Metal Shredder Hammers Manufacturer

When it comes to shredder hammer, Qiming Machinery has had manufactured high-quality shredder hammer over 30 years. As shredder wear parts specialists, we have developed advanced alloys and manufacturing techniques that really pay off in demanding applications such as solid waste shredding. We stock an array of hammers and grates for common shredders, so you can normally get the parts you need in a matter of days.

Function

The most-frequently replaced wear part is the bell-shaped hammer. Hammers impart the enormous kinetic energy of a shredder’s spinning rotor onto the metal being shredded. Hammers weigh nearly one-half ton new and number about a dozen on the rotor. The rotor with hammers and other wear parts collectively weighs as much as 60 tons. A motor as large as 10,000 hp is needed to attain an operating speed of about 500 rpm. In general, hammers need to be replaced when they have worn down to less than half of their initial weight. If only one hammer needs to be replaced, operators typically replace the opposite hammer, too, to keep the rotor in balance. On average, hammers are replaced once a day. If your operation could benefit from less downtime and fewer change-outs due to hammer wear life, give Qiming Machinery a call. Discover for yourself why our customers report excellent satisfaction with our high-hardness shredder hammers.

 

Material Selection

Qiming Machinery has used different materials to suit different working conditions. We are focused on designing and building first-class equipment that gives our customers the highest availability and minimizes downtime.

Manganese Shredder Hammer

Manganese Shredder Hammer

Manganese Shredder Hammers

We are the best manganese shredder hammer manufacturer in China. Our manganese shredder hammer span life can 20% more than other suppliers. The manganese materials are: Mn14Cr2, Mn18Cr2, Mn22Cr2

Manganese shredder hammer has a very high resistance to crack propagation. If operating conditions cause the yield strength in a region to be exceeded and a crack forms, the crack tends to grow very slowly. In contrast, cracks in low alloy steel castings tend to grow rapidly, which can lead to quick failure and the need for replacement.

Alloy Steel Shredder Hammer

Alloy Steel Shredder Hammer

Alloy Steel Shredder Hammers

Our engineer had used 30CrNiMo alloy steel to cast a shredder hammer. Under this material, the shredder hammer can get different hardness: The bar of shredder hammer’s hardness around: 35-40 HRC, The working area of shredder hammer’s hardness around 45-55 HRC. Because of different hardness, the shredder hammer can get more span life.

Chemical Composition 

CSiMnNiPSCrMo
0.26 – 0.34max 0.40.5 – 0.81.8 – 2.2max 0.025max 0.0351.8 – 2.20.3 – 0.5
TIC Insert Shredder Hammer (1)

TIC Insert Shredder Hammer

TIC Insert Shredder Hammers

Qiming Machinery offers design and wears life analysis with three common alloys for improved wear life: Mn14Cr2, Mn18Cr2 with tungsten carbide insert.

Under this material, Qiming Machinery TIC inserts shredder hammer can get better metallurgy for longer wear life and significant cost savings. Its span life can be 2.5-3 times than normal manganese shredder hammer.

Benefits

  • Alloy Selection. We can produce austenitic manganese steel, alloy steel, and TIC inserts steels for different working conditions.
  • Hammer Styles Selection. We can supply bell-shaped, standard, light iron, weight-efficient, and other different styles for customer different inquiry.
  • Quality Promise. Our foundry is the OEM foundry for China’s famous shredder plant manufacturer. A set of our manganese shredder hammer can crush more than 6,000 tons of metal recycling material.
  • Foundry Price. As a casting foundry, we can direct to export the goods to you.
  • Strictly Quality Control System.  All of our parts are backed by the ISO9001:2008 quality control system. On the other hand, after finish the product, we will supply full detail reports.

Shredder Hammers Styles

Normally, there are 4 kinds of shredder hammer styles which are bell-shaped, standard, light iron, weight-efficient.

bell-shaped style hammer

bell-shaped style hammer


standard style hammer

standard style hammer


light iron style hammer

light iron style hammer


weight-efficient style hammer

weight-efficient style hammer

Shredder Hammers Hook Styles

There are 3 kinds of hook styles to suit different installation inquiries:

FRONT HOOK

FRONT HOOK


INSIDE HOOK

INSIDE HOOK


SIDE HOOK

SIDE HOOK

Study on the low alloy wear-resistant steel for shredder hammers

High manganese steel is widely used in casting small weight hammer (normally less than 90kg). However, for metal recycle shredder hammer (normally weight around 200kg-500kg), manganese steel is not suited. Our foundry uses low alloy steel for casting big shredder hammers.

