Effectively improve the service life of the cemented carbide drawing die

At present, foreign guy die grinding process widely used high-speed mechanical polishing machine, and grinding hard alloy plating the surface of the metal pin, the equipment running smoothly, the specifications of the grinding needle and using standardized products precision is higher. Mold groove size using the outline of the recorder and the pore diameter measuring instrument to detect, and check the drawing mould specialized microscope to check the surface finish. But many domestic manufacturers are still in the backward equipment, use manual operation to grinding groove, as a result, there are the following problems: volatile pass parameters, work hard to work out straight cone; Sizing area and workspace junction easy grinding out transition Angle, make the wire in the sizing area produces secondary compression, increase the external friction, shorten the sizing zone length, shorten the service life of mould; Wear of the grinding needle fixed frequency varies from person to person, the use of non-standard, causing pass the consistency of the poor. Detection methods are backward, and can only rely on simple tools such as visual or a magnifying glass, microscope inspection, and pay attention to the mould surface finish, the groove size cannot effectively detect, much less control.

2 choose good groove design of the tungsten carbide wire drawing dies

Wire drawing die pass generally divided into curve type (i.e., R series) and linear (i.e., cone type series).

Drawing die groove type

From wire drawing die in the basis of an analysis of the deformation uniformity, appears to be type curve is linear, the groove is in the smooth transition of designed under the guidance of theory, the groove structure according to the nature of work can be divided into "population area", "lubrication area", "workspace", "sizing area", "the day" area five parts, each junction "chamfering", smooth transition, the whole groove grinding into a large, solitary surface with different curvature the groove of the mold at the time of the drawing speed conditions, can still apply. By the late 1970 s to the early 80 s, with the increase of wire speed, pull the service life of mould has become outstanding problems. In order to adapt to the requirement of high speed wire, America's T.M axwall and E.G.K ennth "linear" theory was put forward. This theory focus on the lubrication and wear factors in the process of drawing, points out that the improved linear pass pull mould should have the following characteristics:

(1) all parts of the groove profile line must be straight, straight work cone drawing force minimum;

(2) the transition part of each part of the mould must be clear, so the parts can give full play to their role, to avoid the transition Angle of sizing area actual length decreased;

(3) the extension of the entrance area and the height of the workspace, the wire into the mould taper hole work in the middle of the paragraph, using the inlet cone Angle and working Angle the upper wedge formed by the area, establish "wedge effect", in the surface of the wire form more dense solid lubricating film, reduce wear and tear, suitable for high-speed drawing;

(4) sizing area must be flat and reasonable length. Sizing area is too long, pull the friction increase, pull wire die easy cause reducing or break line, after sizing area are too short, difficult to get good shape stability, size precision and surface quality of wire rod, die at the same time also will soon wear out-of-tolerance.

Through practical application, using linear theory to design the drawing die, its service life than the R type guy modulus increase 3-5 times more.

3 reasonable installation of wire drawing machine are used to

(1) the installation of the wire drawing machine foundation is solid, avoiding the phenomenon of vibration;

(2) when installation to debug wire tensile axis and the die hole centerline is symmetrical, uniform wire and pull stress;

(3) drawing process to avoid frequent start parking, because when you start drawing the friction caused by the tensile stress is bigger than normal drawing of friction, this will increase the mold wear.

4 is used for drawing wire passes through pretreatment

(1) : surface pretreatment for wire rod surface dirt, adhesion is more impurities, first drawing again after cleaning and drying; For wire rod surface have more scale, must first after acid fine, drying and then to drawing; For surface peeling wire, pits, the phenomenon such as double skin, and through the polishing machine for grinding after the drawing;

(2) heat treatment: the hardness is too large or uneven hardness of wire rod, first by annealing and tempering hardness, keep good hardness uniformity and wire drawing again.

5 maintain appropriate drawing surface shrinkage

Cemented carbide drawing die itself has characteristics of hard and brittle, if used for bedding face of shrinkage reducing drawing, it is easy to lead to scrap mold can withstand stress and rupture, so according to the different wire mechanical properties, select the appropriate surface shrinkage for drawing. With cemented carbide mold drawing stainless steel wire, general single-channel surface shrinkage rate less than 20%.

6 of lubricant with good lubrication performance

In the stretching process, the quality of the lubricant and lubricant supply adequacy are affecting the drawing die service life. Therefore require oil-based lubricant is stable, good oxidation resistance, has excellent lubricity, cooling and cleaning, in the whole process always maintain the best state of lubrication, so that can form a layer of thin film under high pressure without damage, reduce the friction force of work area, improve the service life of the mold.

Use process, to observe the condition of the lubricating oil, if it is found that serious color change or increase metal powder in lubricating oil, to be replaced in time or filter, avoid lubricants lubrication performance degradation due to oxidation, and to avoid drawing die off tiny metal particles in the process of damage.

7 regular service grinding carbide wire drawing dies

Drawing die in the process of long-term use, die wall by metal wires strongly friction and scouring effect, inevitably produce wear phenomenon, the most common is appeared at the entrance of the workspace wire ring groove cao (dent). Pull mold ring groove, exacerbated the die wear, because the ring groove on the peeling off due to loose the mold core material by metal wire into small particles die workspaces and sizing area, abrasive role, while the wire into the die hole like grinding needle die wear. If not timely repair switch, then the ring groove will continue to accelerate expansion, increase the repair is difficult, even in the depth of the annular groove is, the make mould collapse completely crushed scrap.

Learn from experience, developed a set of standards, strengthen the daily maintenance, often for maintenance of molds is very cost-effective. Once the mold appeared any slight wear and tear, promptly polishing, then make mould restore to its original state of polishing time shorter, and groove size has no obvious change in the mold.