Editor's note
100 years ago, American mechanical engineer F. W Taylor and metallurgical engineer M. White established the best component W28Cr4V for cutting high-speed steel after extensive and systematic cutting tests (C 0.75%, W 18%, Cr 4.0%, V 1.0%), the carbon steel speed during cutting was 30m/min, which was more than ten times higher than before. This achievement brought about an epoch-making revolution in machining, which made the Tool materials show an extraordinary development speed after entering the 19th century, creating unprecedented glory. In the past 100 years, despite the emergence of various new tool materials, high-speed steel has not been eliminated by history, has been used and developed to this day, and even occupied a dominant position for a long time.
Today, we will re-examine the development of high-speed steel, which may bring some useful inspiration for the further development of tool materials. Here, I also put together four experts from Zhao Bingyan, Wu Yuanchang, Zhao Buqing and Wu Lizhi at the Heye 2006 High Speed ​​Steel Application Technology Exchange Conference to clarify the readers.
Many people may have a better understanding of the general principles of tool heat treatment, but the research on differential heat treatment of tools and tool materials is not deep. I have been working in the heat treatment process for nearly 40 years. I have accumulated a lot of successful experiences and failure lessons. I deeply understand the difference between the tool and tool materials and the importance of individualized operation. The following is a brief introduction to the heat treatment of different tools:
Turning blade
According to the GB4211 standard, the turning tool strip can be divided into two types: square and rectangular. The working conditions of the turning tool are relatively harsh. Generally, there is no coolant, dry cutting, heavy cutting, interrupted cutting, high-speed cutting, etc. The cutting tool is required to have high wear resistance and high red hardness. In view of the above situation, the heat treatment process is: austenitization at a high temperature of 1230-1240 °C, the metallographic level can reach 8-9, and then tempered 4 times, overheated 3 to 4 (rectangular turning tool overheated 1 to 2) The final tissue hardness is 65-67HRC. Practice has proved that the car is overheated and durable. In 1988, I tested the life of the super 12-level 12×12 square turning tool. As a result, all three samples reached the first-class standard.
Hob
Hob is a relatively expensive metal cutting tool. It requires high red hardness and wear resistance. Therefore, the quenching temperature is relatively high, but it is slightly lower than the turning tool. It is often graded at 1225~1230 °C, 580-620 °C, and the metallographic structure is organized. Level 9.5 to 10 levels. The first tempering should be treated with 350-380 ° C or secondary bainite, then tempered at 550 ° C × 1 h for 3 times, overheated 1 to 2, or even 3, the final tissue hardness can reach 65HRC or above. .
Although the hob is an easy-to-handle tool, the large hob with a modulus of 6 or more must be strictly guarded due to its low hardness and cracking of the keyway.
Straight tooth three face milling cutter
Usually, such products have high cutting speed and high requirements on wear resistance and toughness due to their high cutting speed, and require high hardness but cannot be chipped. The author has dealt with such quality problems many times: the user's response to the milling cutter with a hardness of 64-65HRC is not wear-resistant. After switching to a milling cutter with a hardness of 66HRC, the service life is doubled. The same composition of materials, different heat treatment products can have such a big difference. The heat treatment process of the straight tooth three-face milling cutter is quenched at 1220~1230 °C, the metallographic grade is 9.5~10.5, the tempering is 3-4 times, the superheat is grade 1, and the final microstructure hardness is 65-67HRC.
Middle tooth Saw Blade milling cutter
The GB6120 standard is suitable for medium-tooth saw blade milling cutters with a diameter of 32~315mm and a thickness of 0.3~6.0mm. The heat treatment process of the special large-thickness milling cutter should be personalized. Generally, the performance requirement of the medium-tooth saw blade milling cutter is the first toughness. However, the hardness should not be too low, generally quenching at 1205~1215 °C, the metallographic grade of quenching structure is 10~11 grade, then graded isothermal, hot clamp, tempering 4 times, tempering process is not allowed to overheat, final tissue hardness 64 ~66.5HRC. In the heat treatment process of such tools, the problem that the keyway is easy to crack and the flatness is too poor is prone to occur.
Large thin saw blade
Due to the rapid development of the decoration and construction industry, the market demand for large Φ250～500×2mm large saw blades. This product mainly requires outstanding toughness, followed by wear resistance. The corresponding heat treatment process is 1180 ~ 1200 ° C high temperature heating, 260 ~ 280 ° C isothermal, metallographic grade can reach 11 ~ 12, and then tempered 4 times, no overheating, hardness can reach 62 ~ 65HRC. The finished product is more effective if it is steam treated or oxynitrided.
