Výběr nástrojových ocelí

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Tato část vysvětluje důležitost výběru nástrojové oceli, aby pomohla našim zákazníkům vybrat správnou ocel pro různé nástrojové aplikace.

First, refer to the article in our blog that explains “Co je nástrojová ocel.” Then, consider how to choose tool steel.

Důležitost výběru nástrojové oceli

The first step in selecting a tool steel is to confirm its intended application. For example, a drill is used for drilling holes, so it needs to be nosit-resistant and resistant to high temperatures. Another example, a punch is used for stamping or shearing, so naturally, the material needs to be both wear-resistant and tough (high toughness means it won’t break easily).

Let’s divide tool steel into six categories, according to its applications:

1. Řezání: Pro vrtáky a frézy je potřeba ocel odolná proti opotřebení a žáruvzdorná.
2. Stříhání a děrování: U razníků a forem musí střižná ocel nebo děrování splňovat požadavky na odolnost proti opotřebení a houževnatost.
3. Molding: Such as plastic molds, forging molds, and steel molds, should be easy to process, and can be polished smoothly.
4. Stretching and extrusion: Such as aluminum frames, cold-drawn steel bars, wear-resistant, and not easy to deform.
5. Válcování: Válcovací kruhová tyč, plochá deska, odolné proti opotřebení, žáruvzdorné požadavky.
6. Miscellaneous: hammering, filing, and scraping, with specific needs for each application.

Výkonové charakteristiky nástrojové oceli

Vlastnosti nástrojové oceli dělíme na vlastnosti primární a sekundární:

Primární vlastnosti

Toto jsou základní vlastnosti oceli:

1. Wear Resistance: The ability of the steel to resist wear and tear. For example, cutting tools must remain sharp for an extended period.
2. Toughness: Steel can resist fracture. For example, the punch needs to withstand the impact.
3. Heat resistance: Steel can also maintain performance at high temperatures. For example, high-speed drill bits are affected by frictional heat.

Hardness is also a very important point, but it is not one of nature’s properties. It needs the right heat treatment to adjust. The higher the hardness, the less deformable it is, making it suitable for high pressure.

Sekundární vlastnosti

These are characteristics that affect the tool-making process:

1. Machinability: the material can be easily machined into the tool’s shape.
2. Broušení: Jak snadno lze ocel brousit (leštit).
3. Leštitelnost: zda lze materiál hladce leštit, jako jsou plastové formy vyžadující hladký povrch.
4. Safety in Heat Treatment: Heat treatment of steel can increase its susceptibility to cracking.
5. Distortion in Heat Treatment: The shape of the material after heat treatment changes greatly.
6. Heat Treating Range: The range of heat-treating temperatures that steel can accept.
7. Availability: This material is not readily available on the market.
8. Cena: Cena samozřejmě není vysoká.

Kompromisy při výběru nástrojové oceli

Při výběru nástrojové oceli existuje kompromis mezi vlastnostmi: zvýšení odolnosti proti opotřebení a tepelné odolnosti obvykle snižuje houževnatost, zatímco zvýšení houževnatosti může zhoršit odolnost proti opotřebení a teplu.

For example, a punch that needs to be wear-resistant might be made of A2 steel, but it is not tough enough and is prone to cracking. If we changed to S7 steel, which has better toughness and is less prone to deformation during heat treatment, the wear resistance would be worse than that of A2.

That’s why we say no one steel is perfect for all needs. According to the application, the best combination of primary and secondary properties is important.

First step in the selection of tool steels

The following table serves as a preliminary guide for selecting tool steel. Simply put, it helps engineers and customers systematically choose the most suitable tool steel for specific application scenarios. First, determine the tool’s function—whether it is for “Cutting,” “Shearing,” or “Forming.” Next, examine the specific working conditions, such as whether it involves “Light cuts, slow speeds” or “Heavy cuts, fast speeds.” Finally, the table indicates the key properties the selected tool steel should possess under these conditions, along with specific performance grade ranges. For example, “Wear resistance” should reach grades 4-8, while “Toughness” should reach grades 1-3. This makes the material selection process more scientific and precise, avoiding incorrect choices based solely on experience. This serves as an invaluable reference tool, enabling users to pinpoint the required performance specifications for steel selection quickly.

Tool-and-die steel comparator

Tool steel selection guide

Příklad výběru nástrojové oceli

When stamping 3/8-inch thick steel plates with A2 steel, the problem of edge cracking may stem from its lack of toughness. Although A2 steel has good wear resistance, it appears weak when subjected to impact. To fix this problem, let’s consider choosing the more ductile L6, A8, S1, S5, or S7 steels. S7 steel may be superior due to its heat-treatment safety and low distortion. However, the trade-off is that S7 steel has reduced wear resistance compared to A2 steel, which may lead to faster wear. It’s a mouthful. Therefore, in practice, no one steel is 100% perfectly suited to all situations and must be selected based on the application.

Další úvahy

In addition to selecting tool steel, it is important to consider whether the tool design is appropriate. Let me give you an example of whether the shape of the punch is suitable. Is the heat treatment process correct, and do the temperatures and times affect performance? Whether the tool is properly used and maintained, and whether it is adequately serviced. In addition to tool steel, consider materials such as martensitic aging steels, steel-jointed carbides, and copper-beryllium alloys. Simply replacing the steel will not necessarily solve the problem; a thorough examination and analysis are necessary.

Abych to shrnul

Tool steel selection aims to achieve the lowest cost per product or the fewest production problems with the most appropriate tool steel. However, tool steel is not a panacea and cannot be expected to never break down. When selecting steel, a combination of use, performance, and cost needs to be considered, and full communication with the steel supplier, the tool manufacturer, and the heat treatment specialist is very important. Feel free to contact us. Our company offers the most common tool steels on the market. For more information, please click on nástrojové oceli.