INOM
EXAMENSARBETE TEKNIK, GRUNDNIVÅ, 15 HP
STOCKHOLM SVERIGE 2021,
Comparing the Effectiveness of Punching to Laser Cutting in Ultra High Strength Steel
FELIX ÖHMAN
KTH
SKOLAN FÖR INDUSTRIELL TEKNIK OCH MANAGEMENT
Abstract
This study examines the efficiency of punching compared to laser cutting in sheets of Ultra High Strength Steel (UHSS). The study was conducted to determine which process is more efficient with respect to sheet thickness, where the quality of the cut edge is also taken into consideration of whether punching is recommended over laser cutting. The need for information surrounding punching in UHSS will grow as UHSS becomes more common.
A simple screener, with dimensions of 1x1 m, with 169 holes, Ø=15 mm, was the sample shape used to test and compare punching to laser cutting. Simulations were made of punching two sheets of Hardox® 500 Tuf with a thickness of 4 mm respectively 5 mm. The laser cutting was also simulated, were a sheet thickness of 4,5,6 and 8 mm was tested, were both a 6 kW laser and a 10 kW laser were used. The lasers use O2 as its high-pressure gas. The punching time was calculated using parameters used for material properties in between S355 and a stainless steel, as it was thought that the punching speed more or less stays the same with varying materials. The cutting time for laser is barely affected by alloying elements and so the cutting time for Hardox®
500 Tuf is estimated to be that of the cutting time of S355. The simulations of punching, laser cutting, and the schematic of the sample screener was done by the company Weland AB.
No physical punching was done due to a lack of proper tooling. The simulations of both punching and laser cutting resulted in punching being seven to eight times faster than laser cutting. But due to the extreme properties of Hardox® 500 Tuf, the cut edge of the punched sheets are speculated to be inferior and not suitable for typical wear plate applications. It is therefore recommended to laser cut Hardox 500® Tuf, until further research is done.
Sammanfattning
Denna studie undersöker effektiviteten av stansning jämfört med laserskärning i plåt av Ultra High Strength Steel (UHSS). Studien genomfördes för att bestämma vilken process som är effektivare med avseende på plåttjocklek, där kvaliteten på den skurna kanten också tas i beaktning vare sig stansning rekommenderas över laserskärning. Behovet av information kring stansning i UHSS kommer att öka i och med att UHSS blir vanligare.
En enkel sikt, med måtten 1x1 m, med 169 hål, Ø = 15 mm, var utformningen av plåten som användes för att testa och jämföra stansning med laserskärning. Simuleringar av att stansa två plåtar av Hardox® 500 Tuf gjordes, med en tjocklek av 4 mm respektive 5 mm. Laserskärningen simulerades också, där en plåttjocklek på 4,5,6 och 8 mm testades, där både en 6 kW laser och en 10 kW laser simulerades. Lasrarna använder O2 som högtrycksgas. Stanstiden beräknades med hjälp av parametrar som används för material med materialegenskaper mellan S355 och rostfritt stål, eftersom man ansåg att stansningshastigheten mer eller mindre förblir densamma för olika material. Skärtiden för laser påverkas knappt av legeringsämnen och därför beräknas skärtiden för Hardox® 500 Tuf vara samma som skärtiden för S355. Simuleringarna av stansning och
laserskärning samt ritningen för provets utformning, gjordes av företaget Weland AB.
Ingen fysisk stansning gjordes på grund av brist på rätt verktyg. Simuleringarna av både stansning och laserskärning resulterade i att stansning var sju till åtta gånger snabbare än laserskärning.
Men på grund av de extrema egenskaperna hos Hardox® 500 Tuf, spekuleras det att kvaliteten på den skurna kanten hos de stansade plåtarna vara undermålig, och lämpar sig då ej för typiska slitplåtstillämpningar. Det rekommenderas därför att laserskära Hardox 500® Tuf tills ytterligare forskning har utförts.
