CN106826090B

CN106826090B - Build-up welding preparation process for connecting rod mold

Info

Publication number: CN106826090B
Application number: CN201611260040.5A
Authority: CN
Inventors: 许向华
Original assignee: KUNSHAN CHAITAI XINCHENG PRECISION FORGING CO Ltd
Current assignee: KUNSHAN CHAITAI XINCHENG PRECISION FORGING CO Ltd
Priority date: 2016-12-30
Filing date: 2016-12-30
Publication date: 2020-02-18
Anticipated expiration: 2036-12-30
Also published as: CN106826090A

Abstract

The invention belongs to the technical field of die surfacing processes, and particularly relates to a connecting rod die surfacing preparation process. The method comprises the following steps: step 1: the air gouging is based on the outline of the cavity, the width of a single side is 10mm, the depth is 3mm, and a carbon rod is used for removing the surface material of the die; step 2: preheating a die, namely preheating a die base material 5CrNiMo to 538 ℃; and step 3: welding, namely welding the die base material in the step 2, and ensuring that the temperature of the die is more than or equal to 350 ℃ in the welding process; and 4, step 4: isothermal cooling and slow cooling after welding, and immediately returning the die welded in the step 3 to a furnace for double-sided heating; and 5: tempering and slow cooling for the first time, in step 4, when the temperature of the die after slow cooling is reduced to 100-150 ℃, immediately charging into a furnace and tempering; step 6: secondary tempering and slow cooling. The process method directly performs surfacing on the original failed mould, the surface of the mould is not reduced during repair, the processing period and the manufacturing cost of the mould are greatly reduced, and the service life of the mould is prolonged to a certain extent.

Description

Build-up welding preparation process for connecting rod mold

Technical Field

The invention belongs to the technical field of die surfacing processes, and particularly relates to a connecting rod die surfacing preparation process.

Background

Automobile connecting rod is mostly H13 with build-up welding material, when the mould wearing and tearing appear, the fracture, when the relevant defect of thermal fatigue, the mode of reprocessing of mould is that the module is whole to be milled processing at a high speed again after falling, and current mould processing has following shortcoming and not enough: 1) the reduction of the base materials causes the die to be scrapped in advance, and the waste of the die base materials is caused; 2) the cost of mechanical processing and heat treatment needs to be high; 3) the only part really acting in the forming process is the surface of the die cavity, and the requirement on the die base body is low. The prior mold base body and the surface adopt the same high-quality H13 mold material, which causes the waste of the mold material.

In addition, the invention discloses a surfacing manufacturing and repairing process of a roll forging die with the publication number of CN103182618A, and provides a die surfacing technology, which is different from the patent in that the invention adds the steps of air gouging and isothermal slow cooling after welding, and improves the technological parameters in many aspects, thereby greatly reducing the processing period and the manufacturing cost of the die and prolonging the service life of the die to a certain extent.

Disclosure of Invention

In order to overcome the defects in the background technology, the invention provides a link rod die surfacing preparation process, the process method directly performs surfacing on the original failed die, the surface of the die is not reduced after the die is repaired, the die processing period and the manufacturing cost are greatly reduced, and the service life of the die is prolonged to a certain extent.

The invention is realized by the following technical scheme

The connecting rod die surfacing preparation process comprises the following specific steps:

step 1: the method comprises the following steps of (1) air planing, wherein the outline of a cavity is taken as a basis, the width of a single side is 10mm, the depth is 3mm, a carbon rod is used for removing the surface material of the mold, the uniform planing speed is kept, the size is 0.5-1.2m/min, during planing, the inclination angle of the carbon rod is 25-30 degrees, the material in the cavity of the mold is removed through air planing, damaged and invalid parts are removed, surfacing welding is facilitated, the shape of the removed cavity is important, the width of the single side is 10mm, the depth is 3mm, and the planing speed and the angle of the carbon rod are well mastered;

step 2: preheating a mould, namely selecting a 5CrNiMo material with relatively low alloy components as a mould base material for the whole mould, preheating the 5CrNiMo material of the mould base material to 538 ℃, and for a small local module, preheating at the temperature of 300-450 ℃, wherein the heating speed is less than or equal to 120 ℃/h;

