According to the stamping experience and the experience of using imported and domestic stamping dies, the forging process and operation of alloy tool steel are put forward.
Key point. By changing the forging deformation step, the internal structure of the metal is improved, and the core carbide particles are further refined and made uniform.
Uniformly distributed. By improving the forging process, the service life of cold-working die steel is increased by 30%~50%.
Mechanical manufacturing; Alloy tool steel; Forging die; 1 preface
Various alloy tool steels are widely used in mold manufacturing industry.
Field. Commonly used are carbon tool steel, low alloy tool steel and matrix.
Steel and medium carbon low alloy steel, etc.
For a long time, the service life of domestic molds is generally low, compared with the advanced level.
Compared with the same molding material, similar or even identical stamping parts, the mold
The service life is only 1/3 ~ 1/2 of developed countries. The main gap lies in the system.
Die material, forging blank quality and die-making technology.
2 Quality of forging blank of stamping die
Through the analysis and study of a large number of failed and scrapped molds, it can be known that no matter
Any failure mode is related to the material properties and internal of the punch and die of the stamping die.
Closely related in quality. Impact failure mainly includes the following situations:
(1) The blade is worn. This mainly happens on the blanking die, which is convex and concave.
Die wear is related to die material properties and heat treatment.
(2) The punch is broken. This form is especially suitable for non-circular punching (or
Punching), which is not only related to material properties and heat treatment,
This is also related to their cross-sectional complexity.
(3) Wear of the molding cavity, local collapse and upsetting of the punch. This kind of loss
The effect mainly occurs in stamping, stretching, bending, punching and flattening forming.
On the mold.
3 significance of forging high alloy tool steel
As a common material for stamping dies, all the forces of high alloy tool steel
Mechanical properties are closely related to the use and life of stamping dies. In the countryside
The mechanical properties of high alloy tool steel are usually improved by forging, but
Domestic high alloy tool steel, especially high alloy tool steel for cold working dies.
(such as Crl2, Crl2MoV), its * * * crystal carbide is extremely uneven, if it is not penetrated.
Modification can not meet the needs of stamping die. So advanced forging is needed.
The process was modified and forged to meet the requirements of die manufacturing.
High alloy steel for forging cold working dies is not limited to obtaining ideal quantity.
What shape, eliminate metallurgical defects (such as forging welding internal porosity, non-oxidizing gas
Pore, grain refinement, compact structure, etc. ), and more importantly, through reasonable
Forging operation greatly improves the mechanical properties of steel.
4. Improve the basic technological elements of forging.
Modification and common free forging of rolled (forged) materials of high alloy tool steel
No, every link has specific requirements. Want to forge it into high quality
The blank of punch and die forging must be determined in advance as follows.
Element.
4. 1 Requirements for original blank
Mold manufacturing is mostly single piece and small batch production, and the mold is forging.
The blank is mainly cut by saw. Both ends are required to be flat (inclined)
Less than 10), the blank size should also consider the machining allowance and fire consumption. for
In order to meet the first upsetting ratio, it is easy to crush the coarse particles of the material.
Carbide.
4.2 heating specification
See table 1 for the forging heating specifications of commonly used high alloy tool steels.
Table 1
4.3 tonnage of forging equipment
High alloy tool steel has higher strength than ordinary carbon steel at forging temperature.
Steel number plus
Thermal temperature
(℃)
Forging temperature (℃)
Initial forging and final forging
Cr 12 1 100 ~ 150 1050 ~ 1 100 850 ~ 900
Cr 12Mo 1 150 ~ 1 180 1070 ~ 1 120 840 ~ 880
Cr12mov1050 ~11000 ~1050 840 ~ 880 plastic difference. In order to facilitate forging near the final forging temperature, it is convenient to
Crushing carbides in steel, thus improving the internal structure of steel and improving the quality of steel during forging.
When using alloy tool steel, the tonnage of forging equipment is higher.
4.4 Selection of Forging Steps for High Alloy Tool Steel
The forging blank of high alloy tool steel die requires its * * * crystal carbide particles.
It should be fine, symmetrical and evenly distributed, without macro-and micro-separation. Unrefined
The rolled (forged) material of domestic high alloy tool steel needs forging before it can be replaced.
The mechanical properties of materials can be changed to meet the requirements of stamping die forgings. It is feasible at present.
There are several effective ways to change satin.
4.4. 1 Upsetting in the fiber direction for more than 3 times. Along the original damaged fiber square
In the axial direction, ensure the forging ratio >; 2. One-time rapid continuous upsetting and stretching 3
More than once. This method is suitable for high speed steel and small high alloy tool steel.
Modification of forging blank. The disadvantage is that if the upsetting and drawing times are insufficient or the forging ratio is too small,
Incomplete forging leads to obvious carbide distribution directionality, and the operation is not feasible.
Hollow cracks are easy to appear at this time.
4.4.2 Repeated upsetting and reverse drawing for more than 3 times. The first upsetting and stretching along the fiber, the first time
Secondary stretching and upsetting are carried out perpendicular to the fiber direction. In this order can be divided into single.
Cross, double cross and multi-cross upsetting and drawing. The key points of this upsetting and drawing process are: primary firing
Complete all transverse upsetting and drawing; Forging ratio >; 2. Height of forging blank before and after upsetting
Double price difference; In order to avoid upsetting protruding cracks, oblique rotation should be adopted.
Second click and quick play; The stretching length adopts square → flat → square feeding. productive practice
Practice has proved that most blanks below 80mm can be satisfied by three kinds of cross upsetting and drawing.
The need to change all kinds of forging blanks of rolled (forged) materials into forgings.
Although the same deformation steps and the same production conditions are adopted, the same deformation steps are adopted.
Because the forger's operation skill is different from the original blank's internal quality
The quantity difference and the effect after forging are sometimes quite different.
5 concluding remarks
Cr 12MoV steel forging blank has no * * * crystal carbide after forging.
Uniformity reaches the national standard level 2 or above, and some can reach the L level, which makes the original
The carbide unevenness of blank rolled (forged) material has been improved by more than 4 grades. along with
Statistics show that this kind of die is made of forged high alloy tool steel.
Its service life has been greatly improved (up to 30%-50%).