Table of Contents
1 Introduction ... 1
1.1 Problem considered ... 1
1.2 Background ... 1
1.3 Social and ethical consideration ... 2
2 Punching and laser cutting ... 3
2.1 Hole appearance ... 3
2.2 Die clearance ... 3
2.3 Tool wear ... 4
2.4 Punch velocity ... 6
2.5 Fiber laser ... 7
2.6 CO2 laser... 7
2.7 Inert vs reactive gas ... 7
3 Method ... 8
3.1 Hardox® 500 Tuf ... 8
3.2 Punching ... 9
3.3 Laser cutting ... 9
4 Result ... 10
4.1 Punching ... 10
4.2 Laser cutting ... 10
5 Discussion ... 12
5.1 Punching velocity ... 12
5.2 10 kW vs 6 kW ... 12
5.3 Hole quality ... 12
6 Conclusions ... 13
7 Future work ... 14
8 Acknowledgement ... 15
9 References ... 16
1
1 Introduction
1.1 Problem considered
Metal sheets are a common form of steel produced, and as such see a lot of processing. There are a myriad of processes to transform the sheet metal into its desired form, but regardless of the final product, there is usually some step of the process where a hole is required. Common processes to make holes in sheet metal at an industrial scale are drilling, punching and laser cutting. A drill, however, can only make circular holes, whilst a punching machine can utilize different tool geometries and a laser cutter can basically cut any shape. Therefore, a lot of companies choose to either use a punching machine or a laser cutter, and sometimes both [1].
There are of course differences between these processes, which in term will decide which one is best suited for the desired outcome. As mentioned, a punching machine is limited by the shape of its inserted tool, while a laser cutter is completely free in that regard. Another difference is the ability of making indentations and bends, which only a punching machine can perform.
Furthermore, punching is usually more limited by sheet thickness than laser cutting, which greatly varies with material. Lastly, a punching machine is generally speaking a lot cheaper and faster than a laser cutter machine [2], [3], and so the question becomes, at what thickness, does it become more efficient i.e., cheaper, to use a laser cutter instead of a punching machine.
1.2 Background
Materials with a yield strength above 550 MPa are often referred to as AHSS (Advanced High Strength Steel), and if the steel also have a tensile strength above 780 MPa, they may be referred to as a UHSS (Ultra High Strength Steel) [4]. Hardox® 500 Tuf, which has a yield strength up to 1400 MPa and a hardness up to 505 HBW (Brinell) [5], will fall under the category of UHSS.
Compare this to a standard structural steel, such as S355, which has a yield strength of up to 355 MPa, a tensile strength of up to 680 MPa, and a hardness of up to 187 HBW [6].
Punching is a process where a work material, in this case a metal sheet, is placed between a punch (tool) and a die, in order to either make a hole or to make an indentation. The die is fixed while the punch is movable and usually connected to hydraulics, this is to create the large forces required to shear and eventually crack the work material.
The punching of steel sheets is a widespread and well-known practice. It is also more efficient and significantly cheaper than laser cutting, usually [2]. Due to the ever-increasing size of databases and more sophisticated computing programs, steel and other alloys are improving at a staggering rate. This leads to that steels today, generally, can withstand significantly harsher environments, carry heavier loads and last longer, than it did some years back in time. This is because of improvements made in material properties such as corrosion resistance, hardness, yield strength, stiffness and so forth. Increasing these material qualities increases the materials ability to retain its shape. One could say that what we usually look for in a good steel, is the ability to resist unwanted change. But this will inherently cause some complications when it comes to processing these steels, since they are designed to resist change.
To punch through a material, the yield strength of the work material must be exceeded, which means that the compressive yield strength (hardness) of the tool must be higher than that of the work material. But one cannot just increase the strength and toughness of the tool to successfully
2
punch through UHSS. The high yield strength and toughness complicates the effects of tool wear as it gives rise to other effects mostly unprecedented in standard mild steel, such as shockwaves and spring back (recoil) [7]. It is therefore important to conduct experiments and gather data about how these new high strength steels behave.
Laser cutting is a thermal process frequently used for processing sheet metal and was introduced as an industrial processing technology over 4 decades ago [8]. It works by focusing a high-energy laser beam at the workpiece. The workpiece absorbs the energy, heating up at the focal point, melting and/or vaporizing the metal which is blown away by a stream of high-pressure gas. This creates a cutting gap in the material or, kerf, as it’s also known as. The quality of the cut edge varies with cutting speed, output power and thickness of the material. Metals with a thickness up to 30 mm can be cut. The most common types of lasers used in conjunction with a CNC machine are fiber laser and CO2 laser [9].