and step 3: welding, wherein a surfacing material is an iron-based surfacing alloy, welding is carried out on the die base material in the step 2, and the temperature of the die is guaranteed to be more than or equal to 350 ℃ in the welding process;

and 4, step 4: isothermal cooling and slow cooling after welding, namely immediately returning the welded mould in the step 3 to a furnace for double-sided heating, wherein the heat preservation time is the thickness mm/70mm (h) of the mould, after discharging, putting the mould into a heat preservation box or a heat preservation blanket for slow cooling, and the isothermal cooling and slow cooling after welding can effectively eliminate some residual stress generated by welding and prevent the mould from cracking;

and 5: tempering and slow cooling for the first time, in the step 4, when the temperature of the mold after slow cooling is reduced to 100-150 ℃, immediately charging the mold for tempering, wherein the tempering temperature is 550 ℃, the heat preservation time t1= the thickness mm/50mm +2 (h) of the mold, discharging the mold, and placing the mold into a heat preservation box or a heat preservation blanket for slow cooling;

step 6: and (5) performing secondary tempering and slow cooling, in the step 5, immediately charging the die into a furnace for tempering when the temperature of the die after slow cooling is reduced to 100-150 ℃, wherein the tempering temperature is 550 ℃, the heat preservation time t1= the thickness mm/50+2 (h) of the die, the unit of the thickness of the die is mm, the unit of the heat preservation time t1 is hours, and after the die is taken out of the furnace, placing the die into a heat preservation box or a heat preservation blanket for slow cooling.

Preferably, in the planing process in the step 1, the carbon rod should not be moved transversely and moved back and forth in a reciprocating manner, and only can move linearly along the planing direction, the planing action is stable, the line is aligned, and the center line of the carbon rod should be ensured to coincide with the center line of the planing trough.

Preferably, in the step 2, the mold is preheated and then slowly cooled, and then the mold is placed in an incubator or an insulation blanket and slowly cooled, so that the temperature of the mold in the next step is guaranteed to be more than or equal to 350 ℃.

Preferably, in step 3, the gas ratio of the electric welding machine is as follows: 75-80% of Ar, 220-25% of CO, 30-38L/min of welding flow, 550A of welding current and 32V of welding voltage.

Preferably, when welding is performed in step 3, the arc starting point and the arc withdrawing point are on the same vertical straight line, the left-right reciprocating amplitude is 100mm, and when welding is stopped, the welding position is knocked.

Preferably, in the steps 3, 4 and 5, the cooling rate in the slow cooling is less than or equal to 50 ℃/h.

Preferably, the hardness requirement of the welding material in the step 5 is HRC 48-52.

Preferably, the hardness requirement of the die in the step 6 is HRC46-50. In order to avoid the cracking of the die and prolong the service life of the die in the forging process, the hardness of the die is 2HRC lower than that of the welding material.

Preferably, after the secondary tempering and slow cooling are completed in step 6, the mold is recorded, printed and finally inspected.

The invention has the beneficial effects that: 1) the former die is integrally manufactured by H13 with higher alloy element, and the surface hardness of the die is improved by surface treatment to meet the use requirement. The scheme has high cost of raw materials of the die. At present, the base material of the die adopts 5CrNiMo with relatively low alloy components, and welding materials are surfacing-welded in a cavity, so that the cost of the base material of the die is greatly reduced; 2) when the die fails to work (such as abrasion, fatigue and deformation), the scrapped die can be reused by adopting a surfacing technology; 3) the components of the surface material of the die boring can be flexibly adjusted according to the requirements by adopting the surfacing technology. The die has the advantages that two metals and two hardnesses of one die can be realized, namely the die has HRC46-50 and the welding material has HRC48-52, the matrix has better toughness, and the surface of the die has better strength, hardness and wear resistance, so that the condition of the die is more suitable for production conditions, the service life of the die can be greatly prolonged, the maintenance period is shortened, and the production cost is reduced; 4) the surfacing technology can be used for carrying out local surfacing on the locally failed die, so that the repair period of the die can be greatly shortened, the die opening times can be reduced, and the working strength of die manufacturing can be reduced.

Drawings

FIG. 1 is a diagram of a mold of the present invention.

