SUM22 Free Cutting Steel Bar

 

SUM22 belongs to lead-sulfur composite free-cutting structural steel. In lead free-cutting steel, lead is distributed in the steel as tiny elementary metal particles and is not solid-melted in the steel. During the cutting process, strong friction occurs between the tool and the workpiece, which makes the lead particles in the steel melt. 

 

Precipitation, which plays a role of lubrication to improve the cutting performance of steel, make the steel chips finely, reduce tool wear, and ultimately extend tool life. Compared with lead-free steel, the cutting performance of lead-containing steel can be increased by 20-50%, while the mechanical properties and heat treatment performance remain basically unchanged, and it has no effect on cold and hot workability and weldability. Lead free-cutting steel has been widely used as important parts for the manufacture of precision instrument parts, auto parts, and various types of machinery. 

 

However, lead free-cutting steel has low contact fatigue, so it is not suitable for parts such as gears and bearings that bear large fatigue stress loads. SUM22 has a tendency to be replaced by it. Its cutting performance is also very good. It is suitable for more strict occasions where SUM22 cannot be used.

 

SUM22 is an S-P composite high-sulfur, low-silicon free-cutting steel. The machinability is significantly higher than that of Y12Pb , and the production efficiency is 30-50% higher than that of Y12Pb steel. Especially when tapping, the tap life is more than twice that of Y12Pb. SUM22 is often used in the manufacture of unimportant standard parts, such as bolts, nuts, and pipes. Connectors, spring seats, etc.

 

SUM22 is produced to adapt to mechanical processing automation and assembly line production. This type of steel can be cut with a higher cutting speed and a deeper amount of cutting, and the cutting resistance is reduced due to the addition of free-cutting elements in the steel, and the characteristics of the added elements and the compounds formed to lubricate the cutting edge The function of the part makes the chips easy to break and reduces wear.

 

Chemical Composition:

 

C:  0.13 max

Mn:  0.70~1.00

P: 0.07~0.12

S:  0.24~0.33

 

Mechanical Properties:

 

1. Tensile strength σb (MPa):

 

(Hot rolled) 390~540;

 

(Cold drawn) Steel thickness or diameter:

 

  • 8~20: 530~755;
  • >20~30: 510~735;
  • >30:490~685;

 

2. Elongation δ5 (%): (hot rolled)≥22; (cold rolled)≥7.0

 

3. Reduction of area ψ (%): (hot rolled) ≥ 36

 

4. Hardness: (hot rolled)≤170HB; (cold drawn)152~217HB

 

Application: 


The machinability of SUM22 is significantly higher than that of Y12, and the production efficiency is 30-50% higher than that of Y12 steel. Especially when tapping, the tap life is more than twice that of Y12. SUM22 is often used in the manufacture of unimportant standard parts, such as bolts and nuts. , Pipe joints, spring seats, etc.