CN105624669A - Sectioned laser cladding remanufacturing method with preheating and heat treatment for complex parts - Google Patents

Abstract

The invention belongs to the field of laser cladding remanufacturing, and provides a sectioned laser cladding remanufacturing method with preheating and heat treatment for complex parts. According to the invention, on the basis of a single-track and single-layer laser cladding experiment, laser cladding parameters are determined with reference to the track shape of laser cladding and the complexity of workpieces; the laser powers of preheating treatment and aftertreatment are selected according to the laser cladding parameters, the lead time of the laser preheating and the lag time of the heat treatment are determined according to requirements on the surface stress and the surface hardness of the parts, the path length of each laser cladding is determined according to the lead time and the lag time, and the preheating, the laser cladding and the heat treatment are successively carried out on each section. The method is capable of effectively reducing the generation of laser cladding cracks relative to common laser cladding, and is capable of processing a curve path and high in adaptability compared with three-beam preheating and heat treatment laser cladding.

Description

A kind of with preheating and heat treated complicated shape segmentation laser melting coating reproducing method

Technical field

The invention belongs to laser melting coating and manufacture field again, particularly a kind of with preheating and heat treated complicated shape segmentation laser melting coating reproducing method.

Background technology

Material processing is subtracted compared to traditional, laser melting coating is a kind of increasing material manufacture method, it it is one of main recovery technique manufacturing field again, laser melting coating heat input is very little, therefore matrix distortion is little, matrix is little and can control to the thinning ratio of cladding layer, and laser cladding layer and matrix metallurgical binding performance are good. Therefore the field such as aerospace, medical science it is widely used in.

Re-manufacturing technology refers to using injuring part as blank, adopts proprietary technology and technique to be processed by injuring part, makes it shape, performance recovery or exceedes level originally. For crackle damage, there is features such as not easily finding, irregular in part injury, brings certain difficulty to laser melting coating reparation.

Laser melting coating is the process of the cooling that is rapidly heated, and the features such as molten bath volume is little, thermograde is big, thermal stresses is big make the defects such as cladding layer unrelieved stress very big very easily generation crackle. Matrix is carried out preheating and thermal treatment is a kind of good method controlling cladding layer stress, it is a kind of feasible method with low power laser Shu Zuowei preheating and thermal treatment thermal source, but unrelieved stress all can be had an impact retardation time by time and the thermal treatment in advance of different preheatings and thermal treatment laser power, preheating.

Zhou Shengfeng, Dai Xiaoqin disclose CN201110352257.X mono-kind and have preheating and the method for after heat function and efficient three beam laser cladding flawless coatings, by laser beam splitter mirror laser is divided into two and it is used separately as preheating and thermal treatment, it is possible to realize the laser melting coating of simple part. But three beams of laser is all the time in a plane, its cladding path can only be straight line, and part crack is complex-shaped, and length is very short, and laser beam track must mate mutually with the crack shape moment, and this method is not suitable for.

Summary of the invention

Provide a kind of with preheating and heat treated complicated shape segmentation laser melting coating reproducing method for the problems referred to above the present invention, utilize simple laser cladding apparatus to realize the preheating and the thermal treatment that manufacture laser melting coating again, effectively slow down the generation of re-melt deposit welding.

The technical scheme of the present invention:

A kind of with preheating and heat treated complicated shape segmentation laser melting coating reproducing method, comprise the following steps:

Step one: on the basis of single track individual layer laser melting coating, determines laser melting coating parameter in conjunction with laser melting coating trajectory shape and workpiece complexity are wrong by trying with experience, comprises laser melting coating power, powder sending quantity and sweep velocity.

Step 2: according to the determined laser melting coating parameter of step one, it is determined that cladding layer microstructure is with change curve with thermal treatment laser power of the change curve of preheating laser power and cladding layer microstructure; Select microhardness height and the little preheating laser power of crystal grain and thermal treatment laser power with the change curve of preheating laser power and thermal treatment laser power according to cladding layer microstructure;

Again according to workpiece unrelieved stress with preheating in advance time changing curve and workpiece unrelieved stress with thermal treatment change curve retardation time, select the little laser preheating of unrelieved stress time and thermal treatment retardation time in advance, time is selected identical with thermal treatment retardation time in advance in preheating, and the sweep velocity of laser preheating is identical with heat treated sweep velocity.