FIG. 2 is a process flow diagram of the present invention.

FIG. 3 is a schematic view of the structure of the carbon rod tilt angle according to the present invention.

Fig. 4 is a schematic structural diagram of the integral cavity of the invention.

FIG. 5 is a trace plot of arcing and arcing of the present invention.

FIG. 6 is a graph showing the tempering curve of the welding material according to the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention and the accompanying drawings of the specification, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments, and all other embodiments obtained by a person of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the protection scope of the present invention.

step 1: and (5) air gouging. The operation sequence is as follows:

1. preparing a workpiece: before planing, it is first checked whether the polarity of the electrode is correct, and the planing gun is connected to the positive pole and the workpiece is connected to the negative pole. And checking whether the cable and the air pipe are connected. And the diameter of the carbon rod is selected and the current is adjusted according to the thickness of the workpiece and the width of the groove. The extending length of the carbon rod is 80-100 mm. The compressed air line is checked and the pressure is adjusted, and the tuyere is adjusted and aligned with the plough groove.

2. Arc striking: when the arc is ignited, the air valve is opened slowly, then the arc is ignited, otherwise, carbon clamping and carbon rod burning are easy to generate. At the moment of arc ignition, the arc should not be pulled too long to be extinguished.

3. Planing:

1) the uniform planing speed is kept, the planing speed is proper and is 0.5-1.2m/min, the single-side width is 10mm and the depth is 3mm based on the outer contour of the cavity.

2) In the planing process, the carbon rod does not need to swing transversely and move back and forth in a reciprocating mode, and can only do linear motion along the planing direction.

3) The inclination angle of the carbon rod is determined according to the requirement of the groove depth, and the inclination angle can be 25-45 degrees, and is generally 25-30 degrees.

4) When planing, the action of the hand needs to be stable, the alignment line is good, the center line of the carbon rod needs to be coincident with the center line of the planing groove, otherwise, the planing groove is easy to be asymmetric in shape.

5) In the early vertical position of the gouging, the gouging is performed by moving from top to bottom so as to facilitate the outflow of the welding slag.

6) To maintain uniform planing speed, the uniform and crisp fizzing sound during planing indicates that electric arcs are stable, smooth and uniform planing grooves can be obtained, and when each section of planing groove is connected, arc striking is carried out on an arc pit to prevent serious pits from being generated when the planing groove is contacted.

7) When the planing is finished, the electric arc is cut off, and the air valve is closed after a few seconds, so that the carbon rod is cooled.

Step 1, quality detection standard:

1. the method is clean, has no black skin and sharp corners, and can remove all cracks;

2. note the angle of the sides, typically 25-30, see FIG. 3;

3. the overall cavity expands about 10mm, as shown in fig. 4, and if there is a crack, it must be cleaned to ensure smooth transition.

Step 2: and (4) preheating the mould. The operation sequence is as follows:

1. in order to avoid the generation of die failure conditions such as thermal fatigue, cracking, block collapse and the like, the hot die steel needs to be preheated before welding, and the heating speed is less than or equal to 120 ℃/h.

2. The preheating temperature is two, according to the non-use of the die material, the 5CrNiMo is preheated at 538 ℃; for small modules or dies with high deformation temperature and matrix hardness reduction too much, the preheating temperature can be adjusted to be 300-450 ℃, and the heat preservation time is/50 +1h of the thickness of the die.

3. And observing and recording the temperature in the box body of the electric furnace to reach the preset temperature by using a monitoring electric furnace liquid crystal display screen, and then carrying out heat preservation.

4. Heating the single surface, wherein the temperature rise speed is 25 mm/h; heating the two sides at a temperature rise speed of 50 mm/h. The temperature rise time can be controlled according to the height of the die parent body.

5. And after the preheating time is over, keeping the mold, and taking out the mold after the next process link is ready.

6. After the furnace is taken out, the furnace is placed in a heat preservation box or wrapped by heat preservation cotton and a heat preservation blanket to ensure that the temperature is more than or equal to 350 ℃ during welding, or the furnace is returned for heating.

Step 2, quality detection standard: after the steel is heated, the preheating removal condition can be judged according to the corresponding relation between the surface color and the temperature of the steel during heating, and the table 1 is referred to.

