CN104561508A - Postweld normalizing method for gas-pressure welding of steel rails - Google Patents

Abstract

The invention discloses a postweld normalizing method for gas-pressure welding of steel rails. The method comprises the following steps: determining the normalizing finishing temperature; for different steel rails, determining different finishing temperatures; after welding, instead of normalizing, welding another welding head at first, and adopting flame softer than the welding flame, namely weak carburizing flame, to heat when the previous welding head is cooled down to guarantee that the internal temperature meets the demand of the normalizing temperature; and adopting the two-stage flame swing method to heat; and adopting the blowing and atomizing method to increase the cooling speed to enable the internal hardness and the external hardness to tend to be uniform. The postweld normalizing method improves the strength, the plasticity and the toughness of the welding heads, enables the hardness to be uniform and properly reduced, eliminates incomplete normalizing and two heat-affected zones, enables the joint quality to meet the demands and can bring about favorable social benefits and economic benefits.

Description

Gas pressure welding of rail postwelding normalizing treatment method

 

Technical field

The invention belongs to the technical field of heat treatment of forged steel pieces, be specifically related to a kind of gas pressure welding of rail postwelding normalizing treatment method.

 

Background technology

Adopt in plasticity pressure gas welding welded rails process, along with the rising of temperature, welding temperature is at 1250 ~ 1300 DEG C, postwelding joint metal grain fineness number is in one-level substantially, belong to the open grain structure that austenite is overheated, make it to remain under comparatively big supercooling degree condition, plasticity, the toughness of this tissue are poor, and hard and crisp, cannot use; Meanwhile, after welding, also there is certain residual stress, after must heat-treating improving SNR, could use on the line better; For this reason, the process stipulation of pressure gas welding welded rails, the necessary normalizing treatment of postwelding; But in actually operating, normalizing treatment existing defects, joint quality does not reach requirement, must work out rational normalizing treatment method.

 

Summary of the invention

In order to overcome the above-mentioned technical problem that prior art field exists, the object of the invention is to, a kind of gas pressure welding of rail postwelding normalizing treatment method is provided, intensity and the plasticity and toughness of soldering tip can be improved, make hardness evenly and have suitable reduction, eliminate normalizing not thoroughly and the phenomenon of two heat affected zones, good Social benefit and economic benefit can be brought.

Gas pressure welding of rail postwelding normalizing treatment method provided by the invention, comprises the following steps:

(1), before welding rail construction, fully understand rail type, the chemical composition of this construction institute welding steel rail, then determine the finishing temperature of normalizing, temperature carries out verification experimental verification after determining, then upper track construction; For different rail, determine different finishing temperatures; As U ₇₁and U ₇₄rail, normalizing finishing temperature is defined as 850 DEG C ± 10 DEG C; U ₇₁mn rail normalizing finishing temperature is 900 DEG C ~ 910 DEG C; PD3 rail (U ₇₅v rail), normalizing finishing temperature is 910 DEG C ~ 920 DEG C;

(2) starting temperature of normalizing must control, at 400 DEG C ~ 500 DEG C, particularly to construct during the broiling summer, takes the positive pyrogenic process in gap, can ensure that postwelding temperature is down to suitable starting temperature; Method is: the not first normalizing of postwelding, but first welds another soldering tip, waits previous soldering tip to lower the temperature;

(3) the flame heating softer than welding flame is adopted, i.e. weak carbonizing flame (flare is longer) heating, particularly fall the lower soldering tip even reaching envrionment temperature is all the more so to temperature, and time lengthening to 5 ~ 6min, to make internal-external temperature difference reduce, ensure that internal temperature reaches normalizing temperature requirement;

(4) adopt the heating of two sections of pendulum pyrogenic processes, the later stage puts fiery width >=80mm, makes normalizing heat affected zone scope be greater than welded heat affecting zone scope, to eliminate two heat affected zones, and will pass through weld metal zone rapidly; Now, butt welded seam district is insulation just, instead of heats up, in order to avoid temperature raises cause coarse-grain;

(5) select suitable surveying instrument, range is greater than normalizing temperature (500 DEG C ~ 1000 DEG C), to ensure the accuracy of normalizing finishing temperature; High temperature season adopts the method for blowing and spraying to improve speed of cooling, makes inside and outside hardness be tending towards even.

Gas pressure welding of rail postwelding normalizing treatment method provided by the invention, its beneficial effect is, improve intensity and the plasticity and toughness of soldering tip, make hardness evenly and have suitable reduction, eliminate normalizing not thoroughly and the phenomenon of two heat affected zones, make joint quality reach requirement, good Social benefit and economic benefit can be brought.

