What are the hardness requirements for hot work die steel?

Hot work die steel has appropriate hardness requirements, focusing on red hardness, thermal conductivity, and wear resistance. Therefore, the carbon content is low, and the alloying elements are mainly to increase hardenability, improve wear resistance and red hardness. Hot Work Die Steel 1

Working conditions of hot work dies Hot work dies include three types: hammer forging dies, hot extrusion dies and die-casting dies. As mentioned earlier, the main feature of the working conditions of the hot work mold is that it is in contact with the hot metal, which is the main difference from the working condition of the cold work mold. As a result, there are two problems:

The surface metal of the cavity is heated. Usually, when the hammer forging die is working, the surface temperature of the mold cavity can reach more than 300 400, and the hot extrusion die can reach more than 500-800; The cavity temperature of the die-casting mold is related to the type of die-casting material and the pouring temperature. For example, when die-casting ferrous metal, the mold cavity temperature can reach more than 1000.

Such a high service temperature will significantly reduce the surface hardness and strength of the mold cavity, and it is easy to cause stacking in use. For this reason, the basic performance requirements for hot die steel are high thermoplastic resistance, including high temperature hardness and high temperature strength, and high thermoplastic resistance, which actually reflects the high tempering stability of steel. Therefore, the first way to alloy hot die steel can be found, that is, the addition of alloying elements such as CR, W, SI can improve the tempering stability of the steel.

Generally speaking, there are two prominent problems with steel for hammer forging die: one is the impact load during work. Therefore, the mechanical properties of steel are required, especially the plasticization resistance and toughness. Second, the cross-sectional size of the hammer forging die is large (<400mm), so the hardenability of the steel is required to be higher to ensure the uniform structure and performance of the entire mold. Commonly used steels for hammer forging buildings are 5CrNimo, 5CrMnmo, 5CrNiw, 5Crniti and 5CrMnmosiv.

Different materials should be used for different types of hammer eye molds. For extra-large or large hammer forging dies, 5crnimo is better. 5Crniti, 5CrNiw or 5Crmnmosi can also be used.

For small and medium-sized hammer forging dies, 5crmnmo steel is usually used.

The pre-hardened steel is used in the pre-hardened state (the hardness is 30-36HRC, and the non-pre-hardened ones are softer) pre-hardened steel has good cutting performance, and the direct engraving can meet the life requirements of 500,000 mold plastic parts, and the mold has good corrosion resistance. S136 is used in the quenching and tempering state (hardness 48-54HRC), in order to meet the requirements of long-term work or the number of parts reaching more than 1 million pieces, the more suitable use method should be quenched and tempered at low temperature. Quenching is to first heat to 1000-1050 for a certain period of time (calculated as 30 minutes 25mm), then quench into oil to cool to 50-100 and immediately temper to prevent cracking.

The hardness can reach more than 48HRC at 200 tempering (at least 4 hours), which has better polishability and better corrosion resistance.

HB is hard and black, which is the transition between H and B. For example, the pencil has 2b and has 2h. b means black, and the higher the number in front of it, the darker it is.

h stands for hardness, and the higher the number in front of it, the harder it is. Got it? Conventional expressions include Brinell (HB), Rockwell (HRC), Vickers (HV), Leeb (HL) hardness, etc., among which HB and HRC are more commonly used.

HB has a wide range of applications, and the supply status is commonly used, and CU and AL are also available. HRC is suitable for characterizing high hardness materials, such as heat treatment hardness, etc. The difference between the two is that the probe of the hardness tester is different, the probe of the Brinell hardness tester is a steel ball, and the probe of the Rockwell hardness tester is a diamond.

1. Differences: 1. The carbon content is different: the carbon content of cold work die steel is generally in; The carbon content of hot work die steel is;

3. The chromium content is different: the chromium content of cold work die steel is 11% to 13%; The chromium content of hot work die steel varies according to the properties of alloy steel;

3. The addition of other elements is not exactly the same: cold work die steel mostly uses multi-alloy steel with carbide forming elements, such as CR, MO, W, V and other elements; The alloying elements added to the hot work die steel include Cr, Mn, Si, Ni, W, Mo, V and other alloying elements.