CO2 lasers are an older and more mature technology, whilst fiber laser is relatively new
technology. Both have advantages and disadvantages compared to each other, but fiber laser is gaining market fast, as the technology has more room to grow. A big difference between these two are the range of materials they can process. CO2 lasers are able to process anything from metals to organic materials such as textiles, plastics and wood whilst fiber lasers can struggle with plastics and cannot cut wood-based materials [8], [3]. This is because of the different output wavelengths; CO2 lasers usually has a wavelength of 10600 nm compared to fiber lasers wavelength of 1060 nm [3]. Another difference is the fiber lasers higher cutting speed in thin metal sheets, sheet thickness up to about 4 mm, compared to CO2 lasers [8].
1.3 Social and ethical consideration
Regarding the social and ethical considerations when it comes to punching/laser cutting sheets of steel, there is little to say. Now, there will always be some sort of risk for personal injury when it comes to large industrial machines, but both punching and laser cutting machines are outfitted with plenty safety measurements to minimize this and are usually operated from a safe distance via a computer of some sort. Furthermore, there is practically no toxic waste in either of these processes, and so the risk for any environmental damage as a result from the use of these processes are also practically none.
Punching machines consume less energy than a laser cuter machine, but requires more
maintenance, so it is difficult to say which one is the most environmentally friendly to operate.
And so, the only concrete thing that could be said about the use of these processes is to use machines that are built with the environment in mind and to use the cleanest energy possible.
Social and ethical consideration will therefore not be brought up any more in this paper.
3
2 Punching and laser cutting
2.1 Hole appearance
The quality of the punched hole can often be assessed accurately by optical inspection alone. The cut edge of the hole consists of two major areas, the blank zone and the grey zone. A good hole quality requires that the cut edge consist of 5-10% blank zone and a homogenous looking grey zone, with a clear and straight separation of the two zones [10]. The blank zone appears blank and consists of a roll over and a burnish. The roll over is a result of plastic deformation, whilst the burnish is a result of shearing. Following the burnish comes the grey zone, which appears grey because of its rougher surface, consisting of a fracture zone and a burr. The fracture zone and the burr are a result of crack propagation, with the crack originating from the end of the burnish. An illustration of the cut edge is represented in Figure 1. For high strength steel the burnish is shorter when compared to mild steel. The length of the burr shortens with increasing tensile strength [7].
2.2 Die clearance
The die clearance plays a large in both the quality of the cut edge and the tool wear. Die
clearance is displayed as a % of the sheet thickness and is the radial distance between the tool and the die, see Figure 2. Recommended die clearance varies with sheet thickness and material, but usually hovers a bit above 10 % of sheet thickness. As the sheet thickness increases, so should also the die clearance as shown in Figure 3 [7]. This can however be a subject to change,
depending on the machine used and the work material. For stainless steels and/or tougher steels, Weland recommends a die clearance of 35% for punching sheets thicker than 4 mm.
Figure 1: Illustration of a cut edge [7].
Figure 3: Recommended die clearance for punching in AHSS [7].
Figure 2: Concept of die clearance [7].
4
The maximum load is barely affected by varying the die clearance, however, after the crack initiation and propagation, the rate of decrease in load is slower when the die clearance is small (2% of t and 5% of t). What should be expected, if the die clearance and material thickness have been appropriately chosen, is a steep increase in force followed by a steep decrease in force. This represents the initial plastic deformation (roll over) and shearing (burnish) followed by crack initiation and crack propagation (fracture zone and burr). If the tool clearance is too tight, there might be a prolonged shearing and/or a double shearing zone, resulting in a slower decrease in load and sometimes, two maximum loads, see Figure 4 [11]. This affects both the cut edge and the tool in a negative manner, significantly increasing the wear of the tool, increasing the residual tensions around the hole and creating micro cracks on the cut edge [10]. This makes die clearance an important parameter.
2.3 Tool wear
As mentioned earlier, the tool wear is also dependent on the die clearance. Tools can wear in many ways, the most common are:
• Abrasive/adhesive
Occurs as a result of friction forces between the tool and the work material. Affects the flank (side of the tool).
