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H.K.D.H. Bhadeshia,
Phase Transformations Group,
Department of Materials Science and Metallurgy,
University of Cambridge,
Cambridge, U.K.
Added to MAP: August 1999.
Determination of weld metal inclusion composition: calculates the distribution of any oxygen and nitrogen present amongst the alloying elements Al, Ti, B, Mn and Si in a steel weld, and obtains an estimate for the amounts of Al, B and N remaining in solution.
| Language: | FORTRAN |
| Product form: | Source code |
SUBROUTINE MAP_STEEL_NANOAL(ALTOT,OXYWT,TITOT,NITPPM,BWT,STATE, & FBORT,CONST,IYES,IAL,IOX,ALSOL,PPMBG1,PPMBG2,PPMBSL, & NITSOL,PPMOAL,PPMOTI,PPMOMN,PPMOSI,PPMTIO,PPMTIN,PPMBN, & OXYMIN,OXY3,OXY4,OXY5,GALAX) DOUBLE PRECISION ALSOL,ALTOT,BWT,CONST,FBORT,GALAX DOUBLE PRECISION OXY3,OXY4,OXY5,OXYMIN,OXYWT,NITPPM,NITSOL DOUBLE PRECISION PERBN,PERBSL,PEROAL,PEROMN,PEROSI,PEROTI DOUBLE PRECISION PERTIN,PERTIO,PPMBG1,PPMBG2,PPMBN,PPMBSL,PPMOAL DOUBLE PRECISION PPMOMN,PPMOSI,PPMOTI,PPMTIN,PPMTIO,STATE,TITOT DOUBLE PRECISION ALSOLC,NITWT,R,T0 INTEGER IAL,IOX
The oxygen level and the amounts of alloying elements present in a low alloy steel weld are very important in determining its microstrucure and mechanical properties. This subroutine determines the distribution of any oxygen and nitrogen present amongst the alloying elements Al, Ti, B, Mn and Si and the amounts of Al, B and N remaining in solution. The soluble Al and B concentrations are determined by calls to subroutines MAP_STEEL_ALUM and MAP_STEEL_BORON . The distribution of the oxygen and nitrogen amongst the alloying elements is carried out by calling MAP_STEEL_PARTIC. Further details of the procedures used can be found by referring to these subroutines.
As the presence of an absolute minimum concentration of 0.012 wt% oxide is necessary for the intragranular nucleation of acicular ferrite, the program also calculates and outputs the following parameters which are a useful guide in determining the appropriate required levels of oxygen and alloying elements:
| OXYMIN | - | the minimum oxygen concentration required to oxidise both Al and Ti completely. |
| OXY4 | - | the minimum oxygen required to ensure intragranular nucleation. This is equal to OXYMIN unless the user indicates that the formation of Ti oxide is unimportant; in this case it is set to the minimum value of 0.012wt%. |
| OXY5 | - | an upper bound on the oxygen level = OXY4 + 0.01. |
| GALAX | - | the percentage of oxygen combined with aluminium divided by the percentage of oxygen combined with manganese. GALAX must be < 3 for the formation of galaxite (Al2O3.MnO). |
In general, the volume fraction of gamma iron formed in the weld should be > 0.2. If not then there is little to be gained by adding oxide or other intragranular nucleation agents. The amount of allotriomorphic and Widmanstätten ferrite is too high. An increase in alloying elements to raise the hardenability, or a change in the welding conditions to increase the cooling rate over the range 900 to 450 °C is recommended.
Given that the volume fraction of gamma iron is > 0.2, the following comments may provide some guidance in the choice of suitable concentrations of oxygen and the alloying elements.
Aluminium and Titanium
The oxidation of Al occurs preferentially to the oxidation of Ti, Mn or Si. If the amount of Al remaining in solution is > 0.006 wt% there will be a tendancy to form excessive quantities of Widmanstätten ferrite, especially when the fraction of allotriomorphic ferrite is small.
The input parameter IYES can be used to stipulate whether or not the formation of Ti oxide is essential. If IYES=1 it is assumed that all of the Ti should be oxidised and OXYMIN calculated accordingly. (The oxide state of the Ti oxide to be formed must be specified by the input parameter STATE.) If there is insufficient oxygen to completely oxidise the Ti, then TiN can be formed. If IYES=0, the formation of Ti oxide is not considered essential and the subroutine outputs a minimum required oxide concentration of 0.012wt%. This corresponds to the crude condition that the type of oxide formed is not considered relevant.
Oxygen
Given that the total concentration of oxygen in the weld is OXYWT (wt%) then the following suggestions can be made:
Boron
If the amount of boron in solution > 20ppm then it is higher than the optimum level necessary to reduce allotriomorphic ferrite. Although beneficial, it could be reduced, resulting in a further reduction in allotriomorhic ferrite.
If the amount of boron in solution > 130ppm then it is so high that it is no longer of use in reducing the volume fraction of allotriomorphic ferrite. Reduce boron concentration drastically.
IAL is set to 1 if the input data for MAP_STEEL_ALUM
are outside the valid range, 0 otherwise.