 

Material Element Selection

The alloy composition design must fully consider meeting the performance requirements of the alloy. The design principle is to ensure enough hardenability and high hardness and toughness. The internal stress of bainite is generally lower than that of martensite, and the wear resistance of bainite is better than that of martensite at the same hardness. The composition of the alloy steel as the following:

 

Carbon Element. Carbon is the key element affecting the microstructure and properties of low and medium alloy wear-resistant steel. Different carbon content can obtain a different matching relationship between hardness and toughness. Low carbon alloy has higher toughness but lower hardness, high carbon alloy has high hardness but insufficient toughness, while medium carbon alloy has high hardness and good toughness. In order to obtain high toughness to meet the service conditions of large and thick wear-resistant parts with large impact force, the range of low-carbon steel is 0.2 ~ 0.3%.

 

Si Element. Si mainly plays a role of solution strengthening in steel, but too high Si will increase the brittleness of steel, so its content is 0.2 ~ 0.4%.

 

Mn Element. China is rich in manganese resources and low in price, so it has become the main additive element of low alloy wear-resistant steel. On the one hand, manganese in the steel plays the role of solution strengthening to improve the strength and hardness of the steel, and on the other hand, it improves the hardenability of the steel. However, excessive manganese will increase the retained austenite volume, so the manganese content is determined to be 1.0-2.0%.

 

Cr Element. Cr plays a leading role in low alloy wear-resistant cast steel. Cr can be partially dissolved in austenite to strengthen the matrix without reducing the toughness, postpone the transformation of undercooled austenite and increase the hardenability of steel, especially when properly combined with manganese and silicon, the hardenability can be greatly improved. Cr has higher tempering resistance and can make the properties of thick end face uniform. so the Cr content is determined to be 1.5-2.0%.

 

Mo Element. Mo can effectively refine the as-cast microstructure, improve the uniformity of cross-section, prevent the occurrence of temper brittleness, improve the tempering stability, and impact toughness of steel. The results show that the hardenability of steel is significantly improved, and the strength and hardness of the steel can be improved. However, due to the high price, the addition amount of Mo is controlled between 0.1-0.3% according to the size and wall thickness of the parts,.

 

Ni Element. Ni is the main alloy element to form and stabilize austenite. Adding a certain amount of Ni can improve the hardenability and make the microstructure retain a small amount of retained austenite at room temperature to improve its toughness. But the price of Ni is very high, and the content of Ni added is 0.1- 0.3%.

 

Cu Element. Cu does not form carbides and exists in the matrix as a solid solution, which can improve the toughness of steel. In addition, Cu has a similar effect to Ni, which can improve the hardenability and the electrode potential of the matrix, and increase the corrosion resistance of steel. This is especially important for wear-resistant parts working under wet grinding conditions. The addition of Cu in wear-resistant steel is 0.8-1.00%.

 

Trace Element. Adding trace elements into low alloy wear-resistant steel is one of the most effective methods to improve its properties. It can refine as-cast microstructure, purify grain boundaries, improve the morphology and distribution of carbides and inclusions, and maintain sufficient toughness of low alloy wear-resistant steel.

 

S.P Element. They are harmful elements, which easily form grain boundary inclusions in steel, increase the brittleness of steel and increase the cracking tendency of castings during casting and heat treatment. Therefore, P and s are required to be less than 0.04%.

 

So the chemical composition for alloy wear-resistant steel is shown in the following table:

Table: Chemical Composition For Alloy Wear-resistant Steel
ElementCSiMnCrMoNiCuV.RE
Content0.2-0.30.2-0.41.0-2.01.5-2.00.1-0.30.1-0.30.8-1.0Rare

 

 

Smelting Process

The raw materials were melted in a 1 T medium frequency induction furnace. The alloy was prepared by scrap steel, pig iron, low carbon ferrochrome, ferromanganese, ferromolybdenum, electrolytic nickel, and rare earth alloy. After melting, samples are taken for chemical analysis before the furnace, and the alloy is added according to the analysis results. When the composition and temperature meet the requirements of tapping, aluminum is inserted to deoxidize; during the tapping process, rare earth Ti and V are added for modification.