• Galling
Galling is closely related to adhesive wear and is the result of heavy friction between the tool and the work material. Affects the flank.
• Chipping
Occurs as a result of high operating stresses compared to the fatigue strength of the tool material.
• Cracking
Occurs as a result of high operating stresses compared to the fracture toughness of the tool material.
• Plastic deformation
Occurs when the compressive yield strength of the material is exceeded.
Figure 4: Double shearing resulting in two maxima in punching force [11].
5
Abrasive wear and adhesive wear work in conjunction. Abrasive wear occurs when there is friction between the tool and the work material with the presence of particles in between or a rough surface on the tool. This will act as a sandpaper, adding more friction and creating more particles. These particles may come from both the tool and the work material, which will adhere to the tool and/or work material. In short, small amounts of material from the tool/work material will adhere to the work material/toll, resulting in tool wear [12]. This type of wear is reduced by reducing friction, either by increasing the die clearance or by first punching a smaller hole in the opposite direction, allowing the punched material to expand inward [2].
Galling may be considered as a severe form of adhesive wear, as a result of high loads and heavy sliding friction between the tool and work material. The particles generated by abrasive wear will adhere to the surfaces, but here they will build up, causing “lumps” on the tool, further increasing tool wear. This type of wear is avoided by reducing friction in the same manner as with
abrasive/adhesive wear and by using higher grade steel [13].The decrease of wear with increasing die clearance is shown in Figure 5.
Chipping results in small pieces of the tool edge breaking off, which might render the tool useless, requiring a tool replacement. Chipping is usually a result of operating stresses too high for the tool materials fatigue strength, but it can also happen if the die clearance is too large. Too large a die clearance will generate high bending stresses on the edge of the punch, increasing the risk of chipping, see Figure 6. To avoid chipping on should pick a tool with a high enough fatigue strength and avoid the use of a too large die clearance [7].
Cracking is more severe than chipping, where a large chunk of the tool is broken off, resulting in costly operational stops. Cracking usually occurs when the operational stresses are too large compared to the tool materials fracture toughness. To avoid cracking, one should pick a tool with a high enough fracture toughness and/or use a chamfered tool to decrease the maximum
punching force. [7].
Figure 5: Galling as a function of die clearance [7].
6
If the compressible yield strength (hardness) of the tool material is lower than operating stress levels, the tool will plasticly deform. This will render the tool useless, resulting in operational stops to replace the damaged tool. As the hardness of the work material increase, so does the requirements of the tool material. To avoid plastic deformation, one should pick a tool with a high enough hardness [7].
Abrasive/adhesive wear and galling are predictable types of tool wear and can be managed with regular inspections and tool maintenance. Most importantly, these types of wear will not cause a spontaneous failure. Chipping, cracking and plastic deformation will cause a spontaneous failure, resulting in costly operational stops and as such, must be avoided if possible. It might therefore be preferable to allow some increase of abrasive/adhesive wear and galling to reduce the risk of chipping, cracking and plastic deformation [7].
Testing tool wear is time consuming and expensive, usually requiring several thousands of holes punched, which is why this paper will not test this aspect when punching in Hardox® 500 Tuf.
However, the experiments will be set up in a way to minimize the risk of spontaneous failure, to simulate realistic operational parameters.
2.4 Punch velocity
The velocity of the punch affects both the tool wear and the hole quality. Increasing the punch velocity also increases the punching force as well as the burr height [14]. An increased punch force leads to more stress on the tool and the machine, increasing risk for failure. An increase in burr height is also not wanted as it may require more mechanical post-processing. This means that an appropriate punch velocity should be set for each machine and material.
Figure 6: Chipping risk as a function of die clearance [7].