Step 3: determining each laser melting coating path length according to the determined preheating of step 2 time and thermal treatment in advance and workpiece is carried out segmentation laser melting coating retardation time, wherein section length S method of calculation are as follows:

$S\≤\frac{T}{\frac{1}{V}+\frac{1}{V_c}}$

Wherein: T is for shifting to an earlier date retardation time, and V is laser melting coating speed, V_CIt is laser head backhaul speed;

Residence time T after laser head back to zero_SMethod of calculation be:

$T_S=(\frac{T}{\frac{1}{V}+\frac{1}{V_c}}-S)/V=\frac{T}{1+\frac{V}{V_c}}-\frac{S}{V}.$

The useful effect of the present invention: on the basis of single track individual layer laser melting coating, determines laser melting coating parameter in conjunction with laser melting coating trajectory shape and workpiece complexity by trial and error, comprises laser melting coating power, powder sending quantity and sweep velocity. Select the laser power of thermal pretreatment and aftertreatment according to the requirement of piece surface stress after the laser melting coating parameter selected and processing and determine time in advance and thermal treatment retardation time of laser preheating. Retardation time is determined each laser melting coating path length in time and thermal treatment in advance according to laser preheating, and part is carried out segmentation laser melting coating. The temperature of matrix can be increased compared to common laser cladding, preheating and thermal treatment, extend molten bath cooling time, be a kind of control cladding layer stress, prevent the good method that crackle produces. Compared to a kind of, there is preheating and the method for after heat function and efficient three beam laser cladding flawless coatings. Preheating, thermal treatment laser are successively applied to repair on part, therefore for the shape not requirement of cladding track, it is possible to be applied in complicated shape preferably and manufacture field again.

Accompanying drawing explanation

Accompanying drawing 1 is complicated shape segmentation laser melting coating reproducing method exemplary plot.

In figure: the first half section of 1 workpiece crack; The second half section of 2 workpiece cracks; 3 laser heads;

4 are repaired workpiece.

Embodiment

Below in conjunction with the drawings and specific embodiments, the invention will be further described, and this segmentation laser melting coating reproducing method detailed process is as follows:

Step one: on the basis of single track individual layer laser melting coating, tries mistake by experiment in conjunction with laser melting coating trajectory shape and workpiece complexity and experience determines laser melting coating parameter, comprises laser melting coating power, powder sending quantity and sweep velocity.

Laser melting coating body material and cladding material are AISI321 and AISI316L austenitic stainless steel respectively, AISI316L austenitic stainless steel has following feature: the transformation not relating to martensite in process of setting, therefore the producing cause of unrelieved stress can get rid of martensitic transformation, in addition AISI316L austenitic stainless steel good welding performance, cladding not easily produces crackle. Laser melting coating parameter is tried wrong reference with experience by experiment and is determined, the laser apparatus that the present invention adopts is Nd:YAG laser apparatus, and spot size is 5mm. The relevant scholar in this area has done a large amount of laser melting coating experiments, find when spot size 5mm, Nd:YAG laser apparatus is used as common laser cladding laser power and generally can be taken as about 1000W, cladding about speed 5mm/s, powder sending quantity can be about 6g/min, when Binding experiment finds that laser melting coating power is 846W, cladding layer microstructure crystal grain is thin, hardness is higher, finally determine that laser melting coating power is 846W, cladding speed V=300mm/min, powder sending quantity is chosen as 7.2g/min according to powder feeding machine. Repairing trajectory shape is a segment circular arc, and its radius is 40mm, and reparation total trajectory length is 31.42mm, such as accompanying drawing.

Step 2: according to the determined laser melting coating parameter of step one, selects microhardness height, the preheating that crystal grain is little and thermal treatment laser power according to cladding layer microstructure with the change curve of preheating and thermal treatment laser power;

/ thermal treatment change curve retardation time is shifted to an earlier date with preheating again according to workpiece unrelieved stress, select the little laser preheating of unrelieved stress time and thermal treatment retardation time in advance, preheating time and thermal treatment in advance can be selected identical retardation time, and the sweep velocity of laser preheating is identical with heat treated sweep velocity.

