In the mold processing, edm wire-cutting processing technology a wide range of applications, but in wire-cutting processing process, mould easy generation deformation and crack, causing the abandonment of parts, make the increasing cost of ongoing problem. So, wire-cutting processing of deformation and cracking mold problem, also more and more cause the attention of people, over the years, the people to the deformation and cracking wire-cutting processing know enough, often caused wire-cutting processing with supplied materials department each other between the processors bitching, a contradiction. In fact, deformation and cracking reason is various, such as materials, heat treatment, structural design, process arrangement and when clamping workpiece linear cutting lines and the problem of choice and so on. In this many factors, we can find the linear cutting machining deformation and cracking of the law? The author through years of thorough research, puts forward the following measures to prevent deformation and cracking.
1 deformation and the main factors of crack
In the production practice, the author with a lot of example analysis, found wire-cutting processing deformation and crack and the following factors.
1.1 and the structure of the parts involved
1.ll that long and narrow the shape of the concave die punch, easy to have the deformation, its deformation the size and shape of complexity, the aspect ratio, cavity and the width of the border than about. The more complex the shape, the long and border than width ratio and cavity, the bigger the deformation of the mould is larger. Deformation law of the central cavity is flat, the punch is usually warping;
2.ll the Angle of the complex shape quenching cavity, pointed to cracks in the extremely easily, even there is cracking phenomenon. It appears the frequency and material composition, hot cylindrical wall thickness is book parts, if in cutting wall, easy generation deformation, general by round into the oval. If the gap will be cut, in the cut when it easy to have the cracking phenomenon;
3.ylindrical wall thickness is book parts, if in cutting wall, easy generation deformation, general by round into the oval. If the gap will be cut, in the cut when it easy to have the cracking phenomenon;
4.y parts of the ShenCao is cut into the external mouth, easy generation deformation, deformation law of the division for the mouth, the size of the deformation and the depth of the slot and material properties about.
1.2 and thermal processing relevant
1.in forging die blank when forging beginning temperature too high or low, at the low temperature forging parts;
2.nd forging the temperature too high, grain growth, the end after forging cooling speed too slow, there are net carbide exhalation of mould billet;
3.f a kind of special annealing not according to the ball annealing process, the ball more than 5 levels of parts of pearlitic;
4.uench heating temperature is too high, austenitic grain bulky, reduce the material strong toughness, increase the brittleness;
5.uenching and tempering workpiece not seasonable tempering not fully parts.
1.3, machine processing and the process
1.the area bigger concave die, intermediate large area resection and prior hollow, cut to the box for larger volume, box shape size will produce certain deformation;
2.no appearance starting point blank all wear silk hole, had to cut into the blank of the from, no matter whether the punch temper and shape how, generally easy to produce the deformation, especially
Quenching a deformation serious, and sometimes even in cutting cracks in;
3.fter heat treatment of grinding parts, no grinding wheel granularity, feed quantity, cooling mode process requirement, after grinding surface has burns and prevent disease micro cracks of parts.
1.4 and relevant materials
1.aw material has serious carbide segregation;
2.ts quench-hardening ability is bad, the yi deformation of materials, such as T10A, T8A, etc.
1.5 and line the process
1.line route choice improper, easy generation deformation;
2.he clamp pressure not reliable way, clamp pressure points of improper selection are easy to produce deformation;
3.the rules must choose improper, easy to crack.
2 prevent deformation and cracking measures
Find the deformation and cracking reasons, can suit the remedy to the case to take corresponding measures to avoid, prevent deformation and cracking. Specific measures can from the following several aspects:
2.1 choose deformation of smaller materials, the correct heat treatment process
In order to prevent and reduce the deformation and cracking, to need wire-cutting processing mould, deal with the selection of materials, and heating and heat treatment until all the sections of the finished product is made to full attention and more attention;
1.trict inspection chemical raw materials, metallurgical microstructure and testing, not qualified for raw materials and coarse grain steel and harmful impurities in the overweight steel unfavorable choose;
2.ry choosing vacuum smelting, refining outside the furnace slag or electricity remelting steel;
3.void to choose its quench-hardening ability is bad, the yi deformation materials;
4.hould be reasonable blank forging, abide by upsetting, pull long, forging and pressing than and other forging rules, the length and the ratio of raw materials in diameter is forging than had better choose in between 2-3;
5.improved heat treatment technology, using vacuum heating, protecting atmosphere heating and full of deoxidizing salt bath heating furnace quenching, and classified the isothermal quenching;
6.hoose the ideal the cooling speed and cooling medium;
7.ardened steel should be timely tempering, try to eliminate quenching stress, reduce the brittleness;
8.ith a long time tempering, improve the mold of the fracture toughness values;
9.ully tempering, obtain a stable organization performance;
10.any times to tempering austenite change fully and eliminate the new stress;
11.or the second brittleness after tempering steel high temperature should be fast cooling water or oil cold), which can eliminate the brittleness category ii;
12.he steel chemical treatment diffusion annealing, before the ball annealing, quenching and tempering treatment, fully refined original organization.
2.2 reasonable arrangement of the machining process
1he size of the blank line, according to the size of the parts to determine, shoulds not be too small. Usually, graphics should be located in central blank or from a blank edge Far and not easy the creation of the deformation of the position, usually should take the blank side of the graphics to more than 10 mm;
2.if the larger cavity or narrow long and complex punch, made to change the traditional blank solid sheet metal habit. Big box cavity, long and narrow cavity, and so easy deformation parts, including part should be between hollow. So hardened into improved conditions, small temperature difference, and the resulting stress small, at the same time, cutting the volume of resection is small, and stress is not balanced by destruction;
3.in the mold use allow, big box cavity parts of pure form Angle place, should be appropriately increase process rounded R, or in the line will clear Angle before drilling empty place, to alleviate stress concentration phenomenon;
4.to the punch parts, the hardening in convex piece of blank before should be the starting point for the appearance of drilling in silk hole, to make the work in cutting stress and keep balance was not damaged, with
From the materials from cut into the cause craze deformation.
2.3 optimization wire-cutting processing technology solutions, choose reasonable parameters
2.3.1 this into cutting method
1.ange a cut in place of the tradition of rough and fine for secondary cutting, so that the first cut of rough after deformation in essence cutting is fixed in time. General fine cutting cut should be based on the first cut deformation amount and decide, generally take 0.5 mm or so can. This way are often applied to complex shape and certainly will generate distortion part or requirements with higher precision, clearance smaller mould;
2.hange the habit of two clamp pressure for the single point clamp pressure, so as to cut the deformation process can free is done, prevent two clamp pressure on deformation of interference, but should pay attention to, the single point clamp pressure parts in the reasonable usually end in the program. This distortion affects only waste parts, to avoid the effect of molding;
3.o easy deformation of the cutting parts, to shape characteristic according to parts of the overall arrangement cut starting point, procedures to and clamp pressure position, to reduce the distortion. Generally should choose relatively flat, already finishing or on the performance of the impact is not big parts of the linear starting point set.
2.3.2 choose reasonable technology parameters
1. with the parameters of the peak value narrow pulses, make the workpiece material in gas phase out, gasification temperature melt temperature are much higher than to take most of the heat, avoid overheating and the surface deformation;
2.effectively to each pulse test, control the focus on the length of the string of discharge impulse, also can solve local overheating problem, eliminate the fatigue;
3.pulse energy the effects on the crack of the very obvious, the greater the power, the more the deeper the crack width; Pulse energy is hours, for example by finishing the rules is accurate, the surface roughness Ra1.25 μ m, general "do not appear to crack.