7
2.5 Fiber laser
In a fiber laser, the amplified light is channeled through an optical fiber cable, not much unlike those used for data transfer. Upon exiting the fiber cable, the amplified light is collimated and then focused by a lens onto the workpiece. This means that the delivery of light from the laser source to the workpiece is here much simpler when compared to CO2 laser, with no heavy and expensive optical mirrors required. Unlike conventional CO2 lasers, the focusing lens is sealed in the cutting head, protecting it from molten metal and metal vapor, reducing the need for
maintenance. The reduced weight of the fiber laser enables for faster acceleration and deacceleration, which means it can take more advantage of its higher cutting speed. Light generation in fiber laser is 200% more efficient than traditional CO2 laser, incentivizing environmentally aware companies to invest in fiber laser. The main drawback of fiber lasers is their high price tag, ranging from 40,000$ - 1,000,000$, depending on power output [3], [15].
2.6 CO
2laser
CO2 lasers are heavier, less precise and consume more power when compared to fiber lasers.
They do, however, excel at cutting in thicker materials. This combined with the ability to
efficiently cut most materials and a lower cost of purchase, between 35,000$ - 80,000$, depending on power out, makes the CO2 laser the choice for shops who are not solely expecting to cut thin metal sheets. This is why the CO2 laser still lives on, it’s cheap, versatile and well tested [8], [3], [15].
2.7 Inert vs reactive gas
The gas used to push away the melt and metal vapor can either be inert, usually consisting
nitrogen and/or argon, or reactive, consisting of air or pure oxygen. If inert gas is used, it is called laser beam fusion cutting. Here the inert gas blows away melt and metal vapor to continually expose the metal to the laser, while also shielding the cut edge from oxidizing with the oxygen in the surrounding air. If oxygen is used, it is called laser beam flame cutting. The gas serves to blow away melt and metal vapor in order expose the metal to the laser, but also to react with the hot cut edge of the workpiece. When the oxygen and metal react heat is created, acting as an additional energy source, allowing for faster and more energy efficient cutting. Unless this is set up properly, it will create burrs around the cut edge, requiring mechanical post-processing [9], [16].
8
3 Method
To determine at what thickness laser cutting becomes more efficient than punching, the time consumed conducting a specific operation, with the respective method and thicknesses, will be compared. The chosen operation is to punch/laser cut a 1 m2 sheet of Hardox® 500 Tuf to a simple screener. This is because screeners are a common product where Hardox® 500 Tuf is used. The sample screener has with 169 holes, each with a diameter of 15 mm. A schematic of the sample screener is shown in Figure 7.
3.1 Hardox® 500 Tuf
Hardox® 500 Tuf combines the workability of Hardox® 450 and the hardness of Hardox® 500.
The result is a wear plate with high strength, high resistance to wear and high impact toughness.
These characteristics are difficult to combine, since high hardness usually means lower
toughness, and vice versa. Hardox® 500 Tuf is through-hardened, with a minimum core hardness of 90% of the guaranteed surface hardness. Hardox® 500 Tuf has a hardness between 475-505 (HBW), a yield strength between 1250-1400 MPa and guaranteed impact energy of 27 J at -20°C.
The steel contains several alloying elements and has a minimal iron percentage of 93.765% [5].
The chemical composition is shown in Table 1.
Table 1: Chemical composition of Hardox® 500 Tuf, where * indicates an intentional alloying element [5]
Element Mn* Ni* Cr* Si* Mo* C* P S B*
Max % 1.60 1.50 1.50 0.70 0.60 0.30 0.020 0.010 0.005
Figure 7: Schematic of the sample screener from Weland
9
3.2 Punching
A sheet thickness of 4 and 5 mm will be tested for punching. This is because of the limitations of the punching machine used to conduct the experiment, where a sheet thickness beyond 5 mm.
would be too much of a risk for both machine and personnel [1]. Both total punching time and edge quality will be “extracted” from a simulated and a physical experiment. A fixed die clearance of 1.5 mm will be used for both thicknesses when punching, which results in a die clearance of 37.5% of thickness and 30 % of thickness for 4 mm and 5 mm respectively. The total punching time was thought not to vary too much with varying materials, and as such the
punching time will be calculated using parameters used for material properties in between S355 and a stainless steel.
3.3 Laser cutting
A sheet thickness of 4, 5, 6 and 8 mm will be tested for laser cutting. Since the quality of the cut edge is consistent for laser cutting at these sheet thicknesses and cutting time is mostly
independent of steel composition [1], a simulation of laser cutting the different thicknesses will suffice. The cutting time with laser is the same for Hardox® 500 Tuf as for S355. Weland uses both a 6kW laser and a 10kW laser, both operating with O2 as the high-pressure gas. Both lasers will be simulated to cut every thickness. The total time of cutting consists of cutting time and non-productive, where non-productive time is time spent moving the cutting head.