IAL is set to IAL+10 if the number of iterations in MAP_STEEL_ALUM is equal to the maximum number specified in MAP_STEEL_NANOAL (currently 20).
IOX is set to 1 if the calculated value for the concentration of oxygen required to oxidise all of the aluminium exceeds the total concentration of oxygen present. It is 0 otherwise.
No information supplied.
None.
IMPLICIT DOUBLE PRECISION (A-H,N-Z)
IAL = 0
IOX = 0
STATE = 1.5
IYES = 1
CONST = 0.616D-4
WRITE(*,*)
WRITE(*,*) 'Input total O, Al, Ti and B concentrations (wt%):'
READ (*,*) OXYWT, ALTOT, TITOT, BWT
WRITE(*,*) 'Input total N concentration (ppm by weight):'
READ (*,*) NITPPM
WRITE(*,*) 'Input temperature for boron solubility (Deg. C):'
READ (*,*) FBORT
CALL MAP_STEEL_NANOAL(ALTOT,OXYWT,TITOT,NITPPM,BWT,
& STATE,FBORT,CONST,IYES,IAL,IOX,ALSOL,PPMBG1,PPMBG2,PPMBSL,
& NITSOL,PPMOAL,PPMOTI,PPMOMN,PPMOSI,PPMTIO,PPMTIN,PPMBN,
& OXYMIN,OXY3,OXY4,OXY5,GALAX)
IF (IAL.EQ.1.OR.IAL.EQ.11) THEN
WRITE(*,*) '*** Error - Data for MAP_STEEL_ALUM out of range.'
STOP
ENDIF
IF (IAL.GE.10) WRITE(*,*) '*** Warning - Number of iterations in '
& ,' MAP_STEEL_ALUM is equal to maximum specified.'
ALSOL = ALSOL*1D4
IF (IOX.EQ.1)WRITE(*,*)'Insufficient oxygen to oxidise all the Al'
WRITE(*,1) 905, PPMBG1, 1000, PPMBG2
WRITE(*,2)' boron ',PPMBSL,'aluminium',ALSOL,'nitrogen ',NITSOL
WRITE(*,3)'Aluminium', PPMOAL,'Titanium ',PPMOTI,'Manganese',
& PPMOMN,'Silicon ',PPMOSI
WRITE(*,4) 'oxide ',PPMTIO,'nitride',PPMTIN
WRITE(*,5) PPMBN
WRITE(*,6) 'OXYMIN: Min. O conc. to oxidise all Al and Ti = ',
& OXYMIN
IF (OXY3.GT.0.0) WRITE(*,6)
& 'OXY3: Extra O needed to oxidise Al and Ti = ',OXY3
WRITE(*,6) 'OXY4: Min O for intragranular nucleation = ',OXY4
WRITE(*,6) 'OXY5: Upper bound on oxygen concentration = ',OXY5
IF (PPMOMN.GT.0) WRITE(*,6)
& 'GALAX: Ratio of oxygen on Al to oxygen on Mn = ',GALAX
STOP
1 FORMAT(/2(/26HSoluble B in austenite at ,I4,
& 12H deg. C = ,F7.1,14H ppm by weight))
2 FORMAT(3(/9HConc. of ,A9,15H in solution = ,F7.1,
& 14H ppm by weight))
3 FORMAT(/'Concentration of oxygen atoms tied up with:',
& 4(/A9,' = ',F7.1,' ppm by weight') )
4 FORMAT(2(/'Concentration of titanium atoms tied up as titanium'
& ,1H ,A7,' = ',F7.1,' ppm by weight') )
5 FORMAT('Concentration of boron atoms tied up as boron nitride'
& ,' = ',F7.1,' ppm by weight'/ )
6 FORMAT(A48,F7.3,' wt%')
END
Input total O, Al, Ti and B concentrations (wt%): 0.03 0.02 0.03 0.002 Input total N concentration (ppm by weight): 100 Input temperature for boron solubility (Deg. C): 940
Soluble B in austenite at 905 deg. C = 11.3 ppm by weight Soluble B in austenite at 1000 deg. C = 19.4 ppm by weight Conc. of boron in solution = 0.7 ppm by weight Conc. of aluminium in solution = 49.5 ppm by weight Conc. of nitrogen in solution = 75.0 ppm by weight Concentration of oxygen atoms tied up with: Aluminium = 133.8 ppm by weight Titanium = 150.3 ppm by weight Manganese = 3.3 ppm by weight Silicon = 12.6 ppm by weight Concentration of titanium atoms tied up as titanium oxide = 300.0 ppm by weight Concentration of titanium atoms tied up as titanium nitride = 0.0 ppm by weight Concentration of boron atoms tied up as boron nitride = 19.3 ppm by weight OXYMIN: Min. O conc. to oxidise all Al and Ti = 0.028 wt% OXY4: Min O for intragranular nucleation = 0.028 wt% OXY5: Upper bound on oxygen concentration = 0.038 wt% GALAX: Ratio of oxygen on Al to oxygen on Mn = 41.090 wt%
Subroutines:
MAP_STEEL_ALUM
MAP_STEEL_BORON
MAP_STEEL_PARTIC
weld, oxide, nitride, solubility, inclusions, intragranular nucleation
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