 

Pouring & Casting

Sand mold casting is used in the molding process. After the molten steel is discharged from the furnace, it is placed in the ladle. When the temperature drops to 1 450 ℃, the pouring starts. In order to make the molten steel fill the sand mold quickly, a larger gating system (20% larger than that of ordinary carbon steel) should be adopted. In order to improve the feeding time and feeding ability of the riser, the cold iron is used to match the riser and the external heating method is adopted to obtain the dense as-cast structure. The size of the pouring large shredder hammer is 700 mm * 400 mm * 120 mm, and the weight of a single piece is 250 kg. After the casting is cleaned, high-temperature annealing is carried out, and then the gating and riser are cut.

 

Heat Treatment

The quenching and tempering heat treatment process is adopted. In order to prevent the quenching crack at the installation hole, the local quenching method is adopted. The box-type resistance furnace was used to heat the casting, the austenitizing temperature was (900 ± 10 ℃) and the holding time was 5 h. The cooling rate of the special water glass quenchant is between water and oil. It is very beneficial to prevent quenching crack and quenching deformation, and the quenching medium has low cost, good safety, and practicability. After quenching, the low-temperature tempering process is adopted, the tempering temperature is (230 ± 10) ℃ and the holding time is 6 h.

 

Quality Control

The main critical points of steel were measured by optical dilatometer dt1000, and the isothermal transformation curve of undercooled austenite was measured by the metallographic hardness method.

The TTT curve of the alloy steel

The TTT curve of the alloy steel

From the TTT curve line, we can know:

  1. There are obvious Bay regions between the transformation curves of high-temperature ferrite, pearlite, and medium temperature bainite. The C-curve of pearlite transformation is separated from that of bainite transformation, showing the appearance law of independent C-curve, which belongs to two “nose” type, while the bainite region is closer to S-curve. Because the steel contains carbide forming elements Cr, Mo, etc., these elements dissolve into austenite during heating, which can delay the decomposition of undercooled austenite and reduce its decomposition rate. At the same time, they also affect the decomposition temperature of undercooled austenite. Cr and Mo make the pearlite transformation zone move to a higher temperature and lower the bainite transformation temperature. In this way, the transformation curve of pearlite and bainite is separated in the TTT curve, and a subcooled austenite metastable zone appears in the middle, which is about 500-600 ℃.
  2. The nose tip temperature of the steel is about 650 ℃, the ferrite transition temperature range is 625-750 ℃, the pearlite transformation temperature range is 600-700 ℃, and the bainite transformation temperature range is 350-500 ℃.
  3. In the high-temperature transformation region, the earliest time to precipitate ferrite is 612 s, the shortest incubation period of pearlite is 7 270 s, and the transformation amount of pearlite reaches 50% at 22 860 s; the incubation period of bainite transformation is about 20 s at 400 ℃ and martensite transformation occurs when the temperature is below 340 ℃. It can be seen that the steel has good hardenability.

 

Mechanical Property

Samples were taken from the trial produced large shredder hammer body, and a 10 mm * 10 mm * 20 mm strip sample was cut by wire cutting from the outside to the inside, and the hardness was measured from the surface to the center. The sampling position is shown in Fig. 2. #1 and #2 are taken from the shredder hammer body, and #3 are taken at the installation hole. The results of the hardness measurement are shown in Table 2.

Table 2: Hardness Of The Shredder Hammers
SamplesDistance from surface/ mmAverageTotal Average
515253545
#15254.554.3505252.648.5
#25448.247.348.546.248.8
#34643.543.544.442.544
The picture of the heavy hammer

The picture of the shredder hammer

It can be seen from Table 2 that the hardness HRC of the hammer body (#1) is greater than 48.8, while the hardness of the mounting hole (#3) is relatively lower. The hammer body is the main working part. The high hardness of the hammer body can ensure high wear resistance; the low hardness of the mounting hole can provide high toughness. In this way, the different performance requirements of different parts are met. From a single sample, it can be found that the surface hardness is generally higher than the core hardness, and the hardness fluctuation range is not very large.

 

Mechanical Properties Of The Alloy Shredder Hammer
Item#1#2#3
impact toughness(J·cm*cm)40.1346.958.58
tensile strength /MPa15481369/
extensibility / %86.677
Reduction of area /%3.88157.09

The data of impact toughness, tensile strength, and elongation are shown in Table 3. It can be seen from Table 3 that the impact toughness of the U-shaped Charpy specimen of the hammer is above 40 J / cm2, and the highest toughness of the mounting hole is 58.58 J / cm*cm; the elongation of the samples intercepted is more than 6.6%, and the tensile strength is more than 1360 MPa. The impact toughness of the steel is higher than that of the ordinary low alloy steel (20-40 J / cm2). Generally speaking, if the hardness is higher, the toughness will decrease. From the above experimental results, it can be seen that this rule is basically in line with it.

