Supply Y20 free cutting steel round bar with excellent quality

Classification can be divided according to the free-cutting elements contained
⑴ Sulfur free-cutting steel
Sulfur forms manganese sulfide inclusions with manganese and iron in the steel. Such inclusions can interrupt the continuity of the base metal, and during cutting When the chip is broken, it forms a small and short curl radius, which is easy to remove, reduces tool wear, reduces the roughness of the machined surface, and increases the tool life. Generally, the machinability of steel increases as the sulfur content in the steel increases. However, the longitudinal and transverse mechanical properties of steel are quite different, the transverse plasticity and toughness are poor, and the fatigue and corrosion resistance properties are also reduced. When the sulfur content in steel is too high, it will cause thermal brittleness, cause difficulties in hot processing of steel, and deteriorate the mechanical properties of steel. Usually the sulfur content is. %～． %, some can be increased to. %, the sulfur content in free-cutting tool steel and stainless steel should be within. %～. %between.
Phosphorus is often added to steel in combination with sulfur, and usually the phosphorus content is in the range. %～. %, phosphorus solid solution in ferrite will increase the hardness and strength, reduce the toughness, make the chips easy to break and remove, thereby obtaining good processing surface roughness, but too high phosphorus content will significantly reduce the plasticity and increase the hardness, but on the contrary The machinability of steel plays a detrimental role.
⑵ Lead free-cutting steel
Lead is in the form of fine metal particles in the steel, evenly distributed or attached around the sulfide. Due to the low melting point of lead, the melt oozes out during cutting to lubricate, reduce friction and improve machinability, but does not affect the mechanical properties at room temperature. The lead content in steel is generally . %～. %. Because lead has a large specific proportion, if the content is too high, it will easily cause severe segregation and form large particle inclusions, which will instead reduce the beneficial effect of lead on cutting processing. Lead and sulfur are combined into low carbon structural steel to improve the cutting effect of the steel more significantly.
⑶ Calcium free-cutting steel
Calcium in steel combines with aluminum and silicon to form low-melting point composite oxides (mainly). During high-speed cutting, the calcium-based oxides adhere to the surface of the cutting tool for lubrication and lightening. Friction effect, thereby increasing the service life of the tool. If it contains elements such as sulfur and lead at the same time, their composite effect will make the cutting effect better.
With the improvement of cutting tools since the 1990s, tools coated with calcium free-cutting steel have a significant effect on gear processing tools such as hobbing cutters and gear shaper cutters with high tool costs.
⑷ Selenium, tellurium and bismuth free cutting steel
The content of tellurium and bismuth is approximately. %～. %, the content of selenium can reach. %. Selenium exists in steel in the form of selenides such as selenium, etc., and its role is similar to that of sulfur. For steel that requires both high machinability and good plasticity, it is better to add selenium to steel than sulfur. Tellurium can be added alone or simultaneously with lead or sulfur to form composite inclusions to reduce cutting resistance and cutting heat, make chips easy to remove, significantly improve the cutting performance of steel, and obtain good machined surface roughness. However, Adding tellurium will slightly reduce the plasticity and toughness of steel. Selenium and tellurium are generally used in alloy steel. Bismuth acts similarly to lead in steel, appearing as inclusions of fine metal particles, evenly distributed or attached around sulfides.
Free cutting element editor
Tellurium
As a free cutting element used in free cutting steel, it first appeared in the patent of 2007. In 2008, the United States successfully developed a tellurium-containing free-cutting steel. It is a sulfur-lead-tellurium multi-component composite free-cutting steel. Its cutting properties are very excellent and can be compared with free-cutting brass. Since selenium and tellurium have similar properties and effects, they are often used interchangeably or added to steel at the same time.
Calcium deoxidation
Since the 1980s, people have studied to improve the machinability of steel through another approach, that is, adding certain deoxidation elements to generate the required deoxidation products and beneficial inclusions. In Japan, this is called It is deoxidized and adjusted free-cutting steel. The former Federal Republic of Germany first proposed a patent for calcium free-cutting steel using calcium deoxidation in 2008. It was introduced and officially produced by Japan later in the year. It is most suitable for use with carbide tools for high-speed cutting, which can significantly increase productivity and reduce tool consumption. In Japan, it has become a kind of free-cutting steel that is used in large quantities in the automobile and tractor manufacturing industries.
