CN101337298A - Low-alloy high-strength steel welding process - Google Patents

Abstract

The invention discloses a technological method for welding low-alloy high-strength steel, which comprises the following steps: a divided edge is formed, a welding area is polished and cleaned, and the strength of welding material is equivalent to that of steel to be welded; Ar+CO2 mixed gas protective welding is adopted, preheating is performed before welding, and the welding speed is 250-300mm/min; a 800MPa solid welding wire is adopted to perform multilayer multirun welding; the interlayer temperature is kept at 150 DEG C plus or minus 20 DEG C during the welding process, a preheating spray gun is used from time to time for temperature compensation, the welding line energy is 16-18KJ/cm, low temperature aging is performed to the whole after welding, and the temperature is 300-400 DEG C. The welding technological method prevents welding cracks from being generated, eliminates residual stress generated during welding large-sized structural members, and serves the purpose that the tensile strength of weld joins equals the tensile strength of parent metal.

Description

A kind of low-alloy high-strength steel welding process

Technical field

The present invention relates to a kind of low-alloy high-strength steel welding process.

Background technology

As the hydraulic support of one of fully-mechanized mining working capital equipment, further perfect along with network structure, method for designing is advanced more, and parameter begins to develop to high workload resistance, big centre-to-centre spacing direction.Increasing along with working resistance of support, the increase of endurancing number of times, if select traditional 16Mn and 15MnVN for use, guarantee the supporting intensity of support, has only the increasing sheet metal thickness, certainly will make the support overall weight overweight, all bring great inconvenience for the transportation of mine hoisting and down-hole, working face carrying.Therefore guaranteeing that practical ways are selected high strength steel exactly for use under the situation that supporting intensity and support gross weight do not exceed standard.Just because of this, the supporting structure material adopts high strength steel just more and more, the main components material is that the different brackets high-strength steel sheet of 450～900MPa level progressively replaces 16Mn (σ s is 320～350MPa) with σ s, but because the research of the welding performance of high-strength steel is started late, each coal machine factory more is from experience, basically be in the situation that the limit is groped, the limit produces,, be easy to generate weld crack because selection of Welding is improper.And a large amount of electron diffraction analysis that tensile strength 500-1000MPa low-alloy high-strength steel weld structure is done show that have the M-A tissue in the high-strength steel weld metal, when alloying element content was low, the M-A tissue was graininess; When alloying element content is high, then be lath-shaped,, when their continued presence, then obviously reduce the impact flexibility of weld metal no matter the M-A tissue is granular or the lath-shaped distribution in the weld metal.

Summary of the invention

The objective of the invention is: the welding procedure that a kind of low-alloy high-strength steel is provided.

The present invention seeks to realize by the enforcement following technical proposals:

A kind of low-alloy high-strength steel welding process is characterized in that, comprises the steps:

(1) the fillet-welded joint place opens monolateral 30 ° or 45 ° of grooves, and banjo fixing butt jointing is opened monolateral 45 ° of grooves or 60 ° of V-butts.

(2) iron rust, the greasy dirt in the polishing removing weld seam periphery 20mm scope before the weldering;

(3) adopt Ar+CO2 mixed gas arc welding, welding current I=240～300A, voltage V=25～30V, gaseous mixture proportioning Ar: CO2=80: 20; Protection throughput 20L/min; Dc reverse connection;

(4) preheat temperature before the welding:

The carbon equivalent of steel part was greater than 0.4 o'clock, and preheat temperature is 100-150 ℃;

The carbon equivalent of steel part did not need preheating less than 0.4 o'clock;

(5) speed of welding: 250～300mm/min;

(6) adopt the intensity of welding material and need the suitable solid welding wire of steel strength of welding to carry out multi-pass welding to connect; Keep 150 ℃ ± 20 ℃ of interlayer temperatures in the welding process, mend temperature with pre-thermic lance at any time, weld heat input is 16～18KJ/cm;

(7) carry out whole low temperature aging Ageing Treatment after the welding, temperature is 300-400 ℃;

Adopt above welding procedure soldering low alloy high-strength steel, reduce cooling velocity by preheating in the welding process, the input of strict restriction weld heat input heat is to the effect of mother metal, adopt multi-pass welding to connect and reduce the unit weld heat input, and the postwelding measure of modulation treatment again, avoid the generation of weld crack, solved the elimination problem of the welding residual stress of large-sized structural parts.Rationally determining of selection by welding material and welding procedure increased the tensile strength of welding point, and through detecting, weld seam tensile strength reaches theoretical rated value, and (σ b 〉=750MPa), the tensile strength of welding point has reached and strong purpose such as mother metal.