 

Embodiment

Below in conjunction with an embodiment, gas pressure welding of rail postwelding normalizing treatment method provided by the invention is described in detail.

Embodiment

The gas pressure welding of rail postwelding normalizing treatment method of the present embodiment, comprises the following steps:

(1), before welding rail construction, fully understand rail type, the chemical composition of this construction institute welding steel rail, then determine the finishing temperature of normalizing, temperature carries out verification experimental verification after determining, then upper track construction; For different rail, determine different finishing temperatures; As U ₇₁and U ₇₄rail, normalizing finishing temperature is defined as 850 DEG C; U ₇₁mn rail normalizing finishing temperature is 900 DEG C; PD3 rail (U ₇₅v rail), normalizing finishing temperature is 910 DEG C;

(2) starting temperature of normalizing controls, at 400 DEG C, particularly to construct during the broiling summer, takes the positive pyrogenic process in gap, can ensure that postwelding temperature is down to suitable starting temperature; Method is: the not first normalizing of postwelding, but first welds another soldering tip, waits previous soldering tip to lower the temperature;

(3) the flame heating softer than welding flame is adopted, i.e. weak carbonizing flame (flare is longer) heating, particularly fall the lower soldering tip even reaching envrionment temperature is all the more so to temperature, and time lengthening is to 5min, to make internal-external temperature difference reduce, ensure that internal temperature reaches normalizing temperature requirement;

(4) adopt the heating of two sections of pendulum pyrogenic processes, the later stage puts fiery width and is greater than 80mm, makes normalizing heat affected zone scope be greater than welded heat affecting zone scope, to eliminate two heat affected zones, and will pass through weld metal zone rapidly; Now, butt welded seam district is insulation just, instead of heats up, in order to avoid temperature raises cause coarse-grain;

(5) select suitable surveying instrument, range is greater than normalizing temperature, to ensure the accuracy of normalizing finishing temperature; High temperature season adopts the method for blowing and spraying to improve speed of cooling, makes inside and outside hardness be tending towards even.

Gas pressure welding of rail postwelding normalizing treatment method, improves intensity and the plasticity and toughness of soldering tip, makes hardness evenly and has suitable reduction, eliminates normalizing thoroughly and the phenomenon of two heat affected zones, makes joint quality reach requirement.

Claims (1)

1. a gas pressure welding of rail postwelding normalizing treatment method, is characterized in that: said method comprising the steps of:

(1), before welding rail construction, fully understand rail type, the chemical composition of this construction institute welding steel rail, then determine the finishing temperature of normalizing, temperature carries out verification experimental verification after determining, then upper track construction; For different rail, determine different finishing temperatures; As U ₇₁and U ₇₄rail, normalizing finishing temperature is defined as 850 DEG C ± 10 DEG C; U ₇₁mn rail normalizing finishing temperature is 900 DEG C ~ 910 DEG C; PD3 rail (U ₇₅v rail), normalizing finishing temperature is 910 DEG C ~ 920 DEG C;

(2) starting temperature of normalizing must control, at 400 DEG C ~ 500 DEG C, particularly to construct during the broiling summer, takes the positive pyrogenic process in gap, can ensure that postwelding temperature is down to suitable starting temperature; Method is: the not first normalizing of postwelding, but first welds another soldering tip, waits previous soldering tip to lower the temperature;

(3) the flame heating softer than welding flame is adopted, i.e. weak carbonizing flame (flare is longer) heating, particularly fall the lower soldering tip even reaching envrionment temperature is all the more so to temperature, and time lengthening to 5 ~ 6min, to make internal-external temperature difference reduce, ensure that internal temperature reaches normalizing temperature requirement;

(4) adopt the heating of two sections of pendulum pyrogenic processes, the later stage puts fiery width >=80mm, makes normalizing heat affected zone scope be greater than welded heat affecting zone scope, to eliminate two heat affected zones, and will pass through weld metal zone rapidly; Now, butt welded seam district is insulation just, instead of heats up, in order to avoid temperature raises cause coarse-grain;

(5) select suitable surveying instrument, range is greater than normalizing temperature (500 DEG C ~ 1000 DEG C), to ensure the accuracy of normalizing finishing temperature; High temperature season adopts the method for blowing and spraying to improve speed of cooling, makes inside and outside hardness be tending towards even.