When you run a hot forging line for brass valves or steel parts, you want every piece to come out perfect. However, problems often happen during the heating or pressing stages. If you don't catch these defects early, you waste a lot of expensive metal and ruin your tools. Most of these issues come from wrong temperatures or poor machine settings.

Cracks on the Surface

Surface cracks are a big headache. They usually look like small splits on the outside of the forged part. This often happens because the metal billet was not hot enough. If the brass is too cold, it becomes stiff. When the heavy press hits it, the metal cannot flow smoothly into the mold, so it tears.

To fix this, you must check your furnace settings. The metal needs to reach the right temperature all the way through, not just on the outside. Also, if you cool the part too fast after forging, it can crack. Slow, natural cooling is usually better.

Folds and Laps

A "fold" happens when the metal buckles and folds over itself during the press. It looks like a deep scratch or a seam on the part. This usually means the starting metal billet was the wrong shape or was placed incorrectly in the die.

If your mold design is too sharp or too complex, the metal might struggle to fill the corners. When the metal hits a wall and turns back on itself, it creates a lap. You can prevent this by using better-designed dies and making sure the operator places the hot billet exactly in the center of the machine.

Under-filling the Mold

Sometimes the forged part does not look complete. Maybe a corner is missing, or the edges are rounded when they should be sharp. We call this under-filling. This is often caused by low pressure from the forging press. If the press does not have enough power, it cannot force the metal into the tiny details of the die.

Another reason for under-filling is using a billet that is too small. If you don't put enough metal in, you won't get a full part out. On the other hand, using too much lubricant inside the mold can also cause problems. The extra oil gets trapped in the corners and stops the metal from filling the space.

Burnt Metal and Overheating

It is tempting to turn the furnace up high to work faster, but this is a mistake. If the metal gets too hot, the internal grains grow too large. This makes the final valve very brittle and easy to break. In some cases, the metal even starts to melt slightly on the surface.

You can see this if the part has a very rough, "orange peel" texture. The best way to stop this is to use an automated induction heater with a temperature sensor. This ensures every single billet is heated to the exact same temperature before it reaches the press.

Die Wear and Deformation

Forging dies take a lot of punishment. Over time, the heat and pressure change the shape of the mold. If the die is worn out, your parts will start to lose their precise dimensions. You might notice the valves getting slightly larger or the threads becoming hard to machine later.

You should inspect your dies regularly. Using a high-quality cooling spray on the mold between every hit helps keep the temperature down and protects the steel. When you see the first sign of wear, it is time to polish or replace the die before it ruins thousands of parts.