2018 Mechanical Engineering Safety Seminar presentation

1. Effect of Boron Content on Steels and
Recommended Practice for Welding
27th September 2018 | By Sasanka Sinha
www.weldaustralia.com.au | info@weldaustralia.com.au | +61 (0)2 8748 0100

2. What Does Boron Do To Steels
• Boron is beneficial to steels in low concentrations
• Improve steel hardness and impact properties
• A minimum of 0.0005% B is recommended in carbon steels and 0.0012% in Q&T
steels
• In higher concentrations, boron can cause significant structural damage
• Can influence the formation of martensite
• Decreased fatigue life
• Increased carbon equivalence
• Decreases ductility and weldability within steels
• A maximum of 0.0008% B is recommended in carbon steels and 0.0030% in Q&T
steels

3. • Low fatigue life results in a shorter
functional lifespan of mining
equipment, excavators, structures,
etc.
• Increased costs for maintenance of
equipment
• Martensite formation may result in
sudden failure of structural supports
• Sudden failure can be catastrophic
to safety
Limitations of High Boron Steel in Mining

4. • ISO 4948 recommends separate
boron concentration ranges for
carbon steels and Q&T steels
• AS/NZS 1554.1 introduced a
maximum boron concentration for
prequalified steels in welding
• No Australian standard covers
welding of high boron steels
• This paper provides guidance for
the welding of high boron steels
Recommended
Boron Range for
Steels
Minimum Maximum
Carbon Steels 0.0005% 0.0008%
Quenched and
Tempered Steels
0.0012% 0.0030%
How Standards Regulate Boron Control

5. Parameters to Consider While Welding
• Concentration
• Boron Concentration
• Carbon Equivalence
• Measuring Boron
• Temperature
• Preheat Temperature
• Interpass Temperature
• Post Weld Heat Treatment

6. • A high boron concentration can
dramatically increase the carbon
equivalence in steels
• This can cause martensite to form
more readily
• Multiple formulas have been
developed to calculate the carbon
equivalency (CE)
Concentration

7. • Recommended practice is to
calculate the carbon equivalent
value
• Manufacturers should check for
boron compliance on the mill
certificate
Concentration

8. • Measuring boron can be done using
the following techniques:
• Energy Dispersive X-ray Spectroscopy
(EDX)
• Inductively Coupled Plasma Atomic
Emission Spectroscopy (ICP)
• X-ray Fluorescence Spectrometry (XRF)
• Optical Emission Spectroscopy (OES)
Concentration
EDX
• Highest Sensitivity
• Requires Electron Microscope
ICP
• High Accuracy
• Reliable Results
XRF
• Portable
• Low Accuracy
OES
• Readily Available
• Low Accuracy

9. • Martensite forms when the cooling
rate in steels are too high
• To restrict grain transformation of
martensite, the cooling rate must be
slowed and/or monitored
• Time temperature graphs can
indicate which cooling rates will not
form martensite
Temperature

10. • The best practice would be to
develop a weld procedure
specification (WPS)
• The WPS should note the preheat
temperature, interpass
temperature, and post weld heat
treatment for the weld
• Welders using a WPS should be
qualified to follow the instructions
of the WPS
Temperature

11. Case Study

12. Case Study

13. • Without best practice, quality
management cannot be achieved
• Safety can only be guaranteed with
quality management
• The implementation of procedures
and practices laid out by Standards
and work instructions ensure both
quality and safety
• Implementation is key!
“When selecting the appropriate weld quality
management requirements, the application
requirements determine the design code or
standard, which sets materials, fabrication and
inspection specifics to economically and safely
deliver the required technology or product.”
- Louise Petrick,
Weld Australia
Quality is Safety

14. For a repair on a mining excavator, a
repair strategy was developed. This
included:
• Inspection of the excavator
• Design of a repair strategy
• Preparation for the repair
• Implementation of a weld
procedure
Case Study: Weld Repair on an Excavator

15. • To understand the weld repair
required, a visual inspection was
conducted
• A visual inspection is a very
powerful tool for failure analysis
• Allows us to determine the root cause
of failure
• Useful to determine the extent of
damage
• Assists in the development of repair
strategy
Inspection of the Excavator

16. Checklists for Repair Strategy
Failure Details
• Crack initiation
point
• Load conditions
on cracked area
• Nature of crack
Repair Information
• Information
available
• Accessibility of
welding
• Availability of
welding
equipment
• Results of
gouging
Personnel
Involvement
• Authorisation of
weld repair
• Ability of welders
• Qualifications
within welding
personnel
Details of
Excavator
• Is it a repeat
repair?
• Machine purpose
and use
• Hours of
excavator
operation

17. Repair Strategies Are Unique
• The machine being repaired may exist under special environmental
conditions (e.g. windy environments restrict the use of gas shielding)
• The location of repair may be difficult to access (e.g. the track frame of the
excavator may restrict access to the repair)
• The size of the repair may affect the repair process

18. Preparation
Checking
Cracks
Check Size &
Position of
Cracks
Cause of
Problems
Study of Repair
Methods
Gouging and
Grinding
Fit-Up of Part
for Welding
Repair
Issue Weld
Procedure
Weld to Given
Procedure
Visual
Inspection,
UT/RT
Weld Profile
Improvement
Painting
Reassembly &
Final Check
Typical Repair Strategy

19. • Visual inspection revealed worn out
edges
• Fractured weld surface revealed lack
of fusion at the weld
• Serious manufacturing deficiency
• Grinding and magnetic particle
testing was done on track frame
• Weld build-up was carried out on
the edges
Case Study – Excavator Preparation

20. Case Study – Excavator Preparation
The edges on the ring were ground to 35 degree chamfers on both sides and a 3 mm gap was added between the two parts.

21. Welding Parameters
Type of
Pass
Welding
Position
Wire Size
(Diameter)
Voltage
(V)
Current
(A)
Root
Pass
Flat 1.2 mm 26 – 28 230 – 260
Filler
Pass
Flat 1.2 mm 28 – 30 240 – 280
Capping
Pass
Flat 1.2 mm 30 - 32 240 – 260
Case Study – Excavator Repair

22. Inside Swing Circle Mounting Seat Outside Swing Circle Mounting Seat
Case Study – Outcome of Repair

23. Case Study – Outcome of Repair
The outcomes of this excavation repair include:
• Ultrasonic testing of all critical joints
• Periodic in service inspection
• Improvement in weld profiling
• Training and certification of welders
• More effective control on shop floor and inspection stages

24. Case Study – Outcome of Repair
By implementing these outcomes, the following was achieved:
• Better practice in welding and general repairs
• Routine inspections to ensure safe operation of excavator
• Reduction in downtime and repair costs
• Improved safety and availability of the excavator

25. • The best practice in welding
operations is to adopt quality
management and process control
throughout the process
• Quality MUST be built into welds
• AS/NZS ISO 3834 outlines the
requirements for effective process
control
• Process control is critical for
ensuring safe operation within
industry
Ensuring Quality in Operations

26. Conclusion
• The concentration of boron in steels must be identified through the mill
certificate
• High boron steels must maintain a steady and slow cooling rate while
welding
• The use of a repair strategy results in good practice within several industries
• The best and safest practice comes with the implementation of a process
and production control system

27. Thank you!
Any questions?