From metallographic structure analysis, the weld metal zone is acicular ferrite+a small amount of bainite, and the fusion area is ferrite+bainite, and the heat affected area is ferrite+bainite, along crystal boundary a spot of pearlite that distributing.Acicular ferrite in the weld seam (AF) can improve the low-temperature impact toughness of original weld seam, and when having a high proportion of acicular ferrite in the weld seam, low-temperature flexibility significantly improves.The weld joint samples fracture is a ductile fracture, although the radius of curvature that adopts is less, the sample flawless occurs, and the circular arc place does not have wrinkling, and ectonexine stretched freely when the back of the body was curved.The weld seam fusion is good, and the heat affected area width is 2mm.Oblique Y groove welding crack test, test specimen face of weld, section crack rate are zero, illustrate to adopt the inventive method also can prevent the generation of welding cold cracking under harsh contained condition.

The specific embodiment

Embodiment 1:

Mother metal: the Q690 low-alloy high-strength steel, the fillet-welded joint place opens monolateral 30 ° of grooves, and banjo fixing butt jointing is opened 60 ° of V-butts, and iron rust, the greasy dirt in the weld seam periphery 20mm scope removed in polishing;

Adopt Ar+CO2 mixed gas arc welding, welding current I=240A, voltage V=25V, gaseous mixture proportioning Ar: CO2=80: 20; Protection throughput 20L/min; Dc reverse connection;

Preheat temperature before the welding: the carbon equivalent of steel part was greater than 0.4 o'clock, and preheat temperature is 120 ℃;

Speed of welding: 250mm/min;

Adopting the Kazakhstan weldering HS-80 of institute solid welding wire to carry out multi-pass welding connects; Keep 150 ℃ of interlayer temperatures in the welding process, mend temperature with pre-thermic lance at any time, weld heat input is 18KJ/cm;

Carry out whole low temperature aging Ageing Treatment after the welding, temperature is 300 ℃;

The tensile strength of postwelding welding point reaches 780MPa, and the weld seam fusion is good, and the heat affected area width is 2mm, bend test is qualified, welding point plasticity is good, and fracture circular arc place does not have wrinkling, and tiltedly the cracking test face of weld is restrained in the welding of Y type groove, the section crack rate is zero.

Claims (1)

1, a kind of low-alloy high-strength steel welding process is characterized in that, comprises the steps:

(1) the fillet-welded joint place opens monolateral 30 ° or 45 ° of grooves, and banjo fixing butt jointing is opened monolateral 45 ° of grooves or 60 ° of V-butts.

(2) iron rust, the greasy dirt in the polishing removing weld seam periphery 20mm scope before the weldering;

(3) adopt Ar+CO2 mixed gas arc welding, welding current I=240～300A, voltage V=25～30V, gaseous mixture proportioning Ar: CO2=80: 20; Protection throughput 20L/min; Dc reverse connection;

(4) preheat temperature before the welding:

The carbon equivalent of steel part was greater than 0.4 o'clock, and preheat temperature is 100-150 ℃;

The carbon equivalent of steel part did not need preheating less than 0.4 o'clock;

(5) speed of welding: 250～300mm/min;

(6) adopt the intensity of welding material and need the suitable solid welding wire of steel strength of welding to carry out multi-pass welding to connect; Keep 150 ℃ ± 20 ℃ of interlayer temperatures in the welding process, mend temperature with pre-thermic lance at any time, weld heat input is 16～18KJ/cm;

(7) carry out whole low temperature aging Ageing Treatment after the welding, temperature is 300-400 ℃;