Stainless steel material processing technology (1) Factory Suppliers Manufacturers Quotes

Stainless steel material processing technology (1)

When some austenitic and martensitic stainless steel materials such as 1Cr18Ni9Ti and 2Cr13 holes are processed by drilling, reaming and boring process, common problems such as accelerated tool wear, poor surface integrity and difficult chip removal are encountered during the processing. Affects the processing quality, production cycle and processing cost of such material parts. According to the theory of metal technology and metal cutting, the difficulty of the above materials is analyzed, and a set of effective stainless steel drilling, reaming and boring processing techniques are explored.

Difficulties in processing stainless steel materials

The main difficulties in processing stainless steel materials are as follows:

1. High cutting force and high cutting temperature

This type of material has high strength, large tangential stress during cutting, and large plastic deformation, so the cutting force is large. In addition, the material has extremely poor thermal conductivity, which causes the cutting temperature to rise, and the high temperature tends to concentrate in a narrow area near the cutting edge of the tool, thereby accelerating the wear of the tool.

2. Hard work hardening

Austenitic stainless steels and some high-alloy stainless steels are austenitic structures. The work hardening tendency is large when cutting, usually several times that of ordinary carbon steel. The cutting of the tool in the work hardening zone shortens the tool life.

3. Easy to stick the knife

Both austenitic stainless steel and martensitic stainless steel have the characteristics of strong chipping and high cutting temperature during processing. When the strong chips flow through the rake face, the sticking phenomenon such as bonding and welding will occur, which affects the surface roughness of the machined parts.

4. Tool wear is accelerated

The above materials generally contain high melting point elements, large plasticity, high cutting temperature, which accelerates tool wear, frequent sharpening and tool change, thereby affecting production efficiency and increasing tool use cost.

Through the above analysis of processing difficulties, the processing technology of stainless steel and related tool parameters should be quite different from ordinary structural steel materials. The specific processing techniques are as follows:

1. Drilling processing

In the drilling process, due to the poor thermal conductivity of the stainless steel material, the elastic modulus is small, and the hole processing is also difficult. To solve the hole machining problem of such materials, it is mainly to select the appropriate tool material to determine the reasonable tool geometry and the cutting amount of the tool. When drilling the above materials, the drills should generally use drills made of W6Mo5Cr4V2Al, W2Mo9Cr4Co8, etc. These materials have the disadvantage of being expensive and difficult to purchase. When using the commonly used W18Cr4V ordinary standard high-speed steel drill bit, due to the small apex angle, the swarf is too wide, the hole cannot be discharged in time, the cutting fluid can not cool the drill bit in time, and the thermal conductivity of the stainless steel material is poor, resulting in concentration. The cutting temperature on the cutting edge is increased, which tends to cause burns and chipping of the two flank faces and the main edge, which reduces the service life of the drill bit.

(1) Tool geometry parameter design

When drilling with W18Cr4V ordinary high-speed steel drill bit, the cutting force and cutting temperature are concentrated on the drill tip. In order to improve the durability of the cutting part of the drill bit, the apex angle can be appropriately increased, and the apex angle is generally selected from 135° to 140°. An increase in the apex angle will also reduce the rake angle of the outer edge and narrow the drill cuttings to facilitate chip evacuation. However, after the apex angle is increased, the chisel edge of the drill bit is widened, resulting in an increase in cutting resistance. Therefore, the chisel chisel edge must be ground. After the dressing, the slant angle of the chisel edge is 47° to 55°, and the rake angle of the chisel edge is 3°~5°, when grinding the chisel edge, the cutting edge should be rounded at the corner of the cylindrical surface to increase the strength of the chisel edge. Due to the small elastic modulus of the stainless steel material, the metal elasticity under the chip layer is restored, and the work hardening is severe during the processing. The back angle is too small, which will accelerate the wear of the flank of the drill bit, and increase the cutting temperature and reduce the life of the drill bit. Therefore, the back angle should be appropriately increased, but the back angle is too large, which will make the main edge of the drill bit thin and reduce the rigidity of the main edge, so the back angle should be 12°-15°. In order to narrow the drill cuttings and facilitate chip evacuation, it is also necessary to open staggered chip flutes on the two flank faces of the drill bit.

(2) Cutting amount selection

When drilling, the amount of cutting should be selected from the basic point of lowering the cutting temperature, because high-speed cutting will increase the cutting temperature, and high cutting temperature will increase the tool wear, so the most important thing in cutting amount is to choose the cutting speed. In general, the cutting speed is preferably 12 to 15 m/min. Feed has little effect on tool life, but too small a feed rate will cause the tool to cut in the hardened layer, which will aggravate the wear; if the feed is too large, the surface roughness will be deteriorated. In combination with the above two factors, the feed amount is preferably selected from 0.32 to 0.50 mm/r.

(3) Cutting fluid selection

In order to reduce the cutting temperature during drilling, an emulsion can be used as the cooling medium.

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