How Much do You Know About Press Brake Tooling Heat Treatment?

The press brake tooling is used to form a tool for processing sheet materials. This tool is composed of various parts, and different molds are composed of different parts. It mainly realizes the processing of the shape of the article by changing the physical state of the formed material. A tool is used to make a blank into a part of a specific shape and size under the pressure of a bending machine.

Any metal must expand when heated. Since the steel is heated, the uneven temperature of each part of the same press brake tooling (that is, the uneven heating) will inevitably cause the inconsistency of the expansion of each part in the press brake mold steel, thus Internal stress due to uneven heating is formed. At the temperature below the transformation point of the steel, uneven heating mainly produces thermal stress, and also produces an isochronous structure transformation, which not only produces structure stress. Therefore, the faster the heating speed, the greater the temperature difference between the die surface and the core of the bending machine, the greater the stress, and the greater the deformation of the die after heat treatment. Therefore, different mold quenching methods are not the same.

How Can H13 Die Steel be Heat Treated to Achieve Hardness of 58℃?

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

What is The Surface Cleaning of The mold After Heat Treatment?

It can be cleaned with stainless steel pickling solution or hydrochloric acid. Sandblasting is also possible. The cost of grinding by a grinder is high, and the processing volume is large, which may cause the size to be substandard. If the hydrochloric acid cannot be washed off, it is estimated that you are using high-chromium die steel? Is it D2 or H13? The oxide layer of high-chromium die steel is more difficult to wash off. It should be OK to use stainless steel pickling solution, which is available in abrasive stores or stainless steel stores.

Don’t have a stainless steel pickling paste? That kind of will do. For the mold steel with high chromium content such as H13, the oxide layer is difficult to wash off with hydrochloric acid. There is another way that I am using myself. Since our mold has been ground with oil stone, the surface is relatively smooth. In fact, it can be ground with only a coarse whetstone, or with an abrasive belt, and then heat treated. When it comes back, sand it with a fine oil stone. The method used is to use the fiber wheel to grind first, then the black skin can be effectively removed, and then grind and polish. Or sandblasting, try sandblasting with 800-mesh boron carbide, and you should be able to remove the black skin without much effort and regrinding.

How Does The Heat Treatment Factory Heat The Metal?

There is a lot of equipment in the heat treatment plant. The furnaces probably include box furnaces, pit furnaces, and box furnaces. Many heat treatments can be processed here, such as the heating process of annealing, normalizing and quenching, and tempering. These are common heat treatments.

In fact, it is a furnace heated by electricity. First, the furnace is heated to a predetermined temperature, and then the workpiece is thrown into it, waited for a period of time to reach the predetermined temperature, then kept for a period of time, and then taken out, or cooled together in the furnace. The pit furnace is generally a piece of carburizing treatment equipment, it is a furnace buried underground. After the workpiece is put in, it is sealed, and then some carbon-rich liquid, such as kerosene or methanol, is dropped into the furnace, and then these liquids are decomposed into carbon atoms and penetrate into the workpiece at a high-temperature surface.

What is Non-heat Treatment Strengthening?

Surface treatment: such as hard chrome plating, to increase the wear resistance of the press bending tooling; shot peening used for parts working under alternating stress, which can greatly improve the fatigue strength; rolling: using rolling tools to surface parts at room temperature apply pressure to plastically deform the metal surface, correct the microscopic geometry of the metal surface, improve the surface finish, improve the fatigue strength of the parts, as well as wear-resistance and hardness.

How to Distinguish Press Brake Tooling With Heat Treated or Not?

A worker accidentally mixed an unheated-treated raw part with a batch of debugged heat-treated parts. How to distinguish them now ?

Heat treatment process 30Cr is normalized, re-quenched, and then tempered, and the green part is cast without heat treatment. Both of them have been shot blasted, and the discoloration cannot be distinguished, and the hardness is between 35-45, which cannot be distinguished by hardness. If it can’t be judged by hardness and heat treatment oxidation color. It is recommended to identify by tapping sound. Castings and quenched + tempered workpieces have different metallographic structures and internal friction, which may be distinguished by light tapping.

What Does Overburning in Press Brake Tooling Heat Treatment Mean?

Exceeding the specified heating temperature will cause the grains to grow, and the mechanical properties will deteriorate, such as increased brittleness, decreased toughness, easy deformation and cracking, etc. Controlling the heating temperature can avoid over-burning. It means that when the steel is heated above a certain temperature in the temperature range of the solids and liquids, the chemical composition of the austenite grain boundary changes, and the local or whole-grain boundary appears sintering. At this time, S, P, and other compounds will be enriched on the grain boundary, resulting in a decrease in the bonding force of the grain boundary and a serious deterioration in mechanical properties. After overburning, the steel cannot be remedied by heat treatment or processing.

Causes And Preventive Measures of Press Brake Tooling Quenching Cracks

• Causes

1. Severe network carbide segregation exists in the mold material.
2. There are machining or cold plastic deformation stresses in the mold.
3. Improper heat treatment operation of the mold (too fast heating or cooling, improper selection of quenching cooling medium, too low cooling temperature, too long cooling time, etc.)
4. The complex shape of the mold, uneven thickness, sharp corners and threaded holes, etc., make the thermal stress and tissue stress too large.
5. The mold quenching heating temperature is too high to cause overheating or overburning.
6. After the mold is quenched, the tempering is not timely or the tempering holding time is insufficient.
7. When the mold is reworked and quenched, it is reheated and quenched without intermediate annealing.
8. The mold is heat treated and the grinding process is improper.
9. High tensile stress and micro-cracks exist in the hardened layer during EDM after heat treatment of the mold.

• Precaution

1. Strictly control the inherent quality of mold raw materials.
2. Improve the forging and spheroidizing annealing process, eliminate the reticulated, banded and chain carbides, and improve the uniformity of the spheroidized structure.
3. After machining or cold plastic deformation, the mold should be subjected to stress relief annealing (>600℃) and then heat quenching.
4. For molds with complex shapes, asbestos should be used to block threaded holes, dangerous sections and thin walls should be wrapped, and graded quenching or isothermal quenching should be used.
5. Annealing or high temperature tempering is required when reworking or refurbishing molds.
6. The mold should be preheated during quenching and heating, and pre-cooling measures should be taken during cooling, and an appropriate quenching medium should be selected.
7. The quenching heating temperature and time should be strictly controlled to prevent overheating and overburning of the mold.
8. After the mold is quenched, it should be tempered in time, the holding time should be sufficient, and the high-alloy complex mold should be tempered 2-3 times.
9. Choose the right grinding process and the right grinding wheel.
10. Improve the mold EDM process, and carry out stress relief tempering.

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