METHOD OF MILLING ENGINE BLOCKS

Abstract: The present invention relates to a method of milling a material comprising aluminium and cast iron. By using a silicon nitride based cutting tool insert at a cutting speed of more than 1000 m/min an unexpected increase in tool life has been obtained.

Description: Typically the sintering aids used are AI2O3, BeO, MgO, TiC>2, Zrθ2 H1O2 and the oxides of the Group III elements of the periodic table scandium, yttrium, lanthanum, cerium, etc. The amount of sintering aid added is of the order of a few wt-%. The sintering aids form during sintering a glass phase, which facilitates the densification. Silicon nitride cutting inserts thus consist of beta silicon nitride in an intergranular glass phase. It is an extremely high demand to develop tool solutions with a long tool life and less frequent tool changes. Dry machining of these type of applications is a strong demand in order to reduce costs, health hazards and environmental impacts. It has now surprisingly been found that by dry machining using Silicon nitride inserts at a cutting speed above 1000 m/min a longer tool life and increased productivity can be achieved. The problem with built up edge and wear disappeared surprisingly with these cutting data using silicon nitride inserts. The problems with built up edge remained with silicon nitride inserts in lower cutting speeds and the wear was also higher. The present invention relates to machining of composite materials (aluminium in combination with cast iron) using silicon nitride inserts. The cutting data is as follows: Cutting speed = 1000-3000, preferably 1100-2500 m/min Cutting feed/tooth = 0.05-0.5, preferably 0.15-0.30 mm Cutting depth = 0.2-2 mm, preferably 0.3-1 mm Chip thickness = 0.09-0.17 mm Example Face milling of engine block was performed under the following conditions. Operation: Face milling, finishing Work piece : Engine block Material : Aluminium 8% Si and pearlitic grey cast iron Cutting speed: See table Feed rate/tooth: 0.26 mm Depth of cut : 0.5 mm Insert style: 28 pcs SBEX1203ZZ-11 and 4 pcs SBEN1203ZZ Grade 1: Coromant grade 6090. Grade 2: WC-6% Co cemented carbide with 4 μm TiN+TiC-coating Milling cutter: Auto FS 260.42 of diameter 250 mm. Tool life/insert is shown in the table Tool life criterion: unacceptable surface finish including component frittering. Result Tool life/insert Grade 1 Grade 2 invention reference Cutting speed 444 m/min 10 pcs 22 pcs 1178 m/min 60 pcs not possible 2356 m/min 70 pcs not possible Conclusions With silicon nitride inserts a higher productivity and a longer tool life are achieved, which leads to less problems with bottlenecks in the production and less frequent changes of tools. Another advantage is the need to turn off coolant, which has environmental as well as cost advantages .

Claims: Claims 1. Method of milling a material comprising aluminium and cast iron c h a r a c t e r i s e d in using a silicon nitride based cutting tool insert at a cutting speed of 1000-3000 m/min, a feed of 0.05-0.5 mm and a cutting depth of 0.2-2 mm. 2. Method according to claim 1 c h a r a c t e r i s e d i a chip thickness of 0.09- 0.17 mm.

Inventors: DAHL KATARINA, HESSMAN INGEMAR, DAHL, KATARINA, HESSMAN, INGEMAR
Applicants: SANDVIK AB
Application year: 2001
Main classification: B23C3
IPC codes: B23C3, B23C5