2. Reasons: 1. The function of adding Cr, Mn, Si and Ni alloying elements to the alloying elements of hot work die steel is to strengthen the ferrite and improve hardenability, the W and Mo alloying elements are to prevent tempering brittleness, and the Cr, W and Si alloying elements can increase the phase transformation temperature, so that the mold will not undergo phase change and large volume changes in the process of alternating heating and cooling, so as to improve its ability to resist thermal fatigue.

2. Cold work die steel is usually composed of high carbon to meet the needs of high hardness and high wear resistance. If in order to improve the impact resistance of the mold, when the toughness needs to be increased, medium carbon steel can be selected, and hot work die steel can be used instead. When alloying elements are added to the cold work die steel, it is mainly to improve the hardenability and wear resistance, and for the mold with high wear resistance requirements, the multi-alloy steel with purified carbide forming elements, such as CR, MO, W, V and other elements, is mostly used.

Manuscript pants Jane.

Hello, according to your problem description, the solution provided to you here is as follows: the hardness of the die steel has nothing to do with the material1The quenching temperature is too high, which is caused by the improper temperature setting of Gongxiao Travel or the error of the temperature control system, the process temperature should be corrected, and the temperature control system should be overhauled and checked.

2.Decarburization, which is caused by the residual decarburization layer of raw materials or quenching and heating, the preventive measures are controlled atmosphere heating, salt bath heating, vacuum furnace, box furnace using packing protection or the use of anti-oxidation coatings; The machining allowance is increased by 2 over tempering, which is caused by the tempering of the temperature set too high, the failure error of the temperature control system or the furnace temperature is too high, the process temperature should be corrected, the temperature control system should be overhauled, and the temperature control system should not be higher than the set furnace temperature loaded, 4When the furnace is installed, the workpieces are placed evenly at reasonable intervals and dispersed into the tank, and it is forbidden to pile up or bundle into the tank for cooling.

5.Improper cooling, the reason is that the pre-cooling time is too long, the cooling medium is not properly selected, the temperature of the quenching medium is gradually higher and the cooling performance is reduced, the mixing is poor or the temperature of the groove is too high, and the measures: out of the furnace, into the tank, etc. Master the cooling characteristics of quenching medium; The oil temperature is 60 80, the water temperature is below 30, when the quenching amount is large and the cooling medium is heated up, the cooling quenching medium should be added or other cooling tanks should be used for cooling; intensify the agitation of the coolant; Remove at MS+50.

Hello, I am happy to serve you and give you the following answers: the hardness of mold steel is related to the material. Mold steel is a special metal material with good heat resistance, corrosion resistance and plasticity, which can be baked at high temperatures without losing strength.

During the late baking process, the grains inside the material will change, and when the temperature reaches a certain level, the grains of the material will change, which will affect its hardness. The reason for this is that the material properties of the die steel determine that its hardness will change after baking; Improper control of roasting time and temperature; oxidation of the surface of the material; Improper handling after roasting, etc.

The method and practice steps to solve this situation are as follows: 1) determine the material properties of the modal leakage Li Gusteel, and determine the baking temperature and time as needed; 2) During the roasting process, regularly inspect the surface of the material to ensure that the surface will not oxidize; 3) After the fire, the die steel should be properly cooled to ensure the hardness of the material; 4) Quench the die steel regularly to maintain the hardness of the material; 5) Regularly frost the die steel to prevent oxidation on the surface of the material; 6) Regularly carry out anti-corrosion treatment on the die steel to prolong the service life of the die steel. Personal Tips:

When using die steel, the roasting temperature and time should be determined according to the material characteristics, and the mold search steel should be regularly treated with anti-corrosion treatment to prolong the service life of the die steel.

Hot work die steel refers to the alloy tool steel suitable for making molds for hot deformation of metals, such as hot forging dies, hot extrusion dies, die-casting molds, hot heading dies, etc. Because the hot work mold works under high temperature and high pressure conditions for a long time, the mold material is required to have high strength, hardness and thermal stability, especially high thermal strength, thermal fatigue, toughness and wear resistance.