Table 1.

Deep brown red	530℃-580℃
		Brownish red	580℃-650℃
Dark cherry red	650℃-730℃

And step 3: and (6) welding. The operation sequence is as follows:

1. the gas proportion and the flow rate can be adjusted to that: ar: 75-80%, Co 2: 20-25%, flow rate: 30-38L/min (different environments, slightly adjusting the flow), and checking whether the protective trachea is unblocked.

2. Welding current: 550A, welding voltage: about 32V.

3. Checking whether the water cooling tank works normally, checking whether the sealing pickaxe and the slag cleaning gun work normally, checking whether the inner diameter of the welding gun contact tip is abraded, and checking whether gas is discharged smoothly, wherein if the working conditions are abnormal, immediate maintenance and replacement are required.

4. The surfacing material is iron-based surfacing alloy, and the welding material has high strength and excellent plasticity, so that the steel has excellent anti-cracking performance, and the steel with poor weldability can be welded without generating cracks. In repair welding of forging dies, it is often used for welding of broken dies and for transition layers of die build-up welding. Hot cracking and cold cracking do not occur. The manipulator and the welding gun are matched with the loose wire and the gas, a proper arcing position is selected, welding is started after the arc is stabilized, the arc swings back and forth, and the amplitude is about 100 mm. Attention is paid to the selection of the arc-extinguishing position. See fig. 5.

5. When welding is stopped, the knocking must be immediately carried out to release the stress.

And (3) quality detection standard: 1. the surface has no welding defects such as air holes, cracks, inclusions and the like;

2. 2-3 machining allowance after welding is reserved at each part of the cavity;

3. ensuring the temperature of the die to be more than or equal to 350 ℃ in the welding process, and if not, immediately returning to the furnace;

and 4, step 4: isothermal and slow cooling after welding. The operation sequence is as follows:

1. immediately feeding the welded die into a furnace, and carrying out isothermal treatment to eliminate stress;

2. setting the temperature of the electric furnace to a preset preheating temperature, and after the electric furnace is thermally stabilized, putting the surfacing welded mold into the electric furnace;

3. observing and detecting the temperature of the liquid crystal display screen of the electric furnace to reach a preset preheating temperature, preserving the heat and recording the time;

4. heating the two surfaces, wherein the heat preservation time is calculated according to the thickness (mm)/70 (mm) (h) of the die, so that the temperature rise time can be controlled according to the height of the parent body of the die;

5. after the furnace is taken out, the furnace must be put in a heat preservation box or wrapped by a heat preservation blanket for slow cooling, and the cooling speed is less than or equal to 50 ℃/h.

Step 4, quality detection standard:

after the steel is heated, the preheating condition can be judged according to the corresponding relation between the surface color and the temperature of the steel during heating. Table 1 may be referred to.

And 5: tempering for the first time and slow cooling. The operation sequence is as follows:

1. an isothermal mold, which is observed, measured and recorded by a thermometer, cooled to 100-150 ℃, and immediately placed in a furnace for tempering;

2. tempering temperature: 550 ℃, time: the thickness of the die is mm/50mm +2 (h), and the temperature value of the liquid crystal display screen of the high-temperature furnace is observed and recorded;

3. after the furnace is taken out, the furnace is put into a heat preservation box or a heat preservation blanket for slow cooling, and the cooling speed is less than or equal to 50 ℃/h;

4. refer to figure 6 for a graph of the temper of the solder.

And 5, quality detection standard: target detection hardness: HRC 48-52.

Step 6: secondary tempering and slow cooling. The operation sequence is as follows:

1. tempering temperature: 550 ℃, time: the thickness of the die is 50mm +2h, and the temperature value of the liquid crystal display screen of the electric furnace is observed and recorded;

2. after the furnace is taken out, the insulation box or the insulation blanket is placed for slow cooling, and the cooling speed is less than or equal to 50 degrees/hour;

3. the target detection hardness is HRC 46-50;

4. the tempering temperature and time are the key for ensuring the quality of the die, and the principle is that the tempering temperature and the tempering time are adjusted from low temperature to high temperature and from short time to long time in turn to finally reach the ideal hardness.

