The French company Premefer was confronted with this situation when they were asked to manufacture two tables for a large size vertical turning machine.
The work piece diameters were 1200 and 1900 mm, with a thickness of 104 mm each. The strength needed was defined as 90-110 kilos, one of the holders can be seen in Fig. 1.
Fig 1. Tool holder manufactured by Premefer
Premefer has 25 years experience in producing tools for cold forming, moulds for plastic parts as well as pieces for general industrial applications, so it was not the first time they were asked to manufacture this type of work, but the size of the work piece made it difficult to find the steel that the customer specified. The first idea was to forge the pieces, but this was discarded due to the delivery time of several weeks offered for the forgings. Then, it was decided to use a round bar of the steel grade 1.2311/40CMD8. Unfortunately, these large diameters are not readily available in the market, and to forge such large diameters can cause problems with centre soundness of the material such as porosity and segregation of the alloying elements.
After consulting with the steel distributor Alpes Metal Diffusion, it was decided to make one piece from Toolox 33 and the other from 1.2311 both cut from plate. Manufacturing from hot rolled plate instead of a forged diameter ensures far superior properties of the work piece due to the homogenous structure throughout the plate.
Toolox, is exclusively made by the Swedish steel maker SSAB, who implement consistent and high quality controls compared with standard steels like 1.2311.
Ultrasonic testing and mechanical tests are made on every single plate of Toolox, and the values are individually stated and certified.
To machine the pieces, Premefer used two axle milling with the following procedure; trimming of the surfaces, slotting, drilling and finally threading, Mr Jacquemin at Premefer noticed important benefits with Toolox compared to 1.2311 when machining the pieces. The tolerances in the geometry after machining were much better with Toolox. The stability was a very crucial parameter due to the large size of the piece. The machining speed was also greatly improved by 20-25 % compared to the piece made in 1.2311 steel. This advantage with Toolox is a result of the low carbon based microstructure.