10
4 Result
4.1 Punching
The estimated punching time and punching force for each thickness, using a round and flat punch, is shown in table 2. No actual punching was executed, due to a lack of proper tooling, where the tools available would risk a breakdown of the punching machine. Weland will procure a specialized tool with a so-called rooftop grinding, which will be able to punch through booth sheets.
Table 2: Simulated punch time and punch force for each thickness.
Thickness 4 mm 5 mm
Punching time 50 s 51 s
Punching force 26 tons (255000 N) 32 tons (314000 N)
4.2 Laser cutting
The cutting time increased with increasing thickness, shown in Figure 8, but the non-productive time for each laser stayed the same regardless of thickness. This results in an increase of
productivity as a function of increasing thickness, shown in Figure 9.
The 10 kW laser is faster than the 6 kW laser for all thicknesses, increasing its time lead with increasing sheet thickness. The 6 kW laser has a higher productivity, i.e., less downtime, for sheet thickness of 6 mm and more.
Figure 8: Total cutting time of the sample for 6 kW laser and 10 kW laser.
11
Figure 9: Productivity of both laser for each thickness.
12
5 Discussion
The simulated data shows that it is much faster to punch through Hardox® 500 Tuf compared to cutting it with laser. It was in fact about seven to eight times faster to punch the sheets rather than to laser cut them, depending on the power output of the laser. This was expected, since punching is known to be faster than laser cutting. However, the hole quality and tool wear must be taken into consideration.
5.1 Punching velocity
As stated before, increased punching velocity increases the stress on the tool, increasing both tool wear and risk for failure, but it also lowers the hole quality by increasing the burr length. The total punching time, and thus the velocity of the punch, was calculated using parameters for a material with properties in between S355 and stainless steel. This means, with a high probability, that the punch velocity is too high for Hardox® 500 Tuf, since its yield strength is higher than that of standard stainless steel. The result of this will probably be early onset of chipping, plastic deformation and cracking of the tool, along with a bad hole quality. Too reduce the stress on booth tool and machine, a lower punch velocity should be applied.
5.2 10 kW vs 6 kW
The 10 kW laser was faster than the 6 kW laser, which is reasonable. This also led to that, for sheet thicknesses of 6 mm and more, the 6 kW laser had a higher productivity than the 10 kW laser. This does not mean the 6 kW laser is faster than the 10 kW laser when cutting steel sheets with a thickness of 6 mm and up, it just shows that it is “busier”, and thus has less room for improvement. Overall, the 10 kW laser is superior, but it is a larger investment. Which laser power output to choose depends on the types of operations that are to be done and the volume of production that is expected. A lower power output is more economically viable for a lower production volume, whilst a higher power output works best with a higher production volume.
5.3 Hole quality
The hole quality of a laser cut sheet can be lower than that a of punched one, but it is usually better, especially when sheet thicknesses increase. It also stays more or less consistent with varying materials and the ranges of thickness analysed in this paper. This, and the fact the people at Weland strongly discouraged punching in Hardox® 500 Tuf, points to the quality of the cut edge when punching to be severely worse than that of laser cutting. The higher manufacturing speed of punching should not matter in this case, since it, with a high probably, produces an inferior result for sheet thicknesses of both 4 mm and 5 mm.
13
6 Conclusions
When it comes to Hardox® 500 Tuf with a sheet thickness of 4 mm and 5 mm, there does not seem to be any reasonable benefits using a punching machine instead of a laser cutter. Using a punching machine will most likely produce sheets with inferior hole quality, not suitable for typical wear plate applications. This is however hard to corroborate with literature studies, as there is close to no data on punching AHSS/UHSS at these thicknesses. Had the physical experiments not been severely delayed, an optical inspection of the cut edges would suffice to determine whether punching was viable at these thicknesses. For now, even though it being more expensive and time consuming than punching, laser cutting is the recommended way to process sheets of Hardox® 500 Tuf, for these thicknesses.
