SUM24L Description:

SUM24L free cutting structural steel, Japanese standard. SUM24L free cutting structural steel, free cutting steel is easy to be (turning, milling, pulling, planing, drilling, etc.) cutting steel, also called automatic machine tool processing steel, referred to as automatic steel. It is to adapt to the automation of mechanical processing and flow line production. This kind of steel can use high cutting speed and deep turning machining, and since joining the free-cutting steel elements make cutting resistance decreases and the join of the element itself characteristics and formation of the compound ACTS as lubricate cutter blade, make the chip easy broken, reduce the wear and tear, thus improve the roughness and precision of the processed parts, improves the knives’ service life and production efficiency.

SUM24L is a free-cutting structural steel in the Japanese standard. SUM24L free-cutting structural steel is produced to adapt to machining automation and assembly line production. This type of steel can be cut with a higher cutting speed and a deeper cutting amount, 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, reduces wear, thereby improves the finish and accuracy of the processed parts, and improves the tool life and production efficiency.

SUM24L Cutting Note:

SUM24L 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 an important part of manufacturing 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.

SUM24L Chemical Composition:


SUM24L Mechanical properties:

Rp0.2 (MPa)
Rm (MPa)
KV (J)
A (%)
Reduction in cross section on fracture
Z (%)
As-Heat-Treated ConditionHBW
267 (≥)415 (≥)211143Solution and Aging, Annealing, Ausaging, Q+T,etc314

Physical properties:

Temperature T
Specific heat
J / kgK
Thermal conductivity
Electric resistance
922 (≥)795 (≥)344222Solution and Aging, Annealing, Ausaging, Q+T,etc
Creep strain limit
(Rp1,0) N/mm2
Creep rupture strength
(Rp1,0) N/mm2