And 6, quality detection standard:

1. final overall check of weld quality

2. And detecting whether the hardness reaches an ideal value HRC46-50.

And (4) marking. The operation sequence is as follows:

1. recording: making corresponding records on a product record book, such as: information such as the number of molds, the model of the mold, the date of production, the producer, etc.;

2. printing: marking and recording by using a steel seal or other methods, such as welding and the like, so as to facilitate tracking;

3. and (4) final inspection: and testing and calibrating according to the average 8-point hardness requirement in the test record table.

Quality detection standard:

1. recording the end of the handwriting, making a serial number record if no correction exists;

2. the number is of a suitable size. The writing is clear and the depth is consistent.

Experimental analysis:

and (3) comparing and analyzing with a die steel manufacturing die:

the product is as follows: a connecting rod mold; the average service life is improved: 0.2 times; forging equipment: and (5) hammering and forging the die.

And (3) benefit analysis:

the forging cost for a new die made from H13 die steel is:

847 (Yuan)/5000 (one) ═ 0.17 (Yuan)/(one)

When the connecting rod die is manufactured by adopting the surfacing technology of our company, the forging cost is as follows:

612 yuan/6000-0.1 yuan (yuan)/(only)

I.e. a saving of 0.07 elements/component.

The above detailed description of the process for preparing a high hardness stainless steel according to the embodiments of the present invention is provided, and the principle and the embodiments of the present invention are explained herein by using specific examples, and the above description of the embodiments is only provided to help understanding the method and the core concept of the present invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, there may be variations in the specific embodiments and the application scope, and in summary, the content of the present specification should not be construed as a limitation to the present invention.

Claims

1. A connecting rod die surfacing preparation process is characterized by comprising the following steps: the surfacing preparation process of the connecting rod mold comprises the following specific steps of:

step 1: air gouging, based on the outer contour of the cavity, wherein the width of a single side is 10mm, the depth is 3mm, a carbon rod is used for removing the surface material of the die, the uniform gouging speed is kept, the size is 0.5-1.2m/min, and the inclination angle of the carbon rod is 25-30 degrees during gouging;

step 2: preheating a mould, namely preheating the whole mould, selecting a 5CrNiMo material with relatively low alloy components as a mould base material, preheating the 5CrNiMo mould base material to 538 ℃, wherein the preheating temperature of a local small module is 300-450 ℃, and the heating speed is less than or equal to 120 ℃/h;

and 4, step 4: isothermal and slow cooling after welding, namely immediately returning the welded die in the step 3 to a furnace for double-sided heating, wherein the heat preservation time is as follows: (the thickness of the mold is mm/70mm) h, discharging, putting into a heat preservation box or a heat preservation blanket, and slowly cooling;

and 5: tempering and slow cooling for the first time, in step 4, when the temperature of the mold after slow cooling is reduced to 100-150 ℃, immediately charging the mold for tempering, wherein the tempering temperature is 550 ℃, the heat preservation time t1 is (the thickness of the mold is mm/50mm +2) h, discharging the mold out of the furnace, and placing the mold into a heat preservation box or a heat preservation blanket for slow cooling;

step 6: in the step 5, when the temperature of the die after slow cooling is reduced to 100-150 ℃, immediately loading the die into a furnace for tempering, wherein the tempering temperature is 550 ℃, the heat preservation time t1 is equal to (the thickness of the die is mm/50mm +2) h, discharging the die out of the furnace, placing the die into a heat preservation box or a heat preservation blanket for slow cooling, and in the planing process in the step 1, the carbon rod does not need to be moved transversely and moved back and forth in a reciprocating manner, and only can do linear motion along the planing direction, the planing action is stable, and alignment lines are aligned, so that the central line of the carbon rod needs to be coincident with the central line of the planing trough;

wherein: in the step 3, the proportion of each gas of the electric welding machine is as follows: ar 75-80%, CO₂20-25%, welding flow of 30-38L/min, welding current of 550A and welding voltage of 32V.

2. The connecting rod die surfacing preparation process according to claim 1, characterized by comprising the following steps: and 3, when welding is carried out in the step 3, the arc starting point and the arc withdrawing point are positioned on the same vertical straight line, the left-right reciprocating amplitude is 100mm, and when the welding is stopped, the welding position is knocked.