Hi, You didn;t mention the construction code.If the construction code is ASME Section-VIII,Div.1..there ia a recommendation for preheating as below. But if the code is EN,there are some formulas to calculate the preheating as well as recommendations too. NONMANDATORY APPENDIX R PREHEATING INTRODUCTION Preheating may be employed during welding to assist in completion of the welded joint. The need for and temperature of preheat are dependent on a number of factors, such as the chemical analysis, degree of restraint of the parts being joined, elevated physical properties, and heavy thicknesses. Mandatory rules for preheating are, therefore, not given in this Division except as required in the footnotes that provide for exemptions to postweld heat treatment in Tables UCS-56 and UHA-32. Some practices used for preheating are given below as a general guide for the materials listed by P-Numbers in Section IX. It is cautioned that the preheating temperatures listed below do not necessarily insure satisfactory completion of the welded joint and requirements for individual materials within the PNumber listing may have preheating more or less restrictive than this general guide. The procedure specification for the material being welded specifies the minimum preheating requirements under Section IX weld procedure qualification requirements. The heat of welding may assist in maintaining preheat temperatures after the start of welding and for inspection purposes, temperature checks can be made near the weld. The method or extent of application of preheat is not therefore, specifically given. Normally when materials of two different P-Number groups are joined by welding, the preheat used will be that of the material with the higher preheat specified on the procedure specified on the procedure specification. R-1 P-NO. 1 GROUP NOS. 1, 2, AND 3 (a) 175°F (79°C) for material which has both a specifiedmaximum carbon content in excess of 0.30% and a thickness at the joint in excess of 1 in. (25 mm); (b) 50°F (10°C) for all other materials in this P-Number.R-2 P-NO. 3 GROUP NOS. 1, 2, AND 3 (a) 175°F (79°C) for material which has either a specifiedminimum tensile strength in excess of 70,000 psi (480 MPa) or a thickness at the joint in excess of 5⁄8 in.(16 mm); (b) 50°F (10°C) for all other materials in this P-Number.597 R-3 P-NO. 4 GROUP NOS. 1 AND 2 (a) 250°F (121°C) for material which has either a specifiedminimum tensile strength in excess of 60,000 psi (410 MPa) or a thickness at the joint in excess of 1⁄2 in.(13 mm); (b) 50°F (10°C) for all other materials in this P-Number.R-4 P-NOS. 5A AND 5B GROUP NO. 1 (a) 400°F (204°C) for material which has either a specifiedminimum tensile strength in excess of 60,000 psi (410 MPa), or has both a specified minimum chromium content above 6.0% and a thickness at the joint in excess of 1⁄2 in. (13 mm);(b) 300°F (149°C) for all other materials in these PNumbers.R-5 P-NO. 6 GROUP NOS. 1, 2, AND 3 400°F (204°C) R-6 P-NO. 7 GROUP NOS. 1 AND 2 None R-7 P-NO. 8 GROUP NOS. 1 AND 2 None R-8 P-NO. 9 GROUPS 250°F (121°C) for P-No. 9A Group No. 1 materials 300°F (149°C) for P-No. 9B Group No. 1 materials R-9 P-NO. 10 GROUP 175°F (79°C) for P-No. 10A Group No. 1 materials 250°F (121°C) for P-No. 10B Group No. 2 materials 175°F (79°C) for P-No. 10C Group No. 3 materials 250°F (121°C) for P-No. 10F Group No. 6 materials For P-No. 10C Group No. 3 materials, preheat is neither required nor prohibited, and consideration shall be given to the limitation of interpass temperature for various thicknesses to avoid detrimental effects on the mechanical properties of heat treated material. For P-No. 10D Group No. 4 and P-No. 10I Group No. 1 materials, 300°F (149°C) with interpass temperature maintained between 350°F and 450°F (177°C and 232°C) R-10 P-NO. 11 GROUP (a) Group No. 1 — None (see Note) Group No. 2 — Same as for P-No. 5 (see Note) 598 Group No. 3 — Same as for P-No. 5 (see Note) Group No. 4 — 250°F (121°C) (b) Group No. 1 — Same as for P-No. 3 (see Note) Group No. 2 — Same as for P-No. 3 (see Note) Group No. 3 — Same as for P-No. 3 (see Note) Group No. 4 — Same as for P-No. 3 (see Note) Group No. 5 — Same as for P-No. 3 (see Note) Group No. 6 — Same as for P-No. 5 (see Note) Group No. 7 — Same as for P-No. 5 (see Note) NOTE: Consideration shall be given to the limitation of interpass temperature for various thicknesses to avoid detrimental effects on the mechanical Thanks & Regards, (Karthik) |
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