The hot work mold is subjected to great impact force when working, and the mold cavity is in contact with the high-temperature metal, which is repeatedly heated and cooled, and its use conditions are extremely harsh. In order to meet the requirements of hot work molds, hot work die steels should have the following basic characteristics:

1) High temperature strength and good toughness. Hot work dies, especially hot forging dies, withstand great impact when working, and the impact frequency is very high, if the die does not have high strength and good toughness, it is easy to crack.

2) Good wear resistance, because the hot work die is not only subject to friction and wear when the blank is deformed, but also subject to high temperature oxidation corrosion and grinding of iron oxide filings, so the hot work die steel needs to have high hardness and adhesion resistance.

3) High thermal stability. Thermal stability refers to the ability of steel to maintain its mechanical properties at room temperature for a long time at high temperatures. When the hot work mold is working, it is in contact with red-hot metal, or even liquid metal, so the surface temperature of the mold is very high, generally 400 700.

This requires that the hot work die steel does not heat up at high temperature and has high thermal stability, otherwise the mold will be plastically deformed, resulting in collapse and failure.

4) Excellent heat fatigue resistance, the working characteristics of the hot work mold are repeated heating and colding, the mold is heated and expanded for a while, and then cooled and contracted, forming a great thermal stress, and this thermal stress is in the opposite direction, alternately. Under the action of repeated thermal stress, network cracks (cracks) will form on the surface of the mold, this phenomenon is called thermal fatigue, and the mold breaks prematurely due to thermal fatigue, which is one of the main reasons for the failure of hot work molds. Therefore, hot work die steel must have good thermal fatigue.

5) High hardenability. The general size of the hot work die is relatively large, especially the hot forging die, in order to make the mechanical properties of the entire die section uniform, which requires the hot work die steel to have high quenching performance.

6) Good thermal conductivity. In order to prevent the mold from accumulating too much heat and resulting in the decline of mechanical properties, it is necessary to reduce the temperature of the die surface as much as possible and reduce the temperature difference inside the mold, which requires the hot work die steel to have good thermal conductivity.

7) Good forming process performance to meet the needs of processing and forming.

More than 50% larger than the material to be processed.

The hardness of the die steel is not mandatory, nor is it a fixed value. Therefore, it is necessary to determine what kind of hardness mold steel is used according to specific requirements. The hardness of several commonly used die steels is as follows:

738 : 28-32hrc

718 : 28-32hrc

s136 : 28-30hrc

nak80 : 38-41hrc

s50c : 18-21hrc

p20 : 28-30hrc

Die steel is a steel grade used to make cold stamping dies, hot forging dies, die-casting dies and other molds. Molds are the main processing tools for manufacturing parts in industrial sectors such as machinery manufacturing, radio instruments, motors, and electrical appliances. The quality of the mold directly affects the quality of the pressure processing process, the accuracy output of the product and the production cost, and the quality and service life of the mold are mainly affected by the mold material and heat treatment in addition to the reasonable structural design and processing accuracy.

Different molds have different hardness requirements. Hardness has a great impact on the life of the mold, so it is best to determine the hardness for different molds and mold steel grades.

Hardening hot work die steel, characterized by the production of mold in quenching and low temperature tempering after machining, at this time the hardness of the mold is about 40hrc, after processing, in the use of secondary hardening, the hardness can reach 48hrc, and the core tissue has not been transformed, so that the mold has the surface layer of the required high temperature strength and the toughness of the heart. In addition, heat treatment is carried out before machining to avoid distortion and surface oxidative decarburization caused by heat treatment. It is mainly used for hot forging dies in the temperature range of 500 600 °C.

4Cr3Mo2NivnBB (HD) steel is a new type of hot work die steel specially designed for hot extrusion ferrous metal and copper alloy die (working temperature up to about 700 °C). With the increase of tempering temperature, the hardness value of 4Cr3Mo2NiVnbb steel is higher than that of the corresponding 3Cr2W8V steel. Under the same hardness conditions, its fracture toughness KIC is 50% higher than that of 3Cr2W8V steel, 70% higher short-time tensile strength at high temperature at 700, twice as high as hot and cold fatigue resistance, and 50% higher thermal wear performance than 3Cr2W8V steel.