Break Out

Break Out is an operational failure mostly associated with the continuous casting of alloys, primarily steel. It refers to the poor/low to no solidification of the slab shell during the process. But the rupture, leakage, or breakage of the slab shell to cause interior molten metal to flow out also falls under breakouts.

Continuous casting is a special die-cast manufacturing method to obtain uniform metal grain structures. The molten metal/alloy gets poured into the mold for rapid chilling before solidification. It enables the poured alloy/metal to get evenly shaped in the molten state without any solidifying interruption.

Breakouts in continuous casting (CC) machines always hold a serious concern for manufacturers. This consolidated yet explanatory article focuses on its sources, types, effects, and preventive measures.

Sources of Break Out in Die Casting

There’s no dedicated reason to initiate this troublesome issue. Instead, multiple mechanical factors associated with every reasonable source trigger the damage, including –

1. Poor Pouring Control –Poor implementation of the initial pouring of molten metal/alloy to start the casting causes open pouring breakouts.
2. Too Thin Shell Wall –Thinner walls can barely support the liquid column above. It leads to disruptions in heat transfer, causing leakage.
3. Damage to Cast Shells –Any physical irregularity/damage due to excessive pouring turbulence triggers compromised casting solidification.
4. Foreign Matters –Contaminants or impurities like slags weaken the shell wall and cause subsequent leakage/bleeding.
5. Heavy Corner Defects– Large seams/scratches or recessed pads at corners increase the resistance to cast withdrawal, initiating suspension breakouts.
6. Large Exterior Faults –Severe corner cracks, surface detachment, and longitudinal cracks contribute to breakouts at the mold exits.
7. Shell-Mold Sticking –Sticking the shell to the mold surface ruptures the machine’s meniscus, letting the molten liquid flow out of molds.
8. Compromised Speed –Too rapid machine operation against a slower cooling rate often triggers breakouts at break-off points.

One or more causes can initiate the problem during any specific casting stage. There are several mechanical, physical, and thermal factors within these reasons to start or deteriorate this particular defect.

Types of Die Casting Break Out

As mentioned, different reasons lead to distinctive breakout types in die-cast parts. However, the most noteworthy versions of this defect include –

• Open Pouring Breakout –Many errors in equipment, process, and handling contribute to this. It’s the breakout caused by an imbalance in temperature to enable insufficient solidification.
• Pouring Breakout –The mold’s inability to withstand molten metal/alloy’s static pressure due to partial shell solidification triggers this type. It makes the die casting prone to rupture, causing more defects.
• Bonded (Sticker) Breakout –Fluctuations in the molding level associated with lubrication loss cover this form. It’s the most observed breakout in the CC machine, characterized by V-shaped rupture on exits.
• Suspension Breakout –It features subsequent blocking of the die-cast part’s withdrawal from the mold. The corner seam to measure more than a 0.35mm limit without any replacement causes this kind.
• Slag Entrapment Breakout –Errors in handling, preparation, pouring, and solidification entrap slag within molten alloys. And the eventual generation of knots comes with residual blank-type breakouts.

Effects of Break Out

Unlike other die-casting defects, breakouts specifically threaten the operation and safety. The primary effects can be outlined as follows –

• Serious safety concerns in operating the entire CC process by encountering hot molten metals.
• Significant increase in production or operational cost due to near-impossible fixation of defects.

Preventing Break Out in Die Casts

As breakouts can affect the entire casting system, full-scale prevention is the best way to deal with it. The following precautions can help ensure maximum accuracy in processing to eliminate the defect.

1. Strict Metal Quality –Maintaining the optimal quality of metals/alloys at any stage is the key. Even slight distortions may take excessive correction in processes.
2. Temperature Uniformity –The pouring platform, as well as the pouring, should have uniform temps. But the molten metal/alloy stream better remain overheated.
3. Control in Pulling Speed –Increasing the temp for decreased pulling speeds or decreasing the temp for increased pulling speed can establish stability against breakouts.
4. Slag Pool Thickness –Avoiding a slag pool to exceed 10mm can help with breakouts. And the blank shell will require even lubrication without solid attachments.
5. Water Flow in Mold –Measuring the water pressure before pouring detects possible blocks for a steady flow. The water quality for casting also requires confirmation.
6. Fixing Corner Seams –Lime or plaster fill for the corner seams at the plate joints alleviates the tendency of breakouts. The allowable fillet radius shouldn’t exceed 0.2mm.
7. Adjustment of Machinery –Precise adjustments of the involved parameters set control over equipment. A calculated and matching adjustment is always desirable.
8. Appropriate Mold Powder –The chosen mold powder must corroborate the chemical composition of alloys. Also, ensure that the powder has validity left.

Lots of complex mechanical alterations during the process end up causing die-casting breakouts. As it’s extremely difficult to rake up, proper countermeasures from the start seem the only viable way.