Topografisk analys av sätthärdat stål
Typ
Examensarbete på grundnivå
Program
Maskinteknik 180 hp (högskoleingenjör)
Publicerad
2023
Författare
Svensson, Isak
Fajersson, Theo
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
The background for this thesis project was that Parker Hannifin AB studied the
surface structure of case-hardened steel. Parker identified different deformations on
the surface, which they referred to as ”höghus” (skyscrapers) and ”grantoppar”
(forest) due to their resemblance to these structures. Curious about the composition
and formation of these deformations, Parker initiated this thesis project. The goal
with this project is to determine how theese deformations affect the surface structure
of the steel and whether it is necessary to post-process the surface. To examine
the surface structure, laboratory equipment such as a scanning electron microscope
(SEM) and an optical 3D profiling microscope were utilized at RISE in Mölndal.
The project started with grinding the surfaces of material samples, which were provided
by Parker. The samples were ground using five different grit numbers to study
if different surface finishes affected the results. All samples were also studied under
an optical 3D profiling microscope before and after they were heat treated to ensure
that the deformations Parker found appeared. This was done to eliminate different
variables from the heat treatment process and to find out how these ”skyscrapers”
and ”forest” occur. All of the samples were also analyzed in SEM to get a better
understanding of the surface. An EDS analysis was also conducted for all samples
to determine the chemical structure of the ”skyscrapers” and ”forest”.
The result of the study was that standard case-hardening leads to the formation
of ”skyscrapers” and ”forest”. The ”skyscrapers” are most likely residual products
from the quenching oil used in the case-hardening process. This conclusion comes
from the EDS analysis, which shows that most ”skyscrapers” consist of coal, sulfur,
silicon, and several other substances that can be found in quenching oil. The ”forest”
consists of iron surrounded by different oxides. During analyses in SEM, a Turing
pattern could be observed for the ”forest”. This means that the ”forest” could be
simulated using a mathematical model. The conclusion for the ”forest” is that the
oxides which form on the surface in the furnace grow faster than the iron. This
means the iron must squeeze through the oxides, which creates the ”forest” pattern.
Beskrivning
Ämne/nyckelord
Sätthärdning , Stål , Svepelektronmikroskop (SEM) , Ytstruktur , Slipning , EDS , Turing-mönster , Härdolja , Oxider