 

Microstructure

Microstructure a small sample was cut from the broken end of the impact sample, and then the metallographic sample was prepared by grinding, pre-grinding and polishing. The distribution of inclusions was observed under the condition of no erosion, and the matrix structure was observed after being eroded with 4% nitric acid alcohol. Several typical structures of alloy shredder hammers are shown in Fig. 3.

Fig. 3 The microstructures of the shredder hammer

Fig. 3 The microstructures of the shredder hammer

Fig. 3A shows the morphology and distribution of inclusions in the steel. It can be seen that the number and size of inclusions are relatively small, without any shrinkage cavity, shrinkage porosity, and porosity. From figures 3b, C, D, and E, it can be seen that both near-surface and near center position

The results show that the hardened structure is obtained from the surface to the center, and enough hardenability is obtained. The microstructure near the center is coarser than that at the surface because the core is the final solidification site, the cooling rate is slow and the grains are easy to grow.

The matrix in Fig. 3b and C is lath martensite with uniform distribution. The lath in Fig. 3b is relatively small, and the lath in Fig. 3C is relatively thick, and some of them are arranged at 120 ° angle. The results show that the increase of martensite after quenching at 900 ℃ is mainly based on the fact that the grain size of the steel increases rapidly after quenching at 900 ℃. Fig. 3D and e show fine martensite and lower bainite with a small amount of small and granular ferrite. The white area is quenched martensite, which is relatively corrosion-resistant than bainite, so the color is lighter; the black needle-like structure is lower bainite; the black spot is inclusions.

Because the installation hole of the shredder hammer is cooled in air and the quenching temperature is low, the ferrite can not completely dissolve into the matrix. Therefore, a small amount of ferrite remains in the martensite matrix in the form of small pieces and particles, which leads to the decrease of hardness.

 

Results

After casting, we sent two sets of shredder hammer to our customer, one set of alloy wear-resistant steel shredder hammers, one set of manganese steel shredder hammers. Based on customer feedback, the alloy wear-resistant steel shredder hammers span life 1.6 times more than manganese shredder hammer.

30CrNiMoRe Alloy Steel For Casting Shredder Hammers

Our Finland customer used manganese steel shredder hammer to crush metal recycle material. However, the manganese hammer just can run around 150 hours. By analysis of the used hammer, the hardness of the used surface is only HB186-222. Only a few grains were found to slip on the use surface, and most of them were consistent with the matrix structure. So our engineer suggests 30CrNiMo alloy steel cast those shredder hammers.

 

30CrNiMo Chemical Composition

Nickel improves the hardenability and toughness of structural steel. When nickel and chromium are used together, the hardenability is very strong, far more than when the two elements are added alone. However, Cr Ni steel is sensitive to temper brittleness, which can be overcome by adding platinum. Adding a certain amount of rare earth in alloy cast steel can refine the structure of steel, purify the grain boundary, improve the inclusions, so as to improve the impact toughness and casting properties of the steel. Compared with other steels, Cr Ni Pt re steel is a kind of wear-resistant material with high hardenability, high strength, and high toughness. The specific chemical composition is shown in Table 1.

Table 1. 30CrNiMoRe Alloy Steel Chemical Composition
Chemical CompositionCMnSiCrMoNiSPRe
Content %0.28-0.360.5-0.750.17-0.370.55-0.850.2-0.31.5-1.8<0.025<0.0250.03-0.06

 

Produce Processing

Smelting: the oxidation process is used in 5T EAF. Oxidation temperature ≥ 1550  decarburization amount ≥ 0.30%. The decarburization rate is not less than 0.01% / min. Before tapping, 1.0kg/t aluminum is inserted, and the alloy is added along with steel flow. Molding: resin sand for core sand, 8 pieces per box. The casting process performance of this steel is similar to that of medium carbon steel. In order to improve the casting density of the working part of the shredder hammer, a riser is placed on the head.

The heat treatment process is 900-920 ℃ water quenching, and tempering at 200 ℃.

 

Results

After finish this product, we sent two sets to our customer. Based on customer feedback, this alloy steel shredder hammer span life can be 2-2.5 times than normal manganese steel hammer.

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