Overall straight shank twist drill
The Drill Bit is the most used hole machining tool and the working conditions are different from other tools. When drilling, the cutting part is deeply buried in the metal, the cutting conditions are harsh, and the bit is required to have high hardness and toughness. The latter is usually more important than the latter; for dry cutting, due to the workpiece High hardness is the first requirement for red hardness. The general heat treatment process of the drill bit is: first quenching at 1210~1225 °C, the metallographic grade of the quenched structure can reach 10.5-11, and then tempered 3 times, overheating 2, can obtain tempering with hardness of 63-66.5HRC. organization.
Due to the increasing number of machining centers and CNC machine tools, the number of difficult-to-machine materials is increasing day by day, and the requirements for drill bits are getting higher and higher. The same drill bit, the usage is different, the heat treatment process is completely different, which is enough to explain the importance of the individualization of the heat treatment process.
Broach
Broaching is widely used in automotive, aerospace and other manufacturing industries. There are many teeth arranged on the broach. Due to the wide broaching range, the tooth increment is gradually increased. Even in the case of a small feed amount, the resistance is quite large. Because of this, the speed of broaching is generally slow. During the broaching process, the axial direction is subjected to a large pulling force. At the same time, the cutting teeth generate heat due to the friction of the workpiece, so the broach has the high hardness characteristic of the general tool. More important is the high strength and toughness. The common heat treatment process of the broach is 1205~1215 °C oil quenching, two or three times of staged cooling, hot heat straightening, and the metallographic grade of the sample quenching structure is 10.5~11.5. It must be straightened after each tempering and the hardness can reach 64~66.5HRC.
At present, the main problem of heat treatment is that the hardness is low and not wear-resistant, and secondly, it is broken. The corresponding heat treatment process should be formulated according to the specific type of broach.
Machine tap
In the cutting process, the main resistance is the torsional moment, and the axial force has canceled each other in each thread. The tap does not need red hardness, and the toughness is the first index, so the quenching temperature is relatively low, the grain number can be controlled very fine, but the hardness can not be low, and must comply with national standards.
Nowadays, due to the new technology of toughening and low-temperature quenching, compared with the traditional process, the quenching temperature is reduced by 15-20 °C, which completely solves the defects such as overheating and brittle fracture of the tap, which is a good thing in one fell swoop.
My personal experience is: hardness is a superficial phenomenon, metallographic organization is the essential thing; we pursue high hardness, but not only high hardness; we require high hardness, under the premise of metallographic organization ideal (not qualified), A good fit between hardness and metallography is achieved. There are several key issues in this that cannot be underestimated:
1) First of all, it is not possible to mix materials, including mixing furnace number, mixed steel number, and mixed specification. The tool factory must be managed by the furnace number. If it is not possible, the heat treatment cannot be done well. For example, M2 steel with qualified components, if heated and quenched at 1220 °C, there may be 6 grain numbers of 9-12.
2) Secondly, different smelting methods affect the heat treatment process. The medium heat-frequency smelting and electro-slag remelting steel and electric arc furnace smelting the same composition of M2 steel, the heat treatment process should be different. The quenching temperature of the latter should be suitably higher, and the former is prone to overheating and the like before quenching.
3) The third is the forging effect heat treatment process. M2 steel of the same specification and the same composition is made of the same specification tool, forging and not forging, and the heat treatment process should not be the same. After the forging, the quenching temperature should be slightly lower. These should be taken care of when formulating the heat treatment process.
4) Fourth, the quenching temperature of the returned workpiece should be 8-15 °C lower than the conventional quenching. For various reasons, a small number of rework is inevitable, so it is necessary to find out what causes rework before quenching, and then how to anneal, so that the right medicine can be prescribed.
5) Fifth, because M2 steel quenching temperature band is relatively wide, from 1180 ° C to 1240 ° C span of 60 ° C, and different tools require different performance, so heat treatment workers must figure out what is the most important tool processing object, Implement individualized indicators into the heat treatment process to fully tap the material potential.
Concerned about surprises
Label: Heat treatment process Tool material Broaching Quenching Difficult to process materials
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Glass bits have a spade-shaped carbide point, used to drill holes in materials of glass, ceramics,etc. They generate high temperatures and have a very short life. Holes are generally drilled at low speed with a succession of increasing bit sizes. Diamond drill bits can also be used to cut holes in glass, and last much longer.
It is an alloy triangular bit mounted on the ordinary Electric Hand Drill, which has high hardness, sharp blade and good precision, and is specially used for opening holes in ceramic tiles. But the drill wears too much into concrete to be used on concrete.
Ceramic Tile Bit,Ceramic Drill Bit,Drilling Through Tile,Ceramic Tile Drill Bit
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