14
7 Future work
Too conclude whether to use punching or laser cutting, optical inspection of the samples meant to be examined in this paper needs to be done. To fully understand tool wear when punching AHSS/UHSS, experiments where several thousand of holes are punched are needed, which would be interesting.
More tests and experiments could be done with the same parameters examining different
AHSS/UHSS. Furthermore, it would be interesting to change parameters such as punch velocity, die clearance, tool geometry, laser power output and laser speed, to try and find the optimal set- up for each material.
15
8 Acknowledgement
I would like to deeply thank my two supervisors, Professor Stefan Jonsson from the Department of Materials Science and Engineering at the Royal Institute of Technology and Mikael Reinberth, Manager and Senior Welding Specialist and from SSAB Group for all their guidance and
support, making this project possible. [17]
16
9 References
[1] L. Kennethsson, Interviewee, Reccomendations for punching and laser cutting, Weland AB. [Interview]. 23 Mars 2021.
[2] U. Persson, Interviewee, Recommendations for punching and laser cutting, Bystronic Scandinavia AB. [Interview]. 1 February 2021.
[3] "CO2 vs. Fiber Laser - Which One Should You Buy?," 12 April 2019. [Online].
Available: https://www.laserax.com/blog/co2-vs-fiber-
lasers#:~:text=The%20main%20difference%20that%20determines,many%20adva ntages%20over%20CO2%20lasers.. [Accessed 12 April 2021].
[4] "WorldAoutoSteel," [Online]. Available: https://www.worldautosteel.org/steel- basics/automotive-advanced-high-strength-steel-ahss-definitions/. [Accessed 1 April 2021].
[5] "Hardox® 500 Tuf," [Online]. Available:
https://www.ssab.com/products/brands/hardox/products/hardox-500-tuf.
[Accessed 1 April 2021].
[6] "Material Properties of S355 Steel - An Overview," 23 August 2015. [Online].
Available: https://www.meadinfo.org/2015/08/s355-steel-properties.html.
[Accessed 1 April 2021].
[7] "Tooling solutions for advanced high strenght steels," [Online]. Available:
https://www.uddeholm.com/files/Tooling_solutions.pdf. [Accessed 22 Mars 2021].
[8] J. Powell and A. Kaplan, "Laser Cutting Tehcnology-A Commercial Perspective,"
Macro Materials Processing, p. 3, 2012.
[9] T. Knell, "Laser cutting of sheet metal-how it works," 18 May 2019. [Online].
Available: https://www.maschinenmarkt.international/laser-cutting-of-sheet- metal--how-it-works-a-829924/. . [Accessed 12 April 2021].
[10] M. Folmerz, Interviewee, Recommendations for punching, SSAB. [Interview]. 24 02 2021.
[11] P. Chumrum, N. Koga and V. Premanond, "Experimental investigation of energy and punch wear in piercing of advanced high-strength steel sheet," Pringer-Verlag, London, 2015.
[12] J. Kerns, "MachineDesign," 14 January 2016. [Online]. Available:
https://danebuller.wordpress.com/adhesion-wear-and-abrasive-wear/. [Accessed 05 May 2021].
[13] A. Söderman and P. Lundström Törnquist, "Stainless-Steel-World," 8 November 2019. [Online]. Available: https://www.stainless-steel-
world.net/webarticles/2019/11/08/galling-is-seriousbut-there-are-solutions.html.
[Accessed 5 May 2021].
17
[14] Y. Kurniawan, M. Mahardika and S. , "Effect of punch velocity on punch force and burnish height of punched holes in punching procces of pure titanium sheet,"
Journal of Physics: Conference Series, 2020.
[15] "Fiber versus CO2 laser cutting," 12 November 2013. [Online]. Available:
https://www.industrial-lasers.com/cutting/article/16486898/fiber-versus-co2- laser-cutting. [Accessed 13 April 2021].
[16] "Basics of Laser Cutting (Knowledge You Must Know)," [Online]. Available:
https://www.machinemfg.com/laser-cutting-basics/. [Accessed 12 April 2021].
[ 1 7 ]
TRITA ITM-EX 2021:2
www.kth.se
