1
Q
Tool for highly abrasive materials
(minerals)
A
- Fe based
- Used to processing minerals
-Complex loading conditions, cyclic stresses, friction, wear, corrosion - The surface of the tool must withstand hevy duty, pressure and relative moments
2
Q
Strategies to withstand heavy wear conditions
A
- Increasig hardness, martensitic phase.
- Small and well dispersed carbides for tool edge
- On the contrary wear from gravel si optimally protected by coarse carbides or borides
- The hard phases have to be harder than the abrasive material
- Hard phases have to be more tough at fracture than the abrasive, in this way will be the ab grain to fracture.
- The matrix has the task of supporting the hard phases
3
Q
Proprerties of matrix for heavy wear cond
A
- High hardness
- High YS
- Certein degree of ductility
4
Q
types of tool steels for heavy wear condition
A
- Normalized low-C steel
- Pearlitic steels
- Spring Q&T steels
- Surface hardening
- “ledeburitic” chromium steels
5
Q
Hardfacing alloys procedure
A
- improve surface abrasion-corrosion resistance
- A protective layer is applied by welding on cheap substrates
- the range of coating materials spans from simple martensitic steels to super hard pahses up to 6% C
6
Q
hardfacing/cladding
A
- Deposition of a material with superior properties by welding
- For preventive purpose or for remedial purpose
- Cladding uses a overlay material similar to the base one but with improved properties
7
Q
Cladding vs thermal spray
A
- Cladding is a welding operation aimed to creating an homogenous layer of filler on the surface.
- Thermal spray is a process consisting in a gun with a flow of powder of metallic or ceramic or composite elements heated in the basic metal zone.
8
Q
Tools for less hard materials
A
- The shape of the tools is preserved using different hardness value (polymers 30-35 HRC mhot metal working 40-50 HRC cold metal 55-65)
- Service hardness is reached by hardening and tempering steels with dissolved carbon, dissolved alloy elements, alloy carbides.
9
Q
Features of the tool steels based on kind of workin (cold, hot,…)
A
- Cold working tool steels high hardening capacity with carbides to improve wear resistance
- Hot working tool steels increased creep resistance with precipitation hardening
- High speed tool steels containing carbides in a creep resistant hardened matrix.
10
Q
Cold work tool steel
A
- Used at room temp
- Divided according to C content
11
Q
Hot work tool steel
A
- service temp 400-1200 °C
- Creep resistantand high-strength Q&T steels
- Oxidation resistance austenitic steels and nickel-based alloys
12
Q
A
