts with nuts and pin bushes to connect the dummy bar head and body, the casting process is smoother, and the time for re-insertion into the crystallizer is greatly reduced.
Steel Material for Hex Head Reamer Bolt
As the various parts of the dummy bar are usually hinged or bolted by hex reamer bolts and pins. The use of hex bolts and pin-bushes play a vital role in the performance and safety of the dummy bar. Dummy bar fasteners are mostly made of the following materials:
- Mild Steel: Has good strength and ductility.
- High Strength Steel: For applications requiring higher strength.
- Alloy Steel: Provides excellent toughness and fatigue resistance.
Manufacturing and Assembly Precautions for Dummy Bar Bolts
The following points should be noted when manufacturing and assembling the dummy bar:
- Manufacturing process: Dummy bar bolts are often forged using a forging process to improve their strength and durability. Heat treatments such as quenching and tempering further improve mechanical properties.
- Assembly Accuracy: Ensure the parallelism and perpendicularity of each part of the dummy bar during assembly to ensure its stability and accuracy in use.
- Maintenance and replacement: Regularly check the wear and corrosion of dummy bar bolts, and lubricate and replace them in time to ensure their normal operation.
