Mold heat treatment analysis

Update:01-11-2019
Summary:The mold will be heated, and the injection mold is heated to process the injection molding of the original material. The...

The mold will be heated, and the injection mold is heated to process the injection molding of the original material. The heat treatment of the mold itself is very critical.

1. How can H13 mold steel heat-treat to reach 58°C?

Heating and quenching at 1050~1100 °C, oil quenching can meet the requirements, but the general hot work mold does not require such high hardness, such high hardness performance will be very poor, not easy to use, generally good performance in HRC46~50, durable.

2. What kind of whitewashing is used on the surface after the heat treatment of the mold?

Question added: I am opening the mold polishing shop. The general molds are all beaten with oil stone and then nitrided. After nitriding, we must use the oil stone to polish the black layer. It is very troublesome to polish. Without the mirror, the material has H13, and there are many kinds of imported ones. If the medicine can wash white, it can be polished directly.

(1) It can be washed with stainless steel pickling solution or hydrochloric acid. Sandblasting is also possible. If the grinding machine is ground, the cost is high, and the processing volume is large, which may make the size not meet the standard. If the hydrochloric acid can't be washed off, it is estimated that you are using high-chromium die steel. Is it D2 or H13? The high-chromium die steel oxide layer is difficult to wash off. It should be possible to use stainless steel pickling, which is available in abrasive shops or stainless steel stores.

(2) Do you have stainless steel pickling cream? That kind of. H13 is a mold steel with a relatively high chromium content, and the oxide layer is difficult to wash off with hydrochloric acid. There is another way, I use it myself. Since your mold has been worn by oilstone, the surface is smooth. In fact, it can be polished only with coarse oilstone or with a sanding belt, and then heat treated. After returning, polish with fine stone. The method I used was to remove the black skin and then grind it with the fiber wheel. Or sand blasting, try to use a 800-mesh boron carbide for sand blasting, you should be able to remove the black skin, and do not need to do too much effort to re-grind.

3. How is the heat treatment plant heat treated on the metal?

There are many equipments in the heat treatment plant. There are probably box furnaces, pit furnaces and box furnaces. Many heat treatments can be used in this process, such as annealing, normalizing and quenching heating processes, and tempering. Heat treatment.

In fact, it is an electric heating furnace, first heat the furnace to a predetermined temperature, then throw the workpiece into it, wait for a period of time to a predetermined temperature, then keep it for a while, then take it out, or cool it together in the furnace. The pit furnace is generally As a carburizing treatment equipment, it is a furnace buried in the ground. After the workpiece is placed in, it is sealed, and then some carbon-rich liquid, such as kerosene or methanol, is dropped into the furnace, and then the liquid is decomposed into carbon atoms and infiltrated into the workpiece at high temperature. surface.

The quenching tank is a quenching place, which is a pool with an aqueous solution or oil. It is the place where the quenching of the workpiece from the box furnace is cooled. Generally, it is directly thrown in, and then it is taken out for a while. There are other devices, such as high-frequency machines, which are ultra-high-power devices that can convert 50 Hz power frequency into a 200K Hz current, such as a common 200 kW maximum power, and then use an internal pass cooling. The coil made of copper tube of water is placed on the outside of the workpiece. Generally, the workpiece is several tens of millimeters. When it is several seconds to ten seconds, you can see that the surface of the workpiece turns red. When the surface temperature reaches a predetermined value, then there is a water. The set is raised and sprayed to the surface of the workpiece to complete the quenching process. This is common.

4. Our recent Cr12 or Cr12MoV materials have been heat treated and cracked several times. Why?

It is best to tell the size, shape and heat treatment requirements of the parts on the metal mold, and the heat treatment process curve you take, otherwise it is difficult to say. These two types of steel are of the type that are high-carbon, high-chromium, Leysite steels and have a tendency to cold crack. The heat treatment process is also complicated.

Let me talk about my experience without the above information: 950-1000C quenching, oil cooling, HRC>58. In order to obtain hot hardness and high wear resistance, the quenching temperature is increased to 1115-1130C, oil cooling. The thin air-cooling is also cooled in the 400-450C salt solution in order to reduce the deformation. Do not temper at 300-375C, which will reduce the toughness of the tool, temper brittleness, and temper immediately after quenching. Quenched above 1100C, tempered 2-3 times at 520C. Please note that too high a quenching temperature tends to decarburize, for which a pre-heat treatment - spheroidizing annealing can be performed before quenching.