Preheating and thermal treatment laser power is considered, in advance/retardation time according to laser melting coating parameter. Laser preheating and thermal treatment can reduce the tensile stress of cladding layer, but tensile stress and the preheating change of time and thermal treatment rearmounted time in advance and change, part unrelieved stress should be considered and with in advance/retardation time change curve. Part residual tension presents the trend of first increases and then decreases with the increase of preheating in advance time, analyzes by experiment, the cladding material tensile stress extreme value in this experiment is appeared in advance to the time is about 2.5 seconds regions. Part residual tension increases in first reducing the trend increased afterwards with thermal treatment retardation time, analyzes by experiment, and appearing at retardation time for the cladding material tensile stress extreme value in this experiment is about 3 seconds regions. Time and thermal treatment scope retardation time are approximately the 2.5-4 second in advance to consider the rational laser preheating of selection, and laser preheating in advance the time identical for retardation time with thermal treatment, consider and select rational laser preheating time and thermal treatment in advance to select T=3s retardation time. Preheating and aftertreatment laser power are selected should be suitably reasonable, and high-power meeting causes the fusing of material or remelting to affect material property, and small power can not play preheating and heat treated effect, and considering power is approximately 300W. .

Step 3: determining each laser melting coating path length according to the determined preheating of step 2 time and thermal treatment in advance and workpiece is carried out segmentation laser melting coating retardation time, wherein section length S method of calculation are as follows:

$S\≤\frac{T}{\frac{1}{V}+\frac{1}{V_c}}$

Wherein: T is for shifting to an earlier date retardation time, and V is laser melting coating speed, V_CIt is laser head backhaul speed;

Residence time T after laser head back to zero_SMethod of calculation be:

$T_S=(\frac{T}{\frac{1}{V}+\frac{1}{V_c}}-S)/V=\frac{T}{1+\frac{V}{V_c}}-\frac{S}{V}.$

The various parameters in this process are determined by the preheating of step 2 and thermal treatment laser power. It is warm-up power that the process that wherein this one-phase mainly experiences comprises first adjustment laser power, carries out preheating; Secondly laser head position back to zero, adjustment laser power is cladding power, stagnates T_SAfter carry out laser melting coating; Last laser head position back to zero, adjustment laser power is thermal treatment power, stagnates T_SAfter heat-treat. Determine, V=300mm/min, V_C=3000mm/min. According to formula

$S\≤\frac{T}{\frac{1}{V}+\frac{1}{V_c}}$

Can be calculated S��13.64mm. Repair path total length is 31.42mm, selects each segmentation S-phase etc. and S=31.42/3=10.47mm, according to formula

$T_S=(\frac{T}{\frac{1}{V}+\frac{1}{V_c}}-S)/V=\frac{T}{1+\frac{V}{V_c}}-\frac{S}{V}$

Can be calculated T_S=0.63s. With common manufacture cladding layer that laser melting coating obtains again compared with, this method gained cladding layer tensile stress reduces, and can processed complex curved path.

Above-described embodiment, only for the technical conceive of the present invention and feature are described, its object is to allow person skilled in the art can understand the content of the present invention and implement according to this, can not limit the scope of the invention with this. All equivalences done according to spirit of the invention change or modify, and all should be encompassed within protection scope of the present invention.

Claims (1)

1. one kind with preheating and heat treated complicated shape segmentation laser melting coating reproducing method, it is characterised in that, step is as follows:

Step one: on the basis of single track individual layer laser melting coating, determines laser melting coating parameter in conjunction with laser melting coating trajectory shape and workpiece complexity, comprises laser melting coating power, powder sending quantity and sweep velocity;

Step 2: according to the determined laser melting coating parameter of step one, it is determined that cladding layer microstructure is with change curve with thermal treatment laser power of the change curve of preheating laser power and cladding layer microstructure; Select microhardness height and the little preheating laser power of crystal grain and thermal treatment laser power with the change curve of preheating laser power and thermal treatment laser power according to cladding layer microstructure;

Again according to workpiece unrelieved stress with preheating in advance time changing curve and workpiece unrelieved stress with thermal treatment change curve retardation time, select the little laser preheating of unrelieved stress time and thermal treatment retardation time in advance, time is selected identical with thermal treatment retardation time in advance in preheating, and the sweep velocity of laser preheating is identical with heat treated sweep velocity;

Step 3: determining each laser melting coating path length according to the determined preheating of step 2 time and thermal treatment in advance and workpiece is carried out segmentation laser melting coating retardation time, wherein section length S method of calculation are as follows:

$S\≤\frac{T}{\frac{1}{V}+\frac{1}{V_c}}$

Wherein: T is for shifting to an earlier date retardation time, and V is laser melting coating speed, V_CIt is laser head backhaul speed;

Residence time T after laser head back to zero_SMethod of calculation be:

$T_S=\left(\frac{T}{\frac{1}{V}+\frac{1}{V_c}}-S\right)/V=\frac{T}{1+\frac{V}{V_c}}-\frac{S}{V}.$