Titanium deoxidation
Since the late 1990s, free-cutting steel with titanium deoxidation has been studied. In 2008, Japan first published a patent for titanium-sulfur composite free-cutting steel deoxidized by titanium. In recent years, trials have begun in a few countries such as Japan.
Effects of other elements[br/>Effects of other elements on the machinability of steel In addition to the above-mentioned easy-cutting elements in free-cut steel, other elements also have a certain impact on the machinability of steel
⑴Carbon. The carbon content in steel is related to the cutting performance of the steel. If the carbon content is too low, a large amount of ferrite will appear in the structure. The hardness and strength of the steel are very low. The chips will easily stick to the blade to form knife burrs. In addition, the chips will be torn and broken, which will reduce the machinability and make the machined surface rough. high. If the carbon content is too high, the amount of pearlite in the structure will increase, the hardness and strength will increase, the cutting resistance will increase, and the machinability will deteriorate. The carbon content in free-cutting structural steel is . %～. % is appropriate.
⑵Manganese. Manganese and sulfur in steel form manganese sulfide inclusions, which makes the chips easy to break, improves the machinability of the steel, and can also eliminate or weaken the thermal brittleness caused by sulfur. Therefore, the manganese content in free-cutting steel should be ensured. %～． %, and maintain an appropriate / ratio.
⑶Silicon and aluminum. Both silicon and aluminum have deleterious effects on the machinability of steel. Silicon is partially dissolved in ferrite, which increases the hardness of steel and makes cutting difficult. Moreover, silicon combines with oxygen in steel to form silicon oxide inclusions with higher hardness, which increases the wear of the tool and reduces its service life. Therefore, the silicon content in free-cutting steel should be low. Aluminum is generally added to steel as a deoxidizer, and most of it combines with oxygen to form small, brittle and hard aluminum oxide inclusions, which increases tool wear. Adding silicon and aluminum to steel will also reduce the oxygen content of the steel, causing the sulfide inclusions to be distributed in elongated strips, worsening the machinability of the steel.
⑷Oxygen and nitrogen. Oxygen is generally harmful in steel because it reduces the mechanical properties of the steel, but an increase in the oxygen content in free-cut steel will cause the sulfide to be distributed in a spindle shape and improve the machinability of the steel. Although nitrogen can improve the strength of steel, it also increases brittleness and will form short chip breaks during cutting. When the steel contains trace amounts of nitrogen (.%), it has a beneficial effect on the machinability and surface quality of the workpiece. However, when the content is too high, the strengthening effect of the steel increases, which is detrimental to the tool life.
Chemical composition editor
The composition (mass fraction) of free-cutting steel in several major countries is shown in the table.
Production process Free-cutting steel can be smelted in various steel-making furnaces, but low-carbon sulfur free-cutting steel should be smelted in a converter. Sulfur alloying is done by adding sulfur or iron sulfide to a steel drum or molten pool. For this purpose, the ferromanganese used is preferably low silicon and low carbon. If there are no special requirements, the silicon content in the steel should be reduced as much as possible to improve the machinability of the steel, and sufficient deoxidation should be carried out to prevent hair lines. Harmful gases such as sulfur and lead produced during the smelting process must be eliminated with powerful ventilation devices, and facilities for preventing and controlling environmental pollution must be used. When the sulfur content in free-cutting steel is high, it will tend to be hot and brittle, which is not conducive to hot processing, so attention should be paid to it. When cold working, strive to have accurate dimensions and good surface quality to improve the cutting performance on automatic machine tools.
Main use editor
Free-cutting steel is mainly used to make instruments, watch parts, automobiles, machine tools and other various machines that are less stressed and have strict requirements on size and finish. Standard parts that require strict accuracy and smoothness but relatively low mechanical performance requirements, such as gears, shafts, bolts, valves, bushings, pins, pipe joints, spring seats and machine tool screws, plastic molding molds, surgery and dentistry Procedure tools, etc. The details are as follows
⒈Automatic lathe processing, metal stamping parts processing
⒉Electronic industry, optical fiber connectors, CD players, scanners, medical equipment
Household appliances, instrumentation industry
⒋Office equipment (computers, photocopiers, cameras, fax machines, etc.)
⒌Clock components, glasses
⒍Electronic terminal pins, timers, carburetors
⒎Decorations, lighting accessories, Cars, motorcycles, chains
⒏ Cleaning car sweepers, toys
⒐ Pens, handbag accessories, belt buckles, fishing gear, etc.
⒑ Stud bolts, screws, nuts, pipe joints, spring seats wait.